JPS5842018A - Method for reinforcing treatment of optical fiber - Google Patents

Abstract

PURPOSE:To reinforce crack parts to restore and enhance the strength of the part, where a coating is eliminated, of an optical fiber, by treating this part with the mixture solution between a corrosive solution, which dissolves the optical fiber, and an organic solvent having a low surface tension. CONSTITUTION:In optical fibers 1A and 1B, quartz glass fibers are used as cores 2A and 2B, and a silicone resin is coated around them. For the purpose of connecting two optical fibers 1A and 1B, the resin of clad parts is eliminated to obtain parts 2A and 2B where coatings are eliminated. They are connected with arc discharge by fusion-fixing to form a fusion-fixing connection part 3. The fusion-fixing connection part 3 is soaked in a surface treatment liquid 4 consisteing of a fluoric acid, which dissolves glass fiber cores 2A and 2B, and the mixture liquid between ethanol and water, which has a low surface tension, for two minutes and is dried. By this treatment, cracks generated on the surface of parts 2A and 2B are dissolved and reinforced, and foreign matters are eliminated, thereby restoring the mechanical strength of these parts considerably.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for strengthening optical fibers. During this process, the coating layer is removed from a predetermined portion of the optical fiber, but this often damages the surface of the optical fiber or leaves the coating incompletely removed. After the coating has been removed, a coating will be formed again on the part where the coating has been removed, but if the coating is formed without taking measures to address the defects mentioned above, problems with strength will remain, which could lead to breakage accidents later. occurs.

In particular, in the fusion splicing method that uses discharge heat, which is often used to reduce splice loss, dust in the air and metal particles from the discharge electrode can also adhere to the fusion splice of optical fibers, resulting in poor strength. The problem gets bigger and bigger.

In order to solve the above-mentioned problems, the present invention attempts to restore the strength of the removed portion of the optical fiber by effectively treating the surface of the removed portion of the optical fiber. Let's explain by example.

In FIG. 1, (1)A% 1l)B is the coated optical fiber, +2)A% +21B is the coated removed part, and both optical fibers (11A%
B is connected by discharge heating, laser heating, etc., with the end surfaces of B being butted against each other, thereby forming a fusion spliced part (3).

In the present invention, for example, as shown in Fig. 2, a special surface treatment liquid (4
) in the liquid tank (5) containing both optical fibers (1) A
s (tl Coating removal part of B (21A % (21B
Surface treatment.

The surface treatment liquid (4) referred to here is a corrosive solution that dissolves in the optical fiber (glass) 1, and a surface tension with a boiling point of 100°C.
(below).

Specific corrosive solutions include hydrofluoric acid and ammonium fluoride aqueous solutions, while organic solvents include alcohols such as methanol and ethanol, ketones such as acetone and methyl ketone, n-pentane and n-hexane. The above-mentioned surface treatment liquid (4) consists of one type of corrosive solution and one or more types of organic solvents.

In the above, the optical fiber ill A to the surface treatment liquid (4)
.

(Coating removal part (2) A/+2 of 11B) When immersed in B' - The organic solvent in the treatment liquid (4) has a small surface tension, so the coating removal part 12
JA 5(2) increases the wettability to B, and on the other hand, increases the wettability to
Various impurities adhering to 1A%(2)B are dissolved and removed, and even minute scratches are repaired.

When using only the corrosive solution, the coating removal area was +21 A.

(2) The wettability for B is insufficient, and penetration of the liquid into extremely small gaps such as the cracks mentioned above is considerably inhibited; however, the surface treatment liquid (4) here contains an organic solvent with a low surface tension. Because they are mixed, the coating removal section (21A
% (The wetting effect spreads not only to the front side of 21B but also to the sharp tip inside the crack.

Due to this wetting effect, the corrosive solution also penetrates to the tip of the crack, so that the coating removal area +21A,
+2) Not only the impurities adhering to the surface of H are dissolved, but the tips of the cracks are also rounded off by the dissolving action of the corrosive solution, and this dulling effect causes small scratches (cracks) to disappear. It is no longer a growing wound.

As a result, the strength deterioration factors are removed in a short time from the coating removed portions (2) A and (2) B of the optical fibers (1) A s fl ) B, and the fusion spliced portion (3) is similarly strengthened. It will be processed.

Hereinafter, the coated removal part (21A s
(After 211j is taken out of the liquid tank (5), organic,
It is heated above the boiling point of the solvent (1) and then subjected to treatments such as washing with water and drying as necessary. Coating with epoxy resin, urethane resin, nylon, etc. should be applied immediately.

In addition, the optical fiber ft to be processed in the present invention
l A % +1) B is a quartz-based optical fiber, a multi-component glass fiber, a plastic clad 7-iper whose cladding is made of silicone resin, etc. Among these, in the case of a glass clad fiber, the clad hemp is removed during fusion splicing etc. Therefore, at the time of coating after the first strengthening treatment, the cladding is again formed in a predetermined shape.

The table below shows the surface tension, boiling point, etc. of each of the organic solvents mentioned above in comparison with that of water. Examples and comparative examples will be explained.

Specific example: A quartz-based GI type optical fiber with a silicone resin coating layer having an outer diameter of 400 μm, a core diameter of 50 μm, and a 7-eye diameter (radius outer diameter) of 125 pm. +2
1A and +21 B' and fusion-connected them by arc discharge (- electrode is tungsten), thereby forming a coating removal part (2) A having a fusion-connected part (3).

(2) B was immersed in HF 8.6 mol/t% ethyl alcohol 1 volume (4) for 2 minutes, and then these coated parts removed from stage 1 [4] (2) A s (2) B 1
When dried by heating to below 00°C, the average tensile strength of the 20th piece was 103 g/125 μmψ.

Comparative example Cover removal part (2+ A % (
21 B which is not subjected to any strengthening treatment, and 1 whose coating is removed (2) A, +21 B to H F
8. 6 moles/1.

Each sample was immersed in a surface treatment solution with the remainder being pure water for 2 minutes and then heated and dried, and their tensile strength was measured. In the former case, the average was 51g/125μmφ.
Even in the latter case, the V was reduced to an average of 85 g/125 μmψ.

As is clear from each of these sides, in the case of the present invention, the strength of the coating removed portion (2) A % 121 B can be recovered to a large extent.

As explained above, when the method of the present invention is affected, the coated portion of the optical fiber is surface treated using a surface treatment solution consisting of a mixed solution of a corrosive solution that dissolves the west fiber and an organic solvent with low surface tension. By doing so, the mechanical strength of the removed coating can be recovered to a large extent in a short period of time.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of an optical fiber, its coating removal section, and fusion splicing section, and FIG. 2 is an explanatory diagram showing one embodiment of the method of the present invention. +IIA% +1) B...Optical fiber 121 A
, , (2) B...Coating removal part (3)...
...Fusion splicing part (4)...6 Surface treatment liquid (5)...Naru liquid Tank patent attorney Hikihi I +1Also If Figure ts 2 Continuation of figure 1 page ■Applicant Koga Denki Kogyo Co., Ltd. 2-6-1 Marunouchi, Chiyoda-ku, Tokyo

Claims (3)

[Claims] (1) In the reinforcing method, the optical fiber from which the coating layer has been removed is coated with a surface treatment solution consisting of a mixed solution of a corrosive solution that dissolves the optical fiber and an organic solvent with low surface tension. A method for strengthening an optical fiber, which features a bump for surface-treating the removed portion. (2) A method for strengthening an optical fiber according to claim 1, in which any one of hydrofluoric acid and ammonium fluoride aqueous solution is used as the corrosive solution. (3) The method for reinforcing an optical fiber according to claim 1, in which one or more selected from alcohols, chthons, and hydrocarbons is used as the organic lysate.