JP2001124958A - Method for connecting optical fiber and light-receiving semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for connecting optical fiber and light-receiving semiconductor device for reducing optical transmission loss. SOLUTION: A flexible light transmission body in a tape shape or a sheet shape is clamped and connected between the optical fiber, and a light-receiving semiconductor device and light transmission body is attached to the optical fiber directly or by using a jig. It is especially effective when the core diameter of the optical fiber is smaller than the light-receiving part of the light-receiving semiconductor device. For the light transmission body, it is preferable that a refractive index lie ±0.2 of within the refractive index of the optical fiber and it is preferable that it be at least one kind selected from among a silicone resin, an acrylic resin, an epoxy resin, a thermoplastic elastomer resin and the derivative of the resins whose hardness is JIS (A-type) 50 degrees or smaller.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for optically connecting an optical fiber and a light receiving semiconductor device, and relates to a technique for reducing a loss at the time of optical communication connection.

[0002]

2. Description of the Related Art In an optical transmission system using an optical fiber, information is transmitted by receiving a signal light from the optical fiber by a light receiving semiconductor device and converting it into an electric signal. A photodiode (PD) is mainly used as a semiconductor device for reception.

[0003] The communication performance of such an optical transmission system is greatly affected by the transmission efficiency of signal light, and the transmission loss not only of the optical fiber but also of the connecting portion affects the communication performance. The current receiving method involves interposing a lens between the optical fiber and the light receiving semiconductor device. However, this structure has a problem that not only the precision connection is required, the cost is high and the versatility is poor, but also a connection loss of several dB to several tens dB is caused by reflection on the lens surface.

In order to reduce this connection loss, the present inventor has proposed a coupling structure (lensless coupling structure, particularly a light guide having a light guide path surrounded by a reflection surface) between an optical fiber and a light receiving element. Kaihei 10-221573). However, this proposal is not effective for connecting a light receiving semiconductor device and an optical fiber on the assumption that a conventional lens is used. In addition, the present inventor has proposed a connection structure (gel pad connection,
Japanese Patent Laid-Open No. Hei 10-111429) has been proposed. But,
This proposal also focuses only on the connection between optical fibers.

The inventor of the present invention has made intensive studies for practical use, and has found that even when a conventional light receiving semiconductor device is connected to an optical fiber, the optical transmission loss can be reduced by interposing a flexible light transmitting member. It is a thing. In particular, the light transmitting body is made into a tape or sheet shape that is easy to handle,
It has been found that the optical transmission efficiency can be easily increased by directly or closely contacting the optical fiber with a jig.

[0006]

SUMMARY OF THE INVENTION The present invention is a method for reducing a loss in connecting an optical fiber and a light receiving semiconductor device.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a method of connecting an optical transmission system for reducing an optical transmission loss by closely interposing a simple flexible transmitting body between an optical fiber and a light receiving semiconductor device.

A first aspect of the present invention is a connection method for an optical transmission system, wherein the light transmitting body is in the form of a tape or a sheet having adhesiveness.

A second aspect of the present invention is the method for connecting an optical transmission system according to the first aspect, wherein the light transmitting body is attached to the optical fiber side directly or by using a jig or the like.

A third aspect of the present invention is the method for connecting an optical transmission system according to the first or second aspect, wherein the core dimension of the optical fiber is smaller than the dimension of the light receiving portion of the light receiving semiconductor device.

According to a fourth aspect of the present invention, there is provided the method for connecting an optical transmission system according to any one of the first to third aspects, wherein the refractive index of the light transmitting body is within ± 0.2 of the refractive index of the optical fiber. According to a fifth aspect of the present invention, the light transmitting body is at least one selected from a silicone resin, an acrylic resin, an epoxy resin, a thermoplastic elastomer resin and a derivative of these resins having a hardness of 50 degrees or less according to JIS (A type). The connection method for an optical transmission system according to any one of claims 1 to 4, wherein the connection method is a seed.

When an optical fiber is directly connected to a light-receiving semiconductor device, if air is involved in the connection surface, light causes transmission loss due to phenomena such as reflection, scattering and refraction. For this reason, it is effective to take measures to prevent air from getting into the connection surface.

The shape of the light transmitting body which can be easily handled anytime and anywhere is a tape shape or a sheet shape. It is easy for ordinary households to wrap the tapes directly around the optical fiber or to attach them with a jig. In particular, in the case of direct attachment, the light transmitting body desirably has adhesiveness. The light transmitting body is preferably attached to the optical fiber. The reason for this is that the optical fiber is more resistant to impacts than the optical semiconductor device, and that the optical semiconductor device is often integrated with an accessory for converting to an electric signal.

The above connection structure is particularly effective when the core size of the optical fiber is smaller than the light receiving portion of the light receiving semiconductor device. In the opposite case, the signal light is transmitted to a portion other than the light receiving section, so that the loss naturally increases. However, the size (diameter) of the light receiving portion of the light receiving semiconductor device is usually 100 μm or more and 10
In many cases, the diameter is not more than 00 μm and larger than the diameter of the optical fiber (fiber diameter: several μm / quartz to several hundred μm / plastic). Optical fiber is available from quartz made by Shin-Etsu Chemical, polymethyl methacrylate resin made by Clave,
Manufacturers such as Asahi Glass can be cited as the products made of fluorine resin. In addition, as a source of the light receiving semiconductor device, Hitachi, Toshiba, Hamamatsu Photonics and the like can be mentioned.

The light transmitting body is required to be flexible, and its hardness is preferably not more than 50 degrees in JIS (A type).
It is preferably 60 degrees or less in IS (D type). If it is too hard, the adhesion at the time of connection will be insufficient and a gap will be created, resulting in a loss during optical transmission. Suitable resins include silicones, acrylics, epoxies, thermoplastic elastomers, and derivatives thereof. Commercial products can be selected from product catalogs such as Shin-Etsu Chemical Co., Toshiba Silicone, Toagosei, Nippon Kayaku, and Asahi Kasei. In addition, these manufacturers can also produce derivatives.
(JP-A-59-133220, JP-A-62-16731)
7, JP-A-3-22553, JP-A-10-17776,
JP-A-10-110102, JP-A-10-26182
1).

It is preferable that the refractive index of the light transmitting body is substantially the same as that of the optical fiber. At least, the difference in refractive index between the light transmitting body and the optical fiber is preferably within ± 0.2. If the difference is too large, light transmission loss due to reflection or the like is caused. A method for adjusting the refractive index of the light transmitting body is known (eg, POF CONFE).
RANCE '97, JP-A-11-43605).

FIG. 1 shows an example of a connection method according to the present invention. It is the figure seen from the side of the connection direction, (1) is before connection,
(2) shows the state after connection. A tape-shaped flexible optically transparent body 2 is wound around an optical fiber 1. 3 and 4 are connection connectors, and 5 is a light receiving semiconductor device. Connector shapes have been proposed by several companies (eg, PN type, SMI
And the like, and the flexible transparent body of the present invention is wound around the optical fiber side of a conventional connector for connecting a receiver.

FIG. 2 shows another example of the connection method according to the present invention. 1 is an optical fiber, 4 is a connector, and 5 is a light receiving semiconductor device. The flexible light transmitting body 2 is attached to the optical fiber by a jig 23. The jig has a shape connectable to a connector. If the optical fiber breaks, the broken part of the optical fiber can be cut to make a connection at a new part.

FIG. 3 is a diagram showing an example of a connection structure using a conventional lens. The optical fiber 1 and the light receiving semiconductor device 5 transmit light through a ball lens 30 made of quartz.

[0020]

Embodiments of the present invention will be described. The present invention
This is a method of connecting an optical fiber and a light receiving semiconductor device with a flexible light transmitting member interposed therebetween. The light transmitting body is in a tape shape or a sheet shape, and is wound around an optical fiber or attached by a jig or the like to make close contact connection with the light receiving semiconductor device. Hereinafter, specific examples will be described with reference to examples and comparative examples.

[0021]

Example 1 A 0.2 mm thick silicone tape was wound around an optical fiber made of polymethyl methacrylate (Mitsubishi Rayon) having a refractive index of 1.5 and a core diameter of 0.5 mm to form a metal-sealed PD (light receiving section having a diameter of 0.1 mm). 8 mm, Hamamatsu Photonics) as shown in FIG. The connection loss at this time was as small as 0.2 dB. In addition, the loss when connecting without interposing silicone was 2.1 dB.

The hardness of the silicone tape is JIS (A)
It was obtained by heating and curing a 20-degree addition reaction type silicone raw material (Shin-Etsu Chemical Co., Ltd.), and had a refractive index of 1.43.

[0023]

Example 2 An optical fiber was cut with a cutter knife and connected in the same manner as in Example 1, and the connection efficiency in this case was measured. The connection loss showed the same value. It is considered that the silicone adhered to the irregularities of the optical fiber and prevented loss due to interfacial reflection. Further, the loss when the connection was made without the interposition of silicone was 6.3 dB.

[0024]

Example 3 Using the same optical fiber and PD as in Example 1, they were connected as shown in FIG. 2 with an acrylic-modified epoxy resin sheet interposed. JIS (A) 5
Degree, refractive index 1.45 and thickness 0.2 mm. This connection caused a loss of 0.3 dB during optical transmission.

[0025]

Comparative Example 1 The hardness of a silicone tape was measured according to JIS (A) 5.
The experiment was performed in the same manner as in Example 2 except that the angle was set to 5 degrees. In this case, the optical transmission loss at the connection portion was 1.3 dB. That is, it is considered that a gap is formed between the optical fiber and the PD due to the rigidity of the light transmitting body, and a large transmission loss is caused during connection.

[0026]

Comparative Example 2 An optical fiber and a light-receiving semiconductor device were connected in the same manner as in Example 1 except that a JIS (A) 10-degree fluorine resin (refractive index: 1.35, 0.2 mm thick, Daikin) having a hardness of 10 degrees was used. did. In this case, no signal light was detected in the PD. It is considered that the fluorine resin reflected the signal light, and almost no signal light was transmitted to the PD.

[0027]

Comparative Example 3 Connection method using a conventional lens (FIG. 3)
, The connection efficiency was measured using the same optical fiber and PD as in Example 1. The connection loss was 1.1 dB.

When the optical fiber and the light receiving semiconductor device are connected by using the simple light transmitting body of the present invention, the optical transmission loss at the time of optical communication becomes extremely small. The connection of the present invention is easy,
It can be easily done by ordinary family members. That is, the present invention greatly contributes to increasing the versatility of the optical communication system.

[Brief description of the drawings]

FIG. 1 is a diagram showing one example of a connection method according to the present invention.

FIG. 2 is a diagram showing one example of a connection method according to the present invention.

FIG. 3 is a diagram showing one example of a conventional connection structure.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 optical fiber 2 light transmitting body 3, 4 connector 5 light receiving semiconductor device 23 jig 30 ball lens

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference)

Claims (5)

[Claims] 1. A method of optically connecting a flexible light transmitting body between an optical fiber and a light receiving semiconductor device, wherein the light transmitting body is tape-shaped or sheet-shaped. How to connect the system. 2. The connection method for an optical transmission system according to claim 1, wherein the light transmitting body is attached to the optical fiber side directly or by using a jig or the like. 3. The connection method for an optical transmission system according to claim 1, wherein a core size of the optical fiber is smaller than a light receiving portion of the light receiving semiconductor device. 4. The method according to claim 1, wherein the refractive index of the light transmitting body is equal to the refractive index of the optical fiber.
4. The connection method for an optical transmission system according to claim 1, wherein the value is within 0.2. 5. The light transmitting body according to claim 1, wherein the light transmitting body is at least one selected from silicone resins, acryl resins, epoxy resins, thermoplastic elastomer resins, and derivatives of these resins having a JIS (A type) hardness of 50 degrees or less. The connection method for an optical transmission system according to claim 1, wherein the connection method is a seed.