JPH01192740A - Method for drawing optical fiber and apparatus therefor - Google Patents

Abstract

PURPOSE:To enable drawing of an optical fiber with hardly any fluctuation in wire diameter, by drawing a preform inserted into a furnace core tube while feeding an atmospheric gas through a specific gas flow passage separately from a passage of the preform at a constant rate. CONSTITUTION:The second cylindrical furnace core tube 20 capable of inserting a glass preform 4 for an optical fiber is provided in the interior of the first furnace core tube 3 in a furnace body 1 of a drawing apparatus (M1) for drawing the optical fiber. This apparatus (M1) is used to draw the optical fiber 5 while admitting an atmospheric gas 6 from gas introduction holes 7 to pass the gas 6 through a gas flow passage (beta) without passing through an inserting passage (alpha) of the preform 4. The gas 6 after passing through the gas flow passage (beta) changes into a steady flow from an outlet at the lower end of the second furnace core tube 20. Thereby, a stable atmospheric gas flow is formed in a hot-melt part (A) of the preform 4. As a result, no fluctuation in gas flow is caused in the hot-melt part (A) at all and the aimed optical fiber without any fluctuation in wire diameter can be drawn.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an optical fiber drawing method capable of drawing an optical fiber with little variation in diameter, and a drawing apparatus used therein.

<Prior art> Optical fibers are produced by feeding an optical fiber base material made of quartz or the like from the top of a drawing furnace, heating and melting the tip, and pulling down the molten part to reduce the diameter. A wire is drawn to the desired diameter from the lower end.

In this case, if foreign matter, oxygen, water vapor, metal ions, etc. in the air are present around the melted optical fiber tip in the drawing furnace, the mechanical strength of the drawn optical fiber will be significantly impaired. To prevent this, the inside of the drawing furnace is usually filled with an atmospheric gas such as N, Ha, etc. to prevent outside air from entering.

An example of such a conventional optical fiber drawing apparatus is shown in FIG. As shown in the figure, the optical fiber drawing device M0
Inside the furnace body 1, a heater 2 and a cylindrical furnace core tube 3 are provided. A glass base material 4 for an optical fiber provided at the tip of a dummy rod 4a is inserted into the upper opening 1a of the furnace body 1, and the drawn optical fiber 5 is pulled out through the lower opening 1b. ing. In order to fill the furnace core tube 3 with atmospheric gas 6, a gas introduction hole 7 is provided near the upper opening 1a of the furnace body 1 to uniformly introduce the gas 6 into the furnace body 1. It is being Also,
Gas seal members 8.9 are provided at the upper and lower openings la and lb of the furnace body 1, respectively. This forms a steady flow of atmospheric gas 6 within the furnace core tube 3, stabilizes the flow of the gas 6 within the furnace core tube 3, and prevents outside air from entering the furnace core tube 3.

Note that the atmospheric gas 6 forming a steady flow is discharged to the outside from an outlet 9a of the optical fiber 5 provided in the lower sealing member 9.

<Problems to be Solved by the Invention> However, according to the conventional apparatus described above, there is a difference in diameter between the connecting portion 4b between the optical fiber base material 4 and the dummy rod 4a, so that the atmospheric gas 6 is not allowed to flow into the upper end of the base material 4. The gas 6
There is a problem that turbulence occurs in the flow of water.

Generally, the inside of the furnace body 1 is kept at a high temperature of nearly 2000°C in order to melt the optical fiber base material 4.
If the steady flow in the heating melting section A is disturbed even slightly, the diameter of the optical fiber will change.

Therefore, in the conventional method, there is a problem in that the diameter of the drawn optical fiber 5 changes due to the disturbance of the atmospheric gas.The present invention has been developed in view of the above-mentioned circumstances, and has been developed to improve the flow of atmospheric gas within the furnace body. It is an object of the present invention to provide a method for manufacturing an optical fiber with stable fiber diameter and less variation in diameter, and an optical fiber drawing device with less variation in diameter.

Means for Solving the Problems> The structure of the optical fiber drawing method of the present invention for achieving the above object is as follows: A glass preform for a rod-shaped optical fiber inserted into a furnace core tube is heated and melted in an atmospheric gas. At the same time, in an optical fiber drawing method in which an optical fiber is drawn by drawing while sending an atmospheric gas to the heating and melting part, an atmospheric gas is formed in the vicinity of the heating and melting part of the base material separately from the insertion passage of the base material. The method is characterized in that the optical fiber is drawn while constantly sending atmospheric gas through the gas flow path.

On the other hand, the configuration of the optical fiber drawing apparatus of the present invention heats and melts a glass base material for a rod-shaped optical fiber inserted into a furnace core tube, and supplies atmospheric gas to this heated melting section from the upper part of the furnace core tube. In an optical fiber drawing apparatus that draws an optical fiber by drawing the glass base material, a second furnace core tube is inserted into the furnace core tube, the inside of which serves as a push passage into which the glass base material can be inserted, through an opening in the furnace main body. The atmospheric gas flow path is extended to the vicinity of the heating and melting part of the base material, and is defined between the furnace core tube and the second furnace core tube, and is defined separately from the insertion path. do.

Effect> Atmospheric gas is constantly supplied into the furnace core tube from a gas passage provided separately from the base material insertion passage of the glass base material, and the heating and melting part of the glass base material is not affected by the insertion of the base material. A steady steady flow is always formed.

Embodiment Hereinafter, a preferred embodiment of an apparatus for carrying out the method of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a cross section of the optical fiber drawing apparatus of this embodiment. Note that the same members as in FIG. 2 according to the prior art are given the same reference numerals and redundant explanations will be omitted.

As shown in the figure, inside the first furnace core tube 3 in the furnace body 1 of the optical fiber drawing device WIM according to this embodiment, there is a glass preform (hereinafter referred to as "preform") 4 for optical fibers. A second cylindrical furnace core into which the furnace core can be inserted is provided.

This second furnace core tube 20 has a flange portion 20 at its upper end.
A is fixed to the opening 1a of the furnace body 1, and its tip is provided so as to extend to the vicinity of the heating and melting section A. The inner side 20b of the second furnace core tube 20 becomes the insertion passage α for the base material 4, and the inner peripheral surface 3a of the first furnace core tube 3 and the outer peripheral surface 20c of the second furnace core tube 20. The space between them becomes an annular gas flow path β. The upper end of this gas flow path β is closed by the flange portion 20a of the second furnace core tube 20. Further, the atmospheric gas 6 is supplied to the gas passage β through a gas introduction hole 7 provided near the upper opening 1a of the furnace body 1.

When the optical fiber 5 is drawn using the drawing apparatus M1 having such a second furnace core tube 2o while the atmospheric gas 6 is introduced through the gas introduction hole 7, the gas 6 is drawn into the base material 4.
Instead of passing through the push-in passage a, it passes through the gas flow path β. after that,
The gas 6 that has passed through the gas flow path β becomes a steady flow from the outlet at the lower end of the second furnace core 20, and a stable atmospheric gas flow is formed in the heated and melted portion A of the base material 4. For this reason,
There is no fluctuation in the gas flow in the heating melting section A, and it is possible to draw an optical fiber with no fluctuation in diameter.

<Effects of the Invention> As explained above in detail with the embodiments, according to the optical fiber drawing method and optical fiber drawing apparatus of the present invention,
By providing the gas flow path separately from the base material push passage,
Since drawing can be performed while constantly supplying atmospheric gas stably, it is possible to provide an optical fiber with little variation in wire diameter.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an optical fiber drawing apparatus according to a preferred embodiment of the present invention, and FIG. 2 is a sectional view of an optical fiber drawing apparatus according to a conventional technique. In the drawing, 1 is a furnace body, 2 is a heater, 3 is a furnace core tube, 4 is a glass base material for optical fiber, 5 is an optical fiber, 6 is an atmospheric gas, 7 is a gas introduction hole, 20 is a second furnace. It is a core tube. Figure 1

Claims (1)

[Claims] 1) The optical fiber is drawn by heating and melting a rod-shaped glass base material for an optical fiber inserted into a furnace core tube in an atmospheric gas, and drawing the optical fiber while sending an atmospheric gas to the heated and melted part. In the optical fiber drawing method, the optical fiber is drawn while constantly sending atmospheric gas through a gas flow path for atmospheric gas that is formed in the vicinity of the heated and melted part of the base material, separately from the insertion path of the base material. An optical fiber drawing method characterized by: 2) An optical fiber that is drawn by heating and melting a rod-shaped glass base material for an optical fiber inserted into a furnace core tube, and drawing the optical fiber while supplying atmospheric gas to the heated and melted part from the upper part of the furnace core tube. In the wire drawing device, a second furnace core tube, the inside of which serves as an insertion passage through which the glass preform can be inserted, is installed in the furnace core tube from an opening of the furnace main body to a vicinity of the heating and melting part of the glass preform. . An optical fiber drawing apparatus, characterized in that the atmospheric gas flow path defined separately from the insertion passage is formed between the furnace core tube and the second furnace core tube.