JPS58130308A - Treatment for reinforcing juncture of optical fibers - Google Patents

Abstract

PURPOSE:To improve the adhesive strength in the juncture of a pair of optical fibers to be connected by forming films by silicone oil on the outside circumferences of said fibers and melt sticking the same then treating the surface of the juncture with a corrosive soln. which dissolves the optical fibers. CONSTITUTION:Prior to butting the end faces of a pair of optical fibers 3A, 3B to be connected to each other and melt sticking the same to each other, films 4A, 4B of silicone oil are formed on the outside surfaces of the fibers 3A, 3B using absorbent cotton or the like. The fibers are cut perpendicularly to make butt end faces 5A, 5B, which are melt stuck and connected with discharge electrodes 6M, 6N whereby a juncture 7 is obtaned. Thereafter, the juncture 7 is dipped in a corrosive soln. 8 consisting of aq. mixed solns. of hydrofluoric acid and strong acid, and is subjected to a surface treatment for a prescribed time. The factors for degrading strength are eliminated by such two ways of the treatments before and after the connection, whereby the mechanical strength in the juncture of the optical fibers is improved remarkably.

Description

[Detailed description of the invention] The present invention relates to a method for fusion splicing optical fibers.

As a method for permanently splicing optical fibers, a method is often adopted in which the ends of a pair of optical fibers are brought into a butt state and each end is fusion spliced by arc discharge or the like.

This method is effective in that it can reduce the splice loss at the joint, but the average strength when tensile force is applied to the joint is extremely small, about 40~/ad, so it poses a strength problem. An investigation and a solution are needed.

In the present invention, in proposing a method for fusion splicing optical fibers, one of the problems mentioned above is resolved as follows: In general, in this type of fusion splicing, the ends of a pair of coated optical fibers to be connected are Remove the coating from the part using a coating removal tool to expose a portion of the optical fiber, and wipe the remaining coating on the exposed part completely with absorbent cotton moistened with an organic solvent such as acetone. Next, the tips of these optical fibers are cut perpendicularly to create proper abutting end faces, and then both abutting end faces are abutted against each other and both are heated by arc discharge using a pair of discharge electrodes or by laser heating. Optical fibers are fusion spliced.

When connecting in such a case, fine scratches occur on the surface of the optical fiber from which the coating has been removed during handling, and these fine scratches become a factor in deteriorating the strength of the spliced portion.

In addition, foreign matter such as dust in the air tends to adhere to the surface of the exposed part that has been cleaned with an organic solvent such as acetone during handling, and if such foreign matter remains attached to the surface, When the two abutting end faces are brought together and heat-fused by arc discharge or laser heating, these foreign substances stick to the surface of the fused part or get mixed into the optical fiber, which also deteriorates the strength of the connected part.

On the other hand, in the exposed part during heat fusion, there are parts that are strongly heated and parts that are hardly heated, and minute cracks occur on the surface of the exposed part due to thermal strain caused by the temperature difference at this time. As mentioned above, it can be said that these various causes lead to problems in the strength of optical fiber connections. In the present invention, which provides a method for strengthening optical fiber connections that can effectively eliminate the above factors, a pair of coated optical fibers fl)i (IIB
Coating from the end of (21A).

(2) B is removed using a coating removal tool (not shown) to expose the optical fiber [3] A, +31 B, and the exposed portion of the optical fiber (31 A% Remove the residue of coatings +21A and +21B by wiping with absorbent cotton.

Thereafter, using synthetic paper impregnated with silicone oil, the coated +21 A % +21 B was removed and the optical fiber (3) A s [3) B was gently wiped to form the optical fiber (3) A , f3 as shown in Fig. 2. ) A film of silicone oil (41A% f4) B is formed on the surface of B.

In addition, in this example, the optical fiber (3) A% (3
Silicone oil film f4) A on the surface of 1B,
f4) Synthetic paper impregnated with silicone oil was used as a means for forming B, but it is also possible to use a fiber material such as absorbent cotton or gauze impregnated with silicone oil, and the silicone oil may be in an emulsion state or grease. In addition, silicone oil dissolved in an organic solvent such as acetone used when wiping off the coating residue of the optical fiber f3) A, [31B may be used, thereby removing the coating residue. Removal and film formation may be performed simultaneously.

A silicone oil coating (4 hA) was applied as described above.

(4) Optical fiber f3) A, (3
1B, the tip side is cut vertically as shown in Figure 3, thereby creating a proper butting end surface f5) A s [5]
Make B 9 to then the two abutting end faces in Figure 4 +51
Match A, +51 B to each other and 1
Pair of discharge electrodes f6)M.

(6) The two-party fiber f due to arc discharge via N
31A, [31B are fusion spliced.

After the fusion splicing, the joint (7) is immersed in a corrosive solution (8) for the required time as shown in FIG.

This corrosive solution (8) is applied to the optical fiber [3) A, (
3) It has chemical properties that require it to dissolve B, specifically hydrofluoric acid, a mixed aqueous solution of hydrofluoric acid and strong acids (sulfuric acid, nitric acid, hydrochloric acid), ammonium fluoride aqueous solution, and even fluoride. A mixed aqueous solution of an acid and an ammonium fluoride aqueous solution is used as the corrosive solution (8).

The connection (7) is thus immersed in the corrosive solution (8);
After wetting the surface with the liquid (8) for the required amount of time and completing the prescribed treatment, the connecting portion (7) is taken out of the corrosive solution (8) and washed with water or alkali. After cleaning and further drying, the outer periphery of the optical fibers +31A, (31B) having the connection part (7) is immediately coated with silicone resin, epoxy resin, urethane resin, nylon, etc.

As mentioned above, in the present invention, the optical fiber [31A% (
3) Before fusion splicing B, a silicone oil coating (4) A % +41 B is formed on the outer periphery of each optical fiber f3) A s [3) B before the fusion splicing. fiber f31 a
% f3) Foreign matter is less likely to adhere to the surface of B, and surface scratches can be prevented from occurring during handling.

Therefore, such original fiber +31 A, (3
When fusion splicing 1B by arc discharge or laser heating, no foreign matter is burned onto the optical fiber surface or mixed into the optical fiber, and there is no possibility of splicing with minute scratches on the surface. Therefore, the connection part (7
) can prevent the strength from decreasing.

In addition, after fusion splicing, the optical fiber [31A, [3]
Its connection (7) by a corrosive solution (8) that dissolves B.
Since the surface is treated for the required time, even if minute cracks occur on the surface of the connection part (7) due to thermal strain during fusion, these will be erased by the dissolving action of the corrosive solution (8). to be teased or teased.

Therefore, it is possible to eliminate the decrease in strength caused by thermal strain during fusion splicing.

Next, a specific example will be described.

Silica-based CI type optical fiber [31A s [al Coated optical fiber t whose outer diameter of B is 125 μm (core diameter 50 μm), outer diameter of primary coating with silicone resin is 400 μm1, and outer diameter after coating with nylon 12 is 900 μm
l) In A% IIIB, from these ends the coating (
2) Aζ(2)B is removed by a known coating remover, thereby creating a stripped optical fiber (31A, (a)
Wipe the outer periphery of B with an acetone-impregnated wiping member (gauze), then lightly wipe the outer periphery of each fiber [31A% [31B] with silicone oil-impregnated synthetic paper to remove the silicone oil coating (4) A s [4) B was formed.

Next, the optical fibers f3) A, (31B) having the coating f41A% +41B are set in an optical fiber cutter and cut vertically so that the length of 31B is about 30 m, and then the respective fibers are [31A%
[31B was set in a fusion splicer using arc discharge and fusion spliced.

Furthermore, after that, the connection part (7) according to the above was added with 45 mo of hydrofluoric acid.
t/L and 4.5 mo of sulfuric acid! It was immersed in a corrosive solution (8) consisting of 7'L of mixed aqueous solution for 1.5 to 10 minutes, and after the immersion treatment, the connection part (7) was washed with water and dried.

The average tensile strength of the optical fiber connections treated by this method (average value of 20 fibers) was 9 Ad at p 147,
The maximum strength was as high as 1 hair after exposure to 244.On the other hand, when only the treatment with the corrosive solution (8) was carried out, the coating [41A% (comparative example in which no 41B was formed) had the same average tensile strength as above. The tensile strength is 64 Kf/all, and the maximum tensile strength is 86 Kg/all.
I didn't show myyl L.

Of course, in the conventional example in which no measures are taken, the average tensile strength is about 40 Kf/-, as described above.

As explained above, the method of the present invention has two parts to be connected to each other.
In a method in which the end faces of a pair of optical fibers are brought into a butt state and the respective end faces in the same state are fused to each other to form a connection part, before the above fusion, a coating of silicone oil is formed on the outer periphery of each fiber. After the above-mentioned fusion, the joint is surface-treated for the required amount of time using a corrosive solution that dissolves the optical fiber, so the two types of treatment before and after the splicing eliminate all factors that cause deterioration of the strength of the spliced part. This will greatly improve the mechanical strength of the original fiber connection.

[Brief explanation of the drawing]

1 to 5 are explanatory diagrams schematically showing one embodiment of the method of the present invention in the order of its steps. 11) A% tl) B ,...Fist coated optical fiber +
21A% +2) B, -, @, Covering 13) Ax
[3) B, ... Optical fiber +41 A% +4
) B...Conflict/butt end face +61M, +61N...
- Discharge electrode (7) - φ... Connection part (8) - 0 - Corrosive solution Patent applicant representative Patent attorney Makoto Ito Continued from page 1 0 Inventor Tategami Magnetic Industry Co., Ltd. Chiba Electric Wire 0 applications within the factory Person Furukawa Electric Co., Ltd. 2-6-1 Marunouchi, Chiyoda-ku, Tokyo

Claims (1)

[Claims] In a method in which the end faces of a pair of optical fibers to be connected to each other are brought into a butt state and the respective end faces in the same state are fused together to form a connection part, before the above fusion, the outer periphery of each optical fiber is coated with silicone oil. After the above fusion,
1. A method for strengthening an optical fiber joint, comprising surface-treating the joint for a required period of time using a corrosive solution that dissolves the optical fiber.