JPH11109138A - Method for removing optical fiber coating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily remove an optical fiber coating without degrading the strength of an optical fiber and coating a boundary part by removing the coating of the optical fiber using the liquid mixture in which hydrogen peroxide or hydrogen peroxide water is added to sulfuric acid. SOLUTION: The coating of an optical fiber is removed using the liquid mixture in which hydrogen peroxide or hydrogen peroxide water is added to sulfuric acid. The liquid mixture is 30:1 tol:1 in the weight ratio of sulfuric acid to hydrogen peroxide. After the coating of the optical fiber is removed using sulfuric acid, the optical fiber is cleaned using alkaline liquid (sodium hydrogencarhonate aqueous solution). The liquid in which 30% peroxide hydrogen water which is hydrogen peroxide diluted with water and sulfuric acid are mixed at the weight ratio of 1:3 is used for removing the coating. The sulfuric acid-hydrogen peroxide water 1 is placed in a beaker 2, and a optical fiber 3 whose clad is to be removed is slowly immersed by the dimension of removal. When this condition is kept for 30 seconds, the coating of the optical fiber 3 is dissolved and completely removed to expose an optical fiber 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for removing an optical fiber coating, and more particularly to a method for removing an optical fiber coating which is simple and highly reliable without deteriorating the strength of an optical fiber.

[0002]

2. Description of the Related Art In general, an optical fiber widely used in an optical communication system or optical applied measurement is coated with a resin for preventing disconnection, deterioration of transmission characteristics, identification, and the like. This resin is
Depending on the type of optical fiber used and the environment in which it is used, there are various types, such as an ultraviolet curable resin or a composite coated with a silicone resin and nylon. However, in any case, it is necessary to remove the coating of the terminal portion in various cases, such as connection between optical fibers, connection with various optical components, or attachment of a connector. Conventionally, the most common method of removing the coating is to mechanically peel off the coating using a blade or a dedicated tool. In addition, in the connection of an optical fiber in a submarine cable, hot sulfuric acid is used to remove the resin of the optical fiber in order to maintain the strength of the optical fiber after connection and ensure long-term reliability.

[0003]

The conventional optical fiber coating removing method has the following problems. First,
The mechanical coating removal method cannot avoid the damage to the optical fiber and inevitably reduces the strength of the optical fiber, so that it cannot be applied to applications requiring long-term reliability. That is, when the coating is mechanically peeled off, the surface of the optical fiber is scratched, and the scratch grows due to the surrounding moisture and the tension applied to the optical fiber, and eventually breaks. .

On the other hand, in the method using hot sulfuric acid, the temperature of sulfuric acid is set to 200 ° C. in order to completely remove the coating of the optical fiber.
It is necessary to raise the temperature to near. For this reason, sulfuric acid vapor rises sharply from the sulfuric acid liquid surface. The removal of the optical fiber coating in such an atmosphere causes the following problems.

(1) Since the sulfuric acid vapor adheres to portions other than the portion to be removed, deformation and alteration of the portion of the coating that should not be removed occur.

(2) A draft chamber for discharging sulfuric acid vapor is required, and the entire coating removing apparatus becomes large. Therefore, the work is not easy.

(3) At the boundary between the portion where the coating is removed and the portion where the coating is not removed, there is a risk that the sulfuric acid remaining in the coating may deteriorate the coating that should not be removed.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned disadvantages of the prior art and to provide an optical fiber coating removing method which can easily remove the coating without deteriorating the strength of the optical fiber and the coating at the boundary. It is in.

[0009]

In order to achieve the above object, the present invention is characterized in that the coating of an optical fiber is removed using a liquid mixture of sulfuric acid and hydrogen peroxide or a hydrogen peroxide solution. And

The mixed liquid preferably has a weight ratio of sulfuric acid to hydrogen peroxide of 30: 1 to 1: 1.

Further, the present invention is characterized in that at least after the coating of the optical fiber is removed with sulfuric acid, the optical fiber is cleaned with an alkaline liquid.

Preferably, the alkaline liquid is an aqueous sodium hydrogen carbonate solution.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) FIG. 1 is an explanatory view showing an embodiment of the optical fiber coating removing method of the present invention. In this embodiment, a liquid obtained by mixing a 30% aqueous hydrogen peroxide solution obtained by diluting hydrogen peroxide (H ₂ O ₂ ) with water and sulfuric acid at a weight ratio of 1: 3 was used. This liquid is hereinafter referred to as a sulfuric acid and hydrogen peroxide.

A sulfuric acid-hydrogen peroxide mixture 1 is placed in a beaker 2 and an optical fiber 3 whose coating is to be removed is slowly immersed therein. Immerse only to the size to be removed. By holding this state for 30 seconds, the coating of the optical fiber 3 is dissolved and completely removed, and the optical fiber 4 is exposed. This situation is shown in Fig. 1 (
b) shows.

If the holding time of the optical fiber 3 in the sulfuric acid / hydrogen peroxide 1 is too short, the coating is not completely removed, and the undissolved portion of the coating easily adheres to the optical fiber 4.
On the other hand, if the holding time is too long, the coating on the portion not immersed in the sulfuric acid-hydrogen peroxide 1 sucks up the sulfuric acid-hydrogen peroxide 1, and the coating is deformed.
to degrade. The immersion time can be determined according to the type of resin used for coating.

Next, the optical fiber 3 is moved up and down to shape the boundary 5 between the strand and the coating. This shaping step makes the boundary between the strand and the coating smooth, and facilitates the removal of sulfuric acid and hydrogen peroxide in the subsequent washing step. This situation is shown in Fig. 1 (c).
Indicates. The number of times of raising and lowering varies depending on the type of the resin to be coated, but several times to ten and several times is sufficient.

By removing the coating according to the above steps, there is no undissolved portion, and the coating can be removed to a desired size. Further, as a result of observing the covering portion at the boundary portion 5 between the strand and the covering, no deterioration such as deformation or discoloration is observed. In this method, since there is no mechanical contact with the optical fiber, there is no deterioration in the wire strength due to the removal of the coating.

The mixing weight ratio between sulfuric acid and hydrogen peroxide is 3
A range from 0: 1 to 1: 1 is suitable. Outside this range, the coating cannot be completely removed unless the temperature is 100 ° C. or higher. In addition, although the sulfate removal performance is improved by raising the temperature, the temperature does not need to be raised as the steam is generated intensely. Therefore, there is no need to provide a special exhaust chamber such as a draft chamber having a high exhaust speed, and there is an advantage that work can be performed anywhere. Further, since no vapor is generated, there is little possibility of deterioration of the coating which should not be removed.

FIG. 1 shows the removal of the coating of only one optical fiber, but it is also possible to remove the coating of a large number of optical fibers at a time, and the working efficiency is higher.

(Embodiment 2) FIG. 2 is an explanatory view showing another embodiment of the optical fiber coating removing method of the present invention. First, after removing the coating in the same manner as in Example 1, the optical fiber 7 from which the coating has been removed is sufficiently washed in the beaker 2 containing pure water 6. By cleaning with pure water 6, the amount of sulfuric acid remaining in the strands and coating of the optical fiber 7 is reduced. However, if the optical fiber 7 is placed in a high-temperature environment even after being sufficiently washed, the coating portion is deteriorated such as discoloration and deformation after a long time. This is because the formation of the compound produced by the reaction between the coating material and the slightly remaining sulfuric acid proceeds.

Therefore, a washing step using an alkaline liquid is performed to prevent this deterioration. In this embodiment, cleaning was performed with a 1% aqueous solution of sodium hydrogen carbonate (NaHCO ₃ ). In an optical beaker 2 containing an aqueous sodium hydrogencarbonate solution 8, the coating is removed and the optical fiber 7 is sufficiently washed in pure water 6.
Was washed. It was confirmed that by performing this washing step, the progress of deterioration of the coating can be suppressed even in a high-temperature environment.

In this embodiment, the coating is removed using sulfuric acid and hydrogen peroxide. However, when performing this washing step, the coating may be removed using only sulfuric acid.

[0023]

According to the present invention, the following excellent effects are exhibited.

(1) It is possible to eliminate the residual coating on the optical fiber after removing the coating.

(2) There is no deterioration in the strength of the optical fiber after the coating is removed.

(3) There is no deterioration such as deformation or discoloration of the coating at the boundary between the optical fiber and the coating.

(4) It is not necessary to use a special exhaust device such as a draft chamber, and the coating can be easily removed.

(5) Since the progress of the coating deterioration is suppressed,
It is possible to remove the coating with excellent reliability.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing one embodiment of an optical fiber coating removing method of the present invention.

FIG. 2 is an explanatory view showing another embodiment of the optical fiber coating removing method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sulfuric-hydrogen peroxide 2 Beaker 3 Optical fiber 4 Optical fiber 5 Boundary part of a wire and coating 6 Pure water 7 Coated optical fiber 8 Sodium bicarbonate aqueous solution

Claims (4)

[Claims] 1. An optical fiber coating removing method comprising: removing a coating of an optical fiber using a liquid mixture of sulfuric acid and hydrogen peroxide or a hydrogen peroxide solution. 2. The method according to claim 1, wherein the mixed liquid has a weight ratio of sulfuric acid to hydrogen peroxide of 30: 1 to 1: 1. 3. A method for removing an optical fiber coating, comprising removing the coating of the optical fiber using at least sulfuric acid, and then cleaning the coating with an alkaline liquid. 4. The method according to claim 3, wherein said alkaline liquid is an aqueous solution of sodium hydrogen carbonate.