JPS58125625A - Production of parent material for optical fiber - Google Patents

Abstract

PURPOSE:In the production of parent materials for optical fiber through the rod-in-tube process, a conjugated parent material is fused and contracted in diameter into cone shapes on both ends to form a parent material resistant to cracking. CONSTITUTION:A parent material for optical fiber 1 is inserted into a quartz glass tube 2 to form a conjugated parent material and it is heated with the heat source to fuse into a integral form 3. The above integral form 3 is easily crushable on both ends, when it is cooled by standing, and so the both ends 31 of the integral form 3 are heated up to 1,400-1,800 deg.C to contract the diameter or heated over about 2,000 deg.C till being cut by fusing on both ends 31, then cooled by standing.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing an optical fiber with less cracking.

The rod-in-tube method shown in FIG. 1 is a widely used method for manufacturing optical fiber motherboards.

This method involves inserting an optical fiber motherboard 1 containing at least a core material into a quartz glass tube 2 to form a composite 12, heating the composite 12 to a high temperature to fuse it, and then drawing it. However, in this method, the heat source 4 is removed after the composite body 12 is fused at high temperature. Natural cooling has the disadvantage that cracks are likely to occur at both ends of the combined composite matrix 6. This is because, except in special cases, the optical fiber base material 1 used in the above manufacturing method and the quartz tube 2, which is the coating layer, have different coefficients of thermal expansion, so they are heated and combined and then cooled. This creates stress between the two. Since stress in the longitudinal direction of the composite base material 5 is concentrated at both ends, cracks are likely to occur at both ends.

The present invention provides a new method for manufacturing an optical fiber base material that eliminates the above-mentioned drawbacks, and the present invention provides a new method for manufacturing an optical fiber base material, in which the fused composite base material 5 shown in FIG. 2(a) is not directly cooled to room temperature. (As shown in bJK, the end portion 31 is further heated to reduce the diameter into a conical shape, or the end portion 51 is cut by melting, and the end portion 51 is
By making it conical and providing a curved portion, stress concentrated on the end portion 31 can be alleviated, and cracking at the end portion K jp' as seen in the conventional method is less likely to occur.

In the present invention, it is sufficient to provide a curved portion at the end 51. When applying pressure uniformly to a cylinder with a closed bottom, the bottom surface is curved (ideally spherical) rather than a flat plate. ) This can be explained by the fact that the pressure resistance is higher on the bottom side.

The heating temperature for diameter reduction in the present invention varies depending on the size of the base material, but is generally carried out by heating at 1400 to 1800°C and cutting at 2000°C or higher.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a method for manufacturing a composite matrix by the conventional Ron-in-tube method, and FIG. 2 is a schematic diagram showing a method for manufacturing a composite matrix according to the present invention. Agents 1) Akira Agent Ryo Hagiwara - Figure 1 Figure 2 (α)

Claims (1)

[Claims] An optical fiber base material is inserted into a glass tube for coating, and then heated to a high temperature to fuse and combine the two, and both ends of the composite base material are reduced in diameter into a conical shape. Method of manufacturing wood.