JPS585703A - Production of optical transmission body - Google Patents

Abstract

PURPOSE:To protect cores by the formation of voids in the inside and the absorption of external impact of a central member by forming a heat shrinkable layer on the outside circumference of the central member, winding optical fibers spirally on the outside circumference thereof then providing a cladding layer on the outside circumference. CONSTITUTION:A heat shrinkable layer 2 such as PE is clad on a central member 1 to serve as a tension member, and single or plural optical fibers 3 are wound spirally thereon. The fibers 3 on the outside circumference of the layer 2 are wound with plastic tapes to form a cladding layer 4. Further, a cladding layer 5 of PE is thermoformed with an extruder. The layer 2 is thermally shrunk by utilizing the heat in this working time to form void parts 6 for optical fibers between the layer 2 and the layer 4, whereby an intended optical transmission body 7 is obtained. External impact is absorbed effectively without increasing the size of the tension member and the optical transmission body is protected simply by providing such void parts 6.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing optical transmission bodies such as optical fibers, optical cable units, and optical cords. For the purpose of protecting the optical fiber, a tension member is provided as an intervening member on which a suitable coating layer is formed.

Normally, the tension of the tension member in the above optical transmission body is designed to allow a certain amount of elongation (approximately 0.5%), but in practical use, elongation that exceeds this often occurs, and in such cases, This puts strain on the optical fiber.

Of course, regarding the occurrence of elongation due to excessive tension,
It would be possible to improve the specifications of the tension member to prevent this, but this would make the tension member larger and more expensive.

The present invention does not involve modifying the tension member, but rather modifies the internal structure of the optical transmitter by means of absorbing elongation using the spatial structure. The purpose is to provide a transmitter at a low cost, and a specific manufacturing method thereof will be explained below using illustrated embodiments.

In the method of the present invention, as shown in FIG.
A heat-shrinkable layer (2) is formed by covering the outer periphery of this with a heat-shrinkable tube such as polystyrene.

Next, one or more optical fibers (3) are spirally wound around the outer periphery of the heat-shrinkable layer (2).

Next, as shown in Fig. 2, a coating layer (4) is formed by wrapping a plastic tag or the like around the outer periphery of the heat-shrinkable layer (2) to hold down the optical fiber (3), and then an extrusion coating is applied. A covering layer (5) made of PE, PvC, etc. is formed on the means as shown in Fig. 3.

At the time of extrusion coating, the heat shrink layer (2) is heat-shrinked using the heat from the extrusion coater, thereby creating a gap between the heat-shrink layer 1 (2) and the value covering layer (4). A cavity (6) for an optical fiber is formed in the space, and a predetermined optical transmission body (7) is obtained.

In addition, when heat-shrinking the heat-shrinkable layer (2) as described above,
Before or after the formation of the coating layer (5), it is also good to shrink the same layer (2) by heating means, especially when the heat during extrusion coating is insufficient, the above-mentioned heating after the next coating can be used in combination. By doing so, the heat-shrinkable layer (2) can be sufficiently shrunk.On the other hand, the above-mentioned optical transmission body (7) is used not only as an optical cord or a small optical cable, but also as an optical transmission body (7). When used as an optical cable unit, a plurality of these optical transmission bodies (7) [7)... are twisted and assembled into an optical cable as shown in Fig. 4, and when making an even larger optical cable, the A plurality of pieces as shown in Fig. 4 are twisted and assembled.

In the optical transmission body (7) manufactured by the method of the present invention, a predetermined tensile strength can be obtained through the tensile core member (1)), while a tension exceeding this can be applied to the optical transmission body (7). When the tension is applied to the body (7), the tension will also be applied to the optical fiber (3).
The length in the stretching direction is increased, and there is no longer any possibility that an unreasonable tension will be applied to the optical fiber (3) due to the optical fiber (3) being bent.

Furthermore, when the winding diameter of the optical fiber (3) is reduced to relieve tension, since there is a gap (6) between the optical fiber (3) and the heat shrink layer (2), the optical fiber (3) ) does not tighten the heat-shrinkable layer (2), and therefore micro-bending of the optical fiber (3) due to tightening tn does not occur, and high transmission characteristics can be maintained.

Of course, the optical fiber (
The coating pressure applied to 3) also causes the heat-shrinkable layer (2) to shrink, causing the voids (
6), the occurrence of microbends can be prevented in this respect as well, and high transmission characteristics can be maintained.

In addition, the absorption and relaxation of external impact, bending properties, etc. are improved by forming the void portion (6).

As explained above, when the method of the present invention is used, it is possible to manufacture an optical transmission body that is excellent in protection effects of optical fibers against tension, transmission characteristics, etc.
Even without increasing the size of the tension member, the allowable elongation value of about 0.5% can be improved to about 2% by simply providing a predetermined gap, and therefore there is no cost increase caused by modifying the tension member.

Of course, since the void portion only causes the heat-shrinkable layer to shrink by heat, there is no difficulty in the manufacturing process, and the optical transmission body can be manufactured continuously in conjunction with other processes.

[Brief explanation of the drawing]

Figures 1 (A) - 3 are explanatory diagrams showing an example of manufacturing an optical transmission body by the method of the present invention in the order of the steps, and Figure 4 is a schematic explanatory diagram showing an example of a cable configuration using the optical transmission body. (1) ... Central member (2) ... Heat shrink layer f3) --- Optical fiber (4) t5J ... Covering layer (6) ... ...Void part (7) ...Patent attorney Yoshio Saito, agent for patent applicant for optical transmission body 1st ryJ (a) 4th flash (b) Fig. 2 Fig. 3

Claims (1)

[Claims] After forming a heat-shrinkable layer around the outer periphery of the central member and winding an optical fiber spirally around the outer periphery of the central member, a desired number of covering layers is further formed around the outer periphery, and before the formation of the covering layer. Alternatively, during or after formation, the heat-shrinkable layer is thermally shrunk to form a void for the optical fiber between the heat-shrinkable layer and a coating layer on the outer periphery of the heat-shrinkable layer. Manufacturing method of optical transmission body 0