JP2002258113A - Optical receiving module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an optical receiving module for which a light receiving element with a small light receiving diameter can be employed. SOLUTION: The light emitted from the end face 5a of an optical waveguide 5 is reflected by the reflection area 9 of a recess 8. Then, the reflected light from the reflection area 9 is received by the light receiving face 7 of a PD 6. A light path length from the end face 5a to the light receiving face 7 is shorter than a conventional length, thus the PD 6 with a small light receiving diameter can be employed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical receiving module, and more particularly to an optical receiving module configured to receive light reflected by a slope of a concave portion formed in a substrate.

[0002]

2. Description of the Related Art In a light receiving module, a configuration in which an optical fiber end face is directly optically coupled to a photodiode (PD) and a configuration in which optical coupling is performed via a reflection mirror (reflection surface) have already been introduced. FIG. 5 is a side sectional view showing a light receiving structure of a conventional optical receiving module.

[0005] In FIG. 5, a conventional optical receiving module includes a PD 100, an optical fiber 102, and an optical fiber 1.
02 on which a V-shaped groove 103 for mounting the silicon 02 (S
i) a substrate. The V-shaped groove 103 is
The depth of the V-shaped groove 103 is used as the reflection surface 104. The reflecting surface 104
The light emitted from the optical fiber 102 is reflected, and the reflected light is reflected on the light receiving surface 101 of the PD 100 mounted on the Si substrate.
It is designed to receive light.

Next, an optical receiving module disclosed in Japanese Patent Application Laid-Open No. 4-208905 will be described with reference to FIGS. FIG. 6 is a side sectional view showing the light receiving structure of the first and second optical receiving modules described in the above publication, and FIG. 6 (a) is a side sectional view showing the light receiving structure of the first optical receiving module.
(B) is a side sectional view showing a light receiving structure of the second optical receiving module.

In FIGS. 6A and 6B, light receiving structures 105a and 105b are provided opposite to an optical waveguide 107 formed on a substrate 106 and an end face 107a of the optical waveguide 107 and have a very small size. Reflective member 10 formed in
9a and 109b and surface light receiving PDs 110a and 110b, respectively.

The reflecting members 109a and 109b have reflecting surfaces 111a and 111b facing the end face 107a of the optical waveguide 107 and reflecting signal light, respectively. The reflection surface 111a gradually moves toward the end face 10 as it goes upward.
It is formed to be inclined in a direction away from 7a. The reflecting surface 111b gradually moves toward the end face 10 as it goes downward.
It is formed to be inclined in a direction away from 7a.

The PD 110a is provided above the reflecting member 109a with the light receiving surface 112a for receiving signal light facing the substrate 106 and the reflecting surface 111a. PD1
10b, the light receiving surface 112b for receiving the signal light is the reflecting surface 1
It is provided buried in the substrate 106 in a state opposite to 11b. With the light receiving structure 105a having such a configuration,
105b reflects the signal light emitted from the end face 107a by the reflecting surfaces 111a and 111b of the reflecting members 109a and 109b, and the light receiving surface 11 of the PDs 110a and 110b.
The light is received by 2a and 112b.

FIG. 7 is a view for explaining a third optical receiving module described in the above publication, and FIG.
FIG. 25B is a perspective view showing a third optical receiving module. In FIG. 7A, the reflecting member 125 used in the third optical receiving module is the Si substrate 1
20 and an oxide film 121 mounted on the surface of the Si substrate 120, and a concave portion 124 is formed. The three side surfaces 122 and 123 of the recess 124 are used as reflection surfaces.

In FIG. 7B, the third optical receiving module described in the above publication includes a reflecting member 125, a Si substrate 126, and an optical waveguide 12 formed on the Si substrate 126.
7 and a surface light receiving type PD 128 buried in the substrate 126 with the light receiving surface facing upward. That is, the reflection member 125 is mounted on the substrate 126 on which the PD 128 and the optical waveguide 127 are formed, with the concave portion 124 facing down.

In the third optical receiving module having such a configuration, the signal light emitted from the end face of the optical waveguide 127 is
The light is reflected by the three reflecting surfaces 122 and 123 of the concave portion 124, and the reflected light is received by the light receiving surface of the PD 128. Further, since the reflection member 125 also has a light collecting function, highly efficient optical coupling can be performed.

On the other hand, in the optical transmission module, when a surface light receiving type photodiode (PD) for monitoring the light output from behind the light emitting element is arranged in the optical transmission module, the PD is vertically arranged so that the light receiving surface is directed sideways. Conventionally, the PD is mounted on a carrier different from the substrate on which the light emitting element is provided, and then the PD is mounted on the substrate on which the light emitting element is provided.

[0012]

However, in the conventional optical receiving module shown in FIG. 5, since the optical path length from the end face of the optical fiber 102 to the light receiving surface 101 of the PD 100 is long, the light incident on the light receiving surface 101 is long. Since the beam diameter becomes large, there is a problem that it is difficult to optically couple with a PD having a small light receiving diameter. Here, the optical fiber 102 and P
In order to reduce the distance from D100, it is necessary to bring the optical fiber 102 closer to the reflection surface 104. However, if the end face of the optical fiber 102 comes into contact with the reflection surface 104, the distance cannot be further increased.

In addition, in the first and second optical receiving modules shown in FIG. 6, apart from the substrate 106, minute reflecting members 109a and 109b serving as components of the reflecting surface must be formed. Further, the first type shown in FIG.
In the optical receiving module of FIG.
9a is supported in a cantilevered state, so there are problems in wiring method and strength, and when light from the end face 107a of the optical waveguide 107 reaches the reflection surface 111a, the upper half of the light beam is reflected by the reflection surface 111a. However, the lower half of the light beam varies in reflection efficiency depending on the state of the bonding surface between the substrate 106 and the reflection member 109a.
In the second optical receiving module shown in FIG. 6B, since the lower surface of the reflecting member 109b is smaller than the upper surface, it is difficult to position the reflecting member 109b and the like.

In the third optical receiving module shown in FIG. 7, the reflecting member 125 must be formed separately from the substrate 126, as in the first and second optical receiving modules. Further, since the reflecting member 125 collects the reflected light from the three reflecting surfaces 122 and 123 of the concave portion 124, the beam diameter of the reflected light becomes large, and the light receiving diameter of the PD 128 must be increased to 70 μmφ. No.

On the other hand, in the conventional optical transmission module, there is a problem that not all of the optical systems of this module can be formed on the same substrate.

An object of the present invention is to provide an optical receiving module that can use a light receiving element having a small light receiving diameter.

Another object of the present invention is to provide an optical transmission module in which all of the optical systems of the module can be configured on the same substrate.

[0018]

An optical receiving module according to the present invention has an optical waveguide formed therein, and a concave portion having a surface including an end surface of the optical waveguide and a slope reflecting light output from the end surface. And a light receiving element provided on the substrate to receive light reflected from the slope.

The operation of the present invention is as follows. Light emitted from the end face of the optical waveguide is reflected by the slope of the concave portion.
Then, light reflected from the slope of the recess is received by the light receiving element. The optical path length from the end face of the optical waveguide to the light receiving element is shorter than that of the related art, so that a light receiving element having a small light receiving diameter can be used.

On the other hand, the optical transmission module according to the present invention comprises:
A substrate, a light emitting element provided on the substrate, and a light transmitting module including a light receiving element for monitoring the light output, wherein the substrate is formed with a recess having a slope that reflects the light output. The light receiving element is provided on the substrate so as to receive light reflected from the slope.

Further, in the optical transmission module, the light receiving element is a surface light receiving type light receiving element, and a width of the concave portion is smaller than a width of the light receiving element.

The operation of the present invention is as follows. Light emitted from the light emitting element enters the concave portion and is reflected by the slope of the concave portion. Then, light reflected from the slope of the recess is received by the light receiving element. Therefore, the light receiving element can be provided on the substrate with the light receiving surface of the light receiving element facing down.

[0023]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view showing an optical receiving module according to an embodiment of the present invention. FIG. 2 shows FIG.
2 is a cross-sectional view taken along line AA of FIG. 1 and 2, an optical receiving module according to the present embodiment includes a silicon (Si) substrate 1;
It has an optical fiber 2 and a surface light receiving type photodiode (PD) 6 as a light receiving element.

A V-groove 3 for mounting an optical fiber 2 is formed in the Si substrate 1. The width of the V-groove 3 is set such that the entire optical fiber 2 does not enter the V-groove 3 but the core 2 a of the optical fiber 2 enters the V-groove 3. Further, the optical fiber 2 is provided on the Si substrate 1 by Si.
A rectangular groove 4 is formed to prevent the adhesive fixed to the substrate 1 from covering the end face of the optical fiber 2.
The depth of the rectangular groove 4 is greater than the depth of the V groove 3.

Further, an optical waveguide 5 is formed on the surface of the Si substrate 1. That is, the position of the core 2a and the position of the optical waveguide 5 are matched so that the optical fiber 2 mounted in the V-groove 3 is efficiently optically coupled to the optical waveguide 5,
Mounted in the V-groove 3.

Further, a recess 8 having a minute size is formed in the Si substrate 1. One surface of the concave portion 8 is a surface including the end surface 5a of the optical waveguide 5, and a reflecting surface 9 as another surface of the concave portion 8 facing the surface including the end surface 5a gradually increases upward. It is formed to be inclined in a direction away from the end face 5a, and a reflective film is formed on the surface thereof.

The concave portion 8 is formed deeper than the position of the end surface 5a, and the bottom of the surface including the end surface 5a and the bottom of the reflection surface 9 are the same, and this base is located below the position of the end surface 5a. I have. The PD 6 is provided on the Si substrate 1 such that the light receiving surface 7 faces downward so that the light receiving surface 7 faces the reflection surface 9, that is, optically couples via the reflection surface 9.

Next, the operation of the optical receiving module according to this embodiment will be described. 1 and 2, light emitted from an optical fiber 2 passes through an optical waveguide 5 and an end face 5 thereof.
a is emitted toward the reflection surface 9 of the recess 8. Light emitted from the end face 5 a of the optical waveguide 5 is reflected by the reflection surface 9. The light reflected from the reflecting surface 9 is reflected on the light receiving surface 7 of the PD 6.
And is received.

As described above, in the optical receiving module according to the present embodiment, since the optical waveguide 5 and the reflecting surface 9 of the minute concave portion 8 are used, the end surface 5a of the optical waveguide 5 and the light receiving surface 7 of the PD 6 are not used. , That is, the optical path length from the end face 5a to the light receiving surface 7 can be shortened as compared with the related art. As described above, since the optical coupling interval can be reduced, the diameter of the light beam incident on the light receiving surface 7 can be set to 20 μmφ or less, which is almost the same as the core diameter of the optical fiber 2. 30 for PD6 used for module
A light receiving diameter of about μmφ can be used.

In the optical receiving module according to the present embodiment, the reflection surface 9 of the concave portion 8 is formed from a position below the end surface 5a of the optical waveguide 5, so that the conventional technology shown in FIG. In comparison, variations in reflection efficiency can be suppressed.

It should be noted that the embodiment of the present invention is not limited to the configuration shown in FIGS. 1 and 2, and it is apparent that the present embodiment can be appropriately modified within the scope of the technical idea of the present invention.

Next, another embodiment of the present invention will be described with reference to the drawings. FIG. 3 is a perspective view showing an optical transmission module according to an embodiment of the present invention, and the same parts as those in FIGS. FIG. 4 is a cross-sectional view along the line BB in FIG. 3, and the same parts as those in FIG.

3 and 4, an optical transmission module according to the present embodiment includes a silicon (Si) substrate 10, an optical fiber 2, an edge emitting laser diode (LD) 11 as a light emitting element, and a rear side of the LD 11. And a surface light receiving type photodiode (PD) 6 which is a light receiving element for monitoring the light output of the light emitting device. The optical fiber 2, the LD 11, and the PD 6 are provided on the same Si substrate 10.

A V-groove 3 for mounting the optical fiber 2 is formed in the Si substrate 10. The width of the V-groove 3 is set such that the entire optical fiber 2 does not enter the V-groove 3 but the core 2 a of the optical fiber 2 enters the V-groove 3. Further, a rectangular groove 4 is formed in the Si substrate 10 so that the adhesive for fixing the optical fiber 2 to the Si substrate 1 does not cover the end surface of the optical fiber 2. The depth of the rectangular groove 4 is greater than the depth of the V groove 3.

Further, the optical waveguide 5 is formed on the surface of the Si substrate 10. That is, the optical fiber 2 mounted on the V-groove 3 is mounted on the V-groove 3 with the position of the core 2a and the optical waveguide 5 matched so that the optical fiber 5 is efficiently optically coupled.

Further, the Si substrate 10 has a step on the end face 5a side of the optical waveguide 5, and the LD 11 is provided on the substrate surface below the substrate surface on which the optical waveguide 5 is formed. That is, the LD 11 is provided on the Si substrate 10 so as to be in position with the optical waveguide 5 so that the LD 11 is efficiently optically coupled to the optical waveguide 5.

Further, the recess 12 is formed in the Si substrate 10.
Are formed. The reflecting surface 13, which is the surface of the concave portion 12 facing the surface on the LD11 side, is formed so as to be gradually inclined upward and away from the surface on the LD11 side, and a reflective film is formed on the surface thereof. .

The PD 6 is provided on the Si substrate 1 with the light receiving surface 7 facing downward so that the light receiving surface 7 faces the reflection surface 13, that is, optically coupled via the reflection surface 13. I have. Here, as shown in FIG.
Since it is smaller than the width of D6, it is not necessary to support PD6 in a cantilevered state.

Next, the operation of the optical transmission module according to another embodiment of the present invention will be described. 3 and 4, light emitted from the front of the LD 11 is L
Light emitted from D11 to the end face 5a of the optical waveguide 5 is sent to the optical fiber 2 through the optical waveguide 5 and output. On the other hand, the light emitted from behind the LD 11 is L
The light emitted from D11 to the PD6 side is emitted with its beam spread, and the lower half of the light beam enters the concave portion 12. The light that has entered the concave portion 12 is reflected by the reflection surface 13, and the reflected light is received by the light receiving surface 7 of the PD 6.

As described above, in the optical transmission module according to another embodiment of the present invention, the Si substrate 10 behind the LD 11
In addition, since the concave portion 12 having the reflecting surface 13 for reflecting the optical output of the LD 11 is formed, the PD 6 can be provided on the Si substrate 10 with the light receiving surface 7 facing downward. All the optical systems can be configured on the same substrate 10.

It is apparent that other embodiments of the present invention are not limited to the configurations shown in FIGS. 3 and 4, and can be appropriately modified within the scope of the technical idea of the present invention.

[0042]

The effect of the present invention is that a light receiving element having a small light receiving diameter can be used. The reason is that the optical waveguide formed on the substrate and the reflecting surface of the concave portion can realize an optical path length shorter than the conventional optical path length from the end face of the optical fiber to the light receiving surface of the light receiving element. This is because the diameter of the incident light beam can be prevented from increasing.

Another advantage of the present invention is that all of the optical systems of the optical transmission module can be configured on the same substrate. The reason is that, since the concave portion having the reflecting surface for reflecting the light output of the light emitting element is formed on the substrate, the light receiving element can be provided on the substrate with the light receiving surface facing down.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an optical receiving module according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a perspective view showing an optical transmission module according to the embodiment of the present invention.

FIG. 4 is a sectional view taken along line BB of FIG. 3;

FIG. 5 is a side sectional view showing a light receiving structure of a conventional optical receiving module.

FIG. 6 is a side sectional view showing a light receiving structure of first and second optical receiving modules described in Japanese Patent Application Laid-Open No. 4-208905, and FIG. 6A is a side showing a light receiving structure of the first optical receiving module. FIG. 4B is a cross-sectional view illustrating a light receiving structure of the second optical receiving module.

FIGS. 7A and 7B are diagrams for explaining a third optical receiving module described in Japanese Patent Application Laid-Open No. 4-208905, wherein FIG. 7A is a perspective view showing a reflecting member 125, and FIG. It is a perspective view which shows a module.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1,10 Substrate 2 Optical fiber 2a Core 3 V groove 4 Rectangular groove 5 Optical waveguide 5a End surface 6 PD 7 Light receiving surface 8,12 Depression 9,13 Reflection surface 11 LD

Claims (5)

[The claims] A substrate having an optical waveguide formed therein and a concave portion having a surface including an end surface of the optical waveguide and a slope reflecting light output from the end surface; A light receiving element provided on the substrate to receive light. 2. The optical receiving module according to claim 1, wherein the recess is formed so that its depth is lower than the position of the end face. 3. The optical receiving module according to claim 1, wherein the bottom of the surface including the end face and the bottom of the slope are the same bottom. 4. The optical receiving module according to claim 3, wherein the bottom side is located below a position of the end face. 5. The optical receiving module according to claim 1, wherein said light receiving element is provided on said substrate such that a light receiving surface thereof is opposed to said slope.