JPH10242504A - Incident light control member and optical module using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the adverse effect of stray light or scattered light, by arranging an incident light control member provided with a pinhole section or a slit section and a light transmitting hole composed of a tapered section communicated with the pinhole or slit section immediately before the light receiving and emitting point of the semiconductor element. SOLUTION: A pinhole member 1 is formed in a cylindrical body having a light transmitting hole 1c at the center. The hole 1c is formed of a pinhole section 1a and a tapered section 1b which is communicated with the pinhole section 1a and gradually becomes larger in diameter. When this pinhole member 1 is used in such a way that the member 1 is positioned immediately before, for example, the light receiving point 11a of a photodiode 11 which is provided as an optical semiconductor element for receiving light with the tapered section 1b of the pinhole member 1 on the photodiode 11 side by aligning the pinhole section 1a with the light receiving point 11a.

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 and an input / output terminal for an optical signal, and to an incident light regulating member for preventing adverse effects of stray light and scattered light, and an optical module using the same. .

[0002]

2. Description of the Related Art In recent years, various optical modules for converting optical signals and electric signals have been developed. For example, the optical module 10 shown in FIG. 6 holds an optical fiber 14 as an optical input terminal, an optical fiber 15 as an optical output terminal, and two photodiodes 11 and 12 as light receiving optical semiconductor elements in a casing 16, Beam splitter 17 inside
It has.

An optical signal 20 input from an input optical fiber 14 is partially reflected by a beam splitter 17 and received by a photodiode 11 for measurement.
The remainder passes through the beam splitter 17 and is output from the optical fiber 15 on the output side. The output side optical fiber 1
If there is a return light 21 from 5, the reflected light is reflected by the beam splitter 17 and the return light 21 is measured by the photodiode 12. That is, in the optical module 10, the original optical signal 20 is monitored by the photodiode 11, and the return light 21 due to reflection or the like can be measured by the other photodiode 12.

[0004]

However, in the optical module 10 as shown in FIG. 6, since the photodiode 12 measures minute return light 21, there is a problem that it is easily affected by stray light or scattered light. . For example, there is a disadvantage that stray light generated by the reflection of the original optical signal 20 by the photodiode 11 is input to the photodiode 12, resulting in noise and the return light 21 cannot be measured correctly.

In order to solve this problem, there is an inconvenience that the design becomes complicated, for example, it is necessary to arrange the photodiodes 11 in a tilted or shifted position.

[0006] Also in other general optical modules, similarly, there is a problem that the stray light or the scattered light enters the optical semiconductor element, thereby causing an adverse effect.

[0007]

SUMMARY OF THE INVENTION Accordingly, the present invention uses an incident light regulating member having a pinhole or a slit and a light passing hole formed of a tapered portion communicating with the pinhole or slit. An optical module is characterized by being arranged immediately before a light emitting / receiving point of a semiconductor element.

[0008]

The incident light restricting member of the present invention can prevent the passage of stray light or scattered light in the direction from the pinhole or slit to the tapered part, passing only linear light passing through the center. . On the other hand, in the direction from the tapered portion to the pinhole portion or the slit portion, stray light or scattered light can be easily passed.

Therefore, for example, if the tapered portion of the incident light regulating member is arranged just before the light emitting / receiving point of the optical semiconductor device where stray light or scattered light is to be prevented from entering, the stray light or scattering light Light can be prevented from being input, and stray light and scattered light generated by reflection on the optical semiconductor element can be easily emitted.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a pinhole member will be described with reference to the drawings as one embodiment of the incident light regulating member of the present invention.

As shown in FIG. 1, the pinhole member 1 is a cylindrical body having a light passing hole 1c at the center, and the light passing hole 1c communicates with the pinhole portion 1a and has a shape gradually expanding. It is formed from a tapered portion 1b.

When this pinhole member 1 is used,
For example, as shown in FIG. 2 (a), just before the light receiving point 11a of the photodiode 11, which is a light receiving optical semiconductor element, the tapered portion 1b of the pinhole member 1 is brought forward and the pinhole portion 1a is What is necessary is just to exactly position and arrange the point 11a.

At this time, a regular optical signal 2 which enters the light receiving point 11a of the photodiode 11 from a predetermined external direction passes through the pinhole 1a and enters the light receiving point 11a. On the other hand, stray light 2a that enters from a direction other than a predetermined direction from the outside can be prevented from passing through the pinhole portion 1a and reflected, and can be prevented from entering the photodiode 11. Also,
The stray light 2b generated by the reflection of the regular optical signal 2 by the photodiode 11 is reflected by the tapered portion 1b and finally emitted to the outside from the pinhole portion 1a.

By arranging the pinhole member 1 in this manner, only the normal optical signal 2 can be incident on the photodiode 11, preventing the stray light 2a from entering from the outside and preventing the stray light 2a from being reflected by the photodiode 11. Stray light 2
b can be easily released to the outside.

As shown in FIG. 2B, the tapered portion 1b of the pinhole member 1 is located just before the light emitting point 13a of the laser diode 13 which is a light emitting optical semiconductor element. And the pinhole 1a and the light emitting point 13
a can be accurately aligned and arranged.

At this time, the regular optical signal 2 emitted from the light emitting point 13a of the laser diode 13 is
a and can be derived to the outside. On the other hand, even if the stray light 2a such as return light attempts to enter from a direction other than the predetermined direction, the stray light 2a cannot be passed through the pinhole portion 1a, is reflected, and can be prevented from entering the laser diode 13.

By arranging the pinhole member 1 in this way, although the regular optical signal 2 is passed, the stray light 2
a is prevented from being incident on the laser diode 13,
The oscillation characteristics of the laser diode 13 can be stabilized.

In order to achieve the above operation, the inner diameter d of the pinhole portion 1a of the pinhole member 1 is important.
It is preferable that this size be in the range of 0.3 to 0.6 mm. This is because when the inner diameter d is less than 0.3 mm, the loss of the regular optical signal 2 increases, and when the inner diameter d exceeds 0.6 mm, the function of preventing the stray light 2a from entering becomes poor.

In particular, it is preferable that the inner diameter d is set to a size that allows the normal optical signal 2 to pass through, or to be slightly smaller than this. In this way, the regular optical signal 2 can be passed as it is or with a slight loss, while the stray light 2a, which is an unnecessary signal, can be largely blocked. The length L of the pinhole portion 1a may be optimal depending on the overall dimensions, the angle θ of the tapered portion 1b, and the like, but is usually preferably 0.5 mm or less.

The angle θ of the tapered portion 1b is not particularly limited, but is preferably in the range of 30 to 120 °. Further, the tapered portion 1b may be in a shape that gradually communicates with the pinhole portion 1a and gradually widens, and may have a curved surface shape or a multi-stage tapered shape. It is preferable that the outer diameter of the pinhole member 1 is set to be substantially the same as that of the optical semiconductor element so as to cover the optical semiconductor element.

Further, although not shown, it is preferable to form a small chamfer at the edge of the pinhole member 1. The surface of the pinhole member 1 is preferably a smooth surface having a center line average roughness (Ra) of 3.2 μm or less in order to enhance reflectivity.

The material of the pinhole member 1 is as follows.
Various materials such as metal, resin, ceramics and the like can be used, but it is preferable to use a metal material such as stainless steel since the reflectivity of the stray light 2a is enhanced and the stray light 2a can be welded and fixed to the casing 16 or the like. And this pinhole member 1
A light passing hole 1c composed of a pinhole portion 1a and a tapered portion 1b may be formed by drilling a hole in the hole.

Next, a slit member will be described as another embodiment of the incident light regulating member of the present invention.

The slit member 3 shown in FIGS.
Has a light passing hole 3c formed of a slit 3a and a tapered portion 3b communicating with the slit 3a. The slit member 3 is formed by the pinhole portion 1 of the pinhole member 1 described above.
a is replaced with a slit 3a, and the slit 3a can prevent stray light from entering.

The slit member 3 is less effective in preventing stray light from entering than the pinhole member 1. On the other hand, the slit member 3 forms a cut from the end surface of the slit member 3 to form a slit portion 3a and a tapered portion 3b. The manufacturing can be simplified because it is only necessary to form the semiconductor device.

As shown in FIG. 3 (c), another embodiment of the slit member 3 may be formed by joining the two members 31, 31 via spacers 32, 32 to form the slit portion 3a. By doing so, the width d of the slit portion 3a can be accurately adjusted.

In the embodiment of FIG. 3, preferred ranges such as the width d and length L of the slit portion 3a and the angle θ of the tapered portion 3b are the same as those in the embodiment of FIG.

Next, an embodiment of an optical module using the pinhole member 1 of the present invention shown in FIG. 1 will be described.

In an optical module 10 shown in FIG. 4, an optical fiber 14 as an optical input terminal, an optical fiber 15 as an optical output terminal, and two photodiodes 11 and 12 as optical semiconductor elements for receiving light are held in a casing 16. , A beam splitter 17 provided therein, and one of the photodiodes 1
The pinhole member 1 is arranged on the front surface of the second member 2.

Now, an optical signal 20 input from the input side optical fiber 14 is partially reflected by the beam splitter 17 and received by the photodiode 11 for measurement, and the remainder is transmitted through the beam splitter 17. The light is output from the optical fiber 15 on the output side. If there is return light 21 from the optical fiber 15 on the output side, the beam splitter 11
And the return light 21 is measured by the photodiode 12. That is, this optical module 10
Is designed so that the original optical signal 20 is monitored by the photodiode 11 and return light 21 due to reflection or the like can be measured by the other photodiode 12.

Since the pinhole member 1 is arranged immediately before the photodiode 12, the return light 21 to be measured enters, but other stray light can be prevented from entering the photodiode 12. . for that reason,
The minute return light 21 can be accurately measured by the photodiode 21.

Further, as another embodiment, an optical module 10 shown in FIG. 5 includes a laser diode 13 as an optical semiconductor element for light emission and an optical fiber 15 as an optical output terminal.
Is held by a casing 16, and the pinhole member 1 is arranged in front of the laser diode 13.

Now, the optical signal 20 emitted from the laser diode 13 passes through the pinhole member 1 and is led out by the optical fiber 15 to the outside. On the other hand, even if stray light due to reflection or the like returns, the stray light is blocked by the pinhole member 1, so that it can be prevented from being incident on the laser diode 13 and the oscillation characteristics of the laser diode 13 can be stabilized.

Although an optical isolator is an element having the same function, an optical isolator requires a Faraday rotator, a polarizer, a magnet, etc., and has a complicated structure and a high cost. The pinhole member 1 can have a very simple structure and a low cost.

The embodiment shown in FIGS. 4 and 5 is a schematic diagram. Each optical module 10 can be provided with a lens or other optical element.
Reference numerals 4 and 15 are held by ferrules or the like. Further, the slit member 3 shown in FIG. 3 can be used instead of the pinhole member 1, and these pinhole members 1 and slit members 3 are not limited to the examples shown in FIGS. Needless to say, it can be used.

[0036]

EXAMPLE An optical module 10 shown in FIG. 4 was manufactured as an example of the present invention.

The pinhole member 1 is made of stainless steel (SUS3
04), the outer diameter was 6 mm, the inner diameter d of the pinhole portion 1a was 0.4 mm, and the angle θ of the tapered portion 1b was 90 °.

Generally, the crosstalk characteristic C of the optical module 10 is represented by the following equation.

C = │10 · log (PD _IN / IN) / (PD _OUT / OUT) │PD _IN : Photodiode 12 for optical signal from IN
Measured value PD _OUT : Photodiode 1 for the optical signal from _OUT
Measurement value of 2 IN: Power of optical signal from IN OUT: Power of optical signal from OUT Now, the optical module 10 of the present invention in which the pinhole member 1 is disposed, and the light in which the pinhole member 1 is not disposed as a comparative example The crosstalk characteristics C described above were compared for the modules.

As shown in Table 1, the crosstalk characteristic C was as low as 21 dB in the comparative example, while the crosstalk characteristic C was as high as 39.6 dB in the example of the present invention.

[0041]

[Table 1]

Incidentally, in the optical module 10 of the present invention, the provision of the pinhole member 1 enables the normal return light 2
Part 1 will also be partially lost. Therefore, when the inner diameter d of the pinhole portion 1a of the pinhole member 1 is changed,
PD _OUT was measured to determine the amount of loss.

As shown in Table 2, the smaller the inner diameter d of the pinhole portion 1a of the pinhole member 1, the larger the loss amount, the smaller the value of PD _OUT. Is set to 0.3 mm or more. However, in order to prevent stray light, it is preferable to make the inner diameter d as small as possible within a range satisfying the above required characteristics.

[0044]

[Table 2]

[0045]

As described above, according to the present invention, the pinhole portion or the slit portion and the incident light regulating member having the light passage hole formed of the tapered portion communicating with the pinhole portion or the slit portion are used. Or, in the direction from the slit portion to the tapered portion, passing only linear light passing through the center, can prevent the passage of stray light or scattered light, while in the direction from the tapered portion to the pinhole portion or the slit portion In contrast, stray light and scattered light can be easily transmitted.

Therefore, if the tapered portion of the incident light regulating member is disposed immediately before the light emitting / receiving point of the optical semiconductor element in the optical module, stray light or scattered light can be prevented from being input to the optical semiconductor element. In addition, it becomes easy to emit stray light and scattered light generated by reflection on the optical semiconductor element. As a result, an optical module having an extremely simple structure and excellent crosstalk characteristics can be provided.

[Brief description of the drawings]

FIG. 1A is a perspective view showing a pinhole member which is an embodiment of an incident light regulating member of the present invention, and FIG. 1B is a cross-sectional view taken along line XX in FIG.

FIGS. 2A and 2B are diagrams for explaining a method of using a pinhole member.

3A is a perspective view showing a slit member which is an embodiment of the incident light regulating member of the present invention, FIG. 3B is a sectional view taken along line YY in FIG. 3A, and FIG. It is a perspective view showing an embodiment.

FIG. 4 is a schematic sectional view showing an optical module of the present invention.

FIG. 5 is a schematic sectional view showing an optical module of the present invention.

FIG. 6 is a schematic sectional view showing a conventional optical module.

[Explanation of symbols]

 1: pinhole member 1a: pinhole portion 1b: tapered portion 1c: light passing hole 2: optical signal 2a: stray light 2b: stray light 3: slit member 3a: slit portion 3b: tapered portion 3c: light passing hole 10: optical module 11: Photodiode 12: Photodiode 13: Laser diode 14: Optical fiber 15: Optical fiber 16: Casing 17: Beam splitter 20: Optical signal 21: Return light

Claims (2)

[Claims] 1. A member disposed immediately before a light emitting / receiving point of an optical semiconductor element for restricting incident light, comprising a pinhole portion or a slit portion and a light passage hole formed of a tapered portion communicating with the pinhole portion or the slit portion. An incident light regulating member, comprising: 2. An optical module having an optical semiconductor element and an input / output terminal for an optical signal, comprising a pinhole or a slit and a tapered part communicating with the pinhole or slit immediately before the light emitting / receiving point of the optical semiconductor element. An optical module in which an incident light regulating member having a passage hole is arranged.