JPS62162654A - Production of optical fiber - Google Patents

Abstract

PURPOSE:To obtain an optical fiber having good transmission loss-temperature characteristic, by repeating steps of coating an ultraviolet curing coating material on a glass based optical fiber and curing the coating material with ultraviolet rays twice of more to apply a primary coating layer to the optical fiber. CONSTITUTION:Steps of coating an ultraviolet curing coating material on a glass based optical fiber drawn into a wire and curing the coating with ultraviolet rays are repeated at least twice to form a primary coating layer having >=50mu thickness. A particularly preferred coating material to be used is an urethane acrylate based coating material having about 10-100kg/cm<2> Young's modulus at 25 deg.C after curing with the ultraviolet rays. The coating layer thickness of the glass based optical fiber just after wire drawing in the first time is preferably <=70mu, particularly <=50mu after curing.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a method for manufacturing a glass-based optical fiber, for example, a quartz glass-based optical fiber, and particularly relates to a method of manufacturing a glass-based optical fiber, for example, a quartz glass-based optical fiber. The present invention relates to a method of manufacturing an optical fiber in which a primary coating layer is applied by applying a coating material and curing it with ultraviolet light.

[Prior art and problems to be solved] Is the primary coat layer of a glass-based optical fiber immediately after being drawn? In order to fully perform these functions, which play a major role in protecting the clean surface condition and improving the bending resistance of optical fibers, the primary coat layer is coated with -C by 50μ or more. Applied in thickness.

Conventionally, the primary coat layer has been formed by applying and baking a thermosetting resin paint, but this method has the drawback of requiring a considerable amount of time to bake.
Recently, research has been carried out to employ ultraviolet curable paints that can be cured in a short time to form the primary coat layer.

According to the experimental research conducted by the present inventors, although UV-curable paints have the advantage of being able to cure in a short time,
Optical fibers in which the primary coat layer is formed using the paint have a problem in the temperature characteristics of optical transmission loss, particularly in the large increase in optical transmission loss at low temperatures.

[Means for solving problems]

It is an object of the present invention to provide a novel method for manufacturing an optical fiber with good optical transmission loss and temperature characteristics while taking advantage of the above-mentioned advantages of ultraviolet curable paint.

The present invention relates to the production of an optical fiber in which a primary coat layer with a thickness of 50 μm or more is applied by applying an ultraviolet curable paint on a drawn glass optical fiber and curing it with ultraviolet rays. relates to a method of manufacturing an optical fiber, characterized in that the optical fiber is formed by repeating a series of steps consisting of applying an ultraviolet curable paint and curing it with ultraviolet rays at least twice.

[Effect]

The drawn glass optical fiber has a slight meandering pattern while the primary coat layer is formed on it, and unlike conventional methods, a 1γ primary coat layer of 50 μm or more is coated once. In the case of forming by curing, since the applied uncured paint coating layer is thick, the meandering described above remains in the coating layer as it is, and the layer is cured in that state. Therefore, meandering of the optical fiber remains in the hardened primary coat layer, and this meandering is due to the difference in expansion coefficient between the primary coat layer and the optical fiber, which increases the microbending of the optical fiber due to temperature changes. This increases the optical transmission loss of the optical fiber, especially at low temperatures.

In contrast, as in the present invention, the primary coat layer is formed by dividing the steps of applying and curing the ultraviolet curable paint into at least two steps, so that the primary coat layer can be formed in one application and curing process. The thickness of the coating layer becomes thinner, and the degree of residual meandering of the optical fiber and the degree of occurrence of microhends are accordingly reduced, and an optical fiber with good optical transmission loss-temperature characteristics can be obtained.

In the present invention, the UV-curable paint constituting the primary coat layer may be either a soft type or a hard type, but it is better to use a soft type paint because it is less likely to cause problems during one-time application. Soft-type paints are preferable because they have a greater degree of improvement and a greater degree of improvement when applied two or more times. Particularly preferred paints have a Young's modulus of 10 to 100 kg/cI at 25°C after UV curing.
It is a urethane acrylate paint with a rating of about I+2. Further, in the present invention, it is desirable that the initial coating layer thickness of the glass optical fiber immediately after being drawn is 70 μm or less, particularly 50 μm or less after curing.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples.

A quartz glass optical fiber with an outer diameter of 1° 25 μm is drawn, which has a cladding layer of silica glass doped with B and F on a pure silica glass core that has been exposed to fire, and a support layer of synthetic silica glass on top of the cladding layer. Urethane acrylate paint (Young's modulus at 25°C after UV curing: 50 kg)
/ (To) 2) was applied and cured with UV light to a thickness of 37 μm.
Form a first primary coat layer (outer diameter: 200 μm), then repeat the same process using the same paint as above to a thickness of 50 μl11 (outer diameter =
A second primary coat layer having a thickness of 300 .mu.m) was formed to obtain a primary coat layer having a total thickness of 17 to 87 .mu.m, consisting of both of the above-mentioned coat layers. Furthermore, a small amount of urethane epoxy acrylate paint (Young's modulus at 25°C after UV curing: 5000 kg/CII+2) was applied and UV cured to form a secondary coat N < outer diameter: 900 μm.
) was applied.

Tomoshi Kai 1 J7 of the first primary coat layer is 60 μm (outer diameter: 245 μl 11), and that of the second primary coat layer;
An optical fiber was manufactured by the same method and operation as in Example 1, except that the γ value was 80 μm (outer diameter: 400 μl11).

An optical fiber was manufactured by the same method and operation as in Example 1, except that the primary coating layer was formed by applying the paint once and curing with ultraviolet light.

Approximately 500 m of each of the optical fibers obtained in Example 1, Example 2, and Comparative Example were placed in a bundle with a diameter of approximately 30 m in a dry tank, and heated to -50°C using a laser diode light source with a wavelength of 1.3 μm. When we measured the increase in optical transmission loss at
The optical fiber of Example 1 is 1. QdB/+m, Example 2
is 0.7dQ/km.

The comparative example was 6.9 dB/+a.

〔effect〕

The present invention makes it possible to take advantage of the advantages of ultraviolet curable paints (fast curing) while solving their disadvantages of light transmission and temperature characteristics. This problem,
This can be solved by applying and curing the primary coat layer in two stages or in multiple stages, but if an ultraviolet curable paint is used, multi-stage application and curing is possible if it is done in the production line. It's actually not that complicated.

Claims (4)

[Claims] (1) In the production of optical fibers, a primary coat layer with a thickness of 50 μm or more is applied by applying an ultraviolet curable coating onto a drawn glass optical fiber and curing it with ultraviolet rays. A series of processes consisting of applying ultraviolet curable paint and curing it using at least two
1. A method of manufacturing an optical fiber, the method comprising: repeating the process several times. (2) The manufacturing method according to claim (1), wherein the thickness of the coating layer formed in the first step of applying the ultraviolet curable paint and curing it with ultraviolet rays is 70 μm or less. (3) The manufacturing method according to claims (1) and (2), wherein the ultraviolet curable paint is a soft type. (4) The UV-cured paint has a Young's modulus of 10 at 25°C.
The manufacturing method according to claim (3), wherein the manufacturing method is of a soft type with a weight of ~100 kg/cm^2.