JPH1160287A - Drawing of optical fiber and drawing device used therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the adhesion of the optical fiber to the inner surface of a travel tube to efficiently produce an optical fiber by allowing the optical fiber drawn from a preform in a heating oven to travel in an optical fiber travel tube of cooling device disposed below the heating oven and having corrugate-like grooves on the inner surface, simultaneously cooling the drawn optical fiber with a cooling gas and subsequently coating the cooled optical fiber with a resin. SOLUTION: This method for drawing an optical fiber comprises allowing a drawn optical fiber 3 to travel in an optical fiber travel tube 5 of a cooling device 4 disposed below a heating oven 1 and having corrugate-like grooves, preferably a spiral groove formed in the longitudinal direction, on the inner surface, simultaneously cooling the traveling drawn optical fiber with a cooling gas such as He gas at a temperature of e.g. <=100 deg.C, and subsequently coating the outer periphery of the cooled optical fiber with a resin. When a long cooling device is used, the efficiency of the optical fiber-passing work through the cooling device is thus improved. When a short cooling device is used, the ability for cooling the optical fiber can also be improved. Thereby, a short setup time on the production of the optical fiber, a short cooling device and a high drawing speed can be contrived.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber drawing method and a drawing apparatus used therefor, and more particularly, to an optical fiber drawing method and a drawing apparatus used in which the setup time of the drawing operation is short and the resin can be coated well even at a high drawing speed. It is about.

[0002]

2. Description of the Related Art In order to prevent disconnection of an optical fiber and deterioration of transmission characteristics, a resin is coated on the outer periphery of the optical fiber. In general, resin coating is performed immediately after drawing an optical fiber. However, if the optical fiber drawn out of the heating furnace has a high temperature, the outer periphery of the optical fiber cannot be efficiently and well coated with the resin. Therefore, conventionally, an optical fiber is forcibly cooled and then coated with a resin.

FIG. 4 is an explanatory view showing an example of an optical fiber drawing apparatus for implementing a conventional optical fiber drawing method with forced cooling. In this case, the lower portion of the optical fiber preform 2 is heated and melted in the heating furnace 1, and the optical fiber 3 is drawn from the heated and melted portion of the optical fiber preform 2.

The obtained optical fiber 3 is forcibly cooled to a temperature of about 100 ° C. or less with a cooling gas such as He gas while running in the optical fiber running pipe 5 of the cooling device 4 under the heating furnace 1. . Thereafter, the outer periphery of the optical fiber 3 is coated with a resin by a resin coating device 6. Next, after the coating resin is cured by a resin curing device (not shown), the direction is changed by a turn pulley 7 and the optical fiber coated with the resin is wound by a winding device (not shown).

In recent years, in order to increase the productivity of optical fiber production, the drawing speed of optical fibers has been increased to 800.
It is desired to increase the speed to m / min or more. In this case, since it is necessary to cool the optical fiber coming out of the heating furnace in a shorter time, the cooling capacity by the cooling gas must be increased. For that purpose, it is necessary to lengthen the cooling device and take a long cooling section. For example, when the drawing speed of the optical fiber is 1000 m / min, generally 10 m
Approximately long cooling devices are required.

[0006]

When an optical fiber is drawn using a conventional long cooling device, there are problems as described below. First, as the length of the cooling device increases, the size of the drawing device increases. With the increase in size, the cooling capacity of the optical fiber decreases.

In other words, it is necessary to increase the flow rate of the cooling gas due to an increase in the size of the apparatus. However, simply increasing the flow rate does not increase the cooling efficiency, so that the optical fiber cannot be cooled and a resin coating failure occurs. If the flow rate of the cooling gas is excessively increased, the flow velocity of the gas becomes too high, causing the optical fiber to oscillate, and the intensity may deteriorate due to the oscillating.

[0008] In the optical fiber drawing process during the optical fiber drawing process, the optical fiber is stuck to the inner surface of the running pipe of the cooling device because of the large size of the device, even in the work of wire passing and hooking.
There is a problem of workability such as disconnection. Further, there is a danger that the debris of the optical fiber adhered to the inner surface of the traveling pipe due to the disconnection may cause a deterioration in the strength of the optical fiber as a product.

For example, the inner diameter of the optical fiber running tube 5 is 40 mm.
When an optical fiber was manufactured using a φ, 6 m long cooling device, the optical fiber 3 could not be cooled at a drawing speed of 600 m / min or more, and as a result, an abnormality occurred in the resin coating layer. In a cooling device having a traveling pipe inner diameter of 15 mmφ and a length of 6 m, the optical fiber is stuck to the inner surface of the traveling pipe and the optical fiber cannot be passed through.

The phenomenon that the optical fiber sticks to the inner surface of the traveling tube is caused by the fact that the optical fiber is easily charged. As an antistatic measure, there is a method using an ionizer, an antistatic spray or the like, but no remarkable effect is obtained.

Accordingly, an object of the present invention is to solve the above-mentioned drawbacks of the prior art, to improve the efficiency of the operation of passing an optical fiber through a cooling device even when a long cooling device is used, and to shorten the cooling operation. An object of the present invention is to provide an optical fiber drawing method capable of improving a cooling capacity even when using an apparatus, and a drawing apparatus used therefor.

[0012]

According to the present invention, an optical fiber is drawn from an optical fiber preform in a heating furnace, and the obtained optical fiber is used as an optical fiber in a cooling device under the heating furnace. In the optical fiber drawing method in which the outer periphery of the optical fiber is coated with a resin after being cooled by the cooling gas while traveling in the traveling pipe, the optical fiber traveling pipe is drawn using a corrugated groove provided on the inner surface thereof. Do.

In the above method, the optical fiber running tube may have a corrugated groove formed on the inner surface thereof in a spiral shape in the longitudinal direction of the tube.

In order to realize the above method, an optical fiber drawing apparatus comprising a heating furnace, an optical fiber running tube having a corrugated groove on the inner surface, a cooling device, and a resin coating device is used.

[0015] In the above apparatus, a corrugated groove may be formed in the inner surface of the optical fiber running tube in a spiral shape in the longitudinal direction of the tube.

[0016]

FIG. 1 is an explanatory view showing a first embodiment of the present invention. The lower portion of the optical fiber preform 2 is heated and melted in the heating furnace 1, and the optical fiber 3 is drawn from the heated and melted portion of the optical fiber preform 2.

While the obtained optical fiber 3 is traveling in the optical fiber traveling pipe 5 of the cooling device 4 under the heating furnace 1, the H
Forcibly cool to a temperature of about 100 ° C. or less with e gas. Thereafter, the outer periphery of the optical fiber 3 is coated with a resin by a resin coating device 6. Next, after the coating resin is cured by a resin curing device (not shown), the direction is changed by a turn pulley 7 and the optical fiber coated with the resin is wound by a winding device (not shown).

FIG. 2 is a sectional view of a part of the cooling device 4 of FIG. A corrugated groove 8 is provided on the inner surface of the optical fiber running tube 5. The direction of the groove is perpendicular to the running direction of the optical fiber. Groove depth 3mm, groove spacing 6
mm. The inner diameter of the optical fiber running tube 5 was 15 mmφ and the length was 6 m, and He gas was injected from the lower portion to the upper portion of the optical fiber running tube 5 at a flow rate of 5 L / min. or,
The cooling device 4 had a double tube structure, and cooling water was flowed through the outer layer 9 to cool the optical fiber running tube 5 provided with the corrugated groove 8.

Since the corrugated groove 8 is provided on the inner surface of the optical fiber running tube 5, the contact surface between the inner surface of the optical fiber running tube 8 and the optical fiber 3 is reduced. The problem of sticking to the inner surface of the fiber running tube 5 can be solved. Further, since the contact surface can be reduced, the inner diameter of the optical fiber running tube 5 and the inner diameter of the cooling device 4 can be reduced, and the cooling capacity of the optical fiber 3 can be improved. As a result, the length of the cooling device 4 can be reduced. That is, when the amount of the cooling gas supplied to the optical fiber running tube 5 is the same, the smaller the inner diameter of the optical fiber running tube 5 is, the higher the flow rate of the cooling gas is, and the higher the cooling efficiency of the optical fiber 3 is. If the cooling efficiency is improved, the length of the cooling device can be shortened.

The corrugation of the inner surface of the optical fiber running tube 5 may be performed over the entire length of the cooling device 4 or may be performed only at several portions in the longitudinal direction of the cooling device 4. The direction of the groove provided on the inner surface of the traveling tube may be vertical or horizontal with respect to the traveling direction of the optical fiber. The pitch of the grooves and the depth of the grooves should preferably be about 2 mm to 20 mm for the cleaning of the inner surface of the running pipe, but other dimensions do not pose any problem.

The material of the cooling device 4 is desirably made of copper, aluminum, or an alloy thereof having good heat conductivity. Further, the cooling device 4 may be further configured as a triple tube structure to flow cooling water or the like around the outer periphery.

According to the present invention, when an optical fiber is manufactured, since the optical fiber and the inner surface of the optical fiber running tube do not stick to each other, the wire drawing operation can be easily performed, that is, the setup time for the wire drawing operation can be reduced. As a result, a stable optical fiber was obtained even at a drawing speed of 1000 m / min.

Further, the corrugated groove on the inner surface of the optical fiber traveling tube 5 has a depth of 3 mm, an interval of 6 mm, an inner diameter of the traveling tube of 15 mmφ as in FIG. 1, and the corrugated groove has a spiral shape. Was used to manufacture an optical fiber. At this time, the length of the cooling device was 3 m, which is half of that in FIG. 1, but even in this case, an optical fiber stable up to a drawing speed of 1000 m / min was obtained. This is because the cooling gas in the optical fiber traveling tube 5 is rotated and rises to the upper part of the traveling tube by rotating the corrugated groove, so that the cooling efficiency of the optical fiber 3 is further improved.

FIG. 3 shows a second embodiment of the present invention, and is a sectional view of a cooling device 4 of the drawing device. This is obtained by inserting a corrugated copper tube 10 inside a conventional optical fiber running tube 5 having a smooth inner surface. The cooling device 4 has a double-tube structure, in which cooling water is supplied to the outer layer 9 by flowing a corrugated copper tube 10 and an optical fiber running tube 5.
Has cooled. When an optical fiber was manufactured by using the cooling device 4, the setup operation could be performed in a short time without any trouble as in Example 1, and a stable optical fiber was obtained even at a drawing speed of 1000 m / min.

[0025]

According to the present invention, the optical fiber does not stick to the inner surface of the optical fiber running tube of the cooling device, so that the setup time during the production of the optical fiber is shortened, the cooling device is shortened, and the optical fiber is drawn. The speed can be increased. Thereby, an inexpensive and high-performance optical fiber can be manufactured.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a first embodiment of the present invention.

FIG. 2 is an enlarged sectional view of the cooling device according to the first embodiment of the present invention.

FIG. 3 shows a second embodiment of the present invention and is a cross-sectional view of the cooling device.

FIG. 4 is an explanatory view showing a conventional optical fiber drawing apparatus.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 heating furnace 2 optical fiber preform 3 optical fiber 4 cooling device 5 optical fiber running tube 6 resin coating device 7 turn pulley 8 corrugated groove 9 outer layer 10 corrugated copper tube

Claims (4)

[Claims] An optical fiber is drawn from an optical fiber preform in a heating furnace, and the obtained optical fiber is cooled by a cooling gas while traveling in an optical fiber traveling tube of a cooling device under the heating furnace. An optical fiber drawing method in which an outer periphery of an optical fiber is coated with a resin, wherein the optical fiber running tube is provided with a corrugated groove on an inner surface thereof. 2. An optical fiber according to claim 1, wherein said optical fiber running tube has a corrugated groove formed on its inner surface in a spiral shape in the longitudinal direction of said tube. How to draw. 3. An optical fiber drawing apparatus comprising: a heating furnace; an optical fiber running tube having a corrugated groove on an inner surface; a cooling device; and a resin coating device. 4. The optical fiber drawing apparatus according to claim 3, wherein a corrugated groove is formed on the inner surface of the optical fiber running tube in a spiral shape in the longitudinal direction of the tube.