JPH07209542A - Reinforcing structure of heat resistant optical fiber juncture - Google Patents

Abstract

PURPOSE:To provide a reinforcing structure of a heat resistant optical fiber juncture which is less deteriorated in strength without increasing transmission loss in a high-temp. region. CONSTITUTION:The optical fiber juncture 3a formed by butting the end faces of heat resistant optical fibers 3 formed by applying heat resistant coatings on the outer peripheries of optical fibers consisting essentially of quartz against each other and fusing the end faces is housed into a V-groove 1a formed on the surface of a heat resistant reinforcing material body 1 consisting of quartz and is fixed by an adhesive 4. Further, a cap consisting of quartz is put thereon from above and is clamped and fixed by the adhesive. This adhesive 4 is an epoxy heat resistant resin. The heat resistant optical fibers 3 are formed by coating the outer peripheries of the optical fibers consisting essentially of the quartz with a polyimide resin.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat resistant optical fiber connecting portion, and more particularly to a reinforcing structure for a heat resistant optical fiber connecting portion.

[0002]

2. Description of the Related Art To connect a UV-coated optical fiber or a silicone-coated optical fiber, which are widely used at present, connection is made by an electric discharge fusion method by abutting the end faces to be connected. At this time, a residual strain due to electric discharge occurs at the connecting portion of the optical fiber, and an optical fiber having a diameter of 125 μm has an initial tensile breaking strength of f = 65 N and f = 5 to 10 N.
The strength is reduced to a certain degree. For this reason, the optical fiber connecting portion is reinforced by a connecting portion reinforcing material or the like. Conventional connection reinforcements are heat shrink tubing,
It consisted of steel wire, hot melt adhesive, etc., and its operating temperature limit in the high temperature range was up to about 100 ° C.

[0003]

Recently, the applications of optical fibers are gradually expanding not only to communications but also to optical fiber gyros and optical fiber line sensors. With the expansion of such applications, the usage conditions of the optical fiber have become more severe, and in particular, the operating temperature range is expanding. Therefore, development of a heat-resistant optical fiber having a coating material of metal, ceramics, or polyimide is under study. However, there have been almost no studies on connection reinforcing materials. High temperature exposure of optical fiber splices fixed with ordinary splice reinforcements softens the hot-melt adhesive in the heat-shrinkable tube and bends the optical fiber, resulting in increased loss due to micro-vent loss, and long-term exposure. In the case of exposure over a period of time, the connecting portion reinforcing material was displaced from the optical fiber connecting portion, and there was a risk of breaking the optical fiber.

On the other hand, when the optical fiber connecting portion is housed in a box-shaped package instead of the V groove, a gap is formed between the box and the optical fiber, which makes it difficult to fix the optical fiber straight. Therefore, when this is exposed to high temperature, the strain applied to the optical fiber is received not only from the longitudinal direction of the optical fiber but also from the lateral direction, and the composite strain increases the transmission loss and the frequency of the optical fiber breakage, and the service life of the splice. There is a problem that the estimation becomes difficult.

The present invention has been made in view of the above circumstances, and solves the above-mentioned drawbacks of the prior art and reinforces a heat-resistant optical fiber splicing portion which does not increase transmission loss in a high temperature range and has small strength deterioration. It is intended to provide a structure.

[0006]

SUMMARY OF THE INVENTION According to the present invention, a heat-resistant reinforcing material main body made of quartz is provided with a splicing portion in which the heat-resistant coating on the outer circumference of an optical fiber containing quartz as a main component is removed and end faces are butted and fused. A reinforcing structure for a heat-resistant optical fiber connection part, characterized in that the heat-resistant optical fiber connection part is housed in a V groove formed on the surface, fixed with an adhesive, and further covered with a lid made of quartz from above to be gripped and fixed with the adhesive. . In addition, the heat resistant optical fiber connection portion was fixed to the V groove of the heat resistant reinforcing material main body and the lid with an epoxy heat resistant resin adhesive. Further, as the heat-resistant optical fiber, a fiber whose outer periphery is made of quartz and coated with polyimide resin is used.

[0007]

The heat resistant reinforcing material main body having the V groove formed on the quartz substrate and the lid made of the quartz plate are used as the reinforcing material of the heat resistant optical fiber connecting portion, and the optical fiber is inserted into the V groove of the heat resistant reinforcing material main body. By fixing with an adhesive, the heat resistance of the optical fiber splicing part was significantly improved, distortion during heating was suppressed, and breakage could be reduced.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1 showing the assembled state of the heat resistant reinforcing material and the heat resistant optical fiber, the heat resistant reinforcing material body 1 is a quartz plate substrate having a thermal expansion coefficient α = 4 × 10 ⁻⁷ / ° C., and a V groove is formed on the surface thereof. ing. The connecting portion 3a of the heat resistant optical fiber 3 made of quartz is inserted into the V groove. As the heat-resistant optical fiber 3, as shown in the enlarged cross-sectional view of FIG. 3, a polyimide resin [made by Toray Industries, Inc., trade name Semifine S
P-740] is a polyimide-coated optical fiber in which the coating layer 5 is formed by thermosetting. The polyimide coating layer 5 after the thermosetting had a thickness t = 15 μm.

The polyimide-coated optical fiber has strong adhesion between the quartz optical fiber and the polyimide coating layer 5, and since the Young's modulus of the polyimide resin is as high as 2.8 × 10 ⁹ Pa, the coating is mechanically removed. Difficult to do. On the other hand, hydrazine and ethylenediamine, which are solvents for polyimide resin, are highly irritating chemicals and their handling is extremely difficult. Therefore, in the present invention, the removal of the coating layer 5 at the time of connecting the polyimide-coated optical fiber 3 is performed by electric discharge. At this time, it was feared that a local residual stress would remain on the optical fiber, and the discharge voltage was kept below the voltage at the time of fusion. After that, the end face was cut at a right angle, and the ends were abutted against each other to be connected by discharge fusion to form a connecting portion 3a.

The connecting portion 3a, which is heat-sealed and connected, is inserted into the V-shaped groove 1a on the heat resistant reinforcing material main body 1 along the longitudinal direction with the connecting portion 3a as the center. Then, as shown in the cross sectional view of FIG. The adhesive 4 is an epoxy resin heat-resistant adhesive, which is a product name 353ND (manufactured by US Epoxy Technology Co., Ltd.), and after potting the same, the lid 2 made of a quartz plate is covered like the heat-resistant reinforcement material main body 1, The adhesive 4 is hermetically fixed.

In the above example, the adhesive 4 is trade name 353.
Although ND (manufactured by US Epoxy Technology Co., Ltd.) was used, the present invention is not limited to this and any other heat resistant adhesive can be used. The adhesive 4 was cured with a hot plate whose surface temperature was set to 250 ° C., and the curing time was about 10 minutes.

Twenty samples of the reinforcing structure of the heat resistant optical fiber splicing portion thus obtained were subjected to a heat cycle test of 10 cycles at room temperature to 200 ° C. as a test condition. As a result, no damage, increase in transmission loss, or damage to the V-groove of the heat-resistant reinforcing material body was observed in any of the samples.

[0013]

As described above, according to the reinforcing structure of the heat resistant optical fiber connecting portion of the present invention, the quartz plate is used as the connecting portion reinforcing material, and the V groove is formed on the surface of the quartz plate, so that heating The strain on the optical fiber at that time can be suppressed only in the longitudinal direction of the optical fiber, and the transmission loss due to bending and the breakage of the optical fiber can be reduced.

[Brief description of drawings]

FIG. 1 is a perspective view showing an assembled state of a heat resistant reinforcing material and a heat resistant optical fiber.

FIG. 2 is a cross-sectional view of the heat resistant reinforcing material and the heat resistant optical fiber after assembling.

FIG. 3 is a cross-sectional view showing a configuration of a polyimide-coated optical fiber.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heat resistant reinforcing material main body 1a V groove 2 Lid 3 Polyimide coated optical fiber 3a Connection part 4 Adhesive 5 Polyimide coating layer

Claims (3)

[Claims] 1. A heat-resistant reinforcing material body made of quartz, comprising an optical fiber splicing part made by butt-bonding end faces of a heat-resistant optical fiber formed by applying heat-resistant coating to the outer periphery of an optical fiber containing quartz as a main component. A reinforcing structure for a heat-resistant optical fiber connection part, characterized in that the heat-resistant optical fiber connection part is housed in a V-shaped groove formed on the surface of, and fixed with an adhesive, and further covered with a lid made of quartz from above and gripped and fixed with the adhesive. 2. The reinforcing structure for a heat resistant optical fiber connecting portion according to claim 1, wherein the adhesive is an epoxy heat resistant resin. 3. The reinforcing structure for a heat-resistant optical fiber connecting portion according to claim 1, wherein the heat-resistant optical fiber has an outer periphery of an optical fiber mainly made of quartz and is coated with a polyimide resin.