JPS5842016A - Method for reinforcing treatment of fusion-fixing connection part of optical fiber - Google Patents

Abstract

PURPOSE:To keep the mechanical strength for a long time, by coating a fusion-fixing connection part, where a pair of optical fiber end parts are butted to each other and are fusion-fixed, with a gas-permeable film after subjecting this fusion-fixing connection part to the surface teatment with a corrosive solution which dissolves optical fibers. CONSTITUTION:Optical fibers 1A and 1B have coating layers eliminated from end parts 2A and 2B and are butted and are fusion-fixed by arc discharge or the like to form a fusion-fixing connection part 5. A corrosive solution 6 such as a hydrofluoric acid which dissolves optical fibers is stored in a liquid bath 7, and the connetion part 5 between optical fibers 1A and 1B is soaked in the liquid bath 7 and is subjected to a required reinforcing treatment. The connection part 5 subjected to the reinforcing treatment is taken out to the outside of the liquid bath 7 and is washed. High polymer materials having a high gas permeability such as a thermosetting silicone resin are applied to the outside circumference of the connection part 5 including end parts 2A and 2B, and a film 8 formed by this aplication is subjected to the heat treatment by a cylindrical heater 9. Thus, the mechanical strength of the connection part is improved, and adhesion of dust or the like is prevented to connect optical fibers stably for a long time.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for strengthening a fusion splice in an optical fiber.

This method has been adopted as a permanent splicing method for optical fibers.One method is to put the ends of a pair of optical fibers together and then fusion splice each end using arc discharge. This type of fusion splicing method is often practiced for reasons such as low loss. Figures 1 to 3 show such a fusion splicing method, and we will explain it below and point out the problems. For the connection, connect the ends of the optical fibers (11A, 11B (21A
.

(2) removing the coating layer from B and forming each end +21 A;
+21 B. is exposed, and then as shown in Figure 2,
The tips of these ends (2) A and +21B are cut almost vertically to create proper abutting end surfaces (31A, (31B), and then both abutting ends ?fi13)A, as shown in Figure 3.
+31B against each other and a pair of discharge electrodes ('41M, +4).
1B, but when connecting in such a case, the above-mentioned end t2)A without a covering.

(2) B is damaged during handling, resulting in minute surface scratches, as well as residual coating layers that are not completely removed from each end (2) A, +21 B and adhere to its surface. Dust in the air, metal particles from the discharge electrode, etc. become combustion residue and adhere to the surface of the fusion joint (5),
The above-mentioned causes, such as deterioration of strength, lead to the above-mentioned strength problems.

For these reasons, the tensile strength of the fusion splice (5) is significantly lower than the tensile strength of normal optical fibers, which is approximately 400 Kf/RdJ, to an average of 30-40/II! 0 The present invention has been made to solve the above-mentioned problems, and a specific method thereof will be explained below with reference to illustrated embodiments.

In the present invention, for example, a corrosive solution (6) as shown in FIG. Connection part +51
The corrosive solution (6) at this time is hydrofluoric acid, a mixed aqueous solution of a hydrofluoric acid aqueous solution and a strong acid, an ammonium fluoride aqueous solution, or an ammonium fluoride aqueous solution and a hydrofluoric acid aqueous solution. A mixed aqueous solution is used.

The strong acids referred to here include sulfuric acid, hydrochloric acid, nitric acid, etc. having an acid constant of about 10' or more.

Incidentally, the acid constant of hydrofluoric acid is 6.7×10-', and it is classified as a weak acid.

In the present invention, as mentioned above, there is an optical fiber inside the liquid tank (7)! Immerse the fusion splice (5) of IIA, (IIB) and soak the fusion splice (5) in the corrosive solution (6) for the required time.
).

In this way, when the fusion splice (5) is wetted with the corrosive solution (6), the surface of the fusion splice (5) is melted by the corrosive solution (6), and any combustion that is stuck to the surface is melted. Residues and the like are also removed by the dissolving action at this time.Of course, minute scratches that have occurred on the surface of the fusion splice (5) are also removed at the same time.Hereinafter, the fusion splice strengthened in this way After (5) is taken out of the liquid tank (7), the corrosive solution (6) adhering to its surface is washed away by water washing, alkaline washing, etc. 〇The following describes the fusion after the treatment. A predetermined coating will be formed on the connection part (5) in order to prevent dust from adhering to its surface, but this requires special measures in conjunction with the above-mentioned strengthening treatment. .

In other words, if prevention of dust adhesion is important, it is better to form a film as early as possible, but for example, due to the insufficient cleaning effect, a corrosive solution (6 ) remains, if a film is formed at an early stage without waiting for the residual components to volatilize completely, the remaining components will remain fixed due to the sealing effect of the film and cause unnecessary corrosion of the optical fiber. As a result, strength deterioration of the fusion splice (5) will reoccur in the long term.

Therefore, it is necessary to take measures to prevent these problems from occurring when forming the above-mentioned film.

Therefore, in the present invention, the fusion spliced part (5) after the cleaning is covered with a coating (8) made of a polymeric material with good gas permeability, and at this time, heat treatment is also used to fuse the spliced part (5). The corrosive solution remaining on the surface of the connection part (5) was actively evaporated, thereby volatilizing the remaining components to the coating (8).

This point will be explained below with reference to an embodiment shown in FIG. A good polymeric material is applied, and the film (8) formed thereon is heat-treated using a cylindrical heater (9).

When treated in this way, there is no problem even if the film (8) is formed early for the purpose of dustproofing, etc. However, if the corrosive solution (6) remains on the surface of the fusion splice (5), The remaining components of the wire (6) are vaporized by the heating at this time, and are transmitted through the coating (8) and dissipated to the outside in a short period of time, so that the above-mentioned unnecessary corrosion does not occur.

In this case, the coating material may include gas-permeable polymeric materials (rubber, plastic, etc.), and among these, thermosetting silicone resin is preferable, and the thinner the coating (8), the better. Increases air permeability.

Further, when the coating material is thermosetting, curing during formation of the coating and removal of the corrosive residual components can be performed simultaneously.

On the other hand, if this heat treatment is performed in an air stream or vacuum, the removal and efficiency per unit time will be increased due to the drying effect, oily effect, etc.
C or more, preferably 100' (!) or more, the vaporization of the corrosive residual components is promoted.

Moreover, the heating temperature at this time is the above-mentioned end part f21 A.

(2) Considering the heat resistance of the coating of B, it is usually kept within its heat resistance limit. Also, as shown in the tRG diagram, by coating the outer periphery of the edge coating layer with a thermosetting resin or a thermoplastic resin with a high melting point, the heat treatment temperature can be increased, and therefore, as described above, the desired removal efficiency can be achieved. In addition, the optical fibers (1) A and (IIB) to be treated in the present invention include not only the above-mentioned quartz-based optical fibers, but also multi-component glass fibers and plastic clad fibers whose cladding is made of silicone resin, etc.
These fusion splices can also be strengthened in the same way.

As explained above, according to the method of the present invention, the mechanical strength of the fusion spliced part is increased by surface-treating the fusion spliced part of the optical fiber with a corrosive solution. The purpose is to form a gas-permeable coating on the fusion splice after the above-mentioned strengthening treatment, and to vaporize the remaining components of the corrosive solution on the surface of the fusion splice to the outside of the coating. Since it is volatilized, problems such as dust adhesion and corrosive residual components can be solved all at once, and therefore an optical fiber fusion splice can be made stable over a long period of time.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing a state in which the coating is removed from the end of the optical fiber;
Fig. 2 is an explanatory diagram showing the end face processing state of the same end portion, Fig. 3 is an explanatory diagram showing the fusion state of the same end part, and Fig. 4 is an explanatory diagram showing the state of strengthening treatment with a corrosive treatment solution in the method of the present invention. FIG. 5 is an explanatory diagram showing the state of formation of a gas permeable film and the state of removal of corrosive residual components in the same method, and FIG. 6 is an explanatory diagram showing other examples. (1) A, (IIB... optical fiber (2) A, (
2) B... End (5)... Fusion joint (6)... Corrosive solution (8)... Gas permeable coating - (9)・・・
...Hita Patent Attorney Makoto Ifuji 112 Figure 3 Figure 4

Claims (1)

[Claims] (11) A method for strengthening a fusion spliced portion formed by abutting a pair of optical fiber ends to be connected to each other, fusing the ends to each other, and kneading. In this method, the fusion spliced portion after surface treatment with a corrosive solution that dissolves the optical fiber is coated with a gas-permeable coating, and the corrosive residual components remaining in the fusion spliced portion are vaporized. A method for strengthening a fusion spliced portion in an optical fiber, characterized in that the fusion splice is made to pass through the coating. (2) In the optical fiber according to claim 1, the corrosive residual component is vaporized by heat treatment. A method for strengthening a fusion splice. (3) A method for strengthening a fusion splice in an optical fiber according to claim 2, wherein the heat treatment is performed in an air stream. (4) The heat treatment is performed in a vacuum atmosphere. A method for strengthening a fusion splice in an optical fiber according to claim 2. (5) The heat treatment temperature is 60°C or higher. Claims 2, 3, and 4 A method for strengthening a fusion splice in an optical fiber according to any one of claims 1 to 6. (6) Strengthening a fusion splice in an optical fiber according to claim 1, wherein the gas-permeable coating is formed of a polymeric material. Processing method 0 (7) A method for strengthening a fusion splice in an optical fiber according to claim 1 or 6, wherein the gas-permeable coating is formed of a high-melting point polymeric material. (8) Corrosion. Method 0(9) of strengthening a fusion splice in an optical fiber ζ according to claim 1, characterized in that hydrofluoric acid is used as a corrosive solution.A mixed aqueous solution of hydrofluoric acid and a strong acid is used as a corrosive solution. A method for strengthening a fusion splice in an optical fiber according to claim 1, characterized in that the Ql strong acid is any one selected from sulfuric acid, nitric acid, and hydrochloric acid. A method for strengthening a fusion splice in an optical fiber according to claim 3. The optical fiber according to claim 3, wherein the αυ strong acid is a mixed solution of two or more selected from sulfuric acid, nitric acid, and hydrochloric acid. A method for strengthening a fusion splice in an optical fiber according to claim 1, characterized in that an ammonium fluoride aqueous solution is used as the corrosive solution. ammonium fluoride aqueous solution as a corrosive solution.
A method for strengthening a fusion splice in an optical fiber according to claim N, characterized in that a mixed aqueous solution of hydrofluoric acid is used.