JP-7855967-B2 - Optical fiber manufacturing method

JP7855967B2JP 7855967 B2JP7855967 B2JP 7855967B2JP-7855967-B2

Inventors

小林弓月
中原慎二

Assignees

住友電気工業株式会社

Dates

Publication Date: 20260511
Application Date: 20220816

Claims (4)

A method for manufacturing an optical fiber, comprising: a drawing furnace for heating and softening a glass base material; a cooling device positioned downstream of the drawing furnace for cooling the glass fibers drawn from the drawing furnace; and a resin coating die for applying resin to the glass fibers that have passed through the cooling device, wherein the glass fibers are coated with the resin, the optical fiber being manufactured by manufacturing an optical fiber. A vibration frequency measurement step involves measuring the vibration frequency of the in-plane vibration of the glass fiber at a measurement surface intersecting the direction of travel of the glass fiber, using a fiber position measuring instrument positioned upstream of the resin coating die. A method for manufacturing an optical fiber, comprising: a contact determination step of determining whether or not the glass fiber has come into contact with the cooling device based on the vibration frequency of the glass fiber measured in the vibration frequency measurement step.
The method for manufacturing an optical fiber according to claim 1, wherein, in the contact determination step, it is determined that the glass fiber has come into contact with the cooling device if the vibration frequency of the glass fiber is outside a predetermined range.
The method for manufacturing an optical fiber according to claim 2, wherein in the contact determination step, the predetermined range is calculated based on the tension of the glass fiber measured by a fiber tension measuring instrument.
A method for manufacturing an optical fiber according to any one of claims 1 to 3, further comprising a line drawing stop step for stopping the line drawing of the glass fiber when the contact determination step determines that the glass fiber is in contact with the cooling device.

Description

This invention relates to a method for manufacturing optical fibers. Conventionally, in optical fiber manufacturing methods where optical fibers are produced by drawing glass fibers from a glass matrix, there is no fixed point to suppress vibration of the glass fiber between the neck-down portion at the tip of the glass matrix and the coating device that applies resin to the glass fiber. As a result, the glass fiber between the lower end of the neck-down portion and the coating device sometimes vibrates like a string (string vibration) with the lower end of the neck-down portion and the coating device as fixed points. Because the string vibration of this glass fiber occurs within an intersecting plane that is perpendicular to the direction in which the glass fiber travels, the glass fiber may come into contact with the wall of the cooling device used to cool the glass fiber drawn from the glass matrix. This contact can damage the glass fiber, reducing the strength of the optical fiber. Therefore, to prevent the reduction in strength of the optical fiber due to this string vibration, a method for manufacturing optical fibers is known in which a fiber position measuring instrument detects the position of the glass fiber in a horizontal direction intersecting the direction of travel of the glass fiber hanging from the glass matrix, and then performs position adjustment control by moving the glass matrix horizontally so that the position of the glass fiber is positioned at the center of the heating furnace that heats the glass matrix (see, for example, Patent Document 1). Japanese Patent Publication No. 2013-220972 This is a schematic diagram of an optical fiber manufacturing apparatus used in the optical fiber manufacturing method disclosed herein.A schematic diagram illustrating the measurement of the position of a glass fiber using the fiber position measuring device shown in Figure 1.A flowchart for determining abnormalities in the manufacturing process of optical fibers according to one aspect of this disclosure. [Description of Embodiments in this Disclosure] First, the embodiments of this disclosure will be listed and described. The present disclosure is a method for manufacturing an optical fiber, comprising: (1) a drawing furnace for heating and softening a glass base material; a cooling device arranged downstream of the drawing furnace for cooling the glass fibers drawn from the drawing furnace; and a resin coating die for applying resin to the glass fibers that have passed through the cooling device, wherein the optical fiber is coated with resin, the method comprising: a vibration frequency measurement step for measuring the vibration frequency of in-plane vibration of the glass fiber at a measuring surface intersecting the direction of travel of the glass fiber using a fiber position measuring instrument arranged upstream of the resin coating die; and a contact determination step for determining whether the glass fiber has come into contact with the cooling device based on the vibration frequency of the glass fiber measured in the vibration frequency measurement step. As described above, the system includes a vibration frequency measurement step that measures the vibration frequency of the in-plane vibration of the glass fiber on a measurement surface intersecting the direction of travel of the glass fiber using a fiber position measuring instrument positioned upstream of the resin coating die, and a contact determination step that determines whether or not the glass fiber has come into contact with the cooling device based on the vibration frequency of the glass fiber measured in the vibration frequency measurement step. Therefore, contact with the cooling device due to the string vibration of the glass fiber is determined based on the vibration frequency of the glass fiber, which allows for faster detection of contact with the cooling device due to the string vibration of the glass fiber compared to determining contact based on the position of the glass fiber on the measurement surface. In the above method for manufacturing optical fibers, (2) in the contact determination step, if the vibration frequency of the glass fiber is outside a predetermined range, it is determined that the glass fiber has come into contact with the cooling device. This allows for easy determination of whether or not the glass fiber is in contact with the cooling device, simply by performing frequency analysis on the positional variation of the glass fiber on the measurement surface. In the above method for manufacturing optical fibers, (3) in the contact determination step, the predetermined range is calculated based on the tension of the glass fiber measured by the fiber tension measuring instrument. This allows for a more accurate determination of whether or not the glass fiber is in contact with the cooling device, as the range of vibration frequencies of the glass fiber, which serves as the basis for determining whet