JP2000121867A - Semiconductor light receiving device, bi-directional optical semiconductor device and light multiplexing/ demultiplexing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a coupling loss of an optical device having the light multiplexing/demultiplexing part of a filter insertion type. SOLUTION: An optical fiber 12 being the transmission path of a signal light is embedded in the upper part of the substrate 11 made of glass roughly parallel with the surface of the substrate 11. A flat light receiving PD 13 is fixed on the upper part of the optical fiber 12 in the substrate 11 while the light receiving surface of the PD 13 is made opposed to the principal surface of the substrate 11. A flat parallelogram shaped filter 15 which intersects the optical fiber 12 at an angle that the filter reflects the signal light of the optical fiber 12 at the area of the under side of the PD 13 in the principal surface and the light receiving surface of the PD 13 is irradiated with the reflected light 14 is inserted into the upper part of the substrate 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a semiconductor light receiving device in which an optical filter is inserted into a waveguide, a bidirectional optical semiconductor device, and an optical multiplexer / demultiplexer.

[0002]

2. Description of the Related Art In an optical communication system, a desired electric signal is converted into signal light by a semiconductor laser device on a transmitting side, and the converted signal light is transmitted to a receiving side via an optical fiber. On the receiving side, the received signal light is converted to the original electrical signal by the photodiode element.

Here, in order to efficiently use an optical fiber which is a transmission line, a single optical fiber transmits signal light bidirectionally, or converts a plurality of electric signals into signal lights having different wavelengths. A technique of multiplexing (wavelength multiplexing) these and transmitting them through one optical fiber is used. In order to perform bidirectional transmission or wavelength division multiplexing transmission in this way, multiplexing and demultiplexing of signal light is indispensable, such as a fiber fusion type coupler or a coupler in which a dielectric multilayer filter is coupled to an optical fiber by a lens. Is used.

In the current telephone network, only data of several tens of kilobits per second can be transmitted. Therefore, in order for ordinary users to enjoy higher-speed data communication services, optical communication must be performed not only on the trunk system of the communication system but also on the subscriber system. It is also required to spread it. For that purpose, a technique for realizing a multiplexing / demultiplexing function at a smaller size and at a lower cost is required.

As a first conventional example, a document "Journa"
l of Lightwave Technology
vol. 12, No. 9, 1994, p. 1597
-1606 ", a PL that realizes a multiplexing / demultiplexing function in a waveguide.
C (Planer Lightwave Circuit)
An element called t) has been proposed.

As a second conventional example, a multiplexing / demultiplexing device having a substrate in which an optical fiber is embedded and having a dielectric multilayer filter provided on the optical fiber and the substrate is disclosed in Japanese Patent Application No. 7-198538. Is disclosed. This dielectric multilayer filter has a slit provided obliquely with respect to the substrate surface in the upper part of the substrate and the optical fiber embedded in the substrate so that the signal light can be reflected on the filter surface and extracted to the substrate surface side. Has been inserted. Note that, also in the first conventional example, since realizing the wavelength demultiplexing function increases the size of the element, a structure in which a filter is inserted into the waveguide is also used.

As described above, when a Y-shaped branch portion is formed by inserting an optical filter into a waveguide,
In order to reduce the transmission loss, it is necessary to reduce the thickness of the filter, and in order to reduce the coupling loss of the reflected light, the positional accuracy of the insertion position is important.

In particular, since the core diameter of a single-mode optical fiber or waveguide used for optical communication is as small as about 10 microns, it is necessary to control the reflection position of signal light in microns.

FIG. 6 shows the result of calculation of the allowable range of the positional shift of the fixed position of the photodiode (PD) with respect to the light receiving sensitivity in the first conventional example. Here, the light receiving diameter of the PD was 80 μm, the distance between the center of the fiber core and the PD was 140 μm, and the incident angle was 30 °.
As shown in FIG. 6, high light receiving sensitivity can be obtained in a range of ± 25 μm from the reference position (± 0), but ± 25 μm
It can be seen that the sensitivity sharply decreases in the region deviated from the range. Here, only the displacement of the PD element is shown, but if the displacement of the slit or the position of the filter in the slit occurs, the sensitivity similarly decreases.

[0010] The optical filter is usually formed by depositing a dielectric multilayer film on a substrate made of glass or polyimide, and the thickness of the substrate is several microns to several tens microns. Must be identified. Generally, identification of the front and back surfaces of a filter is performed by providing a marker with a paint or a scratch on the substrate surface.

[0011]

However, in the above-mentioned conventional optical multiplexer / demultiplexer equipped with a filter, it is not easy to discriminate between the front surface and the back surface of the filter. Since the light reflection position is shifted, there is a problem that a coupling loss occurs.

In addition, it is necessary to add a marker to each filter. Further, in the case of a filter transmitting light, the marker is visible from both sides of the filter, which is not suitable for automatic identification. .

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned conventional problems and to reduce the coupling loss in an optical device having a filter insertion type multiplexing / demultiplexing unit.

[0014]

To achieve the above object, the present invention provides an optical filter having an in-plane asymmetric planar shape.

Specifically, a semiconductor light receiving device according to the present invention is provided with a substrate provided with an optical waveguide for transmitting signal light, and provided on the optical waveguide so as to branch the signal light from the optical waveguide. A plate-shaped optical member that generates branched light,
A semiconductor light receiving element provided on the substrate and receiving the branched light; and the optical member has a planar shape having no symmetric axis on a light receiving surface.

According to the semiconductor light receiving device of the present invention, since the optical member for splitting the signal light has a planar shape having no symmetric axis on the light receiving surface, the planar shape of the light receiving surface of the optical member and the opposite side of the light receiving surface are opposite to the light receiving surface. Since the plane shapes of the surfaces are different from each other, it is easy to distinguish between the light receiving surface (front surface) and the surface opposite to the light receiving surface (back surface).

A bidirectional optical semiconductor device according to the present invention is provided with a substrate provided with an optical waveguide for transmitting signal light, and provided on the optical waveguide so as to branch the signal light from the optical waveguide.
An optical member comprising: a plate-shaped optical member that generates branched light from signal light; a semiconductor light receiving element provided on the substrate and receiving the branched light; and a semiconductor light emitting element optically connected to an end of the optical waveguide. The member has a planar shape that does not have a symmetry axis on the light receiving surface.

According to the bidirectional optical semiconductor device of the present invention, since the optical member for splitting the signal light has a planar shape having no symmetric axis on the light receiving surface, the planar shape of the light receiving surface of the optical member is opposite to the planar shape of the light receiving surface. Since the plane shapes of the side surfaces are different from each other, it is easy to distinguish between the front surface and the back surface of the optical member.

An optical multiplexer / demultiplexer according to the present invention comprises: a substrate provided with an optical waveguide for transmitting signal light; and a plate-shaped optical member provided on the optical waveguide so as to split the signal light from the optical waveguide. And the optical member has a planar shape having no axis of symmetry in the light receiving surface.

According to the optical multiplexer / demultiplexer of the present invention, since the optical member for splitting the signal light has a planar shape having no symmetric axis on the light receiving surface, the planar shape of the light receiving surface in the optical member and the opposite side of the light receiving surface. Since the plane shapes of the surfaces are different from each other,
It is easy to distinguish between the front surface and the back surface of the optical member.

In the semiconductor light receiving device, the bidirectional optical semiconductor device or the optical multiplexer / demultiplexer of the present invention, it is preferable that the light receiving surface of the optical member has a parallelogram shape.

In the semiconductor light receiving device, the bidirectional optical semiconductor device and the optical multiplexer / demultiplexer of the present invention, the light receiving surface of the optical member is
It is preferable that the inner angles have different triangular shapes.

In the semiconductor light receiving device, the bidirectional optical semiconductor device and the optical multiplexer / demultiplexer of the present invention, it is preferable that the optical waveguide is made of an optical fiber embedded in a substrate.

In the semiconductor light receiving device, the bidirectional optical semiconductor device or the optical multiplexer / demultiplexer of the present invention, the substrate is made of quartz,
PL where optical waveguide is formed on substrate by refractive index difference of quartz
It is preferable to use a C circuit.

In the semiconductor light receiving device, the bidirectional optical semiconductor device or the optical multiplexer / demultiplexer of the present invention, the substrate is made of resin,
It is preferable that the optical waveguide be formed of an optical circuit formed on the substrate by a difference in the refractive index of the resin.

[0026]

(First Embodiment) A first embodiment of the present invention.
An embodiment will be described with reference to the drawings.

FIGS. 1A and 1B show a semiconductor light receiving device according to a first embodiment of the present invention, wherein FIG. 1A shows a cross-sectional configuration of the front, and FIG. I have. FIG.
1A, for example, an optical fiber 12 serving as a signal light transmission path is buried in an upper part of a substrate 11 made of glass substantially parallel to the substrate surface. Above the optical fiber 12 on the substrate 11, a surface light receiving type PD 13 as a semiconductor light receiving element is fixed with a solder material with the light receiving surface opposed to the main surface of the substrate 11. On the upper part of the substrate 11, an optical fiber 1 is provided in a region below the PD 13 on the main surface.
2 is reflected, and the reflected signal light (branch light) 14
The optical fiber 12 at an angle at which the light
A filter 15 is inserted as an optical member that intersects.

The PD 13 receives the split light 14 of the signal light and converts the received split light 14 into an electric signal.

Here, the filter 15 will be described with reference to FIG. 2A and 2B show an optical filter according to the present embodiment, wherein FIG. 2A shows a front configuration, and FIG. 2B shows a side configuration. As shown in FIG. 2B, the filter 15 has a substrate 15a made of polyimide and having a film thickness of about 10 μm, and silicon oxide (SiO ₂ ) and titanium oxide (TiO ₂ ) are laminated on the substrate 15a. And a dielectric multilayer film 15b serving as a light receiving surface. Therefore, since the film thickness of the substrate 15a occupies almost half of the filter 15, if the front and back surfaces of the filter are different,
The reflection position of the incident signal light differs by about 10 μm, and the branched light 14 is shifted by 10 μm with respect to the light receiving portion of the PD 13 shown in FIG. Therefore, by forming the surface shape (filter shape) of the light receiving surface of the filter 15 into a parallelogram as shown in FIG. 2A, the acute angles of the inner angles of the parallelogram in the drawing are defined as the upper right and lower left. In such a case, the front side of the filter should be the front side. By doing so, it is possible to reliably identify that the acute angle of the inner angle is always the front surface when located at the upper right and is always the back surface (surface opposite to the light receiving surface) when located at the lower right. become.

Therefore, in the case of a shape that does not become line-symmetric even if any straight line is drawn in the light receiving surface, the shape rotated around the straight line does not match the original shape, and therefore, the identification marker is used. Even if it is not provided, the front surface and the back surface can be distinguished only by the filter shape. Thereby, when the filter 15 is inserted into the substrate 11 and the optical fiber 12, the displacement caused by changing the front and back surfaces of the filter 15 can be prevented, so that the coupling loss of the received light in the light receiving unit of the PD 13 can be reduced.

In addition, the step of providing a marker can be omitted, and automatic identification becomes easy. Although a conventional rectangular filter can be formed only by dicing in two directions, that is, a vertical direction and a horizontal direction, it is apparent that a filter having a parallelogram shape can also be formed only by dicing in two directions.

In the present embodiment, the side where the acute angle of the parallelogram toward the filter surface is on the upper right is the surface, but the side where the acute angle is on the lower right may be the surface.

Further, as shown in an optical filter according to a modified example of the present embodiment in FIGS. 3A and 3B, the filter shape may have a triangular shape having different internal angles. . Here, in FIGS. 3A and 3B, the same components as those shown in FIG. 2 are denoted by the same reference numerals, and description thereof is omitted. Thus, filter 1
Even if 5 has a triangular shape in which the angles of the internal angles are different from each other, since it has no in-plane symmetry axis, for example, FIG.
As shown in (2), if the surface at the time when the corner having the maximum inner angle is located at the lower right is the light receiving surface, the front and back surfaces of the filter 15 can be reliably identified.

Furthermore, in the case of a triangular shape, the area per sheet becomes small, so that the cost can be reduced. Further, since the inner angle always has an acute angle, the substrate 11 or the optical fiber
It becomes easy to insert into the very narrow slit provided in.

Alternatively, a PLC circuit using quartz for the substrate 11 and using a difference in the refractive index of quartz for the optical waveguide may be formed.
Also, an optical circuit using a substrate made of polyimide for the substrate 11 and using a difference in the refractive index of polyimide for the optical waveguide may be configured.

(Second Embodiment) Hereinafter, a second embodiment of the present invention will be described with reference to the drawings.

FIGS. 4A and 4B show a bidirectional optical semiconductor device according to a second embodiment of the present invention, wherein FIG. 4A shows a cross-sectional configuration of the front, and FIG. Is shown.
In FIG. 4, the same components as those shown in FIG. FIG.
As shown in (a), for example, the light receiving element 1 is formed below the step in the first substrate 21 made of silicon and having the step, and the light emitting element 2 is formed above the step. Are formed.

The light receiving element 1 is a light receiving device similar to that of the first embodiment, and includes an optical fiber 12 as an optical waveguide embedded on a second substrate 22 made of glass.
The surface light receiving type PD 13 fixed above the optical fiber 12 on the second substrate 22, and the signal light of the optical fiber 12 is reflected above the second substrate 22 in a region below the PD 13 on the substrate surface. A filter 15A is formed that intersects the optical fiber 12 at an angle at which the reflected branch light is emitted to the light receiving portion of the PD 13. Here, filter 1
5A is semi-transparent so as not to block the signal light emitted from the light emitting element unit 2. Further, as shown in FIG. 4B, the planar shape of the filter 15A is a parallelogram, and the front and back surfaces of the filter 15A can be easily identified.

The light emitting element section 2 is fixed to the upper part of the stepped portion of the first substrate 21 by, for example, a solder material, and is connected to the filter 15A of the optical fiber 12 with respect to the filter 15A.
A semiconductor laser element 23 is optically coupled to an end opposite to D13.

According to the present embodiment, even in a bidirectional optical semiconductor device, the filter 15A for branching the signal light of the optical fiber 12 has a filter shape that allows easy identification of the front and back surfaces. In the assembling process of the part 1, the front and back surfaces are not mistaken, and the automatic assembling is facilitated. Therefore, a displacement caused by changing the front and back surfaces when the filter 15A is inserted can be prevented, so that the coupling loss of the received light in the light receiving element unit 1 can be reduced.

It is needless to say that the surface shape of the filter 15A is not limited to a parallelogram shape as long as it does not have a symmetry axis in the filter formation surface.

Further, a PLC circuit using quartz for the second substrate 22 and using a refractive index difference of quartz for the optical waveguide may be formed. Further, an optical circuit using a substrate made of polyimide for the second substrate 22 and using a difference in the refractive index of polyimide for the optical waveguide may be configured.

(Third Embodiment) Hereinafter, a third embodiment of the present invention will be described with reference to the drawings.

FIG. 5 shows a plan configuration of an optical multiplexer / demultiplexer according to a third embodiment of the present invention. As shown in FIG.
An optical waveguide 32 using a difference in the refractive index of quartz is formed on a substrate 31 made of quartz, and a filter 15B is provided at a branch portion 32a of the optical waveguide 32 on the substrate 31 so as to cross the optical waveguide 32. Is provided.

In the case of the semiconductor device having the PD according to the first and second embodiments, the sensitivity of the signal light can be obtained as long as the signal light reaches the light receiving surface of the PD. Although the capacity is relatively large, the allowable amount in the case of a PLC or the like that couples branched light to another optical waveguide as in the present embodiment is very small. Therefore, identification of the front and back surfaces of the filter 15B has a greater effect on the coupling efficiency of the optical waveguide 32.

Even in such a case, if the surface shape of the filter 15B is a shape having no axis of symmetry in the filter forming surface, for example, a parallelogram shape or a triangular shape having different angles of the inner angles, the filter 15B is formed. It is possible to reliably prevent misalignment caused by changing the front and back surfaces when inserting into the substrate 31. As a result, the coupling loss in the branch part 32a can be reduced.

Although quartz is used for the substrate 31, polyimide may be used, and the optical waveguide 32 may be formed using the difference in the refractive index of polyimide.

[0048]

According to the semiconductor light receiving device, the bidirectional optical semiconductor device or the optical multiplexer / demultiplexer of the present invention, the planar shape of the light receiving surface (front surface) of the optical member and the surface (rear surface) opposite to the light receiving surface are different. Since the optical members are different from each other, it is easy to distinguish the front surface and the back surface of the optical member. Therefore, the front and back surfaces of the optical member do not differ during the assembly of the device, and the displacement of the branched light caused by the different front and back surfaces can be prevented. As a result, insertion loss and branch loss of signal light due to multiplexing / demultiplexing can be reduced, and desired electrical and optical characteristics in the device can be obtained.

In the semiconductor light receiving device, bidirectional optical semiconductor device or optical multiplexer / demultiplexer of the present invention, if the light receiving surface of the optical member has a parallelogram shape, the front and back surfaces of the optical member can be easily identified. In addition, similar to the conventional rectangular optical member, it can be formed by dicing in two directions, that is, the horizontal direction and the oblique direction.

In the semiconductor light receiving device, bidirectional optical semiconductor device and optical multiplexer / demultiplexer of the present invention, the light receiving surface of the optical member is
If the inner angle has a triangular shape different from each other, the front and back surfaces of the optical member can be easily identified, and the optical member can be made smaller than the conventional rectangular optical member and can be easily inserted into the substrate.

In the semiconductor light receiving device, the bidirectional optical semiconductor device and the optical multiplexer / demultiplexer of the present invention, when the optical waveguide is formed of an optical fiber embedded in a substrate, the optical waveguide can be formed easily and reliably.

In the semiconductor light receiving device, the bidirectional optical semiconductor device or the optical multiplexer / demultiplexer of the present invention, the substrate is made of quartz,
PL where optical waveguide is formed on substrate by refractive index difference of quartz
With the C circuit, the size of the device can be reduced.

In the semiconductor light receiving device, the bidirectional optical semiconductor device or the optical multiplexer / demultiplexer of the present invention, the substrate is made of resin,
If the optical waveguide is formed of an optical circuit formed on the substrate by the difference in the refractive index of the resin, the size of the device can be reduced and the cost can be reduced.

[Brief description of the drawings]

FIGS. 1A and 1B show a semiconductor light receiving device according to a first embodiment of the present invention, wherein FIG. 1A is a front sectional view and FIG. 1B is a side view.

FIGS. 2A and 2B show an optical filter of the semiconductor light receiving device according to the first embodiment of the present invention, wherein FIG. 2A is a front view and FIG.
Is a side view.

3A and 3B show an optical filter of a semiconductor light receiving device according to a modification of the first embodiment of the present invention, wherein FIG. 3A is a front view and FIG. 3B is a side view.

4A and 4B show a bidirectional optical semiconductor device according to a second embodiment of the present invention, wherein FIG. 4A is a front cross-sectional view and FIG. 4B is a side view.

FIG. 5 is a plan view showing an optical multiplexer / demultiplexer according to a third embodiment of the present invention.

FIG. 6 is a graph showing an allowable range of a positional shift of a fixed position of a photodiode with respect to a light receiving sensitivity according to a first conventional example.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 light receiving element section 2 light emitting element section 11 substrate 12 optical fiber 13 PD (semiconductor light receiving element) 14 signal light (branched light) 15 optical filter (optical member) 15A optical filter 15B optical filter 15a substrate 15b dielectric multilayer film 21 first Substrate 22 Second substrate 23 Semiconductor laser device 31 Substrate 32 Optical waveguide

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Tomoaki Uno 1006 Kazuma Kadoma, Kazuma, Osaka Matsushita Electric Industrial Co., Ltd. F-term (reference) 2H037 BA02 DA06 2H047 LA14 TA32

Claims (18)

[Claims] A substrate provided with an optical waveguide for propagating signal light; and a plate-shaped member provided on the optical waveguide so as to split the signal light from the optical waveguide and generating a split light from the signal light. A semiconductor light-receiving element provided on the substrate and receiving the branched light, wherein the optical member has a planar shape having no symmetric axis on a light-receiving surface. Light receiving device. 2. The semiconductor light receiving device according to claim 1, wherein the light receiving surface of the optical member has a parallelogram shape. 3. The semiconductor light receiving device according to claim 1, wherein the light receiving surface of the optical member has a triangular shape in which the angles of the internal angles are different from each other. 4. The semiconductor light receiving device according to claim 1, wherein said optical waveguide comprises an optical fiber embedded in said substrate. 5. The semiconductor light receiving device according to claim 1, wherein said substrate is made of quartz, and said optical waveguide is made of a PLC circuit formed on said substrate by a difference in refractive index of said quartz. 6. The semiconductor light receiving device according to claim 1, wherein the substrate is made of a resin, and the optical waveguide is made of an optical circuit formed on the substrate by a difference in the refractive index of the resin. 7. A substrate provided with an optical waveguide for propagating signal light, and a plate-shaped member provided on the optical waveguide so as to split the signal light from the optical waveguide, and generating a split light from the signal light. An optical member, comprising: a semiconductor light receiving element provided on the substrate and receiving the branched light; and a semiconductor light emitting element optically connected to an end of the optical waveguide, wherein the optical member is provided on a light receiving surface. A bidirectional optical semiconductor device having a planar shape having no axis of symmetry. 8. The optical semiconductor device according to claim 7, wherein the light receiving surface of the optical member has a parallelogram shape. 9. The bidirectional optical semiconductor device according to claim 7, wherein the light receiving surface of the optical member has a triangular shape in which the angles of the internal angles are different from each other. 10. The bidirectional optical semiconductor device according to claim 7, wherein said optical waveguide comprises an optical fiber embedded in said substrate. 11. The bidirectional optical semiconductor device according to claim 7, wherein said substrate is made of quartz, and said optical waveguide is made of a PLC circuit formed on said substrate by a difference in refractive index of said quartz. . 12. The bidirectional optical semiconductor device according to claim 7, wherein the substrate is made of a resin, and the optical waveguide is made of an optical circuit formed on the substrate by a difference in the refractive index of the resin. . 13. The optical system comprising: a substrate provided with an optical waveguide for transmitting signal light; and a plate-shaped optical member provided on the optical waveguide so as to branch the signal light from the optical waveguide. An optical multiplexing / demultiplexing device, wherein the member has a planar shape having no symmetric axis on a light receiving surface. 14. The optical multiplexer / demultiplexer according to claim 13, wherein the light receiving surface of the optical member has a parallelogram shape. 15. The optical multiplexing / demultiplexing device according to claim 13, wherein the light receiving surface of the optical member has a triangular shape in which the angles of the inner angles are different from each other. 16. The optical multiplexer / demultiplexer according to claim 13, wherein said optical waveguide is made of an optical fiber embedded in said substrate. 17. The optical multiplexer / demultiplexer according to claim 13, wherein the substrate is made of quartz, and the optical waveguide is made of a PLC circuit formed on the substrate by a difference in refractive index of the quartz. 18. The optical waveguide according to claim 13, wherein the substrate is made of a resin, and the optical waveguide is made of an optical circuit formed on the substrate by a difference in the refractive index of the resin.
3. The optical multiplexer / demultiplexer according to claim 1.