JP2002202439A - Optical waveguide body, optical waveguide device having it and optical module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an excellent fiber stub type optical device, an optical parts mounting substrate and an optical module using it which are small sized and are easily aligned and in which the coupling state of an optical isolator part is not changed by alignment with an LD. SOLUTION: In an optical waveguide body F, a first multimode optical fiber 2A and a first coreless optical fiber 5A are successively connected in a line to the other end part of a first single mode optical fiber 1A having a lens part (tip sphere 9) for optically connecting an optical semiconductor element to one end part, and a second coreless optical fiber 5B, a second multimode optical fiber 2B and a second single mode optical fiber 1B are successively in a line to the optical fiber non-connecting end part of the first coreless optical fiber 5A via, for example, the optical isolator 4 being an optical device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical module having an optical semiconductor element such as a light emitting element or a light receiving element which is suitably used for an optical communication device, an optical sensor and the like. Further, the present invention relates to an optical waveguide provided with an optical isolator, an optical sensing device, and a wave plate for measurement and the like, which are used in the optical module to block reflected return light from the outside, and an optical waveguide device using the same.

[0002]

2. Description of the Related Art A laser diode (hereinafter, also referred to as an LD) used as a light source for optical communication reflects an emitted light at a certain place and returns to an active layer of the LD again. And a wavelength shift, etc., which deteriorates the signal. In particular, analog signals are easily degraded by the above-mentioned reflected return light, and the higher the density of the signal, the more easily the reflected return light is affected. Therefore, with the increase in analog transmission data such as CATV, large capacity, and high speed, Optical isolators have become an essential component.

In order to prevent such a problem of reflected return light, the LD is usually mounted in the same package as an optical isolator that transmits light only in one direction, and constitutes an LD module which is a kind of optical module. ing.

[0004] The general operation of an optical isolator will be briefly described below. As shown in FIG. 7, the optical isolator 4 is configured such that the Faraday rotator 20 is sandwiched between two polarizers 19A and 19B. In such a configuration, the forward light 22 is transmitted as it is, and the backward light 23 is blocked. The Faraday rotator 20 has a Faraday effect by applying a magnetic field from outside, and a Faraday rotator 20 having a Faraday effect without an external magnetic field due to spontaneous magnetization. Are not shown in some cases.

Next, an example of a conventional LD module will be described. As shown in FIG. 10, the LD module J1
Is at least the LD 15 and the lens 6 in the package 18.
A, 6B, the optical isolator 4, one end of the single mode optical fiber 1 and the like are housed. In the figure, reference numeral 16 denotes a light receiving element (hereinafter, also referred to as PD), reference numeral 17 denotes a peltier cooler, and reference numeral 32 denotes a rubber boot for protecting the extra length of the optical fiber.

The light emitted from the LD 15 is transmitted to the lens 6A.
And passes through the optical isolator 4 and the lens 6
The light is condensed by B and is incident on the single mode optical fiber 1. Each optical component is built in the package 18 and the rubber boot 32 in order to shield it from the external environment. In addition, a ball lens, a biconvex lens, an aspheric lens, a graded index lens (hereinafter, referred to as a GRIN lens), or the like is used as the lenses 6A and 6B.

In such an optical module J1, the optical isolator 4, the lenses 6A and 6B, etc., are aligned as independent parts after being fixed separately to the holder, so that the number of parts is large and adjustment is complicated and large. There was a problem of becoming.

As shown in FIG. 11, an optical isolator 4 is mounted on a fiber stub using a core-enlarged optical fiber 10 provided with a tip ball 9, in order to reduce the size of the entire optical module and facilitate alignment. A device J2 has also been proposed (see Japanese Patent Application Laid-Open No. H10-68909).

This optical device J2 is a fiber stub type in which an optical isolator 4 is disposed on a ferrule 3 holding a core-enlarged optical fiber 10 formed at the tip of a tip sphere 9 at the center, and is entirely fixed in a sleeve 13. It constitutes an optical device. Even if the optical device J2 is provided with the optical isolator 4, the optical device J2 can be assembled with the same man-hour as the optical module without the optical isolator, and can be manufactured very easily.

Further, since the core-expanded optical fiber is used, the tolerance of defocus (corresponding to the distance between the core-expanded optical fibers in the direction parallel to the optical axis) is large, so that the optical fibers are separated from each other and the Even if an optical element such as an isolator is provided, there is an advantage that coupling loss is small.

Further, such a core-expanded optical fiber is
It is made by locally heating a general single mode optical fiber. The single-mode optical fiber is heated to diffuse the dopant such as Ge doped in the core, thereby widening the diffusion region of the dopant and reducing the relative refractive index difference.

If the core diameter is increased without changing the relative refractive index difference between the core and the clad of the optical fiber, the single mode condition is broken and a multimode is excited. In the case of the core-expanded optical fiber, the expansion of the core and the decrease in the relative refractive index difference occur at the same time due to the diffusion of the dopant due to heat, and r × (D) ^1/2 is automatically kept constant. Here, r is the radius of the core of the optical fiber, D is the relative refractive index difference between the core and the cladding, r × (D) ^1/2 is an amount proportional to the normalized frequency, and if this is constant, the single mode condition is Will be kept.

FIG. 8 shows the characteristics of optical coupling using a core-expanded optical fiber. On the horizontal axis, the distance between optical fibers (interval:
Or, the width of a groove formed in a core enlarged portion described later), and the vertical axis indicates light coupling loss. w indicates each mode field diameter (hereinafter abbreviated as MFD), and corresponds to each curve. The wavelength of light is 1.31 generally used in optical communication.
μm, and the grooves (between the fibers) were filled with air (refractive index n = 1).

When the MFD is 10 μm, the loss between the optical fibers is 70 μm and the loss is 1 dB or more.
Is 40 μm, the loss is 1 dB or less even when the distance between the optical fibers is 800 μm. Therefore, it can be seen that the coupling characteristics are clearly improved as the MFD increases.

Further, a multimode optical fiber GI
An example in which a (graded index) fiber is used like a lens and an optical isolator is installed in a cylindrical member is known (see US Pat. No. 5,325,456). In this case, G is sandwiched between both ends of the optical isolator.
An I-fiber is installed for optical coupling.

Here, the GI fiber is an optical fiber having an axially symmetric refractive index distribution such that the refractive index gradually decreases from the central axis of the optical fiber, and is generally used for multi-mode transmission. Most GI fibers have an approximately squared index profile. Since this refractive index distribution has a lens effect like the GRIN lens, a coupling optical system can be configured by using a GI fiber having an appropriate refractive index distribution and an appropriate length. Further, as parameters indicating characteristics of the GI fiber, there are a refractive index difference Δ between the clad and the center of the core, a core diameter D, and a convergence parameter A.

Furthermore, since the light beam in the GI fiber exhibits a sine curve behavior as shown in FIG. 9, its length is represented by a pitch (P) corresponding to the period of the light beam behavior. In FIG. 9, the abscissa represents the pitch, the ordinate represents the position of the light beam in the GI fiber, and the portion where the light spreads most is indicated as 1, relative to each other. Note that P = 1 corresponds to one cycle (2π) of the sine curve. It is P = 0.25 at the shortest pitch that the light incident from the point light source becomes parallel light, and again, P = 0.5 at the shortest pitch.
It is.

[0018]

However, there are the following problems when using a core-expanded optical fiber.

The core-expanded optical fiber is manufactured by heating the optical fiber as described above. In order to enlarge the core to 40 μm or more, heating at a temperature of 1000 ° C. or more for several hours to several tens of hours is required, which is extremely troublesome. In addition, a portion where the core diameter is changed from 10 μm to 40 μm requires a tapered portion in which the core diameter is gradually increased. In order to produce this tapered portion, a large temperature difference must be applied to the optical fiber to locally heat it. In addition to simply forming a tapered core, the length and angle of the tapered portion greatly change optical characteristics, so that a sharp temperature gradient and delicate control are required.

Although the core enlargement is several millimeters, this thermal processing is required once for each device, which is inefficient.

The optical system using a GI fiber as a lens has the following problems.

A GI fiber, which is a multi-mode optical fiber, is connected to the tip of the single-mode optical fiber and inserted from both ends of the pore. The pore requires a clearance, and the optical fiber has a μm inside the pore. A unit displacement always occurs. That is, when the optical fibers are inserted from both ends and are brought into contact with each other, an axial deviation always occurs. In addition, it is impossible to correct the displacement because it is inside the pore.

Further, since the GI fiber has the same function as the lens, it is essential to adjust the focal length. The optical fiber must be fixed while maintaining an appropriate width, and there is a problem that the loss increases if the optical fiber moves during the fixing operation. When positioning the optical fiber inserted into the pore from both ends by pressing the optical fiber against the optical element, it is assumed that the thickness of the optical element is adjusted to the coupling length of the GI fiber. Further, a loss occurs at the intersection of the thickness of the optical element. In addition, since the element and the end face of the fiber come into contact with each other, there is a problem that it is difficult to fill a refractive index matching material or the like.

Therefore, the present invention solves the above-mentioned problems,
It is an object of the present invention to provide an optical waveguide that is compact, integrated, easily aligned with a light receiving and emitting element, and suitable for an optical module, an optical waveguide device including the optical waveguide, and an optical module.

[0025]

In order to achieve the above object, an optical waveguide according to the present invention comprises a first single-mode optical fiber having a lens portion for optically connecting an optical semiconductor element to one end. A first multi-mode optical fiber and a first coreless optical fiber are sequentially connected in a line, and a second coreless optical fiber is connected to an optical fiber non-connection end of the first coreless optical fiber via an optical element. , A second multi-mode optical fiber, and a second single-mode optical fiber are sequentially connected in a line.

Further, the optical waveguide device of the present invention comprises: holding the optical waveguide by a ferrule; or disposing an optical fiber constituting the optical waveguide in a fiber mounting groove formed in a substrate. The optical element constituting the optical waveguide is disposed in an element mounting groove formed so as to cross the fiber mounting groove.

In the optical module of the present invention, the optical waveguide device according to the first aspect has an optical semiconductor device for optically connecting to the lens portion of the first single mode optical fiber of the optical waveguide. Arranged.

More specifically, for example, an optical waveguide device which can also be referred to as a fiber stub type optical device has a structure in which an optical waveguide is arranged from a light receiving / emitting element side to a first single mode optical fiber, a first multimode optical fiber, and other optical fibers. A coreless optical fiber having the same outer diameter and having no core, a second multi-mode optical fiber, and a second single-mode optical fiber are connected in this order, and these are arranged in a ferrule and optical such as an optical isolator and a wavelength filter. An element mounting groove for mounting an element is provided so as to cross the coreless optical fiber (separate into first and second coreless optical fibers), and an optical element is disposed in the element mounting groove. It is characterized by the following.

Also, in the optical component mounting substrate having a fiber mounting groove for fixing the optical fiber and a conductor pattern for mounting the light emitting / receiving element, the optical waveguide is arranged from the light emitting / receiving element side to the first single mode optical fiber. A first multi-mode optical fiber, a coreless optical fiber having the same outer diameter as another optical fiber and having no core, a second multi-mode optical fiber, and a second single-mode optical fiber are connected in this order and fixed on the substrate. In addition, an element mounting groove for installing an optical element is provided so as to cross the coreless optical fiber (separate into first and second coreless optical fibers), and the optical element is arranged in the element mounting groove. It is characterized by being provided. Further, the optical component mounting board is characterized in that a plurality of fiber mounting grooves for fixing optical fibers are provided in parallel.

Finally, the fiber stub type optical device is installed on the substrate for mounting optical components. However, since a ferrule for holding the optical fiber is required, there is a limit to the reduction in height. By mounting the optical waveguide and the optical element directly on the top, the height can be reduced and the number of parts can be reduced. Further, alignment of an optical element with an array element such as a laser array is easy if an optical component mounting substrate is used. The arraying of optical waveguides also requires
This is possible because an optical waveguide that is assembled after adjusting the coupling optical system is used.

Further, the light receiving / emitting element side of the optical waveguide is processed to be spherical in order to obtain optical coupling with the light receiving / emitting element.

Further, in the fiber stub type optical device and the optical component mounting substrate, the optical element installed in the gap provided in the middle of the optical waveguide is an optical isolator. The optical isolator has a plane of polarization 45 between a pair of polarizers whose planes of polarization are inclined at 45 degrees to each other.
Although a Faraday rotator for rotating the Faraday rotator is arranged and integrated, the magnet for applying a magnetic field to the Faraday rotator can be omitted if the Faraday rotator has spontaneous magnetization.

Further, an optical module comprising the above-mentioned fiber stub type optical device and an optical element for receiving or emitting light is arranged on a substrate.

Further, an optical module is formed by arranging optical elements for receiving or emitting light on the optical component mounting board.

The GI fiber used as a multi-mode optical fiber and the coreless optical fiber sandwiched between the GI fibers play a very important role in adjusting the focal length, preventing axial deviation, and simplifying assembly. Since the fiber is originally a single fiber, no axial deviation occurs in principle when the fiber is divided.

The focal position is precisely determined in advance by the length of the coreless optical fiber, and is guaranteed. There is no need for complicated work such as adjustment within the pores. The above-mentioned advantage is made possible only by the structure for dividing the coreless optical fiber.

Thus, it is possible to obtain a compact configuration in which optical elements such as an optical isolator are mounted in a fiber stub almost free of alignment, and a similarly compact optical component mounting substrate can be obtained. Further, an optical module having a stable coupling state of the optical elements can be easily configured.

[0038]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments according to the present invention will be described below in detail with reference to the drawings. In the drawings, the same members are denoted by the same reference numerals, and description thereof will be omitted.

As shown in FIG. 1, an optical waveguide F according to the present invention has a first single mode optical fiber 1A having a lens portion (a tip sphere 9) at one end for optically connecting an optical semiconductor element.
At the other end of the first multimode optical fiber 2A and the first
The coreless optical fibers 5A are sequentially connected in a line, and the second coreless optical fiber 5B and the second multimode are connected to the optical fiber non-connection end of the first coreless optical fiber 5A via, for example, an optical isolator 4 as an optical element. Optical fiber 2
B and the second single mode optical fiber 1B are sequentially connected in a line. The fiber stub type optical device S1, which is an optical waveguide device, includes the optical waveguide F held by the ferrule 3.

More specifically, the fiber stub type optical device S1 includes a ferrule 3 made of alumina, zirconia, glass, stainless steel or the like, a first single mode optical fiber 1A, and a first multimode optical fiber first GI.
Fiber 2A, coreless optical fiber 5 having no core
(The first coreless optical fiber 5A, the second coreless optical fiber 5B) and the second GI which is the second multimode optical fiber.
An optical waveguide F in which a fiber 2B and a second single-mode optical fiber 1B are connected in cascade is housed. One end of the first single mode optical fiber 1 </ b> A protruding from the ferrule 3 is processed into a front sphere 9 as a lens portion for optically coupling with a light receiving / emitting element as an optical semiconductor element, and the other end is an end face of the ferrule 3. Is a so-called pigtail shape in which a predetermined length of the second single mode optical fiber 1B is provided by polishing. The coreless optical fiber 5 divided in the ferrule 3 is optically connected via an optical element (for example, the optical isolator 4) disposed in the element mounting 7.

Here, the length of the coreless optical fiber 5 is adjusted so that the beam spots of the two GI fibers 2A and 2B coincide at the center. The light propagating through the single mode optical fiber is capable of only a single mode and maintains a constant MFD. By having a forward ball,
Even if the light incident conditions change, the light emitted from the single mode optical fiber always enters the multimode optical fiber having the lens effect under the same conditions except for the power, so that the optical coupling characteristics are stabilized. Further, when the light incident portion is a multi-mode optical fiber, the light emitting condition greatly changes depending on the light incident condition, so that the coupling characteristics at the insertion portion of the optical element cannot be guaranteed. Therefore, by connecting the coreless optical fiber, the focal length can be strictly adjusted in advance to prevent axial deviation between the optical fibers.

Note that the first single mode optical fiber 1A protrudes from the tip end surface 3b to a length necessary for mounting for optical coupling with the light receiving / emitting element.

More specifically, the first single mode optical fiber 1A having an MFD of, for example, 10 μm, P (pitch)> 0.
25 first GI fiber 2A, the beam waist of light emitted from the first GI fiber 2A and the first GI fiber 2
Assuming that the distance between the emission end faces of A is d, the coreless optical fiber 5 having a length of 2d and the second G having the same length as the first GI fiber 2A
The I-fiber 2B and the second single-mode optical fiber 1B were connected in cascade, and the tip of the first single-mode optical fiber 1A was processed into a spherical tip 9 to form an optical waveguide F. Further, the optical waveguide F is inserted and fixed in the through hole 3a of the ferrule 3 having a diameter of about 1.25 mm and a length of about 12 mm, for example. Further, an element mounting groove 7 having a width of about 1 mm is formed so as to cross the through hole 3a at the portion of the coreless optical fiber 5.

The second single mode optical fiber 1B
Is polished so that the rear end faces 3c of the ferrule 3 coincide with each other, or is made into a pigtail shape having an extra length of the fiber as it is. The polarizer 1 is placed in the element mounting groove 7.
9A, 19B and the Faraday rotator 20 are integrally molded, and the optical isolator 4 manufactured by cutting is installed.
A translucent refractive index matching adhesive 8 whose refractive index is matched to the coreless optical fiber 5 is provided between the light entrance / exit surfaces of the polarizers 19A and 19B of the optical isolator 4 and one end of the coreless optical fiber 5. As described above, the magnetic field applying means is omitted. The surface of the optical isolator 4 has a reflection amount of 0.2.
% Or less of an antireflection film (not shown).

The collimating condition when a point light source is present on the end face of the GI fiber is P = 0.25, but the coupling efficiency is actually the highest when the beam waists from the two GI fibers are identical. . When P = 0.25, the beam waist is located exactly at the emission end face of the GI fiber, and the beam waist does not match when an optical element is sandwiched between the GI fibers. Therefore, in order to form a beam waist at a position distant from the emission end face of the GI fiber, a condition of P> 0.25 is required.

The light entering from the front sphere 9 of the first single-mode optical fiber 1A is expanded in beam diameter by the first GI fiber 2A, and becomes a beam having a beam waist at the center of the first coreless optical fiber 5A. 4
, Again passes through the second coreless optical fiber 5B, is converged to 10 μm by the second GI fiber 2B, and propagates to the second single mode optical fiber 1B. The fiber stub type optical device S1 is connected to a connector (not shown) having the same shape as the ferrule 3 on the rear end face 3c and having a ferrule holding a single mode optical fiber for transmission at the center.

According to the present invention, alignment is almost free even if an optical element such as the optical isolator 4 is inserted into the transmission path. Although a GI fiber is used as the multimode optical fiber, the focal length has been adjusted by the length of the coreless optical fiber 5 and is guaranteed at the time of assembling the optical waveguide. There is no. This is not only a simplification of the process, but also a defect of the coupling efficiency can be confirmed at the initial stage of the process, that is, before fixing the optical element, etc., so that the efficiency of the entire process and the damage due to defects can be greatly reduced. Will be possible.

Although an example in which the optical isolator 4 is particularly used in the element mounting groove 7 for dividing the coreless optical fiber 5 has been described, it goes without saying that the present invention can be applied to an optical element such as a wavelength plate or a wavelength filter.

The optical waveguide device of the present invention may have the configuration shown in FIG. That is, the optical fiber constituting the optical waveguide F is disposed in the fiber mounting groove 12 formed in the substrate 14 and the optical element 4 constituting the optical waveguide F is traversed through the fiber mounting groove 12. The optical waveguide device S2 provided in the formed element mounting groove 7 may be used. According to this configuration, an optical module can be manufactured extremely easily, and further, compared with a fiber stub type optical device,
Since the ferrule is not used, it is possible to contribute to miniaturization and reduction in height.

In the optical module of the present invention, the optical waveguide F and an optical semiconductor element for optically connecting to the lens portion of the first single mode optical fiber 1A of the optical waveguide F are provided on the substrate. For example, FIG.
As shown in FIG. 6, a fiber stub type optical device S1 is mounted on a substrate 14, or as shown in FIG. 6, an optical waveguide F is mounted on a substrate 14, and an optical semiconductor element is optically connected thereto. You may comprise.

[0051]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, more specific embodiments of the present invention will be described in detail.

Example 1 This will be described with reference to FIGS. 2 (a) to 2 (f). As shown in FIG. 2A, at the tip of a silica-based single mode optical fiber 1A having an MFD of about 10 μm, Δ =
0.85%, core diameter 105 μm, convergence parameter A =
3.37 × 10 −6 μm−2, the GI fiber 2A was fused by electric discharge machining, and the GI fiber 2A was cut so that P = 0.258 (653 μm).

If the surrounding medium is n = 1.46 (corresponding to the refractive index of the coreless optical fiber 5), the GI fiber 2A
From the end face 15 to the beam waist of the emitted light formed by the GI fiber 2A is 550 μm.

Next, as shown in FIG. 2B, n = 1.
The coreless optical fiber 5 having a refractive index of 46 was fused to the GI fiber 2A by electric discharge machining and cut into a length of 1100 μm. Then, as shown in FIG. 2C, a GI fiber 2B and a single mode optical fiber 1B having the same configuration as the GI fiber 2A are fusion-spliced in this order.
As shown in (d), a tip 9 of R = 5 μm was formed on one end of the single mode optical fiber 1A by polishing.

Next, as shown in FIG.
The zirconia ferrule 3 having a length of 12 mm and a length of 12 mm was inserted and fixed in the through hole 3a. For this fixation, epoxy technology thermosetting epoxy adhesive EPOTECH 353ND
Was used. Further, an element mounting groove 7 having a width of 1 mm was formed so as to cross the through hole 3a at the portion of the coreless optical fiber 5. In this process, a DISCO dicer blade SDC320R10MB01 was used.

Then, as shown in FIG. 2 (f), the optical isolator 4 formed by integrally molding the polarizers 19A and 19B and the Faraday rotator 20 in the groove 7 for mounting the element and then cutting the same is installed. . Here, an ultraviolet-curing adhesive or a thermosetting adhesive 8 whose refractive index is matched with that of the coreless optical fiber 5 (for example, an ultraviolet-curing epoxy adhesive # 9539 manufactured by NTT Advanced Technology, an ultraviolet-curing epoxy manufactured by Daikin Industries, Ltd.) Type adhesive optodyne, epoxy technology thermosetting adhesive EPOTECH 353ND
Etc.) were used.

The optical isolator 4 includes polarizers 19A and 19A.
B (thickness 200 μm, refractive index 1.5), Faraday rotator 20 (magnetic garnet, thickness 350 μm, refractive index 2.
2), each light-transmitting surface having an anti-reflection film formed thereon, and then an epoxy-based light-transmitting adhesive (for example, a thermosetting adhesive EPOTECH 353ND manufactured by Epoxy Technology).
It is joined by. The optical isolator 4 is 10 mm
After performing collective alignment and bonding with a large element having a size equal to or larger than a corner, the element is cut into a 400 μm square. The thickness is 750μ
m. Further, since a spontaneously magnetized garnet is used here, no magnet is required.

In the fiber stub type optical device of the present invention, when mounted on an LD module, the end face of the core-enlarged optical fiber on the LD side is formed as a front spherical portion 9 to prevent reflection and improve coupling efficiency at the same time. However, a lens may be provided depending on the design of the optical module.

Example 2 As shown in FIG. 3, an electrode 11 (electrode 11) for mounting the light receiving / emitting element on the optical waveguide F of Example 1 was used.
A, 11B) and a substrate 1 having a V groove 12 for fixing a fiber.
4 is an optical component mounting substrate S which is an optical waveguide device mounted on
2. In the drawing, reference numeral 24 denotes a stopper groove for stopping the tip of the optical waveguide F.

The manufacturing procedure of the optical waveguide F is the same as that of the first embodiment, and the optical characteristics are guaranteed when the optical waveguide F is assembled.

After the optical waveguide F is fixed to the substrate 14, an element mounting groove 7 is formed at the coreless optical fiber 5 and the optical isolator 4 is installed. Adhesion is performed with the refractive index matching adhesive 8 (refractive index matching ultraviolet curing adhesive # 9539 manufactured by NTT Advanced Technology) so as to fill the input / output end face of the isolator. The substrate 14 has a very precise relative positional accuracy between the fiber fixing V-groove 12 and the light receiving / emitting element mounting electrode 11 (±
0.5 μm), and the optical coupling with the front sphere 9 becomes possible only by mounting the LD on the electrode 11, and a module can be manufactured extremely easily. Furthermore, compared with the fiber stub type device, the size can be reduced by not using the ferrule, which contributes to a reduction in the height of the module.

Example 3 FIG. 4 shows an optical component mounting substrate S of Example 2.
2, an optical waveguide device S3 in which an array of electrodes 11 and V-grooves 12 is formed to correspond to an array element such as an LD array. After aligning and fixing the optical waveguide F in the array of the V-grooves 12, the device mounting groove 7 is formed, the optical isolator 4 long in the lateral direction is installed, and the partial cross section of the optical waveguide F and the insertion of the optical isolator 4 are set. The refractive index matching adhesive 8 is filled and fixed so as to fill the gap between the emission surfaces. In the array element, the area for receiving and emitting light is very close, and if a bulk lens is used, the optical fiber cannot be kept close to the lateral direction. Further, as shown in FIG. 4, since grooves are formed in the fiber array at once, the process can be simplified, and since the optical waveguide F is close to the optical waveguide F, it can function sufficiently with a very small optical isolator 4. Material can be saved.

Example 4 FIG. 5 shows an example in which an LD module M1 is constructed using the fiber stub type optical device S1 formed in Example 1 above. A fiber stub type optical device S having an LD-side end face formed into a spherical fiber in a V-shaped groove of a substrate 14
1 was fixed. By mounting the substrate 14 on the peltier cooler 17, the LD 15 was maintained at a constant temperature and operated in a stable state. The PD 16 monitors the light of the LD 15 to stabilize the light intensity. The sleeve 13 is externally fitted with a connector (not shown) for optical coupling. The whole is hermetically sealed in a package 18.

With the above configuration, all the optical adjustments of the LD module are completed only by aligning the LD 15 with the spherical fiber. Further, since all of the optical system is inside the ferrule 3, the size can be reduced, and the LD module M1 which is extremely stable and has little change over time can be provided.

Example 5 FIG. 6 shows an LD module M2 including the optical component mounting substrates S2 and S3 formed in Examples 2 and 3 above. The electrode 11 (11A, 11A,
11B), the LD 15 and the PD 16 are mounted, and then mounted on the Peltier cooler 17 and the single mode optical fiber 1 is mounted.
The extra length of B was hermetically sealed with solder 26 in the pipe 25 and pulled out.

With the above configuration, all the optical adjustment of the LD module M2 is completed only by mounting the LD 15 and the PD 16 on the optical component mounting board B1. According to the LD module M2, downsizing can be achieved as compared with the fiber stub type optical device S1 using the ferrule 3.
An extremely stable LD module M2 with little change over time could be provided.

[0067]

As described in detail above, the optical waveguide of the present invention, the optical waveguide device having the same, and the following remarkable effects can be obtained.

Since an optical lens is not used, it can be manufactured at a low cost with a simple configuration.

The basic optical waveguide is only required to adjust the connection between the multi-mode optical fiber and the coreless optical fiber, and the number of adjustment axes is small, so that the assembly is easy.

The multi-mode optical fiber and the coreless optical fiber sandwiched between the multi-mode optical fibers play the role of adjusting the focal length, preventing axial deviation, and simplifying assembly. Since a single fiber is cut off, no axial deviation occurs in principle.

The focal position is precisely determined in advance by the length of the coreless optical fiber, and is guaranteed. It is not necessary to perform a complicated operation such as adjusting the inside of the fine hole when inserting from both ends of the fine hole of the ferrule.

When an optical element is inserted into the optical waveguide, a groove may be formed in the coreless optical fiber portion. Even if the groove position is shifted within the range of the coreless optical fiber, no problem occurs even if it is shifted, so that it is extremely easy to manufacture. The insertion of the optical isolator can be performed almost alignment-free.

Although an optical system using an optical fiber is required, the production is troublesome and the core-enlarged optical fiber which is difficult to control need not be used.

A fiber stub type optical device, which is an optical waveguide device in which an optical waveguide is housed in a ferrule, is small and has high stability. Furthermore, an optical component mounting substrate, which is an optical waveguide device in which an optical waveguide is mounted on a substrate, can be further reduced in size and height.

An excellent optical module which is small, easy to manufacture, inexpensive, and has little change over time can be provided.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically illustrating a fiber stub type optical device (optical waveguide device) according to the present invention.

FIGS. 2A to 2F are cross-sectional views schematically illustrating a process for producing a fiber stub optical device according to the present invention.

FIG. 3A is a top view showing an optical component mounting substrate (optical waveguide device) according to the present invention, and FIG. 3B is a view A of FIG.
FIG. 4 is a cross-sectional view taken along a line A.

FIG. 4A is a top view showing an optical component mounting substrate (optical waveguide device) according to the present invention, and FIG.
FIG. 4 is a cross-sectional view taken along line B.

FIG. 5 is a cross-sectional view for schematically explaining an optical module according to the present invention.

FIG. 6 is a sectional view schematically illustrating an optical module according to the present invention.

FIG. 7 is a perspective view schematically showing the operation of the optical isolator.

FIG. 8 is a graph showing the relationship between the coupling interval of a core-enlarged optical fiber and diffraction loss.

FIG. 9 is a schematic diagram illustrating the behavior of light in a GI fiber.

FIG. 10 is a partial cross-sectional view illustrating a conventional optical module.

FIG. 11 is a cross-sectional view illustrating a device in which an optical isolator is mounted on a conventional core-enlarged optical fiber.

[Explanation of symbols]

 1, 1A, 1B: Single mode optical fiber 2A, 2B: GI fiber (multimode optical fiber) 3: Ferrule 3a: Through hole 4: Optical isolator 5: Coreless optical fiber 6A, 6B: Lens 7: Element mounting groove 8 : Refractive index matching adhesive 9: tip sphere 10: core enlarged optical fiber 11: electrode 12: V groove (fiber mounting groove) 13: sleeve 14: substrate 15: LD (light emitting element) 16: PD (light receiving element) 17 : Peltier cooler 18: Package 19A, 19B: Polarizer 20: Faraday rotator 22: Forward incident light 23: Reverse incident light 24: Stopper groove 25: Pipe 32: Rubber boot J1: Optical module J2: Optical device M1 M2: Optical module S1: Fiber stub type optical device (optical waveguide device) F: Optical waveguide S2, S 3: Substrate for mounting optical components (optical waveguide device)

Claims (4)

[Claims] 1. A first multi-mode optical fiber and a first coreless optical fiber are sequentially connected in a line to the other end of a first single-mode optical fiber having a lens portion for optically connecting an optical semiconductor element to one end. And a second coreless optical fiber, a second multi-mode optical fiber, and a second single-mode optical fiber are sequentially connected in a line to an optical fiber non-connection end of the first coreless optical fiber via an optical element. An optical waveguide, comprising: 2. An optical waveguide device comprising the optical waveguide according to claim 1 held by a ferrule. 3. An optical fiber forming the optical waveguide according to claim 1 is disposed in a fiber mounting groove formed in a substrate, and an optical element forming the optical waveguide is mounted on the fiber mounting groove. An optical waveguide device, wherein the optical waveguide device is disposed in an element mounting groove formed so as to cross. 4. A light comprising a substrate and the optical waveguide according to claim 1 and an optical semiconductor element for optically connecting to a lens portion of a first single mode optical fiber of the optical waveguide. module.