JPH06324229A - Production of optical fiber coupler - Google Patents

Abstract

PURPOSE:To suppress the fluctuation of branching ratios and the characteristics of excess loss and to suppress the fluctuation in characteristics after thermal impact test by adhering the front and rear of an optical coupling part to protective members by an adhesive having a prescribed viscosity. CONSTITUTION:Screw rods and guide rods are removed from the chassis of the device while the fused and stretched fibers of optical fibers 1, 2 are held butted in clamps. The fused and stretched fibers are held between two sheets of the protective members 17 which are quartz plate. The front and rear of the optical coupling part 11 are then adhered by the adhesive 16 of an epoxy resin of a UV curing type (one pack type or two pack type). The fused and stretched fibers of two pieces of the optical fibers 1, 2 are adhered and fixed by using the adhesive 16 having 1000 to 50000cps viscosity at 20 deg.C. The clamps are removed and the clamps, screw rods, guide rods, etc., which are tentative jigs are removed. Further, the fused and stretched fibers of the optical fibers 1, 2 are housed into a protective case 14. The protective members 17 and the protective case 14 are adhered and fixed to each other by the adhesive 20. Both ends of the protect case 14 are solidified and hermetically sealed by the adhesive 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an optical fiber coupler used for optical communication and optical sensors.

[0002]

2. Description of the Related Art In an optical fiber communication system, an optical fiber coupler is used as an important component for branching, coupling, demultiplexing, and multiplexing light. In particular, an optical fiber coupler obtained by processing an optical fiber has excellent coupling properties with the optical fiber and has a low loss of passing light, and is therefore used in many fields.

In an optical fiber coupler, a plurality of single-mode optical fibers are bundled, and a part of them is fused and stretched to form an optical coupling portion. Light incident on one of the plurality of optical fibers is It branches to another optical fiber at a constant branching ratio.

FIG. 2 is a diagram showing an essential part of a method for manufacturing an optical fiber coupler. In the optical fibers 1 and 2, the protective coating material 3 is previously removed from the portions to be fused, and the optical fibers 1 and 2 are fixed in contact with each other by the clamps 4 and 5, respectively. The clamps 4 and 5 include a screw rod 22 and a guide rod 23.
And a pulling mechanism composed of a drive motor M. The contact portions of the optical fibers 1 and 2 are heated by the oxyhydrogen flame 6 to fuse the two optical fibers 1 and 2. When the drive motor M is rotated here, the clamps 4 and 5 move in the direction of the arrow, and the optical fibers 1 and 2 are stretched in the axial direction to form the tapered optical coupling portion 11.
At this time, light of a predetermined wavelength is made incident on the optical fiber 1 from the light source 7, the output light amount from the optical fiber 1 is detected by the photodetector 8, and the output light amount from the optical fiber 2 is detected by the photodetector 9. The stretching is stopped while detecting the branching ratio, and when the desired branching ratio is reached, the drive motor M is stopped to stop the stretching. The fusion-stretched drawn products of the optical fibers 1 and 2 obtained as described above have a tapered optical coupling portion 11 which is extremely thin and has a low mechanical strength. The branching ratio changes and the operating characteristics become unstable. For this reason, the fusion-stretched drawn products of the optical fibers 1 and 2 are adhesively housed in the protective member so that external stress is not applied.

The optical fiber coupler manufactured in this manner must be one whose characteristics do not deteriorate due to storage in the protective member. In order to stabilize the characteristics, in Japanese Patent Laid-Open No. 3-107111, the Young's modulus of the adhesive is limited to a specific range, and the fused drawn products of the optical fibers 1 and 2 are fixed to manufacture an optical fiber coupler. A method is disclosed.
Further, Japanese Patent Application Laid-Open No. 3-168709 discloses a method for manufacturing an optical fiber coupler by fixing the fusion-stretched drawn products of the optical fibers 1 and 2 with an adhesive having high heat resistance and a low thermal expansion coefficient. .

[0006]

However, even in the methods described in these publications, the excess loss of the optical fiber coupler increases after the fusion-stretched drawn products of the optical fibers 1 and 2 are bonded and stored in the protective member. I couldn't hold back. As a result, the yield of products has deteriorated.

The present invention has been made in order to solve the above-mentioned problems, and manufactures an optical fiber coupler in which the characteristics do not deteriorate even when the fused and drawn products of the optical fibers 1 and 2 are accommodated in a protective member. The purpose is to provide a method.

[0008]

The method for manufacturing an optical fiber coupler according to the present invention, which has been made to achieve the above object, comprises:
As shown in FIGS. 1 and 2, a plurality of optical fibers 1 and 2 are bundled, and a part of the optical fibers is fused and stretched while being heated to be optically coupled, and then bonded to a protective member 17 to be housed in an optical fiber coupler. , The protective member 1 before and after the optical coupling portion 11 with an adhesive 16 having a viscosity of 1000 to 50,000 cps at 20 ° C.
It is characterized in that it is bonded to 7.

[0009]

After the optical fiber coupler is heated, melted, drawn and optically coupled, the front and rear of the optical coupling portion 11 are adhesively housed in the protective member 17. At that time, the adhesive 16 having a viscosity of 1000 to 50,000 cps
Since the optical fiber coupler is used, the optical fiber coupler has almost no fluctuation in the characteristics of the branching ratio and the excess loss before and after the adhesive housing. Also, the adhesive strength becomes sufficient.

When the viscosity of the adhesive 16 is 1000 cps or less, the adhesive 16 easily penetrates, but the adhesive 16 penetrates too much into the mating surface of the optical fibers 1 and 2 by a capillary phenomenon, so that the front and rear of the optical coupling portion 11 are securely fixed. The adhesive strength will be insufficient because the sufficient amount will not remain in the necessary places. Further, the adhesive 16 flows to the optical coupling portion 11, and the fusion stretched products of the optical fibers 1 and 2 are deformed by the stress generated until the adhesive 16 is cured, and the branching ratio fluctuates. If the viscosity of the adhesive 16 is 50,000 cps or more, the adhesive 1
Insufficient penetration into the adhesive surface of 6 makes the coating uneven, and the stress applied to the optical coupling portion 11 at the time of curing becomes uneven,
The fusion-stretched drawn products of the optical fibers 1 and 2 are deformed, and the branching ratio changes. Further, the penetration of the adhesive 16 is insufficient and the adhesive strength becomes insufficient.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of a method for manufacturing an optical fiber coupler to which the present invention is applied will be described in detail below with reference to the drawings.

FIG. 1 is a side sectional view and AA of an embodiment of an optical fiber coupler manufactured by a manufacturing method to which the present invention is applied.
FIG.

FIG. 2 shows an embodiment of a method of manufacturing an optical fiber coupler to which the present invention is applied.

First, the embodiment will be described with reference to FIG.
Optical fibers 1 and 2 (125 μm in diameter) are attached to the device for fusion drawing. The device has clamps 4 and 5 for holding the optical fiber at two points and pulling them in opposite directions, and a burner for obtaining an oxyhydrogen flame 6 for heating the optical fiber. The clamps 4 and 5 are connected to a pulling mechanism including a screw rod 22, a guide rod 23, and a drive motor M. The screw rod 22 has left and right screw threads cut on both sides of one round rod, and is pivotally supported by a chassis (not shown) of the apparatus. The screw rod 22 is connected to the drive motor M via a drive transmission mechanism. The clamp 4 is screwed with the right screw of the screw rod 22, and the clamp 5 is screwed with the left screw of the screw rod 22. And the clamps 4 and 5
A guide rod 23 supported by the chassis of the apparatus is slidably engaged. Further, the apparatus has a light source 7 (wavelength 1.3 μm) that oscillates laser light of a predetermined wavelength, a light amount detector 8 and a light amount detector 9. Further, the screw rod 22 and the guide rod 23 can be removed together with the clamps 4 and 5 from the chassis (not shown) of the apparatus. That is, the clamps 4 and 5, the screw rod 22 and the guide rod 23.
Also serves as a temporary jig for moving to the next step while fixing the mutual positions of the optical fibers that have been fusion-stretched.

In the optical fibers 1 and 2, the protective coating material 3 is removed in advance from the portion to be fused, and the clamp 4 and the clamp 5 are used to hold the optical fiber 1 at two locations.
Of the optical fiber 1 to the light amount detector 8 and the output side of the optical fiber 2 to the light amount detector 9. When the drive motor M is rotated after heating the central portion with the oxyhydrogen flame 6 to bring it into a semi-molten state, the clamps 4 and 5 move outward, respectively, and the optical fibers 1 and 2 are pulled and melted. The optical coupling portion 11 is formed by stretching and stretching. At this time, the light amount detector 8 and the light amount detector 9 detect the output light amounts from the optical fibers 1 and 2, and extend while confirming the branching ratio. As the fusion drawing is performed, the light amount detector 9
The amount of light detected (the amount of light output from the optical fiber 2) gradually increases, and conversely, the amount of light detected by the light amount detector 8 (the amount of light output from the optical fiber 1) gradually decreases. When the desired branching ratio (for example, the detected light amount of the light amount detector 8 and the detected light amount of the light amount detector 9 match, that is, the branching ratio 1: 1), the drive motor M is stopped and the oxyhydrogen flame 6 is stopped. And stop the fusion drawing.

Eight fused stretched products of the optical fibers 1 and 2 are manufactured by the above process, and the branching ratio and excess loss of each fused stretched product are measured. This step is performed in Examples 2 to 7 and Comparative Example 1
・ 8, and the measurement results of the branching ratio and the excess loss are shown in Table 1 before the adhesive storage.

In the fusion-stretched drawn products of the optical fibers 1 and 2 obtained by the above process, the screw rod 22 and the guide rod 23 are removed from the chassis of the apparatus while being held by the clamps 4 and 5, and as shown in FIG. It is sandwiched between protective members 17 made of a single quartz plate, and the front and rear of the optical coupling portion 11 are adhered by an ultraviolet curing epoxy resin adhesive 16 (one-liquid type or two-liquid type). At this time, the fused stretched products of the eight optical fibers 1 and 2 were the adhesive 16 having a viscosity of 500 cps in Comparative Example 1 and the adhesive 16 having a viscosity of 1000 cps in Example 2.
Example 3, the adhesive 16 having a viscosity of 5000 cps, Example 4 the adhesive 16 having a viscosity of 10,000 cps, Example 5
Adhesive 16 having a viscosity of 20000 cps in Example 6 and 2500 in Example 6
Adhesive 16 having a viscosity of 0 cps was added to Example 7 at 50,000 cps.
An adhesive 16 having a viscosity of s is adhered and fixed to Comparative Example 8 using an adhesive 16 having a viscosity of 187,000 cps. Here, the clamps 4 and 5 are removed, and the clamps 4 and 5, which are temporary jigs, and the screw rod 22 and the guide rod 23 are removed.

Further, the fusion-stretched and drawn product of the optical fibers 1 and 2 thus fixed and adhered to the protective member 17 is used as a protective case 14 (outer diameter 3.3 mm, inner diameter 3.0 mm, length 50 mm stainless steel pipe). It is housed in a quartz plate protection member 17
The adhesive 20 (silicone adhesive KE45RTV, manufactured by Shin-Etsu Chemical Co., Ltd.) is adhesively fixed between the protective case 14 and the protective case 14, and further, both ends of the protective case 14 are fixed with the adhesive 20 and sealed, and the optical fiber coupler is Completed (see cross-sectional view of FIG. 1A-A). At this time, the branching ratio and the excessive loss of the eight optical fiber couplers of Examples 2 to 7 and Comparative Examples 1 to 8 after the adhesive is housed in the viscosity of each adhesive 16 are measured. The measurement results of the viscosity of each adhesive 16 are shown in Table 1 after the adhesive was stored.

Further, a thermal shock test of shrinking and expanding the adhesive 16 of the eight optical fiber couplers at -40 ° C. to 85 ° C. was carried out 5 times, and then, Examples 2 to 7 and Comparative Examples 1.8 were carried out.
The branching ratio and excess loss of the eight optical fiber couplers are measured. The measurement results of the viscosity of each adhesive 16 are shown in Table 1 after the thermal shock test.

As a result of the above measurement, the viscosity was 500 cps and 1870.
The two optical fiber couplers using the adhesive 16 of 00 cps had large fluctuations in the characteristics of the branching ratio and the excess loss before and after being adhesively housed in the protective member 17 and after the thermal shock test. The six optical fiber couplers using the adhesive 16 of 1000 to 50,000 cps showed almost no change in characteristics.

The branching ratio and the excess loss of the optical fiber coupler are defined by the following equations, respectively.

[0022]

[Formula 1]

P1: incident light amount to the optical fiber 1 P3: emitted light amount from the optical fiber 1 P4: emitted light amount from the optical fiber 2

[0024]

[Table 1]

[0025]

As described above in detail, in the method of manufacturing the optical fiber coupler of the present invention, the viscosity at 20 ° C. before and after the optical coupling portion is 1000 to 50000 in the adhesion to the protective member.
By using the cps adhesive, the characteristics of branching ratio and excess loss hardly change before and after the adhesive is housed in the protective member after fusing and drawing multiple optical fibers, and after the thermal shock test. However, it is possible to obtain an optical fiber coupler whose characteristics hardly change.

[Brief description of drawings]

FIG. 1 is a side sectional view and a vertical sectional view of an embodiment of an optical fiber coupler manufactured by a manufacturing method to which the present invention is applied.

FIG. 2 is a schematic front view showing a process in the middle of an embodiment of a method for manufacturing an optical fiber coupler to which the present invention is applied.

[Explanation of symbols]

1 and 2 are optical fibers, 3 is a protective coating, 4 and 5 are clamps, 6 is an oxyhydrogen flame, 7 is a light source, 8 and 9 are photodetectors, 11
Is an optical coupling portion, 14 is a protective case, 16 and 20 are adhesives, 17 is a protective member, 22 is a screw rod, 23 is a guide rod,
M is a motor.

Claims (1)

[Claims] 1. A method of manufacturing an optical fiber coupler, which comprises bundling a plurality of optical fibers, fusion-drawing and heating a part of them to optically couple them, and then adhesively accommodating them in a protective member.
Viscosity at 20 ℃ before and after the optical coupling part is 1000 ~ 50,000 cp
A method of manufacturing an optical fiber coupler, characterized in that it is adhered to a protective member with an adhesive of s.