KR100513846B1 - Bi-directional transceiver using photonic crystal structures - Google Patents

Abstract

Disclosed is a bidirectional optical transceiver using a photonic crystal. The bidirectional optical transceiver using the photonic crystal according to the present invention includes a light emitting device for outputting a transmission light of a first wavelength λ ₁ , a monitor photodetecting device for controlling an output optical signal of the light emitting device, and a second wavelength λ ₂ . A light receiving element for converting the received light into an electrical signal and outputting the light, and guiding the transmitted light of the first wavelength λ ₁ to the optical fiber link, and guiding the received light of the second wavelength λ ₂ to the light receiving element, And an optical guide formed of a photonic crystal. The bidirectional optical transceiver using the photonic crystal according to the present invention can be manufactured in one compact body, and in the case of 2D, the semiconductor process can be used as it is, thus eliminating the alignment and assembly process, thereby reducing the manufacturing cost.

Description

Bi-directional transceiver using photonic crystal structures}

The present invention relates to an optical transceiver, and more particularly, to a bidirectional optical transceiver using a photonic crystal or photonic crystal superprism having a photonic bandgap (hereinafter referred to as 'PBG') in a specific wavelength band. .

 Wavelength Division Multiplexing (WDM) technology is the next generation that extends transmission capacity, reduces system cost and enables efficient network construction by simultaneously transmitting optical signals of different wavelengths on one strand of optical fiber. It is a technology that can support both exponentially increasing data and IP with optical communication technology. Recently, due to the remarkable growth of the high-speed information and communication market including the Internet and the asymmetric digital subscriber network (ADSL), the demand is exploding all over the world. It's going on. However, there is a need to implement a low-cost optical subscriber network for efficient use of high-speed information communication networks and realization of fiber-to-the-home (FTTH).

As a key technology for realizing the optical subscriber network early, a bidirectional transmit / receive module has been proposed, and various methods for developing the bidirectional transmit / receive module have been proposed. Two typical techniques are Time Division Multiplexing (TDM) and WDM.

The TDM method is a method of transmitting a transmission signal and a reception signal through one single-mode optical fiber in different time slots by dividing time zones. In US Pat. No. 5,793,789, Rafael Ben-Michael et al. Of Lucent Tech. Presented by This patent integrates a laser diode, a receiving photodetector and an optical mode converter, and transmits and receives in each time slot by a single mode optical fiber, which is very promising in the optical subscriber network. One of the techniques. However, this method has a disadvantage in that the signal processing speed is halved because the transmission and reception are processed in different time zones.

In addition, the WDM method is a method of transmitting and receiving a transmission signal and a reception signal using two wavelengths of 1.3um / 1.55um. This WDM method integrates a laser diode, a receiving photodetector, and an optical waveguide device into a hybrid or single chip on a PLC (Planar Light Circuits) substrate, and transmits and receives using a wavelength of 1.3um / 1.55um. Various methods have been proposed so far.

In Japan's NTT, Junichi Yoshida published a paper entitled "Low-cost optical transceiver for access networks" in OFC97 Technical Digest Thl1 (invited) pp.275-276. 1 shows the published bi-directional optical transceiver. It has a 1.3 μm SS-Laser Diode (21), Monitor Photo Diode (22), Waveguide Photo Diode (23), on a Planar Light Circuits (PLC) Platform (10). And a 1.3um / 1.55um WDM filter (Filter) 24 by the hybrid (Hybrid) integration, a technology capable of 1.3um bidirectional Time Compression Multiplexing (TCM) or 1.3um / 1.55um Wavelength Division Multiplexing (WDM) communication has been developed. This method is an excellent technology, but has the disadvantage of increasing the optical coupling loss during hybrid integration of several individual devices on the PLC platform, making the PLC platform difficult, and bulkier than using an integrated chip.

The present invention is to solve the problems of the prior art as described above, an object of the present invention is to provide a compact integrated bi-directional optical transceiver using the photonic crystal PBG or photonic crystal dispersion phenomenon.

The bidirectional optical transceiver using the photonic crystal of the present invention for achieving the above object is a light emitting device for outputting a transmission light of a first wavelength (λ ₁ ) is set in response to an electrical signal input from the outside, a part of the transmission light A monitor light detector for controlling the output light signal of the light emitting device in response to the monitor result by absorbing the light, and receiving light having a second wavelength λ ₂ input from an external optical fiber link. A light-receiving element for converting to and outputting the light-transmitting element, and guiding the transmitted light of the first wavelength λ ₁ output from the light-emitting element to the optical fiber link, and receiving the second wavelength λ ₂ input from the optical fiber link. And guides the received light to the light receiving element, and includes a light guide formed of photonic crystal.

Preferably, the light emitting element, the monitor light detecting element, the light receiving element, and the light guide are integrally formed on a substrate.

Preferably, the optical guide is formed of a first region formed of photonic crystal A having PBG in the wavelength region of the transmission light, a photonic crystal B having PBG in the wavelength region of the transmission light and the wavelength region of the reception light. And a third region formed of photonic crystal C having PBG in the wavelength region of the received light.

On the other hand, the optical guide is formed of a photonic crystal having a PBG in the wavelength region of the received light, it may include a waveguide connecting the input and output terminals of the optical guide and the light receiving element.

The light guide may be formed of a photonic crystal having a PBG in a wavelength region of the received light, and may be disposed such that an incident angle of the received light is 45 degrees.

Preferably, the bidirectional optical transceiver using the present photonic crystal is formed integrally adjacent to the input and output terminal of the optical guide, and further comprises a lens for condensing the transmission light to correspond to the core radius of the optical fiber link.

Preferably, the input and output terminal portion of the optical guide may have a tapered shape for condensing the transmitted light to correspond to the core radius of the optical fiber link.

The bidirectional optical transceiver using the photonic crystal of the present invention for achieving the above object is a light emitting device for outputting a transmission light of a first wavelength (λ ₁ ) is set in response to an electrical signal input from the outside, a part of the transmission light Monitors the transmission light by monitoring the transmission light and controls the output light signal of the light emitting device in response to the monitoring result, and receives the received light of the second wavelength λ ₂ input from an external optical fiber link. And a photonic crystal having different refractive angles in the first wavelength and the second wavelength band, respectively, and outputting the converted light into the first wavelength and the second wavelength band, and transmits the transmitted light of the first wavelength λ ₁ output from the light emitting element. A superprism (su) for outputting to the optical fiber link and outputting the received light having a second wavelength λ ₂ input from the optical fiber link to the light receiving element per prism).

Preferably, the light emitting element, the monitor light detecting element, the light receiving element, and the superprism are integrally formed on a substrate.

Preferably, the bidirectional optical transceiver using the photonic crystal of the present invention further comprises a lens integrally formed adjacent to the input and output terminal of the superprism, and condensing the transmitted light to correspond to the core radius of the optical fiber link. do.

In addition, the bidirectional optical transceiver using the photonic crystal of the present invention is formed integrally adjacent to the input and output terminal of the superprism, and has a tapered optical guide for condensing the transmitted light so as to correspond to the core radius of the optical fiber link. It may further include.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

2 is a conceptual diagram illustrating a preferred embodiment of the present invention using a photonic bandgap. Referring to the drawings, the bidirectional optical transceiver using the photonic crystal of the present invention, the light emitting device 120, the monitor light detecting device 130, the light receiving device 140, the light guide 150, and the light collecting device 160 And all devices are integrally formed on a substrate.

The light emitting device 120 outputs a laser beam (transmitted light) having a first wavelength λ ₁ corresponding to an external electric signal as a laser diode. The transmission light λ ₁ is guided by the light guide 150, collected by the light collecting element 160, and transmitted to the external optical fiber link.

Optical detection monitor chulsoja 130 adjacent to the light emitting device 120 by detecting a portion of the output transmission light (λ ₁₎ monitors the output of the transmission light (λ _1). Prolonged use of the laser diode there is a size of the laser beam may vary, the monitor optical detection chulsoja 130 transmits light (λ by the feedback and then monitoring the transmission light (λ ₁₎ to obtain the transmission light (λ ₁₎ of desired size, ₁ ).

The light receiving element 140 detects an optical signal having a second wavelength λ ₂ transmitted through an optical fiber link or the like as a photo diode and outputs it as an electrical signal.

The optical guide 150 guides the transmission light λ ₁ output from the light emitting element 120 to the optical fiber link, and the reception light λ ₂ input through the optical fiber link to the light receiving element 140. It is formed into a crystal.

Photonic crystal refers to an artificial crystal in which PBG is formed in the energy spectrum of electromagnetic waves by periodically arranging materials having different dielectric constants. When electromagnetic waves having a wavelength belonging to PBG are incident, they do not propagate into the medium and reflect. Therefore, it becomes an effective reflecting mirror. That is, the photonic crystal is formed by periodically arranging dielectric materials, and the size or position of the PBG varies depending on the refractive index, the period, and the shape of the periodic structure.

As described above, by configuring the light guide using the PBG of the photonic crystal, the propagation direction of the light can be controlled by transmitting or reflecting only light having a specific wavelength.

3A and 3B are views for explaining the light guide portion in FIG. 2, and show a plan view of the PBG characteristics and the light guide portion of the photonic crystal forming the light guide 150, respectively.

Light guide 150 picture having a first wavelength (λ ₁₎ a first region formed of a photonic crystal A having a PBG in the band, the first wavelength (λ ₁₎ and second wavelengths PBG in (λ ₂₎ band Nick And a second region formed of crystal B and a third region formed of photonic crystal C having PBG in the second wavelength (λ ₂ ) band. As shown in FIG. 3B, a waveguide having a 'ㅗ' shape is formed of the photonic crystal B so that the transmission light λ ₁ and the reception light λ ₂ are guided without escaping to the outside. In the drawing, the photonic crystal C is arranged in one region of the waveguide penetrating right and left to form 90 degrees with respect to the transmission light λ ₁ and 45 degrees with respect to the reception light λ ₂ . Photonic crystal A of a predetermined thickness is disposed.

Left transmission light (λ _1), which is incident from the (light emitting elements) is spread by straight along the waveguide to the right (fiber optic links), can Kwang (λ _2), which is incident from the right side (fiber link) is reflected by the photonic crystal C After passing through the photonic crystal A, it propagates to the upper side (light receiving element).

4A and 4B show another embodiment in which an optical guide is constructed using PBG of photonic crystal. Since the light emitting elements 220 and 320, the monitor photodetecting elements 230 and 330, and the light receiving elements 240 and 340 are the same as the above-described examples, the light guides 250 and 350 will be omitted.

In FIG. 4A, the optical guide 250 connects the optical fiber link and the light receiving element 240 and includes a waveguide formed of photonic crystal having PBG in the wavelength band of the received light λ ₂ . Therefore, the reception light λ ₂ propagates along the waveguide, and the transmission light λ ₁ does not have a PBG with respect to the photonic crystal, so it goes straight.

In Figure 4b the light guide 350, it can be formed in a wavelength band of Kwang (λ ₂₎ in the photonic crystal having a PBG, the number is arranged to achieve an angle of 45 degrees relative to the Kwang (λ _2).

Condensing element 160 is a lens for condensing the transmitted light so as to correspond to the core radius of the optical fiber link, is formed integrally adjacent to the input and output terminal of the optical guide. In addition, the light collecting element 160 may be configured in the tapered form of the input and output terminal portion of the optical guide.

FIG. 5 is a graph showing an example of PBG calculation for TM mode in a photonic crystal having a triangular hole structure. When forming a photonic crystal having a triangular hole structure in GaAs having a dielectric constant of 11.4, when the radius r of the hole is 0.46a (a is the interval between holes) and a is selected at 715.5 nm, 1.5 μm (λ ₂ ) Has a PBG and at 1.34 탆 (λ ₁ ), a structure without PBG can be made. Similarly, when r is 0.47a, PBG is obtained at both wavelengths, and in the case of 0.99a, PBG is 1.34 µm, and 1.5 µm has no PBG. 6A and 6B show simulation results using the FDTD method when a TM mode wave having a wavelength of 1.34 mu m and 1.5 mu m in this structure is incident, respectively.

When a prism that is refracted at different angles depending on the wavelength of incident light is made of photonic crystal, the dispersion angle can be made larger than that of a general prism. For example, in the case of a general prism, when the white light is incident, the dispersion angle is only about 10 degrees, but the prism made of photonic crystal shows a dispersion angle of about 50 degrees for a wavelength difference of 1% as shown in FIG. You can get it. Because of these characteristics, such prisms are called photonic crystal superprisms.

8 illustrates a preferred embodiment of the bidirectional optical transceiver using the 2D photonic crystal superprism. Referring to the drawings, the bidirectional optical transceiver using the 2D photonic crystal superprism includes a light emitting device 420, a monitor light detecting device 430, a light receiving device 440, a 2D photonic crystal superprism 450, and a light collecting device (not shown). It consists of o).

The transmission light of the first wavelength λ ₁ output from the light emitting element 420 is transmitted to the external optical fiber link through the 2D photonic crystal superprism 450 and the light converging element, and is transmitted from the second wavelength λ _2. ), The received light is refracted by the 2D photonic crystal superprism 450 at a predetermined angle and transmitted to the light receiving element 440.

In the case of using the side emitting LD as the light emitting device, as described above, the 2D photonic crystal superprism is used, and in the case of using the surface emitting LD as the light emitting device, the bidirectional optical transceiver can be provided using the 3D photonic crystal superprism. have. In the case of 2D, as in the case of using PBG, it can be manufactured in one-piece, and in the case of 3D, the 3D photonic crystal superprism manufactured separately on the PD and LD pairs can be bonded or manufactured directly on top.

In the above described and described with respect to preferred embodiments of the present invention, the present invention is not limited to the specific preferred embodiment described above, the technical field to which the invention belongs without departing from the spirit of the invention claimed in the claims Anyone of ordinary skill in the art that various modifications can be made, as well as such changes are within the scope of the claims.

As described above, according to the present invention, by using the PBG of the photonic crystal or the dispersion effect of the photonic crystal, all the components can be manufactured in a monolithic manner and a compact bidirectional optical transceiver can be provided. . In addition, in the case of 2D it is not necessary to align and assemble process can reduce the manufacturing cost.

1 is a conceptual diagram illustrating a conventional bidirectional optical transceiver;

2 is a view showing a preferred embodiment of a two-way optical transceiver using PBG of the photonic crystal according to the present invention,

3a and 3b are views showing in more detail the configuration of the light guide portion in FIG.

4a and 4b is another embodiment of a bidirectional optical transceiver using a PBG of the photonic crystal according to the present invention,

5 is a graph showing PBG versus TM mode in a photonic crystal having a triangular hole structure,

6A and 6B show an example of calculating the FDTD when the incident wavelength enters the TM mode of 1.34 µm and 1.5 µm, respectively.

7 shows a superprism implemented with photonic crystals, and

8 is a view showing a preferred embodiment of a two-way optical transceiver using a photonic crystal superprism according to the present invention.

* Explanation of the major symbols in the drawings *

120,220,320,420: Light emitting element 130,230,330,430: Monitor photodetector

140,240,340,440: Light receiving element 150,250,350: Optical guide

160: light collecting element 450: superprism

Claims (11)

A light emitting device configured to output transmission light having a first wavelength λ ₁ corresponding to an electric signal input from the outside; A monitor photodetector for absorbing a portion of the transmitted light to monitor the transmitted light and controlling an output optical signal of the light emitting device in response to the monitor result; A light receiving element for converting the received light having a second wavelength λ ₂ input from an external optical fiber link into an electrical signal and outputting the electrical signal; And Formed of at least one photonic crystal having a photonic bandgap in a predetermined wavelength region, guiding the transmission light of the first wavelength λ ₁ to the optical fiber link, and the number of the second wavelengths λ ₂ . And a light guide guiding new light to the light receiving element. The method of claim 1, And the light emitting device, the monitor photodetecting device, the light receiving device, and the light guide are integrally formed on a substrate. The method of claim 1, The optical guide, A first region formed of photonic crystal A having a photonic bandgap (PBG) in the wavelength region of the transmitted light; A second region formed of photonic crystal B having PBG in the wavelength region of the transmitted light and the wavelength region of the received light; And And a third region formed of photonic crystal C having PBG in the wavelength region of the received light. The method of claim 1, The optical guide, And a photonic crystal having a PBG in the wavelength region of the received light, the waveguide connecting the input / output terminal of the optical guide and the input terminal of the light receiving element. The method of claim 1, The optical guide, And a photonic crystal having a PBG in the wavelength region of the received light, wherein the incident angle of the received light is 45 degrees. The method of claim 1, And a lens formed integrally adjacent to the input / output terminal of the optical guide and condensing the transmitted light to correspond to the core radius of the optical fiber link. 2. The method of claim 1, The input and output end portion of the optical guide is a bi-directional optical transceiver using a photonic crystal, characterized in that for condensing the transmission light so as to correspond to the core radius of the optical fiber link. A light emitting device configured to output transmission light having a first wavelength λ ₁ corresponding to an electric signal input from the outside; A monitor photodetector for absorbing a portion of the transmitted light to monitor the transmitted light and controlling an output optical signal of the light emitting device in response to the monitoring result; A light receiving element converting the received light of the second wavelength λ ₂ input from an external optical fiber link into an electrical signal and outputting the electrical signal; And It is formed of a photonic crystal that is refracted at different angles according to the wavelength of the incident light, and outputs the transmission light of the first wavelength (λ ₁ ) to the optical fiber link, and receives the received light of the second wavelength (λ ₂ ) Bi-directional optical transceiver using a photonic crystal, characterized in that it comprises a; super prism (output) to the light receiving element. The method of claim 8, And the light emitting element, the monitor light detecting element, the light receiving element, and the superprism are integrally formed on a substrate. The method of claim 8, And a lens formed integrally with the input / output terminal of the superprism and condensing the transmitted light so as to correspond to the core radius of the optical fiber link. The method of claim 8, It is formed integrally adjacent to the input and output terminal of the superprism, and a tapered optical guide for condensing the transmitted light to correspond to the core radius of the optical fiber link; bidirectional light using a photonic crystal further comprises a Transceiver.