Optical fiber drawing method and optical fiber drawing device

Abstract

The purpose of the present invention is to reduce the spatial volume inside a drawing furnace so as to mitigate variations in pressure inside the furnace, and also stabilize sealing on the insertion opening side for glass base material. At the start of drawing, sealing is carried out at the outer peripheral surface of glass base material (11) by a first sealing part (17) of a sealing mechanism. After the proximity of a tapered part of the glass base material (11) starts passing through the first sealing part (17), a switch is made to a second sealing part (18) disposed above the first sealing part (17), and sealing is carried out by the second sealing member (18) at the outer peripheral surface of a sleeve member (20) affixed around the outer periphery of a dummy rod (12).

Description

technical field [0001] The invention relates to an optical fiber drawing method and a drawing device for heating and melting a glass base material for an optical fiber to draw an optical fiber. Background technique [0002] The drawing of an optical fiber in a drawing furnace is performed by heating and melting a glass base material for an optical fiber (hereinafter referred to as a glass base material) with a heater or the like. Since the temperature in the drawing furnace is greater than or equal to 2000°C, the temperature is very high. Therefore, graphite is usually used for the core tube surrounding the glass base material. This graphite is oxidized and consumed in a high-temperature oxygen-containing atmosphere. In order to prevent this, a rare gas such as argon or helium or nitrogen (hereinafter referred to as inert gas or the like) is fed into the drawing furnace. [0003] In addition, the upper end of the glass base material is usually tapered in diameter, connecte...

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Problems solved by technology

[0004] However, in this method, the glass base material falls as the wire drawing progresses, and the space volume in the upper chamber increases accordingly. Therefore, the pressure in the furnace fluctuates, and the flow of the inert gas or the like fed into the above-mentioned furnace core tube changes with the increase of the space volume in the upper chamber. As a result, the amount of heat transfer in the fusion zone of the glass base material changes, and the diameter of the glass fiber during drawing changes.

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