JPH04365004A - Connecting method for coated optical fiber - Google Patents

Abstract

PURPOSE:To provide the splicing method of optical fiber capable of obtaining high connection strength. CONSTITUTION:Film layers 2 at end sections of two optical fibers 1 to be splined are removed to expose optical fibers 3 by preset lengths, end faces of the exposed optical fibers 3 are optically connected, an adhesive primer 4 is applied on the surface of the exposed optical fibers 3 and film layers 2 nearby, re-coating resin 5 is molded on it to increase the binding strength among the re-coating resin 5, exposed optical fibers 3 and film layers nearby, and the strength of the connection portion is improved.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for connecting optical fibers that provides high connection strength.

0002

2. Description of the Related Art An optical fiber core 1 is, for example, a composite of an optical fiber 3 and a coating layer 2 consisting of a primary coating layer, a buffer layer, a secondary coating layer, etc., as shown in a cross-sectional view in FIG. By the way, the optical fiber core 1 with such a structure
Conventionally, as shown in FIG.
is removed to expose a predetermined length of the optical fiber 3, and the end faces of the exposed optical fiber 3 are fused and spliced.
The recoating resin 5 was molded onto the surface of the exposed optical fiber 3 and the coating layer 2 in its vicinity.

0003

[Problem to be Solved by the Invention] However, when a large number of optical fiber core wires having the above-mentioned connection parts are assembled and coated with polyethylene etc. to form an optical fiber cable, and this is used as an optical cable for submarine transmission, etc. ,
There has been a problem in that the optical fiber core inside the cable breaks at the connection part due to the handling and tension that the cable is subjected to when laying or burying the cable or due to tidal currents on the ocean floor.

0004

[Means for Solving the Problems] The present invention has been made as a result of intensive research in view of the above situation, and its purpose is to provide a method for connecting optical fibers that can obtain high connection strength. It is in. That is, the present invention removes the coating layer at the ends of two optical fibers to be connected to expose a predetermined length of the optical fibers, fusion splices the exposed optical fiber end faces, and then connects the exposed optical fibers and In an optical fiber connection method in which recoating resin is molded on the surface of the coating layer in the vicinity, an adhesive primer is applied to the surface of the exposed optical fiber and the coating layer in the vicinity, and then re-coated on the coated primer. It is characterized by molding the coating resin.

The method of the present invention will be specifically explained below with reference to the drawings. FIGS. 1A to 1C are process explanatory diagrams showing embodiments of the method of the present invention. First, the coating layers 2 at the ends of the two optical fiber cores 1 to be connected are removed to expose a predetermined length of the optical fibers 3, and the end surfaces of the exposed optical fibers 3 are fused and spliced together by arc discharge. (
Figure A), then apply an adhesive primer 4 to the surface of the exposed optical fiber 3 and the coating layer 2 in its vicinity (
(Figure B), recoating resin 5 is molded on the applied primer 4 (Figure C), and if necessary, the recoating resin 5 is subjected to ultraviolet ray irradiation or heat treatment to harden the resin 5 and connect. conduct. In the method of the present invention, an adhesive substance such as silicone, polyurethane, epoxy resin, polybutadiene, etc. is used for the primer 4 applied to the surface of the exposed optical fiber and the coating layer 3 in the vicinity thereof. The recoating resin 5 molded on the primer 4 is made of a material with a small coefficient of linear expansion and a large Young's modulus, such as nylon resin, polyethylene,
A polyester elastomer or the like is used, and in particular, it is preferable to use the same material as the secondary coating layer or buffer layer of the optical fiber core 1 because it does not give a strange feeling and is easy to handle. In the method of the present invention, in order to avoid damaging the optical fiber 1, the coating layer 2 of the optical fiber core wire may be removed, for example, leaving the primary coating layer as described above. In this case, the primer may be removed after fusion splicing. It will be applied to the surface of the primary coating layer.

[0006]

[Operation] In the method of the present invention, the coating layer at the ends of two optical fibers to be connected is removed, the exposed end faces of the optical fibers are fusion spliced, and then the fusion spliced portion is recoated with resin. When reinforcing and fixing by molding, an adhesive primer 4 is applied to the surface of the exposed optical fiber and the coating layer in the vicinity, and a recoating resin 5 is molded on top of this, so that the fusion spliced portion of the optical fiber 3 is is strongly reinforced by the recoating resin 5, and the optical fiber 3 will not break at the fusion spliced portion due to external force during installation.

[0007]

[Examples] The method of the present invention will be explained in detail below using examples. Incidentally, the same members as in the conventional one will be described with the same reference numerals. Example 1 The outer diameter is 400 μm, and the diameter of the core optical fiber 3 is 125 μm.
Optical fiber cores 1 having the same three-layer structure as shown in FIG. 3 were interconnected. The coating layer 2 at the ends of the two optical fiber cores 1 to be connected is removed to expose the optical fiber 3 to a length of 15 mm, and the exposed optical fiber 3 is removed.
The end faces of the two were fused and spliced together using arc discharge heating. Approximately 30 optical fibers 3 were fusion spliced in this way, and
These were given 2% elastic elongation and 20 pieces that did not break were screened and used as samples. Next, for each of these samples, a silicone resin is applied as a primer 4 to the surface of the exposed optical fiber 3 and the coating layer 2 in the vicinity thereof, and a recoating resin 5 is applied on top of this.
As a mold, urethane acrylate, which is the same material as the secondary coating layer of the optical fiber 3, is molded over a length of 50 mm centering on the fusion spliced part of the optical fiber to a thickness of 450 μm in diameter, and then it is irradiated with ultraviolet rays and cured. I made a connection. Comparative Example 1 An optical fiber core was formed in the same manner as in Example 1, except that the recoating resin 5 was directly molded onto the surface of the exposed optical fiber 3 and the coating layer 2 in its vicinity without applying a primer. Connected line 1. For each sample obtained in this way, a tensile test of the connection part was carried out at a gauge length of 400 mm and a tensile speed of 500 mm.
The test was carried out under the conditions of mm/min. The results are shown in Table 1.

[0008]

[Table 1] ■50% value: Center value of 20 samples (average value of 10th and 11th), median.

As is clear from Table 1, the example product of the present invention has the following properties:
The tensile strength was higher than that of the comparative example. This is done by applying an adhesive primer 4 to the exposed optical fiber 3 and the coating layer 2 in its vicinity, and then
This is because since the recoating resin 5 was molded on top, the recoating resin 5 was firmly bonded to the optical fiber 3 and the coating layer 2 in its vicinity, and the reinforcing effect of the recoating resin 5 was fully exhibited.

0010

[Effects] As described above, according to the method of the present invention, the connecting parts of optical fiber cores are firmly fixed, and even under harsh conditions such as when laying submarine transmission cables, optical fiber cores can be disconnected at the joints. There is no problem, and it has a remarkable industrial effect.

[Brief explanation of drawings]

FIG. 1 is a process explanatory diagram showing an embodiment of the method of the present invention.

FIG. 2 is a cross-sectional view of an optical fiber.

FIG. 3 is an explanatory diagram of a conventional method for connecting optical fibers.

[Explanation of symbols]

1 Optical fiber core 2 Coating layer 3 Optical fiber 4 Primer 5 Recoating resin

Claims (1)

[Claims] Claim 1: After removing the coating layer at the ends of two optical fibers to be connected to expose a predetermined length of the optical fibers and fusion splicing the exposed optical fiber end faces, the exposed optical fibers and their In an optical fiber connection method in which recoating resin is molded on the surface of the nearby coating layer, an adhesive primer is applied to the surface of the exposed optical fiber and the coating layer in its vicinity, and then recoating is performed on the coated primer. A method for connecting optical fiber cores characterized by molding resin.