JPH0721567B2 - Optical distribution circuit and manufacturing method thereof - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to an optical distribution circuit for distributing an optical beam propagating through an optical fiber to a plurality of optical fibers and a method for manufacturing the same.

[Background of the Invention]

Along with the rapid progress of optical fiber transmission technology, research and development of optical data links using optical fibers for data transmission between computers and computers and between computers and terminals have been actively conducted. In configuring this optical data link,
An optical star coupler capable of mixing optical signals from a plurality of input optical fibers and evenly distributing them to a plurality of output optical fibers with low loss is an essential device.

Conventionally, there is a biconical taper type shown in FIG. 7 as a typical example of an optical star coupler (published by Hisayoshi Yanai, “Optical Communication Handbook”, Asakura Shoten, September 1, 1982, first edition, first edition 324).
~ Page 325). This is because a large number of optical fibers 1 are put together at one place, twisted while being heated and fused, and a tapered region 5 is formed in the central portion of the optical fiber 1 for input (the tapered region 5 The optical signal from the left side) is distributed to a plurality of output optical fibers (right side of the tapered region 5). In addition, in FIG. 7, the arrow indicates the traveling direction of the optical signal. As a heating source for this optical fiber,
An oxyhydrogen burner and an electric furnace are used. However, since the method using the oxyhydrogen burner can raise and lower the temperature very easily, the work can be completed in a short time. However, the twisting / fusion / extension part 5 can be changed due to the wind pressure of the burner, flame temperature, disturbance, etc. The shape is easily deformed. That is, it is almost impossible to control the shape of the twisting / fusing / stretching portion 5, the yield is extremely low, and there are problems in reproducibility and mass productivity. The method using an electric furnace can suppress the above disturbance, but since the temperature rise and fall is very slow, there is a problem in that the optical fiber undergoes an extra change during the temperature rise and fall. As described above, it is difficult to produce good optical characteristics with good yield by the conventional method. Further, since the yield is very bad, it is difficult to reduce the cost.

[Object of the Invention]

An object of the present invention is to solve the above problems and to provide an optical distribution circuit that is stable against mechanical vibration and shock, and a method for manufacturing the same.

[Outline of Invention]

The gist of the present invention is that a twist portion or a twist / fusion portion (hereinafter referred to as a twist portion) is provided on both sides of the above-mentioned twist / fusion / extension portion.
And that the twisting / fusion / extending part and the twisting part are housed in a container having an open top surface.

〔Example〕

FIG. 1 shows an example of a conventional optical distribution circuit. It has two input port fibers and two output port fibers.
This is an example of a × 2 port type optical distribution circuit. Quartz glass tube 8
Has a twisting / fusion / stretching portion 7 and twisting portions 6a and 6b, and a resin 100 is provided between the quartz glass tube 8 and the optical fiber.
Is filled. Adhesive 9 is sealed at both ends of the quartz glass tube 8 and the quartz glass tube 8 and the optical fibers 1a and 1b
Is fixed. The input / output port fibers 1a and 1b are optical fibers with a coating material 4 (for example, silicone or silicone and nylon). 130 is a glass fiber from which the coating material 4 has been peeled off. 110a and 110b are holes for filling the quartz glass tube 8 with the resin 100. By filling with this resin 100, it is possible to prevent the fluctuation of the optical characteristics (the fluctuation of the optical output) and the breakage of the optical fiber against mechanical vibration and shock. It is preferable that the resin 100 has a small heat shrinkage upon curing, is easily cured at a low temperature, and has an elastic property to have a buffering effect. Since it comes into contact with the outer peripheral surface of the glass fiber, it must be made of a material having a high transmittance. Preferred materials include rubber materials such as silicone rubber (eg, KE103RTV and KE106LTV manufactured by Shin-Etsu Chemical), fluorine-based rubber, jelly-like materials (eg, polybutene, soft polybutene, metallic quartz grease), and UV curable resin such as Urethane acrylate, epoxy acrylate, etc.), a visible light curable optical adhesive (for example, a methacrylate ester-based adhesive), and the like. The adhesive 9 may be of any type such as thermoplastic, thermosetting, elastomer, and mixed type.

However, in the case of this conventional optical distribution circuit, extra steps such as vacuum defoaming are required to fill the resin 100 into the hollow glass tube without generating bubbles, and the resin should be injected with extreme caution. Since the outer diameter of the coated optical fiber is 0.3 mm or more, the outer diameter of the optical fiber bundle becomes thicker (several mm or more) when the number of optical fibers exceeds several tens, and the inner diameter of the hollow glass tube also exceeds the above. There is a drawback that the optical fiber bundle has to be thick in order to facilitate insertion.

FIG. 2 shows an embodiment of the optical distribution circuit of the present invention which solves these conventional drawbacks. This is a structure in which a twisting / fusion / stretching portion 7 and twisting portions 6a and 6b are arranged in a half-divided quartz glass tube 120 and covered with a resin 100. (The same reference numerals as those in FIG. 1 are the same articles, and therefore detailed description thereof is omitted.) FIG. 3 shows another embodiment of the optical distribution circuit of the present invention. This is a structure in which a reinforcing material 130 (for example, a resin, an adhesive, a metal material, etc.) is provided on a half-divided quartz glass tube 120 filled with the resin 100 in FIG. In FIGS. 2 and 3, a U-shaped glass container or a mere plate glass may be used in place of the half-divided quartz glass tube 120, and the open state is shown on the upper surface of the container, as shown in FIG. The disadvantages of using the conventional hollow glass tube 8 described above are solved, the optical fiber bundle can be inserted into the container, and the resin and the adhesive can be easily filled.

Further, as an improvement of the present invention, as shown in FIG. 4, the I / O port fiber bundle may have a structure in which both ends are fixed in advance with an adhesive or a covering material 140 and covered with a resin 100.

That is, after forming a twisted portion, a twisted portion, a fused portion, and a stretched portion by the method shown in FIG. 5, which will be described later, a sheet of a material (for example, a fluororesin sheet) to which the resin 100 does not adhere is formed on the inner surface of the half glass tube 120. By covering the twist portion and the twist / fusion / extension portion with the resin 100, the optical distribution circuit of FIG. 4 can be realized. Since the configuration of FIG. 4 is covered with the soft resin 100, the light distribution circuit itself can be bent, which is an advantageous configuration when it is arranged in a narrow space. Note that another resin for reinforcement may be further applied on the resin 100.

FIG. 5 is a diagram showing an embodiment of a method of manufacturing an optical distribution circuit of the present invention. The half-divided quartz glass tube 120 is supported by supports 23a and 23b, and an optical fiber bundle is arranged in the half-divided quartz glass tube 120. Then, the halved quartz glass tube 120 is heated by the oxyhydrogen burner 15 to indirectly heat the optical fiber bundle. In the twisting / fusion / stretching process, the light source 19 (for example, He
-Ne laser light source) is made incident to irradiate the far field patterns 20a and 20b of the output port fiber onto the screen 21, and the far field pattern light quantity is observed. 11a and 11b are chucks for fixing the optical fiber bundle, 12 is a rotating mechanism for rotating the chuck 11b in the direction of arrow 14 (direction of rotating about the axes of the optical fibers 1a and 1b), and 13 is the chuck 11b and the chuck. A chuck moving mechanism that supports a rotating mechanism (12) and moves on a base (10) in the axial direction of the optical fiber (direction of arrow 16). First, the optical fiber bundle is fixed to the chucks 11a and 11b, the chuck rotating mechanism 12 is driven to rotate in the direction of arrow 14, and the optical fiber bundle is twisted several times. Then oxyhydrogen burner
The halved glass tube 120 is heated at 15 to soften the optical fiber bundle. At the same time, the chuck moving mechanism 13 is driven to move in the direction of arrow 16. While moving, the chuck rotating mechanism may be driven in the direction of arrow 14 as required. Then, when the light quantity of the far field pattern becomes equal (detected by a photodiode, optical power meter, etc.), the movement in the direction of arrow 16 is stopped and the oxyhydrogen burner is extinguished. Next, put an adhesive on both ends of the half glass tube 120,
The half glass tube 120 and the optical fiber bundle are fixed. After that, resin is filled in the half-divided glass tube 120 to complete the light distribution circuit having the configuration of FIG. It is easy to fill the adhesive and the resin, and bubbles are hardly mixed in the adhesive and the resin. Further, since the optical distribution circuit of the present invention twists the optical fiber bundle in advance to bring the outer diameter of the optical fiber bundle close to a circular shape and then heats it to perform twisting, fusing, and stretching, the twisting, fusing, and stretching portion is performed. The core shape of the optical fiber of
Since the shape is almost similar to the core shape of the optical fiber before heating, there is a characteristic that the coupling characteristics do not easily change depending on the incident mode. In particular, when an optical distribution circuit for a single mode fiber is constructed, the outgoing polarization characteristic of the output port fiber becomes a configuration in which the incident polarization characteristic can be easily stored. Further, since the method of manufacturing the optical distribution circuit of the present invention is an indirect heating method, the shape of the twist, fusion, and extension does not change due to the wind pressure of the oxyhydrogen burner, flame, disturbance, or the like. Therefore, the above-mentioned shape can be precisely controlled, so that the distribution variation and the insertion loss can be suppressed to be extremely small. Insertion loss L of the optical distribution circuit of the present invention
Can be approximated by L≈10 log ₁₀ n (dB), where n is the number of ports. The distribution variation also depends on the stretch length, and by controlling it in cm order,
It could be up to 0dB. Then, changes in optical characteristics due to mechanical vibration and impact tests were examined. First, the vibration
10 to 55Hz, all amplitude 1.5 mm, with respect to two directions each 4 hours, the insertion loss variation width L _D = 0.04 dB, the distribution variation fluctuation width [Delta] L _D <0.1d
It was B. Impact is L _D <0.2d for 10 times each in 100G2 direction
B, ΔL _D <0.15 dB. The temperature cycle is -20 ℃
~ + 80 ° C., to 10 _{cycles, L D <0.4dB, ΔL D} <0.3dB
Therefore, it was possible to make a great improvement compared to before the resin was filled.
The increase in the insertion loss L due to the filling of silicone (KE103RTV) as the resin was 0.2 dB or less.

The present invention is not limited to the above embodiment. For example, container 12
In addition to quartz glass, 0 may be quartz glass containing a refractive index controlling dopant. The optical fiber may be a multi-component glass fiber, but in that case, the container 120 may be made of multi-component glass. The base 10 shown in FIG. 5 may be arranged obliquely or vertically, instead of horizontally. The number n of input / output ports may be 2 to 100 or more. A heat source may be used to cure the adhesive and the resin. Further, the present invention can be applied not only to the even distribution type but also to branch circuits having different distribution ratios, for example, 2 × 2 port type branch circuits having different distribution ratios such as 0.8: 0.2 and 0.9: 0.1. . This can be achieved by controlling the stretch length. FIG. 6 shows an example of the experimental results. This is an experimental result of the 2 × 2 port type optical distribution circuit, and it is well shown that the distribution ratio can be changed by the extension length. The optical fiber is GI type, the core diameter is 50 μm, the outer diameter is 125 μm, and Δn is 1%. In addition to the oxyhydrogen burner, an electric furnace, high-frequency heating furnace, etc. can be used as the heating source.

〔The invention's effect〕

As described above, according to the present invention, it is possible to obtain an optical distribution circuit in which variations in optical output are small and which is stable against mechanical vibration and impact. It also has good characteristics against temperature fluctuations. Furthermore, even if the number of ports n becomes very large, it can be easily made in an integrated process, and a significant cost reduction is possible.

[Brief description of drawings]

1 is an example of a conventional optical distribution circuit, FIGS. 2 to 4 are embodiments of the optical distribution circuit of the present invention, and FIG. 5 is an embodiment of a method of manufacturing the optical distribution circuit of the present invention, and FIG. FIG. 7 shows an example of an experimental result of the light distribution circuit of the present invention, and FIG. 7 shows a conventional light distribution circuit. 1,1a, 1b ... optical fiber, 6a, 6b ... twisted part, 7 ... twisted / fused / stretched part, 8 ... hollow glass tube, 9 ... adhesive, 11a-11f ... chuck, 12 ...... Chuck rotation mechanism,
13 ... Chuck moving mechanism, 15 ... Heating source, 100 ... Resin, 120 ... Half glass tube, 110a, 110b ... Resin injection hole, 130 ... Reinforcing agent, 20a, 20b ... Far field pattern, 21 …… Screen, 19 …… Light source.

Claims (4)

[Claims] 1. A light distribution circuit having a twist, fusion, and extension at the center of a fiber bundle and twists on both sides of the twist, fusion, extension, and twist. The optical distribution circuit is characterized in that it is housed in a sealed container and is covered with a resin. 2. A light distribution circuit according to claim 1, wherein a half-divided quartz glass tube, a U-shaped glass container, or a plate glass is used as the container having an open upper surface. 3. A step of forming a twist portion in the optical fiber bundle, and a step of twisting, fusing, and welding the optical fiber bundle using a heating source.
A method of manufacturing a light distribution circuit, which comprises a step of forming a stretched portion and a step of placing the twisted portion and the twisted / fused / stretched portion in a container having an open upper surface and covering with a resin. 4. The process according to claim 3, wherein the step of forming the twisting / fusing / stretching portion is performed by placing a fiber bundle in a container whose upper surface is open, and indirectly connecting the fiber bundle from the lower surface of the container. The above-mentioned twist, fusion, and
A method for manufacturing an optical distribution circuit, which comprises forming a stretched portion.