JPS6283329A - Method for welding glass fiber bundle - Google Patents

Abstract

PURPOSE:To produce an optical fiber without any inclusion of gases and impurities and which is uniform in the lengthwise direction by bundling glass fibers having larger diameter at both end parts than that at the central part, covering the bundle with a glass tube and successively heating and melting the bundle from the lower part to the upper part. CONSTITUTION:The glass fiber bundles are welded by the following stages 1-3. In the stage (1), a glass fiber 10 having larger diameter at both end parts 14 than that at the central part 12 is made. In the stage (2), the desired number of the glass fibers 10 obtained in the stage (1) are bundled in parallel and the bundle is covered with the glass tube 22. In the stage (3), the bundle of the glass fibers 10 covered with the glass tube 22 is vertically retained and successively heated and melted from the lower part to the upper part. By such a method, the shape of a wedge A is formed between the central parts 12 of the glass fibers 10 and the wedge A moves upward as the melt zone moves upward. Accordingly, the air between the central parts 12 is discharged through a clearance 26 and a hole 16.

Description

[Detailed Description of the Invention] [Industrial Application Field] By bundling a large number of thin glass fibers and heat-welding them, optical fibers with a complicated refractive index distribution in the cross section or polarization-constant optical fibers with stress applying parts can be produced. I may make it.

This invention can be used in such cases,
The present invention relates to a method for welding glass fiber bundles.

[Prior technology] - Called the hot press method, there is a method in which glass fiber bundles are placed in a mold, processed and formed, and then drawn and spun. - Glass is placed in a glass tube with one end connected to a vacuum pump. m
There are methods such as filling and sealing RA and drawing and spinning it.

[Problems to be Solved by the Invention] When a large number of thin glass fibers must be fused and bonded in parallel to each other in a sealed state, the glass fibers may remain separated from each other, Alternatively, gas and other impurities may be trapped between the glass fibers, often resulting in discontinuous fibers. , often resulting in defective products.

[Means for Solving the Problems] This invention does not use glass fibers with the same thickness over the entire length as in the past, but instead uses glass fibers with the same thickness over the entire length as in the conventional case.
The main feature is that the glass fiber 10 having a structure in which both end portions 14 have a larger diameter than the central portion 12, as shown in L), is used.

Then, as shown in FIGS. 6(b) to 7(d), a large number of glass fibers 10 having the above-mentioned structure are bundled, a glass tube 22 is placed on top of the bundle, the glass tube 22 is held in a vertical state, and the glass fibers 10 are stacked upward from the bottom. The above problem is solved by successively heating and melting the materials.

[Explanation (1) As shown in FIG. 1(a), the center portion 12 of the glass fiber 10 is thinner than both end portions 14. As will be described later, only the central portion 12 is actually used. The radius difference between the center portion 12 and both end portions 14 may be approximately 0.2 to 0.51++s.

In order to make such a glass fiber 10, ■ make the center part L thinner by etching, and ■ make the center part 12 thinner at both ends.
A method such as adding thicker end portions 141 is used.

(2) A large number of such glass fibers 10 are made and
) If they have the same diameter, they are arranged in a hexagonal dense arrangement, and if they have different diameters, they are arranged in parallel in close contact with each other.

Then, as shown in the same figure (C), only the two ends 14 are heat-sealed, the glass rod 20 for support is welded, and the glass tube 2
2 to seal the space between the glass rod 20 and the glass rod 20, and provide an air vent hole 16 in the upper part.

(3) Then, the heating furnace 30 sequentially heats the glass tube from the bottom upward. The whole z melts and becomes one.

Then, at the boundary between the melted and integrated part and the unmelted part, as shown in FIG.
The central portions 12 of the two form a wedge shape A. As the melting portion moves upward, this wedge shape A also moves upward, so that the air present between the central portions 12 is discharged through the gap 26 and the hole 16 described above.

Therefore, it is possible to obtain a glass fiber 10 having a clean continuous interface without trapping gas or other impurities between the glass fibers 10.

(4) Finally, the welded body 40 shown in FIG. 4(e) is obtained. As described above, both end portions are cut off and only the central portion 42 is used as a base material, and then the desired optical fiber is obtained by drawing.

[Application Example] As shown in FIG.
The glass fibers 10b made of a material with a low refractive index (for example, F-doped fibers made by plasma method) are arranged so as to have the desired refractive index distribution at the center, and are surrounded by a suitable quartz tube. 22 and melted and integrated. As a result, a photoconductive fiber with a large NA can be obtained.

Further, as shown in FIG. 3, a core 10c is a glass RAM fabricated by a VAD method, a stress-applying part 10d is a glass fiber having a different coefficient of thermal expansion, and glass fibers 10e made of pure quartz are arranged for the rest. By covering the quartz tube 22 and melting and integrating it, a stress-applied type polarization constant optical fiber can be manufactured.

[Effect of the Invention J A desired number of glass fibers 10 having a structure in which both ends 14 have a larger diameter than the center part 12 are bundled in parallel, a glass tube 22 is placed on top of the bundle, the glass tube 22 is held in a vertical state, and As it heats and melts in an upward direction, as shown above,
The narrow diameter portions of both ends 14 are fusion-welded while maintaining a constant distance from each other and forming a wedge shape A.

Therefore, an optical fiber that is uniform in the length direction can be manufactured without trapping gas or impurities.

[Brief explanation of drawings]

FIGS. 1(a) to (e) are explanatory diagrams showing the method of the embodiment of the present invention in the order of steps, and FIGS. 2 and 3 are explanatory diagrams of applied examples. 10 Glass fiber 12: Center part 14: Both ends 16: Hole

Claims (1)

[Claims] A step of making a glass fiber 10 having a structure in which both end portions 14 have a larger diameter than the central portion 12, a step of bundling a desired number of glass fibers 10 having the above structure in parallel;
It is characterized by comprising the following steps: a step of covering the glass tube 22 thereon, a step of holding the bundle of glass fibers 10 covered with the glass tube 22 in a vertical state, and sequentially heating and melting it from the bottom upwards. Method for welding glass fiber bundles.