JPH0766091B2 - Optical fiber fusion splicing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Outline] When fusion splicing optical fiber strands, the coating of the end portions of the optical fiber core wires is peeled off, and then the optical fiber strands are gripped by a connecting jig. At that time, an ultraviolet curable resin is applied to the surface of the optical fiber element wire so as not to damage the surface of the optical fiber element wire, and a protective coating for the fusion splicing work is formed in advance.

[Industrial application field]

 The present invention relates to a fusion splicing method for optical fibers.

An optical fiber for optical transmission has a form of an optical fiber cable in which a plurality of optical fiber core wires made of silica-based glass as a main component and having a protective coating are applied to form a jacket to form an outer cover. It is common to take. Here, there are two types of optical fiber strands, a core glass type of silica-based glass fiber and a converging type, which is an optical fiber main body for transmitting light. The protective coating of the optical fiber core wire is a coating that protects the optical fiber element wire, and the coating on the optical fiber element wire is usually formed by a primary coat and a secondary coat. The primary coat is formed of a silicone resin or the like on the fiber strand, and the secondary coat is formed of a thermoplastic resin such as nylon on the primary coat. Further, the optical fiber cable is made by bundling a plurality of optical fiber core wires with an outer jacket.

The connection of the optical fibers in the above-described form is performed by peeling off the jacket of the optical fiber cable, peeling off the coating of the bundled optical fiber core wires, and then abutting the end faces of the pair of optical fiber wires and melting them by arc discharge or the like. It is necessary to connect and connect the optical fibers, and then to protect and coat the optical fiber wires, and then bundle a plurality of optical fiber core wires and coat them with a jacket. Here, the fusion splicing is
After peeling off the coating on the end of the optical fiber core wire, grind the end surface of the optical fiber wire, hold the optical fiber wire in a connection jig, and butt the end surfaces of the pair of optical fiber wires together by arc discharge or the like. It is melted and connected.

The connection jig directly contacts the surface of the optical fiber strand to grip the optical fiber strand. Then, fine scratches are formed on the surface of the optical fiber strand. Here, minute scratches on the surface of the optical fiber strand grow due to bending and vibration in the optical fiber cable facility, and are major factors such as breakage of the optical fiber strand.

Therefore, there is a demand for a method of protecting the optical fiber wires, especially during the fusion splicing work of the optical fiber wires.

[Conventional technology]

Usually, conventional optical fiber connection is performed by the following procedure.

First, the jacket of the optical fiber cable is removed, the optical fiber core wire is stripped from the jacket, and each end of the optical fiber core wire is covered with a stripping jig such as a nonic by a stripping jig.
Peel off. The end faces of the individual optical fiber wires are ground and smoothed, and then the optical fiber wires are connected to the V groove portion 3a of the connecting jig 3.
Attach to and hold. The V-groove 3a of the connection jig 3 is adjusted by shifting it vertically and horizontally, aligning the optical axes of the pair of optical fiber strands to be connected, butting the end faces of the optical fiber strands together, and by arc discharge. Fusion splice. After making the connection, the connected optical fiber strand is dipped in hydrofluoric sulfuric acid (a mixed solution of hydrofluoric acid and sulfuric acid) to repair the scratches on the surface of the optical fiber strand due to the holding of the connection jig during fusion splicing work. As a result, the surface of the optical fiber strand becomes smooth, and as a result, the tensile strength of the optical fiber strand is enhanced. The repaired optical fiber strand is dipped in a solution of an ultraviolet curable resin or sprayed with a solution of the resin to apply the resin to the surface of the optical fiber strand. And
The applied ultraviolet curable resin is irradiated with ultraviolet rays to be cured, thereby forming a protective film as an initial coating on the surface of the optical fiber element wire, and reinforcing the connected portion of the optical fiber element wire. After that, a protective coating is applied to the surface of the optical fiber strand, and there are various methods for applying it. For example, a silicone resin is applied and cured, and then a protective coating formed by pouring a thermoplastic resin such as nylon 12 into the mold using a mold to solidify the optical fiber is applied to the optical fiber core wire. To complete the protective coating. Then, a plurality of optical fiber core wires are bundled, the outer cover is packaged, and the connection of the optical fibers is completed. In this conventional method for connecting optical fibers, highly dangerous hydrofluoric acid is used to repair the scratches on the optical fiber wires after fusion-splicing the optical fiber wires. as a result,
There is a problem in that attention must be paid to the handling of hydrofluoric acid, and the surface of the optical fiber strand cannot be completely repaired.

A connection method that does not require the use of hydrofluoric acid has also been proposed. One of them is a method of connecting an optical fiber by forming a protective layer for protecting the optical fiber element wire in advance by fusion splicing at the time of manufacturing the optical fiber core wire. Specifically, a thin film of a resin having a relatively high hardness, that is, an organic thin film, which serves as a protective layer, is previously formed on the optical fiber strand. The optical fiber core wire has a protective layer coated with a silicone resin and a thermoplastic resin such as nylon. When peeling off the coating of such an optical fiber core wire, of the secondary coating of the thermoplastic resin such as nylon forming the coating and the primary coating of the silicone resin, the silicone resin of the primary coating remains without being completely removed. As a result, there is a problem in that when the remaining silicon resin is completely removed with a case or the like, the organic thin film under the silicon resin is also peeled off.

As a further improved connection method, a layer having good peeling property (for example, a non-reactive polysiloxane is applied in advance between the coating of the optical fiber core wire and the thin film on the optical fiber core wire during the production of the optical fiber core wire. There is a method of additionally forming the formed layer). However, as in the case of the above-mentioned connecting method, during the manufacturing, it is possible to additionally form a special coating layer only for protecting the optical fiber strand during the fusion splicing work over the entire length of the optical fiber strand. In designing the coating of (1), new constraint conditions are imposed, and it is not possible to design that satisfies the constraint conditions such as the ordinary optical fiber core wire. When designing a coating for a commonly used optical fiber core, the coating thickness etc. are optimized to satisfy various conditions so that the optical fiber element wire will not be damaged or the transmission characteristics deteriorate due to temperature changes or external pressure. ing.

[Problems to be solved by the invention]

According to the conventional optical fiber connecting method, after the optical fiber element wires are fusion-spliced, the optical fiber element wires can be immersed in hydrofluoric acid to remove fine scratches existing on the surface of the optical fiber element wires. However, care must be taken when handling chemicals, as they may not be able to completely repair the scratches and use highly dangerous chemicals. Further, in the optical fiber splicing method that does not require the use of hydrofluoric acid, the protective layer for protecting the surface of the optical fiber element wire at the time of fusion splicing is formed in advance over the entire length of the optical fiber core wire at the time of manufacturing. However, it is not designed in consideration of various constraints on the usual coating of the optical fiber core, but rather the number of steps in the manufacturing process of the optical fiber core is increased and the manufacturing cost is increased.

Therefore, according to the present invention, unlike the conventional optical fiber connecting methods, it is not necessary to use a highly dangerous chemical agent (here, fluorinated sulfuric acid) at the time of connecting work, and various coatings for the optical fiber core wire are provided. This is an optical fiber connection method using a normal optical fiber core wire that satisfies the constraint condition.

[Means for solving problems]

The present invention peels off the coating of the end portion of the optical fiber core wire to expose the surface of the optical fiber elemental wire, and then forms a protective coating at the time of fusion splicing work on the exposed surface with an ultraviolet curable resin, and thereafter, An optical fiber fusion splicing method is characterized in that the optical fiber strands are fusion spliced.

[Action]

By removing the coating on the end of the optical fiber core and immediately applying a thin UV curable resin evenly and without eccentricity due to the coating, a protective coating can be formed during fusion splicing work. . As a result, when the end face of the optical fiber strand is ground or the optical fiber strand is gripped by the connecting jig, the scratches caused by contact with the optical fiber strand do not attach to the surface of the optical fiber strand, and the surface of the optical fiber strand is completely covered. Can be protected.

〔Example〕

As shown in the perspective view of FIG. 1, the coating of the end portion of the optical fiber core wire is completely peeled off by a stripping jig such as nonic to form an optical fiber element wire 1, and the surface of the optical fiber element wire 1 is covered. A UV-curable resin whose viscosity is adjusted to approximately 500 cps is applied by surface tension to a film thickness of several microns, and the surface of the applied optical fiber strand 1 is irradiated with UV light to cure the UV-curable resin and protect it. Form 2. afterwards,
The end face of the end portion of the optical fiber element wire 1 on which the protective coating 2 is formed is ground. Further, the protective coating 2 which protects the surface of the optical fiber element wire 1 in advance before fusion is removed by a solvent from the tip of the optical fiber element wire 1 by a few millimeters. Then, the optical fiber strand 1 from which the protective coating 2 is removed only at the tip is mounted and gripped in the V groove portion 3a of the connecting jig, and the V groove portion 3a is moved vertically and horizontally to align the optical fiber strands 1 of the pair of optical fiber strands 1. The end faces are abutted against each other, and each optical fiber element wire 1 is brought into contact with an electrode for arc discharge to perform arc discharge. As a result, the ends of the butted optical fiber strands 1 are fused and the end faces of the optical fiber strands 1 are connected. However, the work after the fusion splicing is the same as that described in the conventional art, and therefore the description thereof is omitted here.

Further, in the present invention, after peeling off the coating of the optical fiber core wire, by using an ultraviolet curable resin which is quick-drying and has good workability,
Immediate application to the surface of the optical fiber wire saves great attention to scratches on the surface of the optical fiber wire during fusion splicing. As a result, the work of connecting the optical fibers can be performed quickly and efficiently, so that the time for connecting the optical fiber cables such as the optical submarine cable can be shortened. As a result, the load on the optical submarine cable due to the water pressure difference is reduced,
Connection work can be done without problems due to the characteristics of the optical fiber. Furthermore, the present invention uses an optical fiber element which is highly dangerous as in the prior art, and is used when the end face of the optical fiber element wire is ground or when the optical fiber element wire is attached and gripped in the V groove portion of the connecting jig. It is not necessary to remove minute scratches on the wire surface, and since an ultraviolet curable resin is used, the film thickness is thin and easy to apply uniformly due to surface tension, and there is no eccentricity due to film thickness unevenness.
It becomes easy to adjust the optical axis of the optical fiber. As a result, safe connection work can be performed without danger, and the time for adjusting the optical axis can be shortened. The present invention is subject to various restrictions because it is not necessary to provide a special coating layer on the surface of the optical fiber wire after peeling off the coating of the optical fiber core wire so as not to scratch the surface of the optical fiber wire. It is possible to use an ordinary optical fiber core wire having no design, so that the characteristics of the optical fiber core wire are not deteriorated. Since the optical fiber connecting method of the present invention protects the surface of the optical fiber wire by curing the ultraviolet curable resin applied to the optical fiber wire, the end surface of the optical fiber wire is ground and the connection treatment is performed. It is possible to easily prevent the surface of the optical fiber strand from being scratched when the optical fiber strand is gripped by the tool.

〔The invention's effect〕

INDUSTRIAL APPLICABILITY The optical fiber connection method of the present invention can safely perform cutting, end face grinding, operation of a connection jig, etc., and does not cause breakage due to forming, vibration, impact, etc. of cable wiring after connection, and deteriorates characteristics. There is an effect that a highly reliable optical fiber cable that does not have the above can be obtained.

[Brief description of drawings]

 FIG. 1 is a perspective view of an embodiment according to the present invention, and FIG. 2 is a perspective view of a conventional example. In the figure, 1 is an optical fiber element wire, 2 is a protective film, 3 is a connecting jig, and 3a is a V groove.

Claims (1)

[Claims] 1. An optical fiber core wire end portion is stripped of coating to expose the surface of an optical fiber elemental wire, and a protective coating for fusion splicing is formed on the exposed surface with an ultraviolet curable resin. An optical fiber fusion splicing method, characterized in that the optical fiber strands are fusion spliced.