KR20010022911A - Switchable optical components - Google Patents

Abstract

FIELD OF THE INVENTION The present invention relates to a number of devices, devices, and networks relating to integrated light and / or semi-coupler technology, which are examples of electrically switchable Bragg diffraction grating devices and structural devices realized using holographic polymer / dispersed liquid crystal materials. Associated with use. Many of these devices and devices are not only particularly suited to the use of wavelength division multiplexing (WDM), but also to the use of switchable add / drop filtering (SADF) and wavelength selective cross-link attenuators, external couplers, thereby also Various other devices are also provided.

Description

Switchable optical element {SWITCHABLE OPTICAL COMPONENTS}

Due to the very high bandwidth capacity, the utilization of optical signals in the transmission of data is increasing. In addition, the bandwidth capacity of the fiber optic cable provided can be further increased by transmitting multiple discrete signals in separate channels within short fibers at a slightly different wavelength, a technique known as wavelength separation multiplexing (WDM). Thus, for example, a slight 1550 nm optical signal fiber consists of 4, 8, 64, 80 or more channels, each of which is, for example, approximately 0.8 nm (for 100 GHz) or approximately 1.6 nm (for 200 GHz). As long as it is separated. Multi-wavelength manipulation results in an important increase in optical transmission or switching where multiple non-interacting signals pass through a switch simultaneously, which carries a totally inconsistent data rate, incompatible and parallel encoding and protocols. do. However, in the above useful signals, it is possible to selectively switch the optical signals that are delivered to the bus (or other optical conduit) for the fiber / conduit whose wavelength is the optical fiber, the desired drop / destination. It is certain that the wavelength will be able to selectively add a signal from the drop to the bus or that the wavelength can selectively pass the signal between the fiber or other optical conduit. Sometimes the first of the two functions is called switchable add / drop filtering (SADF), and the second is called wavelength selective cross-connection (WSXC). In other applications, it is necessary to switch the entire fiber signal, including the full wavelength channel (such switching is sometimes referred to as "spatial switching"). In addition to being used in the telecommunications industry, in complex fiber optics structures for sensors and computer data networks, the optical signal must be efficiently transferred through the N arrays entering the optical fiber either efficiently or through the path, where the fiber It may be a single mode or a multimode, and must also be switched efficiently from the M arrays drawn out from the optical fiber. The spatial switch will sometimes be referred to as NXM or cross connect.

Although many techniques have been proposed for years to perform optically NXM switching, none of these techniques have proven to meet all requirements at the same time. This is partly due to the diversified structures required for the switch. For example, N fiber external switches, which are N fibers that map each fiber optical fiber that enters one or more or only one fiber outputs, are referred to as NXM cross-connections. Regardless of the initially installed connection, any connection is not blocked if possible. In some applications, a reconfigured unoccluded switch is sufficient. In other applications, a switch is needed that performs a multicast or broadcast or other various function of sending a signal that sends a signal coming into one or more outputs. The data capacity required for a fiber optic network is also becoming increasingly complex, with 2 × 2 or 4 × larger than the smaller switches (e.g., 64 × 64, 1024 × 1024, and larger switches) in the previous method. There is also a need to improve switching technology to extend from 4).

It is also desirable for such a switch to be integrated, such as each miniaturized switching element, which can be combined with a number of others on a single chip or substrate for installation by a further extended NXN or NXM cross-connect structure. However, for single channel operation, the design of the above-described structure, particularly the extended switch, is very complex, in multichannel WDM operation (eg wavelength selective switching with NxMxm, where m is the number of WDM channels). Complexity is increasing dramatically.

Another requirement for optical switches of the type described above, in particular optical elements and structures, is to contact them efficiently with optical fibers, which is a method for transmitting high bandwidth signals over long distances in a way to reduce coupling losses. In general, it is used a lot. Other important operating parameters include minimal insertion loss, crosstalk and polarization sensitivity, ensuring good optical separation at all switch states, good helical bandwidth and good dynamic range for on / off contrast and good low power consumption There is something to do. Low operating power, high switching speed, low power consumption, stability, long service time / temperature insensitivity and high reliability are also important parameters. However, for many reconfigured network and protection switch functions, a switching speed in the range of 1 microsecond to 1 millisecond is suitable and sufficient.

In addition, in the present state of the art, neither spatial switching nor wavelength selective switching techniques are sufficiently satisfactory. One reason for this is that the various network controls and the necessary reconfiguration functions are generally made of different and inconsistent technologies. If a number of different discrete network control functions could be implemented on the basis of one underlying technology, the optical network system would have evolved to significant levels of efficiency in terms of manufacturing and its cost.

All-optical switches are increasingly regarded as essentially next generation networks. Since there was no satisfactory product performing the same function as the optical switch, it is necessary to convert the optical signal into an electronic signal for switching. Such techniques are expensive, time consuming, can impose bandwidth limits on the system, and also provide many sources of potential errors. It is also possible to limit the flexibility of the system, which is generally not an efficient method of operation.

In the switching application described above, one or more signals of a multiwavelength or multichannel line are optionally included to selectively add, drop, pass, or occlude a variety of individual individual wavelengths or channels (or entire channels). To attenuate the optical signal and to selectively cross-connect the optical path, including multi-channel or multi-wavelength optical paths, which facilitate transmission of one or more channels therebetween, and / or optical paths out of the waveguide plane Therefore, for all of the above purposes for selectively combining multiple wavelengths or multiple channels, the direction in which the optical signals are transmitted through the waveguide, the necessity to change the optical signals to dynamic filter optical signals, in particular multi-wavelength or multi-channel There are a number of applications that exist. It will be possible to perform all these functions using optical devices and / or structures that are relatively easy to manufacture and inexpensive to produce. Specifically, multiple optical networks are paralleled together, with additional functions such as programmable attenuation on all chips, occurring simultaneously, performing spatial switching, wavelength selective switching, switchable add-drop filtering, and wavelength selective cross-connection switching. In order to utilize the one-shot manufacturing technique that combines the multi-function on a single chip for this purpose, it is preferable that a manufacturing technique for manufacturing using a single material technology is provided rather than assembling each device separately. .

Justice

In the following paragraphs, various terms are used, which are considered to have the following definitions.

A "bragg diffraction grating or diffraction grating" is a periodic structure formed by spatially varying refractive index distributions or similar fluctuations that occur through the boundaries of defined volumes or induced regions. Simple Bragg diffraction gratings are periodic in one dimension. More complex diffractive structures, which may include the object of the present invention within this definition, are indicative of volume distribution holograms, diffractive lenses, or other computer generated or optically recorded refractive index distributions, in most cases substantially three-dimensional volumes. Combining the transmitted refractive index distribution, the incident laser or other light beam or light beam received through the guided light from the desired output state or from one waveguide mode to another waveguide mode, from the waveguide mode to the free space mode or vice versa It may be a refractive index distribution designed and manufactured for this purpose.

"Switchable diffraction grating or switchable Bragg diffraction grating" means diffraction grating

Periodic changes can be adjusted, induced or extinguished by an electric field

It is a diffraction grating of volume measurement. This is a non-switchable standard

It is different from the diffraction grating. This definition shows the variation of the period of the diffraction grating.

It does not mean just the rate of spatial change. Simple example

Where the switchable diffraction grating of either transmission or reflection type

Device, or, in the switched-on state,

Ringable diffraction gratings are filtered or high-quality conventional fiber or waveguide bra

Compared with the diffraction grating, it has other diffraction characteristics and switches off (sw

In the itch-off state, it is effectively dissipated and low loss waveguide

Or with a volume of transparent optical material.

Until recently, no mechanism for switchable Bragg gratings has been utilized. Any semiconductor diffraction grating can be switched, but this is only limited to the geometry and the controlled dynamic range of spatial exponential fluctuations is relatively insignificant. Usually the liquid crystal diffraction grating formed by the electrode of the physical structure is switchable, but this is mainly related to the free space non-volume measuring diffraction grating, which is excessively scattered when used as a fiber optical signal, In the second range, switching is relatively slow. Switchable multi-faceted diffraction gratings associated with the use of structured electrodes to create spatial periodicities such as magneto-optical materials and lithium niobate materials have been shown to vary in their depth in the depth of the diffraction grating depending on the spatial period and the lithographic process of the produced electrode pattern. Limited to the application. Such diffraction gratings are not practical in space periods well below 1 micrometer of structured electrodes, so smaller periods are more important in various fiber optic applications, and the diffraction gratings also cannot penetrate an unlimited volume of electrode periods. Because of this, volumetric (bragg) diffraction gratings are not inclined.

"Holographic polymer / dispersed liquid crystal or H-PDLC"

Polymer networks with any microdroplet complex or interpenetrating L.C.

Including other morphological variants. This of the switchable diffraction grating

The group consists of ultrafine droplet dispersion of liquid crystals in polymer host, holographic recording and

Cycles as small as 500 nanometers or less

The branches are based on volumetric diffraction gratings with periodic structures. Like that

Switching a diffraction grating by patterning the electrode

Contrary to fabrication, it is uniform for the entire diffraction region and monolithic (

It is obtained by applying an electric field to a monolithic electrode. On H-PDLC

Examples are described below, but are not limited to the following.

1. R. L. Sutherland, L. V. Natarajan, V. P. Tondiglia, T. J. Bunning, Bragg diffraction gratings in acrylate polymers consisting of periodic polymer-dispersed liquid crystal plates, Chem. of Materials, 1993, 5, 1533.38.

2. R. L. Sutherland, L. V. Natarajan, V. P. Tondiglia, T. J. Bunning and W. W. Adams, Development of Photopolymerization / Liquid Crystal Composite Materials for Dynamic Holograms, Proc. SPIE Vol. 2152, Paper 38.

3. V. P. Tondiglia, L. V. Natarajan, R. L. Sutherland and T. J. Bunning, W. W. Adams, Volume holographic image storage and electro-optical reading in polymer dispersed liquid crystal films, Opt Lett. v. 20, p. 1325, 1995.

4. R. L. Sutherland, L. V. Natarajan, V. P. Tondiglia, T. J. Bunning and W. W. Adams, Switchable Holograms in New Photopolymer-Liquid Crystal Composites, Proc. SPIE Vol 2404, p. 132, 1995.

5. R. L. Sutherland, L. V. Natarajan, V. P. Tondiglia, T. J. Bunning and W. W. Adams, electrically switchable volume diffraction gratings in PDLC, Appl. Phys. Lett., Vol. 64, p. 1074, 1994.

6. US Patent 4,938,568, July 3, 1990. John D. Margerum, et al.

7. US Patent 5,096,282. March 17, 1992. John D. Margerum, et al.

8. A. Golemme, B.L. Volodin, B. Kippelen, and N. Peyghambarian, Photo-Refractive Polymer-Dispersed Liquid Crystals, Optics Letters, Vol. 22, no. 16, p. 1226-1228, August 15, 1997.

9. Keiji Tanaka, Kinya Kato, Shinjui Tsuru, Shigenobu Sakai, Holographically Formed Liquid Crystal / Polymer Devices for Reflective Color Displays, Journal of the SID, Vol 2, No. 1, p. 37-40, 1994.

10. Emily W. Nelson, Adrian D. Williams, Gregory P. Crawford, Louis D. Silverstein, and Thomas G. Fiske, Full-Color Reflective Display, IS & T's 50th Annual Conference, p. 669-673.

11. G. Crawford and S. Zumer, Network of Polymers and Porosity, Taylor and Francis, 1996, London.

Any of the "electrically switchable Bragg diffraction gratings (ESBGs)" of a wide range of devices and device geometries have been realized utilizing H-PDLC material technology.

The present invention relates to a switchable optical element. In particular, it relates to optical elements, including switchable waveguide diffraction gratings, utilized in waveguide optics and suitably used in wavelength separation multiplexing (WDM) systems. It is also utilized as switchable add / drop filtering (SADF) and wavelength selective cross connection (WSXC), semi-coupler or edge-polishing fibers, attenuators and other optical diffraction gratings or wavelength discrete devices, devices in which the devices are used, A method of assembling the device and the device, and a switchable optical device used in the integrated structure of the device.

1A and 1B are structural diagrams of waveguides having ESBGs in a core region and a cladding region, respectively.

2A and 2B are structural diagrams of a transmitting ESBG in off-state and on-state, respectively.

3A and 3B are structural diagrams of an ESBG in off-state and on-state, respectively.

4A and 4B are structural diagrams of single switchable waveguides in on-state and off-state, respectively.

5A is a schematic diagram of a switchable add / drop single channel filter in the present invention.

5B is a structural diagram of various coupling modes that may be present in the filter of FIG. 5A.

FIG. 5C is a graph showing the optical performance at various ports for the filter in FIG. 5A without apodization, and FIG. 5D is a graph showing the performance at the ports apodizing.

5E is a structural diagram of an integrated planar four-channel array filter utilizing the device of FIG. 5A.

5F is a structural diagram of an integrated optical cross-connect switch.

6A and 6B are structural diagrams showing two embodiments of cross point switches in the present invention.

FIG. 7A is a graph comparing the filter response of the cross-connect shown in FIG. 6A with the filter of FIG. 5A.

FIG. 7B is a graph specifically showing the overall response to the cross connection of FIG. 6A.

7C and 7D are graphs showing typical light response of the cross-connect shown in FIG. 6B.

8A and 8B are structural diagrams showing cross-arrays between composite waveguides for composite wavelengths utilizing the cross-connect elements of FIG. 6B.

9 is a structural diagram of an ESBG used as part of a resonator.

10A is a structural diagram of a resonator embodiment for a channel drop filter.

10b and 10c are examples of such filters with higher order coupled resonators.

10D-10F are structural diagrams of three guide-channel dropping filters with resonators in the present invention.

FIG. 11 is a graph showing the response of a matched bus resonator of the type shown in FIG. 10A.

12A-12E illustrate a method of making an integrated arrangement of the present invention.

13A and 13B illustrate alternative fabrication techniques of the integrated arrangement of the present invention.

FIG. 14A is a structural diagram of a semi-coupling device in the technique of the present invention, and 14B is a chart of the exponents and dimensions of the various components in the device of the type indicated in FIG.

14C and 14D are cross-sectional views along the line c-c in FIG. 14A with electrodes above and below the ESBG and on edges of the ESBG.

Figure 15 is a structural diagram of a switchable Bragg filter with a semi-binding device of the present invention.

16 is a structural diagram of a method of manufacturing a device of the type indicated in FIG.

Figure 17 is a schematic diagram of a switchable out-coupler utilizing the semi-bonding technique of the present invention.

18 is a structural diagram of an adjustable attenuator utilizing the anti-binding technique of the present invention.

FIG. 19A is a graph showing the photoelectric transfer through a fiber as a function of the electro-optically switched ESBG for two different polarizations, and FIG. 19B shows the power transfer as a function of wavelength for three-step attenuation. It is a chart.

20 is a structural diagram of a channel add / drop crosslinking device utilizing the anti-bonding technique of the present invention.

Figure 21 is a schematic diagram of a 2x2 spatial switch utilizing a semi-coupler and ESBG technique.

22A and 22B are structural diagrams of a diffraction grating auxiliary coupler between two fibers.

22C is a graph showing the performance of the coupler of FIGS. 22A and 22B.

In accordance with the above, the present invention provides an element which is selectively reconstructed on the waveguide optical path, for example, whose path may be a waveguide formed in the composite optical structure.

do. The device includes at least one ESBG whose path is optically contacted, and optionally at least one electrode, and then an electrode for applying a voltage across the ESBG, the first voltage being applied across the ESBG. In this case, there is no change in the optical signal for the path, and in the case where the second voltage is applied across the ESBG, there is a change in the optical signal on the path. If the optical signal is a multi-channel WDM signal, the selected channel may be dropped from the path when the second voltage crosses the ESBG, where dropping causes the channel to be reflected back through the path or routed through the ESBG. It may be dropped / out-coupled from.

The device may comprise a second waveguide optical path coupled optically with the ESBG where there is at least one selected channel transmitted between the paths when the second voltage crosses the ESBG. In detail, the channel may be dropped or added to the optical path by being transferred between the optical path and the second optical path through the ESBG when a voltage across the ESBG is applied to the optical path. If the WDM signal appears in both paths, WSXC transmission of at least one selected channel may be done between the paths if a second voltage is applied across the ESBG.

Multiple ESBGs or ESBG devices may be optically coupled to both paths with different channels transmitted between their paths by each ESBG when a second voltage is applied and applied. In some embodiments of the present invention, there is one ESBG in optical contact with each path, at least one optical path interconnecting the ESBGs, and interconnecting the ESBGs to form a ring, which is generally a preferred embodiment. There are two paths to let. One of the rings may be installed between the paths so that each WDW channel is transferred between paths. The two preferred signal-carrying optical fibers have the same value as the initial validity index, and for example, different effective indices can be obtained by having an optical path of a different size ring than that of the primary optical path.

The optical path may also have other indices which can be obtained, for example, by having optical paths of different sizes. The difference in the diffraction grating index is the exponential change of the ESBG diffraction grating It is preferred that n is equal or greater.

Rather than photointegrating, the device may be a switchable semicoupling device such as, for example, a switchable drop filter, a switchable external coupler or a switchable attenuator. In the attenuator, the ESBG has a submicron diffraction grating.

The ESBG may also be some resonator. When the resonator is used as a channel drop filter, the device includes a first drop resonator and a second drop resonator, each separated by half or one wavelength of an integer wavelength dropped in a transmission direction of an optical signal on each optical path. do. Each resonator may also be a multipolar resonator formed of resonator sections, either in series coupling or in parallel coupling. The resonator element may also be a guide channel dropping filter in which the resonator is located between the optical paths. It may also be a split resonator having a phase delay section between split resonator sections.

The ESBG with two waveguides or optical paths may be used for cladding for both optical paths where the cladding overlaps. ESBGs that do not overlap the cladding of the two optical paths may extend or cover the two optical paths, thus affecting the interconnect. In any device associated with two optical paths, the side lobes are suppressed by apodization. As indicated above, all of the above is preferably validated through the use of integrated optical technology except for the semi-coupled embodiment.

In a semi-bonded embodiment, an optical fiber having a core with a cladding around is provided, wherein the index of the core is n ₁ and the index of the cladding is n ₂ if the cladding is at least partially selected. And the effective index of the fiber is n _e . In that region the ESBG is anchored to the fiber, which in its initial state has an index with an index n _B where n _B is substantially equal to n ₂ . The electrical device also includes an electrode that selectively applies a voltage across the ESBG. The effect of the ESBG on light is applied to the ESBG, which changes as the crossing voltage changes, thus changing the state of the ESBG. Light applied to the optical fiber is substantially unaffected by the ESBG when the ESBG is in the initial state. This happens, for example, if the mechanism is not actually applying any voltage across the ESBG. The change in n _B resulting from varying the voltage across the ESBG may result from the selected attenuation of the light over the fiber, especially if the ESBG has a diffraction grating with subwavelengths. In general, the attenuation is substantially independent of the wavelength.

The ESBG may generate light from the fiber when the voltage across the ESBG at one or more selected wavelengths coupled through the ESBG in at least one direction or in the initial state changes from a voltage that generates the ESBG. The ESBG diffraction grating may also have a period of generating light at one or more selected wavelengths that are retroreflected along the fiber, so that the one or more selected wavelengths may be filtered from the light propagating within the fiber. Two of the fibers may be installed in the fiber region with adjacent removed cladding and in an ESBG mounted between the fibers in both regions. In this reconstruction, when the ESBG has a selected index, all the light on either of the fibers passes through the ESBG unchanged to the other fiber. If the fibers have substantially the same exponent, light applied to any of the fibers is transmitted through the ESBG to other fibers when the ESBG is in its initial state. When in the second state due to the voltage across the ESBG group, at least one selected wavelength of light, determined by the period of the diffraction grating, is prevented from passing through the ESBG and such light continues to the original fiber. It is spread. The fiber is also 2 Of = _{i- in} this case having at least one or more wavelengths of the multi-wavelength optical signal under conditions where _i 'is satisfied, where Is the period of the diffraction grating, _i , _i 'is the propagation constant for each of the two fibers, and there is a coupling between the fibers only at that wavelength. When the fibers have different indices, the difference in the effective indices is the exponential change of the ESBG diffraction grating It is better than or equal to n.

The present invention also includes installing an ESBG having a subwavelength diffraction grating, where the diffraction grating may have a period of substantially less than 0.5 μm. The subwavelength diffraction grating has two interfering light beams such that the half angle θ between the appropriate wavelength and the beam is greater than in sin θ = λ / 2 Λ, where λ is the central wavelength of the optical signal of the ESBG being utilized. Exposing the film to the film (a); (B) exposing the film through a suitable bicomponent image mask; exposing the film through a master diffraction grating; (c) can be obtained by exposing the H-PDLC film.

An integrated optical network having a plurality of nodes with at least one ESBG formed at each node forms at least one of the selected optical waveguides of the waveguides passing through the node to form a selected optical waveguide on a suitable substrate and at each node. In addition to forming ESBGs with electrodes, they may also be made by covering the waveguides and ESBGs. The ESBGs may be made by exposing an H-PDLC film to each node to form an H-PDLC film on an electrode film or each node to form an ESBG diffraction grating thereon. Covering of waveguides and ESBGs covers the waveguide / H-PDLC film with a cover plate by forming a second electrode on the cover face at each node, and then applying an H-PDLC film to the corresponding node on each cover plate. By overwriting. Exposure of the H-PDLC film will then expose (a) an interfering light beam having an appropriate wavelength to each H-PDLC film that will have its beams selected at each other; Exposing (b) each of the films through a suitable mask. Selected optical waveguides may also be formed on the first and second substrates, wherein the optical waveguides are mounted adjacent to each other during the covering step process, and the waveguides on the two substrates cross at least one selected node. In this embodiment, the H-PDLC film with ESBG diffraction grating formed at that node is formed on either substrate or separately formed and mounted between the substrates. The electrode film may be formed on each substrate of the waveguide of each node.

Finally, in the present invention, an integrated optical network having N guide wave light inputs and M guide wave light outputs according to the state of the ESBG, a waveguide crossing at a node, and one crossing at a node on a waveguide at each node An ESBG switch element is included that operates either to pass an optical signal on the waveguide or to transmit at least one portion of the optical signal to other waveguides crossing each node. For WDM signals, an ESBG switch element may be provided to the node for each wavelength to be transmitted at the node. In a more preferred example, the waveguides have substantially the same exponent n ₁ , where the ESBG switch element at each node has an optical contact with each waveguide. ESBG having a diffraction grating with n, at least one waveguide interconnecting the ESBG classes, index n ₂ (where n ₁ -n ₂ n) and an ESBG having a waveguide for connecting the ESBGs.

The objects, features and advantages of the present invention described above will be apparent from the following detailed description of the preferred embodiments of the present invention as described in the accompanying drawings.

The '950 application describes various free space, waveguide and fiber optical devices utilizing ESBG technology to perform various switching, reflection, filtering, routing and other functions for optical signals on short or multi-wavelength lines. Bragg diffraction gratings may be classified as free space or waveguide diffraction gratings, or may be classified as transmission or reflection diffraction gratings within each category. Each ESBG class corresponding to each of these types is converted into a switchable form. As shown in Fig. 1A, the ESBG 12 may be located in the guiding region 14 of the planar waveguide or in its core. Alternatively, as shown in FIG. 1B, the ESBG 12 may exist in a minor area or cladding area thereof. As indicated in the '950 application, ESBGs are utilized to perform various functions; However, these functions are usually characterized by transmission or reflection functions. Because the desired performance and suitable design structure differ when used for transmission rather than when used for reflection, the ESBGs used for these functions also have somewhat different structures, material properties, periods, spatial index variations and other parameters. different.

In particular, the transmission diffraction grating is mainly used for spatial separation of the beam in an alternate path, with no distinction of wavelength-channel, thus it is useful for 2x2 spatial switches. (The term "space switch" should not be confused with the word "free space switch"; space switching refers to the separation of the entire beam or the path of the guided wave; free space propagation refers to uninduced light beams.) Since the present application mainly relates to the guided wave in the waveguide and / or the optical fiber rather than the free space switching, almost all of the following description relates to the waveguide structure.

Transmission diffraction grating

In the transmission diffraction grating, the refractive efficiency at the Bragg matched angle and wavelength is given by the following approximation.

de = sin ² [ n L / λcos θ] (1)

Where θ is the Bragg angle, Is the wavelength, L is the interaction length, n is the magnitude of the spatial exponential fluctuations, which varies over a wide range of formulas and processes of H-PDLC (about n 0.001 ~ 0.05), which is one of the advantages of this material system for ESBGs.

Full refraction is de = 1 or n L / λcos θ] = 1/2. (When this principle is clear and describes coupling in a single mode waveguide, this formula changes significantly, which means that the diffraction grating in the core Or should be further modified depending on whether or not it is in the overlay area, but is generally seen to be inherently dependent on fundamental parameters.) In terms of beam steering efficiency, It is desirable for n to be relatively large, for example by 2 to 5% and thus L to be small, for example by = 50 μm. In the diffraction grating, the wavelength dependent on the coupling is relatively weak because a 1% change in wavelength causes a change of only about 1% in the coupling strength.

The direction of the ESBG 12 with the transmission diffraction grating and its electrode 20 is shown in Figs. 2A and 2B; The Bragg plane points to the diffraction grating vector 22 nearly opposite the direction of the incident beam 24. The diffraction grating vector is a term used in the art as a vector orthogonal to the plane of the diffraction grating, and its length or size is inversely proportional to the space of the plane. The diffraction grating for free space transmission of FIG. 2A and FIG. 2 is the simplest case. It is also understood that a similar structure can be substituted for the guided wave in a limited area.

Also shown in FIGS. 2A and 2B and the elliptical "football" of liquid crystal microdroplets are dispersed in the Bragg plane of the ESBG film, intersecting at the shortest possible distance to efficiently rearrange the liquid crystal molecules within each droplet. The voltage is applied to create the maximum possible field, and in the case of free space, the only opportunity for electrode placement is only used in the practical planar structure shown. From the planar device, it can be seen that there are electrodes only at the "front and back" of the diffraction grating (refer to the front side where the light enters). However, the volume of the three-dimensional diffraction grating can be roughly compared. For transmission diffraction gratings in waveguide structures, additional selections are used and the electrodes may be applied as described above or above and below (or right / left). In the case of waveguide diffraction gratings, although either of these structures may be considered useful in principle, the substantially planar structure and the thickness of the film suggest that the up-and-down arrangement of the electrodes is normally a practical choice. In the face structure, free space applications where ESBG is not a thin film that is substantially parallel to the propagation of light, but rather a thin film that is perpendicular to the propagation of light, are found in certain applications that depend on the birefringence of liquid crystals and the above exponential relationship with other elements There is a choice,)

The physical locus of the transmission diffraction grating containing the ESBG in the planar device is either in the core region 14 or in the overlay (or known as cladding) region 16, as shown in FIGS. 1A and 1B. There may be. The interaction between the diffraction gratings is stronger than in the former case, but the loss may actually be reduced further in the latter case. The choice between these alternative designs is necessary for computer simulations that predict the measurement of performance and losses that require a high degree of accuracy and specific devices based on numerical modeling, which allows the evaluation of the relative benefits of alternative manufacturing pathways. . However, in general, both structures are useful for the use of H-PDLC based on ESBG family and are functionally equivalent for many applications. Despite this functional equivalence, the overlay structure, along with the advantages of continued use, makes it relatively easy to manufacture and reduces the loss of waveguides or optical fibers; However, in many applications the core structure provides good overall performance.

Reflective diffraction grating

ESBG class 12 having a reflective diffraction grating in the plane, the waveguide context is made in the direction of the Bragg plane indicated in FIGS. 3A and 3B, so that a portion of the pi propagating backwards is reflected, where the reflected wavelength band ( band) = 2 n _eff Is determined. Where n _eff is the effective mode index of the film, Denotes the physical period of the diffraction grating. In reflective diffraction gratings, it is desirable to emphasize the wavelength selectivity since the main application is switchable wavelength filtering for WDM. The width of the spectrum of the reflective node is calculated using a mathematical model of known waveguide design, but is only an approximate value.

Formula (2)

In this case, unlike the transmission diffraction grating, It is preferable that n / n is generally smaller than 0.1%, and L is as long as possible to 2000-3000 micrometers. In the field of H-PDLC chemistry, this can be maintained in the desired state by adjusting a certain amount of liquid crystals down in the pre-ESBG liquid, by changing process conditions or by changing the formula. The reflectivity of the diffraction grating for reflection at the center of the wavelength is approximately

Formula (3)

It is preferred that the value is almost 1, which is Even if n / n is small (almost 0.001), it can be obtained by increasing L / Λ (about 4000).

Thus, in spatial switching, the transmission diffraction grating is optimized for small L and large Δn (denoted as "short and thick diffraction gratings" for educational purposes), while the reflective diffraction grating used for wavelength filtering Optimized for long L and small Δn (long, thin diffraction gratings). The main advantage of the group of materials used as ESBG-based H-PDLC materials is the ability to accommodate these requirements in a group of devices, and this diversity allows the attachment of various devices onto the substrate of any device. By changing the equations and processes over a range of difficult materials, different material groups can combine these two different groups of devices on one substrate in one manufacturing process. The possibility of this category does not exist, for example, in semiconductor diffraction gratings exhibiting the multifunctionality disclosed herein for ESBGs.

Larger differences between the transmission and reflecting diffraction gratings are shown in FIGS. 2A-3B in terms of electrode placement. In the reflective diffraction grating, the diffraction grating vector 22 is positioned substantially parallel to each other in a completely different direction from the transmission diffraction grating in which the forward and backward propagation light and the diffraction grating vector are in the "y" direction (e. Direction). Aspheric microdroplets 26 ("football of liquid crystal") in the ESBG 12 are always located in a direction parallel to the diffraction grating vector; Thus, the microdroplets of the reflective diffraction grating extend in the same direction as the light propagation (not substantially the same as the transmission diffraction grating extending substantially perpendicular to the direction of the light propagation). The direction of the liquid crystal "football" and the LC molecules therein indicates that the electric field is rearranged efficiently, and in the reflective diffraction grating, the electrode can only be located above or below the diffraction grating or on the side of the diffraction grating. In order to optimize the efficiency of the electrical signal, the electrodes must cross any one of these spaces for a short distance. In the case of a reflective diffraction grating of a thin film, it is not a cross but a direct direction. In the following both transmissive and reflective diffraction gratings and all planar devices will be discussed, but since this is a normally preferred configuration, hereafter the electrodes 20 will be used in parallel to the surface of the substrate and the overlay film to which the top and bottom of the ESBG are applied. . However, other configurations are not yet shown in the present invention.

As in the case of a transmission diffraction grating, the reflective diffraction grating is in principle located either in the core region 14 or in an overlay region 16 having a similar function, with each pros and cons also having a Will be the same as

The detailed physics and chemical properties of H-PDLC can be seen from the reference examples mentioned, and the simplified physical model shown in FIGS. 2 and 3 merely provides a physical evaluation of the basic ESBG design parameters using H-PDLC. The purpose is to help. Thus, the description of H-PDLC microdynamics herein may be too simplified or may be partially modified in order to aid the scientific understanding of H-PDLC in the future without limiting or significantly changing the invention described herein. .

H-PDLC Formulation Requirements for Waveguides

There are two requirements with respect to the refractive index n in H-PDLC formulation that reduces the functionally flexible structural loss described above.

First, the formulation of the H-PDLC ranges from less than 0.01% (long and thin reflective diffraction gratings) to 5% (short and thick diffraction diffraction gratings) where exponential spatial variation Δn / n can be widely designed after exposure to holographic The chemical adjustment of such ratios up to the lattice) must be made. In this way, whether an exponential spatial change is produced in the state of the non-source of the diffraction grating, this spatial change will be controlled by increasing or decreasing the amplitude by applying an electric field to the film to make it substantially 1 to 10 V / μm, for example. . Ideally, an electric field is applied to directly suppress the spatial exponential fluctuations to the extent that it can be said to be extinct, or in general, the electric field is acted to reduce the substantial exponent fluctuations and the diffraction grating is used in transmission or reflection mode. In doing so, the polarization of the light guide wave and other factors depends on the detailed liquid crystal droplet form. Thus, in this respect, the present invention may be switched between the active-diffraction grating and the inactive state-diffraction grating by either applying or removing a suitable electric field, which does not substantially change the optical function described. .

In addition, after exposure and processing, in order to bind to the optical fiber or to interact with the optical fiber in a device using a semi-coupler, or otherwise preferably added, such as silicon dioxide (silica) cladding by a known deposition method, Some such structures are highly desirable that provide H-PDLC formulations in which the average index n is obtained where the typical single mode dielectric core / cladding range changes (over the same range obtained by applying an electric field). However, in unplanned silica or other devices in direct contact with optical fibers, H-PDLC with a larger index in the range of N = 1.53 or higher may be utilized, which is bound to interact with other polymer waveguides. Put it.

Switchable Waveguide Diffraction Gratings

4A and 4B show a waveguide Bragg diffraction grating, which is the basic building block of the all planar design of a block to be considered below. This simple ESBG, connected to a transmission diffraction grating in an integrated structure, has a bus or waveguide 31, a core 12, for example, in which silicon is immersed in the substrate 33, mounted on or within the core. There is an ESBG 12 formed. An electrical signal is applied to the ESBG 35 via the electrode 35. Figure 4b shows such a situation where the ESBG has a free space period change index when no voltage is applied to the ESBG, which is substantially consistent with the waveguide in the same phase. As a result, all channels of the WDM signal applied to the waveguide 31 pass through the waveguide 31 without change. In FIG. 4A, when an appropriate voltage is applied to the ESBG, the diffraction grating is in FIG. 4A for at least one wavelength of the received signal. _While converting the effective exponent of the waveguide, denoted as ₂ , and while the remaining channel of the received signal is transmitted undisturbed, this causes the phenomenon of dropping the reflected or transmitted signal from the ESBG. The channel or wavelength reflected or dropped is the period of the ESBG diffraction grating. Will be a function of.

The manufacturing process of ESBG and the like generally involves attaching a diffraction grating on a silicon micro-light structure using one of several processes. The manufacturing process involves attaching an H-PDLC precursor solution onto silicon with embossed grooves or V-grooves, which are also produced by oxidation to form silicon dioxide photocladding for the waveguide. Lower electrodes are attached onto silicon or elsewhere and drop conductively. The H-PDLC is then polymerized by a single laser beam with an interfering laser beam (visible or ultraviolet depending on the chemistry of the selected H-PDLC variable), or a bicomponent phase mask known in the field of fiber Bragg diffraction gratings. . The following polymerization, mask and etch process does not constitute an ESBG section but removes H-PDLC from all regions. The induced section is then spin-coated with a second passive polymer having an index that matches H-PDLC.

This process is useful for H-PDLC, where the index is nearly matched, which is silicon dioxide (N). While slightly larger than 1.44), other processes are suitable for H-PDLC, where its index is greater, such as 1.53. In this case, after hanging the electrode with lower conductivity, the cladding may be a suitable polymer with a slightly smaller index. In an alternative process, silicon forms a mechanical planar substrate without grooves. Subsequently, a plurality of polymer films are first attached to the cladding layer and then to the H-PDLC layer and then subjected to holographic polymerization to make masking and diffraction gratings. Etching is then performed to form the ridge waveguide, spin-coating and masking the cladding layer to attach the upper electrode region formed of a metallic or transparent conductive film.

In all designs for the integrated optical circuits below, the complex ESBGs can be formed at the same time by simply applying the above process to a mask representing the required number of ESBGs, which is a single substrate. There are additional possibilities within each of the various devices for different H-PDLC formulations, different diffraction grating periods, and orientations. This results in an integrated device having auxiliary elements of various individual characteristics. However, the present invention described herein is based on an optical design that suitably uses H-PDLC in the ESBG class, which should not be considered as being limited or restricted to any particular manufacturing process.

The following paragraphs describe the basic building blocks described above by describing functional devices incorporating two or more waveguides, one or more of which relate to the class of ESBGs.

5 shows a preferred configuration of an exchangeable add / drop single channel filter. The basic functionality is to control the addition or interruption of specific channels, for example between the optical bus and the local or drop waveguide. In a bus waveguide, the input signal (consisting of a number of independent wavelength channels) is propagated from left to right as shown in the figure. The diffraction grating connected to the drop channel is moved in the back wave propagation direction (right to left as shown) in the drop waveguide.

Bus waveguides and drop waveguides are not the same (ie they differ in propagation constants) unless critical synchronous couplings are caused by only close proximity of induction, unless via a diffraction grating auxiliary coupling mechanism. This mismatch can result in packaging the device in that a butt connected to a single mode optical fiber will be more effective relative to the other than one of the two waveguides due to the mode matching concept.

When filters are exchanged in the circuit by suppressing the spatial index modulations that make up the diffraction grating in the ESBG region, the components are transmitted through all channels. Key performance samples for telecommunication applications include on / off greater than 35 dB, pass frequency band characteristics comparable to well designed fiber diffraction gratings including apodization to suppress side lobes, low dependent polarization loss, filtered and contiguous Includes switch-off insertion loss of less than 0.3dB in the channel, and low drift power-on of either zero-power rationality or low power.

FIG. 5 shows a substrate 33 with a pair of waveguides 31a and 31b that are somewhat comparable to the width of the core and separated by distances within the extinction region of the waveguide. Thus, the extinction regions of the two waveguides overlap. For illustration purposes, the ESBG or diffraction grating is shown inside or outside the waveguide 31a. However, the ESBG can be in either the waveguide or the extinction region.

As schematically shown in FIG. 5B, there are a number of coupling mechanisms for the light shown as entering port 3 on the left side of the waveguide 31b for illustration purposes. If there is no coupling to the wavelength included in the input, the input signal or light output at port 3 will propagate through waveguide 31b and exit through port 1 on the right side of the waveguide. By understanding and numerically evaluating the various coupling mechanisms, the desired channel add / drop process can be enhanced and undesirable coupling not affected by the switch of the ESBG can be minimized.

The second coupling mechanism is called the exchange Bragg mechanism and will occur for wavelength λ _j determined by the period Λ of the ESBG diffraction grating. More specifically, the diffraction grating is paired out of the wavelength channel λ _j from the WDM signal on the bus 31b and sends it toward the port 4 in the opposite direction below the waveguide 31a. The diffraction grating period Λ for the exchange Bragg coupling occurring for the wavelength λ _j is determined as follows.

Formula (4)

Here, n _a is the effective index of the waveguide 31a, and n _b is the effective index of the waveguide 31b. The effective exponent of the waveguide is the modal index of the waveguide based on the index of the core and cladding region of both waveguides and the modal field solution. The index for both waveguides is estimated at λ _j . The bandwidth of the filter response is given by

Formula (5)

Where κ is a coupling coefficient that can be determined using a known manner of link mode approximation calculation. κ can be controlled by changing the diffraction index, and in ESBG, can be converted to optical electrons. Sidelobe reactions often occur outside the main channel bandwidth for the exchange Bragg coupling. These can be suppressed by apodizing the diffraction grating coefficient κ in various ways. A simple way to apodize κ is to increase the distance between two waveguides away from the center of the device, as shown in FIG. 5A, ie to swing the ESBG further away from the bus waveguide and the center closest to the end.

Exchange Bragg couplings also include extinction and direct Bragg coupling, both of which can be disturbed or degraded by an ideal spectral response. The quench coupling shows that the modal index of the two waveguides is substantially equal so that the light of FIG. It occurs with a drop wavelength equal to ₁ and also occurs when passing between two waveguides with a somewhat irregular tendency output to port 2 in addition to port 4. λ ₂ and λ ₃ also pass to port 2 as a result of this action. This coupling is undesirable because it causes crosstalk without substantially changing by exchanging ESBG. As shown in FIG. 5B, the direct Bragg reflection also degrades the ideal spectral response by generating a slight drop or exchange wavelength, such as λ ₁ , such that, for example, it is reflected on the waveguide 31a as a result of the action of the ESBG 12. Let's do it. The direct bragg coupling can be of considerable size and cannot be completely removed. But. Since it is a phase-matching process, one way to reduce the impact is to make the phase-match wavelengths very different for exchange Bragg and Direct Bragg. This can be done by varying the exponent value for each of the waveguides 31a and 31b. In the spectral domain, both Bragg mechanisms reach a stopband. A prerequisite for ensuring that the coupling mechanism does not disturb badly is that the stopbands do not overlap in the wavelength domain. This condition,

Formula (6)

Here, Δn is the exponential change of the diffraction grating having a difference in the exponential space along the diffraction grating when the diffraction grating is operated. As the difference between the effective waveguides of the two waveguides increases, the direct Bragg has a less adverse effect on the filter performance, and the filter or drop characteristics of the element are desired wavelengths from the signal on the waveguide 31b, for example as a result of propagation. Is ideally dropped as the minimum loss. Incidentally, because the decay coupling is also caused by an exponential match between the waveguides, the various effective exponents of the two waveguides substantially eliminate the decay coupling.

Thus, the maximum filter bandwidth depends on the delamination between the ESBG's exponential change Δn and the two filter waveguides. The bandwidth scales linearly with the diffraction grating exponent. For an ESBG spatial exponential modulation parameter of n = 0.01, the eigenvalue for exponential change, the waveguide for waveguide separation of 1 μm, and the bandwidth may be 1 nm. This is sufficient for WDM application. This bandwidth can be made large by linearly chirping the diffraction grating period, ie by making a slight spatial transformation in the diffraction grating period.

For sufficiently small wavelengths, the ESBG diffraction grating can phase-match the radiation mode, which leads to power loss. For an exchange-bragg filter designed according to the above rule in which the effective exponents of the two waveguides differ by at least Δn, the radiation-matched region has a wavelength of 5 nm and is smaller than the center of the exchange Bragg. For high index ESBGs having an index of about 1.53, these wavelengths are rearranged from the central wavelength with a difference of 50 nm. The radiation loss can be minimized by simply placing a diffraction grating on the filter waveguide and having the filter waveguide make a higher exponent than the input bus waveguide.

5C shows simulated optical performance using the following virtual parameters. Bus waveguide width = 8μm, N = 1.4492, drop waveguide width = 4μm, N = 1.53, length = 10mm, diffraction grating note = 523nm, ESBG spatial index band = 0.01, minimum inductive separation = 3μm. Ports 1, 2, 3, and 4 indicate the corresponding ports in FIG. 5B. In this example, apodization does not apply. In FIG. 5D, the gain of coupling apodization is shown by the curved shared region between the waveguides.

Based on this kind of modeling, the design shown in FIG. 5A is known to have an almost optimal filter shape, with box-shaped drop bandwidths and side lobes suppressed by apodization. Also, the device is not very sensitive to length, as the spectral response shape remains similar if the length is increased to maximize the dropped power crack. Such filter defects require longer devices with narrower bandwidths, which are not a substitute, and are designed below by the resonator type. Also, power is dropped in the opposite direction of propagation, and the design requires two mismatched waveguides (ie, their propagation constants are not substantially equal).

Figure 5e shows a four-channel arrangement that independently drops any one of the four wavelength channels inside the dropport (i.e., if the input is used in the opposite direction, the input is replaced by the output and conversely the output is replaced by the input). The exploded planar design extends close to the single element SADF. In addition, the bus and drop waveguides are inconsistent, limiting the practicality of this design for WSXC. In practice, the limit of growth depends on the loss at each node that accumulates as the array extends to address a larger number of channels.

However, for two waveguides as different as Δn, the real problem is that the core length of the higher exponential waveguide must be made smaller than the diameter of the optical fiber in order to remain in single mode. This causes the coupling loss to occur when the butts are connected by fiber twist. For a small index ESBG (core index of 1.47, cladding index of 1.444), the square core width is 4 mu m and consequently the butt coupling loss is about 20%. For a large index ESBG (core index of 1.53, cladding index of 1.444), if the core length is 1 μm, the interstitial loss can still be made to be not so large 30%. However, in this case, a square core width of 2 占 퐉 can give an insertion loss of 60% which cannot be tolerated or used.

FIG. 5F shows a plane integrated into a 2 × 2 space switch that functions in substantially the same way as the plane integrated into the 2 × 2 space switch described in FIG. 5F shows that such a switch can be constructed using planar integration.

Wavelength Selective Cross-Connect (WSXC)

The function of WSXC is almost related to SADF, except for the configuration in which it is internally connected to two or more optical buses instead of a bus distributed to local nodes. In general, WSXC selectively exchanges M-channel WDMs between N × N entry and exit fibers to dynamically reconstruct and relate to each other within a structure that treats each wavelength as a separate and independent “substantial fiber”. N × N × M WSXC connects N fibers and M wavelengths. Future networks will rely on such devices for WDM to realize their full potential to double network capacity. Based on industry plans, devices will need to be classified in sizes ranging from 2 x 2 x 2 to 128 x 128 x 80 or more.

Several WXSC approaches are being actively researched in many laboratories. These include INP incorporating WDM routers combined with phase shifters or spatial switches, modular passive WGR routers and acousto-optic filters connected to thermo-optical or other switches. No leading technology has yet been established, and most current approaches are expensive.

According to the present invention, the single switch point of the WXSC is a four port enabled switch with two inputs and two outputs. This switch is electro-optically activated by the ESBG, which toggles the periodic spatial index modulation that constitutes the diffraction grating for each selected element on or off. By programming the control voltage for each ESBG element on an integrated chip or substrate comprising a plurality of such elements, a very large number of switching states can be realized to reroute and reconfigure the exchange of WDM signals.

6A and 6B show two different initial cross-point switches based on ESBG. Each of the two major embodiments uses 2 ESBGs per element. The function of each element is to perform an initial wavelength selective cross-point function. When the switch is not activated, all wavelength channels of a particular input port will pass through unaffected by that particular output port. When the switch is activated, the particular wavelength channel (if present) of each input port will be cross-connected to the alternate output port. All wavelengths not selected remain unaffected.

6A and 6B, unlike the initial SADF apparatus, the two bus wavelengths are the same (with the same propagation constants) and have only substantially different propagation constants in their internal "s" or "ring" induction. Thus, they provide a more effective coupling to the optical fibers.

Referring to the beginning of FIG. 6A, the ESBG 12a is in the extinction region of the waveguide 31a and the diffraction grating 12b is in the extinction region of the waveguide 31b. The waveguides are sufficiently separated so that their extinction regions do not overlap. ESBGs 12a and 12b are curved or connected by "s" type waveguide 37. In this configuration, the waveguides 31a and 31b may be of the same size and material, and may have the same index. Therefore, in order to minimize insertion loss, a significantly simplified configuration and standardized coupling are used for all waveguides. However, undesirable coupling (i.e., extinction and direct Bragg coupling) has a waveguide 37 smaller than the waveguide 31 to have an exponent that differs from the exponent of the waveguide 31 by an amount in excess of Δn. As such, it is significantly suppressed. Thus, the configuration of FIG. 6A provides good suppression of undesirable coupling and improves insertion loss performance, but is more complex and expensive than the configuration shown in FIG. 5A. In FIG. 6A, the diffraction grating is not shown as an apodize reducing the side-band, but this or other technique can be used in this embodiment for such side-band reduction.

Instead of the only single waveguide 37 interconnecting the ESBGs 12a and 12b, the pair of waveguides 37a and 37b performs this function while the ESBG 12 and waveguide 37 form a closed ring 39. 6B differs from FIG. 6A in that it is provided to perform. In the arrangement shown in FIG. 6A, the signals traveling between the waveguides 31 in either direction, while increasing the potential for crosstalk, all travel through the same waveguide cross-section 37. In FIG. 6B, for crosstalk While reducing the potential, the signal from input 1 on waveguide 31b travels through waveguide segment 37a, while the signal from input 2 on waveguide 31a travels through waveguide segment 37b. In light of this, there is an advantage of the ring configuration of FIG. 6B that is better than that shown in FIG. 6A. In the embodiment of FIG. 6A, the signal unaffected by the cross connection travels in the opposite direction on the waveguide 31. In the embodiment of FIG. 6B, all signals propagate in the same direction within any waveguide. There is another important advantage. It is believed that the design of Figure 6b, where the drop signal propagates side by side with the input, will make it easier to interact with large scale integration, connectivity, and other elements of the optical network. Although the design of 6a may be preferred for the selected application, the design of FIG. 6b is the preferred design to date.

The configuration of Figs. 6A and 6B, in which there are two ESBG classes that are coupled, is also advantageous in that wavelength selectivity can be improved in that each signal is doubled filtered. As a result, sidebands can be suppressed up to 50 dB, which is not possible with a single ESBG.

Figure 7a compares the filter response of the single exchange Bragg filter shown in Figure 5a (collision line) with the S cross-connect (solid line). Here, the S ESBGs are also used to efficiently affinity the response. Curve.) It can be seen that the response of the S-crossing connection is visually doubled the exchange Bragg filter response. Thus, the sidelobe is significantly reduced while the flat passband is preserved. 7B shows a detailed throughput response, where inband crosstalk may be less than 30 dB. In cross-connections, it is important to sufficiently remove the dropped wavelength from the input bus since new signals will be re-injected at the same wavelength, and in-band crosstalk is likely to be minimized. In-band crosstalk can also be enhanced by either increasing the reflectivity of the diffraction grating, increasing the spatial index variation of the ESBG, increasing the mean index of the ESBG region, or making the ESBG longer. Free adjustment of these parameters using H-PDLC is another advantage of this group for optimizing this design.

7C shows a typical computer photoresponse at ring junction 39. This is similar to S-crossing, except that a fake spike on power trapping in the ring is observed. In addition, the in-band response is somewhat overlapped because of the ring response. If the two ESBG classes are marked with "s" in Figure 6a for the "ring" in Figure 6b, then in each design the "s" or within each ring the ESBG classes will be electrically switched at the same time, as described cross- Will be combined to perform the connect function.

If the configuration of Fig. 5A is mainly SADF, and the configurations of Figs. 6A and 6B are defined as WSXC, virtually both can be used as SADF. In view of this, in the device shown in Figs. 5 and 6, the device of Fig. 5A provides a box-like response, the side lobe is easily reduced by the apodization, the length is emphasized, and the production is simple and direct. There is an advantage to this. However, since it is necessary to mismatch the waveguide in order to achieve useful performance, the manufacturing becomes more difficult and there is a possibility of causing a coupling loss problem. The more complicated embodiments of FIGS. 6A and 6B are easier to manufacture because the waveguide 31 is of uniform size and undesirable coupling modes are more easily and effectively suppressed. When the device is only used for drop filters (e.g., multi-channel WDM for embodiment bus 31b), this may be, for example, a primary transmission bus, which can be used to provide a single channel to be transmitted to the appropriate local bus 31a. 6A configuration is preferable. However, if the device is a WSXC or SADF (e.g. additionally a channel is transferred from the main bus 31b to the local bus 31a), then the signal on bus 31a of the preferred waveguide also causes diffraction grating 12 and waveguide 37 When used as an add and drop filter, such as through a bus 31b), the configuration of FIG. 6B may be good to minimize potential crosstalk.

8A and 8B are diagrams showing cross-coupling between composite waveguides for composite wavelengths. For example, FIG. 8A shows two waveguides 31a and 31b, each of which carries four channels or four wavelengths. At the junction of these two waveguides, four transmitting rings 39 ₁ -39 ₄ are mounted, each of which is like a ring 39 shown in Figure 6B, each ring having a corresponding wavelength channel to which the ring is specific. It has an ESBG diffraction grating period to perform the add / drop function for 1-4. Thus, one or more of the rings 39 are optionally provided with current so that information on the selected channel is added, dropped and transmitted between the waveguides 31. Thus, this is a design for two ESBG fibers based on WSXC with four wavelengths (e.g., a 2x2x4 network). Rings 39 ₁ -39 ₄ can also be transmitted between the main bus and the local bus, each of which accepts a limited subset of wavelengths on the main bus.

FIG. 8B shows a more complex network in the form of a benenet net of 6, 3-exchange sections connecting four input and four output waveguides, sometimes referred to as a 4x4x3 configuration. This embodiment is similar to that of the embodiment shown in FIG. 8A to be transmitted to any one of four channels input to four waveguides output to any one of the four waveguides.

The network design shown in Figures 8A-8B merely illustrates the possible design options for constructing the network of the present invention, and a network suitable for a certain number of input and output fibers, a certain number of channels may use such or other network configurations. Which includes the " s " form of FIG. 6A.

The use of the Venenet net of FIG. 8B for interconnects, having the advantage of not being reorderablely blocked, is known in the art as an effective blockless structure. However, it is by no means the only possible structure that provides this advantage of interconnecting the ESBG wavelength switched regions within a multifiber network. An overview of network structures is known by "An Introduction to Photonic Switching Fabrics", H.S. Hinton, Plenum Press, 1993.

Clearly, the complexity of the coupling increases by the increasing number of waveguides and channels. However, the network employing the ESBG technology of the present invention includes an explanatory network design that provides substantially synergy, as described below, and since the entire device can be assembled using a fairly advanced circuit assembly technique, The consequences of a significant increase in the size or complexity of the network do not result in a corresponding increase in cost. This is another important technical advantage. Thus, the benefits of ESBG based on add / drop and WSXC devices include on-chip assembly, possibility and low cost fabrication, single-stage diffraction grating assembly optionally connected to high channels, low crosstalk and insertion in dozens of microsecond ranges. Loss, fast switch speed. Perhaps the most important, flexible chemistry and assembly of ESBG allows many other optimized elements. At the same time, the exponent, diffraction grating properties, period, direction and other parameters are varied to assemble together on a difficult single substrate, if not possible, using different H-PDLCs of any material technology.

Resonator device

The resonator is still another waveguide and diffraction grating configuration available for the implementation of SADF and WSXC elements. The resonator is defined for this application as a waveguide structure based on diffraction gratings where the storage of optical energy in a set area is an important principle of device function.

Resonators based on waveguide filters have some properties that are superior to filters based on other mechanisms. These characteristics include the ability to synthesize arbitrary filter shapes by a resonator of dependent-coupling plurals, different from interference filters, and the ability to control passband by other techniques than converting device lengths. The resonator also has no side lobes outside the troublesome band. Instead, the out-of-band response is monotonically reduced at a rate determined by the number of resonators made of the channel drop filter.

The resonator can be realized using a Bragg diffraction grating combined with a quarter wave shift on or near the waveguide, as shown for the waveguide 60 in FIG. Quarter waveshift 62 serves as a cavity, while diffraction grating 63 serves as a mirror dispersed on one side. At the selected wavelength, the optical energy is captured, vibrated and rotated in the waveguide region 64 of the quartershift cross section (wave 65). The period of the diffraction grating is determined by the following equation.

Formula (7)

Where n _e is the resonant waveguide Valid exponent of the mode computed in _j .

The waveguide selected as the dropping channel is completed by laterally connecting the resonator to one or more bus waveguides. As shown in Figs. 10A-10C, there are several ways to accomplish this. In all cases, the two resonators require 100% extraction of the desired channel. This second resonator, called a reflection resonator, is required to eliminate back waves generated by the first resonator, called a drop resonator.

In the resonator filter of FIG. 10A, the filter output drop, port 2, is directly connected to the drop resonator 68. The reflector resonator 70 is connected to the bus waveguide 72 but is spatially located from the quarter-wave cross section 62 of the resonator 68 by an integer wavelength in addition to the half waveguide. While the filter output is dropped forward in FIG. 10A, it can be dropped in the opposite direction by attaching the drop port 2 in the opposite direction of the drop resonator 68. The non-disappearing end of the diffraction grating cross section must be made long enough so that power is not avoided through them. While the remaining wavelength passes through without affecting transmission port 1, one of the multiple wavelengths input into port 3 will drop into drop port 3. The length of the diffraction grating 68 and its exponential change between the quarter-wave section 62 and the drop port 2 determine the device bandwidth.

In the resonator configuration different from that of FIG. 10, ESBGs consisting of several diffraction grating elements are all in concert by coordinating with their respective electrode-applied signals, or by making a single monolithic electrode over the entire resonator part consisting of multiple ESBGs. It can be seen that the switch is on or off.

10B-10D show three examples of high grade filters that improve filter performance by connecting multiple resonators. The channel drop filter in FIG. 10B is similar to that of FIG. 10A in that bus waveguide 72 is connected to a series of drop resonators 68 'and also to the same series of reflector resonators 70'. Each resonator is connected to its neighbors by the cross section of the corresponding diffraction grating. The length L2 of the diffraction grating connected between the quarter waveshifts 62 determines the detail of the filter shape.

The channel drop filter of FIG. 10C is similar in performance to the channel drop filter shown in FIG. 10B, and the connected drop resonators 68a and 68b and the connected reflector resonators 70a and 70b are adjacent to each other instead of successively. It is different from the filter shown in.

On the other hand, this is not necessary if the resonator waveguide 74 and the bus waveguide 72 are matched. The main difficulty with using inconsistent induction is to reduce the power transfer efficiency from the input bus to the resonator, with an effect similar to that of the synchronous coupler. Thus, in general, it is more difficult to realize larger line widths if the bus and resonator waveguides are very strong connections and / or the diffraction grating exponents are not large. Also, because the mode disappears in space for other reasons, higher class filters can be realized by a series of connected resonators as shown in FIG. 10C. However, it is desirable to match the fiber with the bus waveguide, and such a device is preferred for ESBGs that use relatively high exponential configurations.

Three induction-channel dropping filters are schematically shown in FIGS. 10D-10F. In these embodiments, the resonator is side connected to both input and output buses (ie, the resonator is in the cladding between the buses where the cladding overlaps). For the channel dropping filter embodiment of the resonator, two resonators are still needed. The main advantage of the configuration shown in FIGS. 10D-10F is that the resonator is independent of the input or output waveguide. Also, for the embodiment of FIGS. 10E and 10F, unlike the situation for a two-induction structure with which these parameters are related, waveguide separation S and resonator length L are independent of design parameters. In Fig. 10d, the two resonators are connected together. When the length of all the diffraction grating cross sections is properly selected, the power drops to the port 2 at resonance. In the embodiment of Figure 10E, the two resonators are separated. However, the phase delay cross section 78 must be guided between each resonator along the bus waveguide. This phase delay can be realized by making the input and output bus waveguides different in length or by changing the waveguide length to change the propagation constant. For matched waveguides, the phase delay of the input bus must be ± π / 2. On the other hand, the delay of the output bus must be π / 2. In this embodiment, power is dropped to the port 4 at resonance. This embodiment is less restrictive than that shown in FIG. 10D because the resonator length and bus-to-resonator separation are independent design parameters.

In another situation, FIG. 10E illustrates a resonator channel for dropping filters using organized waveguides 72 and 74 with split resonators 76 a and 76b located between waveguides 72 and 74. Split resonators are needed to complete the complete signal extraction. The advantage of this configuration is that the input and filtered bus waveguides can be optimized in and out of fiber coupling, while the resonator has other advantages, such as being able to independently achieve low losses. The phase delay cross section 78 must be inserted along the bus waveguide into between the two resonators. The phase delay between the quarter-wave cross section of each resonator is ± π / 2 on the input bus 72 and on the output bus 74. must be π / 2. In either case, multiple 2π phases can be added to the waveguide delay without affecting performance.

The channel drop filter of FIG. 10F is similar to that shown in FIG. 10E, except that a plurality of parallel connected resonators are provided between the buses as the embodiment of FIG. 10C. The plurality of connected resonators may also be connected in series as shown in FIG. 10B rather than in parallel. For the embodiment of FIG. 10E, a delayed cross section 78 is required. The description of the previous embodiment of a plurality of resonators connected in series or in parallel also applies to the embodiment of FIG. 10F.

FIG. 11 shows an example of a response in this case with a matching bus / resonator, relative to power at various ports as a function of deviation from the channel center wavelength.

Flat surface integration

To integrate a number of different elements of the above categories into a single substrate, planar-waveguide phases based on integration, as previously described, and later as more complex structures described in FIGS. 12A-12E and 13A-13B. It is desirable to adopt a structure based on. One way of making such integration depends on the extension of the assembly process using the silicon micro-optical bench technique described above, where the waveguides are purely processed in sequential order on etched silicon substrates produced by well-established methods in the microelectronics industry. The waveguide consists of high index regions (doped with silica or polymer) arranged in the silica cladding. Thus, one way of integrating multiple devices is to extend such assembly to a more complex network of devices and elements. 12a-12e show a frontal straight extension of the integration method to surround the engagement of another device. Waveguide structure 48 is first manufactured. ITO or other electrode 20 is placed where needed (FIG. 12A). The H-PDLC film 30 is then applied to the structure by spin coating or other polymer coating technique (FIG. 12B). The biphasic mask 52 then enters where it includes the diffraction grating parameters predesigned to produce the direction and various periods necessary for the diffraction grating and to perform the other functions described above (FIG. 12C). FIG. 12D shows a cover plate (eg, glass or silica) with a top electrode mounted on and emerging on a substrate, and FIG. 12E shows a final assembly.

Another method of multidevice integration is shown in FIGS. 13A-13B. As noted above, the ESBG may be located in either the core or cladding region of the planar waveguide. Although the core position generally results in stronger interactions and better performance, some of the cladding located in the ESBG, which can also be called an "overlay" ESBG, is a diffraction grating covering the underlying waveguide structure. This applies.

More specifically, overlay ESBG opens up the possibility for a large scale integration technique where a monolithic ESBG film is sandwiched between the upper and lower networks of the waveguide. The overlay approach can be transferred to the integrated planar waveguide technique by the sandwich technique shown in FIGS. 13A and 13B. Lower layer 46 is a silica-based structure that includes a plurality of silica bases and polymer waveguides 48 in a network accessing a surface in a selected interaction region. Matching top silicon layer 46 includes a second network of waveguides 48. The design is such that the waveguide from the top plane at the selected loci or node 50 contacts, intersects, or coincides with the waveguide from the bottom plane, otherwise it is fully clad to protect the low loss propagation.

Where the waveguide of the upper section exposes the extinction zone intersection exposed to the waveguide of the lower section at the real angle between the two waveguides, the ESBG film 12 positioned between them uses the fiber base device described later and the principle is the same, Connect them with 2x2 space switch 44. One of the substrates may be an H-PDLC film formed thereon having an ESBG diffraction grating in a manner described elsewhere therein. Or H-PDLC with floating ESBG formed therein, floating ESBG decals can be loaded between the substrates. The electrode is preferably formed on the substrate at each node.

The waveguide in the upper section exposes an extinction zone intersection that exposes the waveguide in the lower section in a parallel pass. The ESBG film feeds SADF, WSXC, another coupler, or the device described above, the upper and lower waveguides in the coupling region, One of the waveguides, or between them, is assumed to be identical or unequal, as required, which may be supplied by well-known methods of channel waveguide design.

By coupling each such device to the network, an unlimited variety of integrated device structures can be assembled at each switching, pass-exchange, and the waveguide selectivity can be combined and modified into many structures.

As a result, the waveguide based on the above-described free space principle can be supplied under the assumption that there is a hole in the silicon layer for light to be connected out of the free space or into the waveguide. This can be used to supply interplanetary communication in order to extend the sandwich structure into multiple layers.

Multiple exposure and reverse overlay nodes in a single process holographic

As described above, in the planar integrated analysis, the center of the sandwich is a collection of overlay ESBG films composed of various respective diffraction gratings having different orientations and periods (diffraction grating vectors) but having a normal layer thickness. An effective one-step fabrication process will be achieved if all such diffraction gratings needed for the multiple functions of the various nodes are made simultaneously.

Well known in optics, a biphasic mask produces two beams when illuminated side by a single laser beam (this is H-PDLC which exposes the beam, typically 488 nm). These two beams then intersect the polymer film in a close approximation, producing ESBG. After exposure, the finished lower (or upper) plane with the ESBG active film in place is removed from the fixture comprising the double multi-mask. Thus, one-step holographic exposure produces multiple, possibly hundreds, of device nodes on a single planar chip simultaneously. Some of them may have different characteristics, and the device node may be of a single type or of various other types. After stabilization, the two intermediates are finally combined and packaged.

Semi-coupler device

In addition, devices suitable for teaching the present invention, and known to fiber optics since the early 1980s, are polished bonders or semi-bonders (also side polished fibers). Single mode optical fibers are bent to a long radius (about 15-50 cm) and bonded into grooves of silica blocks, which are used to hold and support while the fiber is polished to expose the oval region of the cladding close to the core. The function of the glass block is to hold the fibers, but also to provide a smooth plane that engages the polished fiber side. As a sufficiently deep polishing depth (eg, within 2 μm of an 8 μm diameter core), the substantial intensity of the extinction optical field is processed. As generally experimented, such semi-coupler devices are used as various splitting ratios by combining with the polished surface. Semi-couplers have also been used as substrates as coupled single mode fibers in metals, polymers or liquid crystal films for the purpose of making fiber optical poloisers, spectral filters and other components.

According to the teachings of the present invention, the semi-coupler can also be easily disposed on a polished surface, or an effective coupling of single mode optical fibers to an overlay type ESBG film, for example any other type of film such as a thermal-optical film. It can be used for low cost. Devices based on optical fibers are simple to manufacture, differ from planar waveguide structures, automatically connect easily into and out of the optical fiber, and can be connected to other fibers.

14A shows such a device 32. 14B is a chart of the exponents and lengths of the various components and the layers to illustrate the device. Substantially other exponential profiles are also intended to be enclosed within the present invention. Known computational approaches based on connection mode theory are used to design the device. FIG. 14C is a cross-sectional view taken along c-c of FIG. 14A, with electrodes 20 for providing vertical electric fields at the top and bottom of the ESBG. FIG. 14D is a view like FIG. 14C for an alternate embodiment with electrodes on the side of the ESBG to provide an opposite electric field. In the FIG. 14D embodiment, it does not need to be a gold electrode or a transparent electrode used for the preferred configuration.

Exchangeable drop filter

Figure 15 shows a single channel (single-wave) filter switch using a half combiner / ESBG technique. By end functionality, such a switch in either state is either a filter (removal) or not a filter of a wavelength channel already determined from the single mode optical fiber 36 carrying a plurality of its wavelength channels (eg, 16 corresponds to 100 GHz, and separates and separates an optical signal separated at a center wavelength of 0.8 nm). However, the plane, the waveguide SADF, and the drop port for this combiner half device are not readily available in connection with the optical fiber. So the device function is just to remove one channel from the bus. In the absence of power, the device performs the function of selectively filtering one wavelength channel at wavelength λ = 2n _eff Δ (which applies a large loss to a particular channel) when it passes through all others with minimum or zero loss. do.

With the power on, the switch passes through all wavelength channels ideally equally without loss. Such switches are useful for certain WDM applications, often in combination with other such components. For example, a series of (16) independent parallel switches can be made separately and independently to handle each of the (16) wavelength channels.

In the device 34 of FIG. 15A, the polished coupler is prepared using long radius band fibers 36 to provide an interaction area of about 3-4 mm in a form that exposes the cross section of the fiber proximate the core. After the sides of the fiber have been polished off, the modal field extends over the surface. At that time, the transparent electrode 20 (shown in Fig. 14A) is disposed on the polished surface, in the form of indium tin oxide, 100-200 nm thick, by a method such as magnetron sputtering. Using spacers known in the liquid crystal display industry, cover glass (dissolved silica) is also applied with a transparent electrode such as indium tin oxide, and then a glass my intersection peer, such as a liquid film of H-PDLC, is applied to the surface. In contrast, polymer conducting electrodes have low losses and simpler design calculations, and can be used with the index closer to silica and ESBG. The thickness of the ESBG film varies from less than 1 µm to more than 10 µm, depending on the design and index of the material used. The waveguide principle of a flat film is well understood. Given a single mode waveguide, the ESBG film is specified by the V-variable and is obtained by

Formula (8)

Where h = thickness of ESBG, lambda = free-space wavelength, n _ESBG = average index of the ESBG film, and n _substrate = index of fiber cladding. As is well known, the condition for single mode propagation is V <3.14. The device function is sensitive to the index of the ESBG film.

If the polymer film average index is relatively high compared to, for example, silica cladding 1.46 to prevent the polymer film in the figure from exceeding the optical power of the fiber, a very thin film is needed for low loss. However, if the polymer configuration has an index that more closely matches the silica cladding, as described above, thicker films can be used and achieve stronger coupling. For example, an ESBG film 8 μm thick can be used if the mean index is reasonable and can be controlled to be equivalent to dissolved silica = 1.46 in the power state and about 0.5% higher in the non-power state.

As shown in FIG. 16, the diffraction grating is transformed into a liquid crystal by holographic polymerisation using an interfering beam from an external 488 nm argon ion laser or other suitable laser, depending on the photosensitive absorbance spectrum included in the analysis, such as the applied laser beam. appear. The effect of the diffraction grating is to couple the forward propagation light to the ESBG film in the fiber mode up to the rear propagation direction.

The required diffraction grating period Λ is the formula λ = (n _eff + n _fiber ) Λ, where λ is the preferred center wavelength to be filtered, n _eff is the modal index of the polymer constituent film, and n _fiber is the modal of the optical fiber Exponent. For example, if it is desirable to filter at λ = 1448 nm, n _eff = 1.47, n _fiber = 1.45, then the diffraction grating should be made such that the period Λ is nearly 493 mm. This period of diffraction grating can be produced with a 488 nm laser beam with an intermediate angle of sin θ = λ ′ / 2Λ by exposing a liquid H-PDLC thin film (captured between the polished coupler surface and the glass cover plate). Where λ 'is the current wavelength of the argon laser 488 nm. In this example, θ will be about 30 degrees. If the spatial index modulation Δn / n <0.001, L = 3000 mu m, then dλ / λ <2.5 × 10 ₋₄ , it is smaller than the channel space, as desired.

In the absence of power, the filter device 34 selectively signals at 1448.0 nm (in this example) by dispersing it in the polymer film while propagating all other wavelengths approximately constant, such as 1447.2 nm, 1448.8, etc. Will remove it. The electric field is applied to the device between the electrodes 20 and will switch the ESBG 12, which means that the period exponential modulation will disappear by reorienting the liquid crystal direction into the spherical microdroplets, and the liquid crystal index is polymer host. And thereby negate the diffraction grating effect. This suppresses filtering in order and allows the channel in the problem of propagating right along the other channel signal. Switching of a single wavelength within these multiple wavelengths is sometimes called a single-channel drop switch.

Performance measurements of such switches include dynamic range (on / off ratio) for affected channels, shape and width of spectral response characteristics, insertion loss for all other channels in power and nonpower states, temperature sensitivity of these properties, and operation. Voltage, operating speed, power consumption and polarization. Depending on its index, thickness, transparent electrode index, and ESBG film thickness, the device may have a significant degree of polarization in its filter properties, loss, dynamic range and other operating characteristics. However, such polarization can be minimized or eliminated by a single H-PDLC formula that closely matches the optical fiber core cladding range.

Exchangeable External Coupler

FIG. 17 shows a device 38 assembled similarly to a Bragg filter but designed as an exchangeable diffraction grating coupler. Diffraction grating couplers are devices known in the early 1970's of fiber optics and use diffraction gratings to couple light propagating equally in different directions from free space into single mode optical fiber 36 or from fiber to free space. For example, the device supervises a portion of a sample that directs a wave to an external detector or array of detectors, or vice versa, to interconnect with a computer processor or in a complex switching system, in free space on a fiber. Supervise the coupling optical power inside. The design of the overlay diffraction grating for this purpose is known in fiber optics and waveguide technology, while the device is not interchangeable as before. The difference operating in the drop switch filter 34 of FIG. 15 is that the period of the diffraction grating is only slightly longer and is a satisfactory condition (in the simplest case, the first order diffraction mode).

Formula (9)

Where θ is the angle of the beam radiated from the vertical to the planar surface. As an example, for λ = 1550 nm, n _eff = 1.47, and the diffraction grating period Λ = 1200, externally connect (or internally) the light to (or at) free space in the induction mode at θ = 10.2 ° in the vertical something to do. It is clear that this external coupling angle is a dependent wavelength, and in this example will vary from 10.2 ° to 5.45 ° over the wavelength range 1550-1650. This diversity is achieved by applying different wavelength channels to different locations or detectors in free space in the form of spectrometers. Thus, multi-wavelength WDM signal propagation in a fiber will be external coupled into free space as a fan-like arrangement of signals, with each channel propagation in a somewhat different direction. Exchanging such a device can be used as a spectrometer-sampled WDM signal, which is a specialized tool for separating signals into space at the same optical power over a variety of channels, or to monitor the performance and health of a multiwavelength network in general. To separate the signal.

By applying an electric field to suppress the diffraction grating spatial exponential modulation through the electrode 20 (not shown, but the same for FIG. 15), the coupling between being emitted and induced can be useless. In the power state of the switch, the light propagating in the fiber then continues substantially through the device and ideally emits the fiber at its far end without loss. In this device, the switching effect is to connect or disconnect the induction and free space modes. The use of such a device is to extract light from the optical fiber in a switchable and channel sensitive manner (a) and to interconnect the fiber to a free space detector or a laser for testing or measuring various wavelength channels (b). (C) interconnecting light from the waveguide plane to the waveguide plane or from fiber to fiber in a complex switching network. Other uses are also known to the skilled artisan in the background. As a suitable diffraction grating period, the integrated structure of FIGS. 4A and 4B is also connected to space, but is generally more connected between waveguides as described above.

Attenuator

Another device consisting of an ESBG film on a semi-coupler is the fiber optic attenuator 40 of FIG. 18. The attenuator is different from a switch that optimizes for two characteristic states, on and off, power and nonpower. On the contrary, the purpose of the attenuator is to provide a long scale of voltage that controls the loss over the range of at least 30 dB (1000: 1) for valuable control of the optical intensity propagating through the fiber. Such a function is desirable, for example, to equalize the strength of the signal from different sources in a fiber optical network.

Except for other assembly schemes for the ESBFG provided, this can be configured similarly to the ESBG apparatus described above. By producing a diffraction grating having a very small period Λ, substantially less than about 0.5 μm is used at 1550 nm as a Bragg reflection filter. ESBG films will cause loss in optical signals, but will not be very selective wavelengths. In the example using the photosensitivity of H-PDLC for 1550 nm and 488 nm, a very short periodic diffraction grating of this type is, for example, an argon laser or the like, which exposes the laser beam to be substantially larger than the previous device, eg greater than 30 degrees. It can be produced by increasing the half angle in between. Such a method is a "subwavelength" diffraction grating, i.e., instead of a coupling in which one cycle is so short that from front to back mode, or from induction to radiation mode, or from induction to induction mode, its role is now particularly indicative of the optical index. It serves as a quasi-homogenous composed optical medium that provides electro-optic index control over the range. In this case, since the diffraction grating periods are hardly equal, the ESBG diffraction grating plays an important role in forming very small droplets. The intermediate angle θ exposed depends on the desired diffraction grating period Λ and can be determined from the period in a manner known in the art (ie sinθ = λ / 2λ, where λ is the center wavelength of the attenuating band and Λ is the diffraction) Grid cycle). Such subwavelength diffraction periods can also be formed using a master diffraction grating or a biphasic mask technique as described above. Due to the dispersion of very small microdroplets the length (on 30-100 nm) and the interplanar space (100-400 nm) are too small, the ESBG film is small in scattering. The optically active properties are so simple that the average crack index can then be adjusted by the field in which it is applied.

In addition, the effect of providing a very short period reduces the polymerisation deformation occurring in the "football" forming the microdroplets 26, resulting in nearly spherical droplets. The abrupt switching of the liquid crystal director in the microdroplets is highly dependent on the spherical formation of the droplets and, as is known from the published Sutherland et al. Study, further the near-spherical droplets will possess a reduced critical electric field. This means that instead of switching at a well-defined threshold voltage from one direction to another, the liquid crystal will rotate as the electric field increases. This results in a long scale voltage that controls the average crack index needed for operation as a fiber optic attenuator.

Another condition for good performance as an attenuator is that the average refractive index (holographic polymerisation following the chemical formula) of the ESBG film can be achieved, as can be accomplished by the proper choice of liquid crystal and polymer host species, with the power on correctly. It must be designed to match the fiber optical cladding index (typically pure silica at 1.46). This means that, with the power off, the average index of the film is, for example, about 1.47, and the approximation of the film in the extinction region of the abrasive optical fiber will result in substantially wavelength independent loss. At full power, the index changes to match the silica cladding at 1.46. In that case, it effectively vanishes inside the cladding from the standpoint of the propagating mode, resulting in zero or very small optical loss (attenuation). There will be a long adjustment range of the attenuator as a function of the applied electric field between no power and a fully powered state.

If the ESBG is an index that fits the glass fiber as described above, the resulting attenuator is also substantially independent polarization. It should be noted that FIG. 19A shows the propagation of optical power through the fiber, acting as an electro-optical function to change the ESBG index, for both polarization TE and TM, which is substantially the same. 19B shows that power is propagated as a function of wavelength for the three stages of attenuation, indicating substantial independence of the wavelength.

The device consists of a fiber optic attenuator whose performance is independent of wavelength and polarization. The average on the pseudo-structure, including pure liquid crystals in the overlay film, further reduces the optical dispersion and does not require a separate directional step. This is because the orientation is naturally occurring in the microdroplets. The insertion loss of the device will be very small.

The film also functions as a wavelength independent of the external cooler because the ESBG or its film effect attenuation allows the mechanism to be selectively externally coupled while increasing the percentage of signal on the fiber 36 through the film. Also, rather than having a homogeneous film, channels or stripes can be formed in the film in a direction parallel to the fiber 36, which has an index that matches the cladding that can be effective to reduce insertion loss. Indicates.

The coupler blocks or adds / drops cross-connections by using a diffraction grating

An additional device group can be prepared by sandwiching the ESBG film in the middle and placing it in the middle of the second coupler on top of the first coupler. The device is assembled with bi-optic fibers 36, 36 ', having four optical ports 42A-42D. In this case, the ESBG film is exposed and polymerized by the cover glass. The cover glass is then removed and its surface is placed in the upper semi-coupler 32 ', which is also provided with ITO or other transparent electrode 20. Relatively, the liftoff (decal) placement proximity is equipped with an ESBG film and polymerized in a laboratory fixture, bonded to a chemically low semi-coupler 32, suspended in water on its substrate, or through other means. It is free from the board | substrate.

In the device shown in FIG. 20, multiple waveguide channels propagate into the device in one single mode fiber. The fibers in the middle of the two bonders are not identical (shown in FIG. 16 of the '950 application), for example, the first fiber ( Since the propagation constant for that _i) the various wavelength channels that (β _'i) and the other of the second fiber to, can be achieved by the use of a single mode fiber having a slightly different diameter and the core index. In this case, in the absence of the diffraction grating film between them, since, _i ≠ β and β _'i Despite their proximity, the coupling will not be reduced or presence.

However, if an ESBG diffraction grating is present between the middle of two unequal couplers, and if the diffraction grating period condition Λ for either channel i satisfies

Formula (10)

The coupling then becomes the co-diffraction grating and the channel i will be connected on the second fiber. On the other hand, all other channels are not connected and will continue to propagate on their fibres. When the ESBG is switched off (ie power is applied to the ESBG), this effect will disappear and all signals propagate unconnected without effect.

Thus, the diffraction grating assisted the combiner using ESBG between the non-identical coupler halves described above. The only one channel is connected from the first fiber to the second fiber, the other propagates unchanged, and all the channels propagate unchanged with power on.

(2 x 2 space switch)

The devices described so far are selective wavelengths. FIG. 21 illustrates another structure designed to minimize dependent wavelengths and to selectively connect light from the fiber 36 of the semi-coupler 32 to a second identical fiber 36 ′ of the semi-coupler 32 ′. As shown in FIG. 21, this apparatus differs from the above embodiment in that it has an ESBG film 12 sandwiched therebetween, and the two halves are bonded to each other at an angle 2θ. If the diffraction grating Λ satisfies the condition,

Formula (11)

At that time, the light is input to the output port 42D of the fiber 36 'from the input port 42A of the fiber 36 to the output port 42D of the fiber 36' using the state where the power of the diffraction grating does not enter. It will be connected to the output port 42C of the fiber 36 at 42B. That is, light will be converted from fiber to fiber. In the power-on state, the periodic exponential change made by the diffraction grating disappears while maintaining all the signals in the fibril, and the connection disappears.

For this application, it is desirable to use large liquid crystal loading and short interaction lengths when formulating H-PDLC to obtain large exponential modulation. In essence, this is an embodiment of the 2x2 space switch described in the '950 application.

22A and 22B still explain another form of diffraction grating assisting the combiner. The two fibers 36, 36 'are loaded into a curved tube in a single silica block. On the polished surface, the ESBG diffraction grating 12 is connected to the two extinction regions with a polymer guiding film. The device is similar to the "s" band planar device described above, except that the ESBG is not limited to the current channel waveguide and is in the planar region. The diffraction grating can connect the fiber mode to slab the mode propagating out of the axis, widening the drop bandwidth, and spread out the area before being externally connected by the second fiber. This results in lowering the efficiency and somewhat reducing the spectral response, as shown in FIG. 22C. However, if the ESBG film is etched to reduce it into narrow channels parallel to the fiber core, rather than having two length planar layers, such a response would be substantially enhanced.

In describing the present invention with respect to various embodiments, various processes for assembling structures with each device comprising a plurality of such devices have been described, and these various devices, structures, and methods have been provided by way of example only, and It will be apparent to those skilled in the art that many changes are possible while practicing the teachings of the invention, including those described above in terms of apparatus, structure and methods, as defined by the following claims.

Claims (85)

An element for selectively reconstructing an optical signal on a waveguide optical path, At least one ESBG in optical contact with the optical path; And An electrode for selectively applying at least first and second voltages across each of the ESBGs, wherein when the first voltage is applied across the ESBGs, there is no change in the optical signal for the optical path and the first 2 is a selected change in the optical signal on the optical path when a voltage is applied across the ESBG. The device of claim 1, wherein the optical signal is a multichannel WDM signal and a selected channel is dropped from the optical path when the second voltage is applied across the ESBG. The device of claim 2, wherein the channel is dropped by reflecting backwards through the optical path. The device of claim 3, wherein the channel is externally coupled from the optical path. The optical signal of claim 1, wherein the optical signal is a multichannel WDM signal, and includes a second guided optical path optically coupled to the ESBG, wherein the optical signal is disposed between the optical paths when the second voltage is applied across the ESBG. At least one selected channel is delivered to the device. 6. The device of claim 5, wherein when the second voltage is applied across the ESBG, a channel is transferred from the optical path and dropped from the optical path. 6. The device of claim 5, wherein a channel is added to the optical path by transferring from the second optical path to the optical path when the second voltage is applied across the ESBG. 6. A device according to claim 5, wherein signals with WDM channels appear on both optical paths and the selected channel is transferred from one optical path to another when a second voltage is applied across the ESBG. 6. The method of claim 5, wherein there are a plurality of ESBGs optically coupled to both optical paths, and different channels are transferred between the optical paths by each ESBG when the second voltage is applied across the ESBG. device. 6. The device of claim 5, wherein there is an ESBG in optical contact with each of said optical paths, said one or more optical paths interconnecting said ESBGs. 11. The device of claim 10, wherein there are two optical paths interconnecting said ESBGs to form a ring. 12. A device according to claim 11, wherein one of the rings is between the optical paths for each channel to be transmitted between the optical paths. 12. The device of claim 11, wherein the optical path and the second optical path have a first effective index, and the optical path to the ring has a second effective index different from the first effective index. 15. The device of claim 13, wherein the optical paths to the ring are of a different size than the optical path and the second optical path. 6. The method of claim 5, wherein there are a plurality of ESBGs optically coupled to both optical paths, and different channels are transferred between the optical paths by each ESBG when the second voltage is applied across the ESBG. device. 6. A device in accordance with claim 5 wherein the optical paths have different indices. 17. A device in accordance with claim 16 wherein the light paths have different sizes. The device of claim 16, wherein the ESBG has a diffraction grating having an index change of Δn, and the difference between the effective indices of the optical paths is ≧ Δn. 6. The device of claim 5, wherein said device is a component of an integrated optical device. 20. The device of claim 19, wherein the optical paths have different indices, the ESBG has a diffraction grating having an index change of Δn, and the difference in the effective index of the optical paths is ≥ Δn. 6. Device according to claim 5, wherein the device is part of a semi-coupled device. The device of claim 21, wherein the device is a switchable drop filter. 22. A device in accordance with claim 21 wherein the device is a switchable external coupler. The device of claim 21, wherein the device is an attenuator. 25. A device in accordance with claim 24 wherein said ESBG has a submicron diffraction grating. 6. The device of claim 5, wherein said ESBG is a resonator. 27. The device of claim 26, wherein the device is a channel drop filter and includes a first drop resonator and a second reflection resonator spaced apart from each other by a sum of wavelengths and half wavelengths of integers of wavelengths to be dropped in a direction of movement of the optical signal on the optical path. Device characterized in that. 28. The device of claim 27, wherein each resonator is a multipole resonator formed of resonator sections coupled in series and in parallel. 27. The device of claim 26, wherein the device is an induction channel dropping filter and the ESBG is a resonator between light paths. 30. The device of claim 29, wherein the resonator is a split resonator having an upper delay section between the split resonator sections. 6. The device of claim 5, wherein each said optical path has a core surrounded by a cladding and said ESBG is in cladding for all of said optical paths. 32. The device of claim 31, wherein the cladding for the optical paths overlaps, and wherein the ESBG is within the overlap of the cladding. 32. The device of claim 31, wherein the ESBG extends over all of the light paths. 6. The device of claim 5, wherein the side lobes are suppressed by apodization. An integrated optical device for selectively reconstructing an optical signal, Board; One or more optical waveguides each having a core surrounded by a cladding and formed in the substrate; An ESBG present in one of the core and the cladding for the waveguide; And An electrode for selectively applying at least first and second voltages across the ESBG, wherein if the first voltage is applied across the ESBG, there is no change in the optical signal when applied to the waveguide, And if a second voltage is applied across the ESBG, there is a selected change in the optical signal. 36. The device of claim 35, wherein the optical signal is a multichannel WDM signal and a selected channel is dropped from the waveguide when the second voltage is applied across the ESBG. 36. The waveguide of claim 35 wherein the optical signal is a multichannel WDM signal and comprises a second guided waveguide optically coupled to the ESBG, wherein the waveguides when the second voltage is applied across the ESBG. At least one selected channel is passed in between. 38. The device of claim 37, wherein a channel is dropped from the optical waveguide by being transferred to the second optical waveguide when the second voltage is applied across the ESBG. 38. The device of claim 37, wherein a channel is added to the waveguide by transferring from the second waveguide to the waveguide when the second voltage is applied across the ESBG. 38. The device of claim 37, wherein signals with WDM channels appear on both waveguides and the selected channel is transferred from one waveguide to another when a second voltage is applied across the ESBG. 38. The method of claim 37, wherein there are a plurality of ESBGs optically coupled to both waveguides and different channels are transferred between the waveguides by each ESBG when the second voltage is applied across the ESBG. device. 38. A device in accordance with claim 37 wherein there is an ESBG in optical contact with each of the optical paths and comprising one or more optical waveguides interconnecting the ESBGs. 43. The device of claim 42, wherein there are two optical waveguides interconnecting the ESBGs to form a ring. 44. A device according to claim 43, wherein one of the rings is between the waveguides for each channel to be transferred between the waveguides. 44. The device of claim 43, wherein the optical waveguide and the second optical waveguide have a first effective index and the optical waveguide for the ring has a second effective index different from the first effective index. 46. A device in accordance with claim 45 wherein the optical waveguides for the ring are of a different size than the optical waveguide and the second optical waveguide. 38. The method of claim 37, wherein there are a plurality of ESBGs optically coupled to both waveguides and different channels are transferred between the waveguides by each ESBG when the second voltage is applied across the ESBG. device. 38. A device in accordance with claim 37 wherein the optical waveguides have different indices. 49. A device in accordance with claim 48 wherein the optical waveguides have different sizes. 49. The device of claim 48, wherein the ESBG has a diffraction grating having an index change of Δn, and the difference in the effective index of the optical waveguides is ≥ Δn. 38. A device in accordance with claim 37 wherein said ESBG has a submicron diffraction grating. 53. A device in accordance with claim 51 wherein said ESBG is a resonator. 53. The device of claim 52, wherein the element is a channel drop filter, the first drop resonator and the second reflection resonator spaced apart from each other by a sum of an integer wavelength and a half wavelength in the direction of movement of the optical signal on the optical waveguide. Device comprising a. 53. The device of claim 51, wherein the device is an induction channel dropping filter and the ESBG is a resonator between channels. 31. The device of claim 30, wherein the resonator is a split resonator having an upper delay section between split resonator sections. 38. A device in accordance with claim 37 wherein each said optical waveguide has a core surrounded by a cladding and said ESBG is in cladding for all of said optical waveguides. 57. The device of claim 56, wherein the cladding on the optical waveguides overlaps, and wherein the ESBG is within the overlap of the cladding. 59. The device of claim 56, wherein the ESBG extends over both the optical waveguides. 38. A device in accordance with claim 37 wherein sidelobes are inhibited by apodization. Invention as shown and described. A semi-coupler element for selectively reconstructing an optical signal, Has a core surrounded by a cladding, the core is index n _1, said cladding has an index n _2, the effective index of the fiber is n _e, the cladding is an optical fiber that is at least partially removed from the selected region; An ESBG mounted to the optical fiber in the region and having an index of n _B in the first state substantially equal to n ₂ ; And An electrical device comprising an electrode for selectively applying a voltage across the ESBG, wherein the influence of the ESBG on the light applied to the ESBG changes as the voltage applied across them changes the state of the ESBG. Semi-coupler device characterized in that. 62. The device of claim 61, wherein light applied to the optical fiber is hardly affected by the ESBG when the ESBG is in the first state. 63. The device of claim 62, wherein the ESBG is in the first state when no mechanism substantially applies a voltage across the ESBG. 63. The device of claim 62, wherein variation in n _B as a result of a voltage change across the ESBG results in selective attenuation of light applied to the optical fiber. 65. The device of claim 64, wherein the light is multichannel light of different wavelengths and the attenuation is substantially channel independent. 63. The apparatus of claim 62, wherein the light is a multichannel multiwavelength signal, wherein the ESBG emits light of one or more selected wavelengths as the voltage across the ESBG changes from a voltage that causes the ESBG to be in the first state. And to be coupled to or from the optical fiber in at least one direction. 63. The method of claim 62, wherein the ESBG has a diffraction grating period that causes light of one or more selected wavelengths of the multi-wavelength optical signal to be reflected back along the optical fiber, thereby filtering the one or more selected wavelengths from the light waves in the optical fiber. A device characterized by the above-mentioned. 63. The apparatus of claim 62, wherein there are two said optical fibers, said regions of optical fibers are adjacent to each other, said ESBG is mounted between said optical fibers in all of said regions, and all light on one of said optical fibers is And pass the ESBG unchanged to another optical fiber when the ESBG has a selected index. 69. The optical fiber of claim 68, wherein the optical fibers have substantially the same exponent, and when the ESBG is in its first state, almost all light applied to one of the optical fibers is transmitted through the ESBG to another optical fiber. Device to be made. 70. The apparatus of claim 69, wherein the ESBG has a selected diffraction grating period, the ESBG having one or more from the multi-wavelength optical signal determined by the period of the ESBG diffraction grating as a result of the voltage applied across it in the second state. Block light of a selected wavelength from passing through the ESBG, wherein light of one or more wavelengths continues to propagate into its original optical path. 69. The optical fiber of claim 68, wherein the optical fibers have different indices, the ESBG has a selected diffraction grating period Λ, and the propagation constants for the two optical fibers are β _i and β _i ', respectively, and at one or more wavelengths of the multi-wavelength optical signal. For a condition that 2π / Λ = β _i -β _i 'is satisfied and there is no coupling between optical fibers through the ESBG except for the one or more wavelengths where the condition is satisfied. 69. The device of claim 68, wherein the optical fibers have different indices, the ESBG has a diffraction grating having an index change of Δn, and the difference in the effective index of the optical fibers is ≥ Δn. ESBG, characterized in that the ESBG has a subwavelength diffraction grating. 74. The ESBG of claim 73 wherein the diffraction grating has a period of substantially less than 0.5 microns. A method of manufacturing an ESBG having a sub-wavelength diffraction grating having a period Λ, the method comprising: (a) exposing a film with two interfering light beams of appropriate wavelengths, wherein the half-angle θ between the beams is sufficiently large so that sin θ = λ / 2Λ is the exposure wavelength at which the ESBG is the center wavelength of the optical signal used; (b) exposing the film through an appropriate bicomponent mask; (c) exposing the H-PDLC film by one of the steps of exposing the film through a master diffraction grating. A method of manufacturing an integrated optical network having a plurality of nodes with one or more ESBGs formed in each node, Forming a selected optical waveguide in the substrate, the at least selected waveguides passing through selected ones of the nodes; Forming an ESBG with an electrode of each node; And Covering the waveguide and the ESBGs. 77. The method of claim 76, wherein forming the ESBG includes forming an electrode film and an H-PDLC film on each node, and exposing the H-PDLC film of each node to form an ESBG diffraction grating thereon. Characterized in that. 78. The method of claim 77, wherein the covering comprises: forming a second electrode film on a cover plate of each node; And covering the waveguide / H-PDLC film with the cover plate, wherein each electrode on the cover plate overlies the H-PDLC film for that node. 78. The method of claim 77, wherein the exposing step comprises: (a) exposing each H-PDLC film with two interfering light beams of a suitable wavelength at a selected angle to each other; (b) exposing all films simultaneously through an appropriate bicomponent mask; And (c) exposing each film through a suitable mask. 78. The method of claim 77, wherein forming the waveguide comprises forming an optical waveguide selected within the first substrate and the second substrate, the substrates being mounted adjacent to each other during the covering step, wherein the waveguides on the two substrates are at least Intersecting at the selected node. 81. The H-PDLC film of claim 80, wherein the H-PDLC film having an ESBG diffraction grating formed therein at the node is one of (a) formed on one of the substrates, and (b) formed independently and mounted between the substrates. Method characterized in that. 81. The method of claim 80, wherein forming the electrode film comprises forming an electrode on each substrate at the wavelength of each node. In an integrated optical network having N guide wave optical inputs and M guide wave optical outputs, An optical waveguide connected to each input and each output and intersecting at the nodes; And Depending on the state of the ESBG, each node's ESBG switch element operative to pass an optical signal on a waveguide intersecting at a node on one waveguide or to deliver at least a portion of this optical signal to another waveguide crossing the node Network comprising a. 84. The network of claim 83 wherein the optical signals on the waveguide optical input are multi-wavelength WDM signals and include an ESBG switch element at each node for each wavelength to be delivered at the node. 84. The apparatus of claim 83, wherein all of the waveguides have substantially the same exponent n ₁ , and wherein the ESBG switch element at each node includes an ESBG having a diffraction grating having an exponential change Δn in optical contact with each waveguide, At least one waveguide interconnects the ESBGs, the waveguide having an exponent n ₂ , wherein n ₁ -n ₂ ≧ Δn.