JPH02283631A - Sintering method for outside matrix of optical fiber - Google Patents

Abstract

PURPOSE:To accomplish the title sintering without causing the sag, shrinkage, etc., of the matrix by gripping dummy parts at both the ends of an outside matrix with the chucks of two motors and by heating the matrix in an oven while moving both the chucks in the same longer direction at an equal speed. CONSTITUTION:Dummy parts 1A, 1A at both the ends in the axial direction of an outside matrix 1 for optical fiber produced by the OVD process are respectively gripped with chucks 5, 6 at the spindles of two rotary driving motors 3, 4. Thence, motors 3 and 4 are rotated in the same direction at an equal speed; at the same time, the matrix 1 is heated in an oven 2 and sintered while moving the chucks 5 and 6 in the same longer direction at an equal speed. Thereby, the distance between the chucks 5 and 6 is always invariant, and the matrix 1 will never subjected to force in its axial direction due to the gravitational force applied on the matrix 1, thus causing no sag and/or shrinkage.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for sintering an optical fiber preform.

[Conventional technology]

While rotating a support rod called a target rod or dummy, the required glass material gas is blown along with an oxyhydrogen flame around the target rod, and glass soot is layered and deposited in a cylindrical shape on the support rod through hydrolysis. The so-called OVD method for producing optical fiber preforms is well known, but since this optical fiber preform is produced using hydrolysis, OH
The optical fiber base material is porous and contains a large amount of ions, but this optical fiber base material is simply heated in a heating furnace, or it is heated while introducing α2 gas into the furnace to react with OH ions, and OH ions are removed from the inside. A so-called sintering process is added to remove the glass and turn it into transparent glass.

An example of a conventional apparatus for actually carrying out this sintering process is shown in FIG.

A chuck 102 is attached to the spindle of the rotary drive motor 101.
A dummy part 1 of the optical fiber external base material 1 is provided here.
A is grasped and suspended. The rotary drive motor 101 is provided on a bracket (103), and this bracket (103)
A female threaded follower 104 is attached to the feed screw shaft 105, such as a ball screw, for example. Note that the feed screw shaft 105 is rotationally driven in an arbitrary direction by the drive motor 106, whereby the bracket 103 is sent in the axial direction of the feed screw shaft 105, and therefore the external base material l is made to travel within the heating furnace 2. .

[Problems to be Solved by the Invention] In the sintering method using the conventional apparatus shown in FIG. Because it is heated inside the furnace, if the heating furnace temperature is too high, the base material will stretch and sag, and if the temperature is too low, the entire base material will shrink when the glass soot contracts.

All of these phenomena are caused by the fact that the external base material 1 is held and suspended at its axial end.

[Means to solve the problem]

This invention was made in order to eliminate the above-mentioned disadvantages, and the dummy parts at both axial ends of the external base material, which are made by depositing glass soot on the outer periphery of the dummy part, are driven by two rotary drive motors. The external base material is gripped by the chucks of the spindles, the rotary drive motor is rotated in the same direction at the same speed, and the chucks are moved in the same direction at the same speed in the longitudinal direction, while the external base material is placed in the heating furnace. 1 is a method for sintering an external optical fiber base material, the method comprising: heating an external optical fiber base material;

[Operation] The optical fiber base material is initially gripped at both ends in the axial direction, and both chuck parts move in the same direction and at the same speed, so the distance between the two chucks is always constant and the gravity applied to the base material is Because of this, the base material is not subjected to any force in the axial direction and therefore does not sag or shrink.

〔Example〕

An example of an apparatus for carrying out the method of the invention will be described with reference to FIG.

The drive motor 13 is directly connected to and rotates a feed screw shaft 9 such as a ball screw. Two female threaded followers 10 and 12 are screwed onto this feed screw shaft 9 at an appropriate interval corresponding to the length of the external base material 1 to be subjected to the sintering process. Each child 10.12 is fitted with a bracket 7.8. Note that instead of the feed screw shaft, reciprocating threads were formed on the outer circumferential surface to intersect with each other. Instead of a positive camshaft or an internally threaded follower, a cam follower that engages with the positive camshaft may also be used.

Rotary drive motors 3 are mounted on brackets 7 and 8, respectively.
4 are mounted such that their respective spindles occupy a coaxial position, and the spindles are provided with chucks 5 and 6, respectively.

The heating furnace 2 is arranged around a central axis connecting the above-mentioned spindles that are coaxially provided, and also has female threaded followers IO and 1.
It is placed at an intermediate position between the two.

When it is desired to sinter an optical fiber base material 1 using this device, the dummy parts 1A and 1A at both ends of the base material 1 in the axial direction are gripped by the chucks 5 and 6, and the drive motor 13 is rotated to connect the female threaded follower. 10 and 12 may be moved in a desired direction.

Since the female screw followers 10 and 12 always move in the same direction and at the same speed, the relative distance between the chucks 5 and 6 remains unchanged, and the optical fiber preform 1 is suspended in a conventional manner with its upper end gripped. Unlike in the case of , it does not cause sagging due to overheating or shrinkage that occurs when the heating furnace temperature is low.

〔Effect of the invention〕

According to this invention, the optical fiber base material is first held at both ends in the axial direction, and since both chuck parts move in the same direction and at the same speed, the distance between the two chucks is always unchanged, and the base material This has the effect that the base material is not subjected to any force in the axial direction due to the gravity applied to it, and therefore does not sag or shrink.Therefore, this optical fiber base material has the advantage of being able to produce high-quality optical fibers. be.

[Brief explanation of drawings]

FIG. 1 is a simplified side view showing an example of an apparatus used to carry out the method of the present invention, and FIG. 2 is a simplified side view showing an example of a conventional apparatus. ■...External base material, 1A...Dummy part, 2...Heating furnace, 3.4...Rotary drive motor, 5.6...Chuck.

Claims (1)

[Claims] 1. Dummy parts (1A) at both ends in the axial direction of the external base material (1) made by depositing glass soot on the outer periphery of the dummy parts (1A).
, 1A) are gripped by the chucks (5, 6) of the spindles of two rotary drive motors (3, 4), and the rotary drive motors are rotated at the same speed and in the same direction,
A method for sintering an optical fiber external base material, characterized in that the external base material is heated in a heating furnace (2) while moving both chucks in the same direction at the same speed in the longitudinal direction.