JPS6216408B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a self-supporting optical fiber cable using an optical transmission fiber (hereinafter referred to as optical fiber).

The most important characteristics required for self-supporting optical fiber cables are sufficient strength to withstand the mechanical stress applied during and after installation, and the inherent low loss and broadband characteristics of optical fibers. The goal is to maintain transmission characteristics.

A conventional self-supporting cable has a tensile strength wire 1 made of a steel wire as a tensile strength member, as shown in Fig. 1a and b.
and a copper wire 2 which is a signal medium, each of which is covered with a covering material 3 and integrated. There is no fundamental change in this structure even when an optical fiber is used.

The inventors of the present invention have learned the following as a result of studying a method for manufacturing a self-supporting optical fiber cable.

First, when using the solid type die 5 and nipple 4 that tightly coat both the tensile strength wire 1 and the optical fiber 2 ₁ shown in FIG. 2a, the coating material 3 shown in FIG.
The "tightening force" in the circumferential and longitudinal directions causes the optical fiber to bend at minute intervals, resulting in an increase in transmission loss due to so-called microbending. Second, when the tensile strength wire ₁ and the optical fiber ₂₁ shown in FIG. Although the tightening force is reduced and an increase in transmission loss can be prevented, slippage occurs between the tensile strength wire 1 and the sheathing material 3 due to poor adhesion between the tensile strength wire 1 and the sheathing material 3 shown in Figure 1a. Tensile strength line 1 does not play its original role.

The present invention has been made to improve these drawbacks, and provides a self-supporting optical fiber cable characterized by using a solid type nipple on the tensile strength line side and a pull-down type nipple on the optical fiber side. This is the manufacturing method.

As shown in FIG. 3, on the optical fiber ₂₁ side, a so-called pull-down type nipple ₇₂ is used, in which the face of the die 8 and the nipple tip are on the same plane, and on the tensile strength line 1 side, the nipple tip is retracted from the face of the die 8. By using the so-called solid type nipple ₇₁ ,
This suppresses the "tightening force" of the coating material 3 to the optical fiber ₂₁ to a minimum, and strengthens the adhesion between the tensile strength wire 1 and the coating material 3.

As shown in FIG. 3, when the finished outer diameters of the tensile strength wire 1 side and the optical fiber ₂₁ side are the same, the inner diameter r of the die 8 on the tensile strength wire 1 side using the solid nipple ₇₁ is the same as that of the optical fiber. 2 It is necessary to make it smaller than the inner diameter R of the die 8 on the ₁ side.

Alternatively, as shown in FIG. 4, the copper wires 2 shown in FIGS. 1a and 1b may be used as optical fibers, and coated optical fibers already coated with one or more layers of plastic may be used. 9 is a glass fiber, 10 is a primary coating made of a thermosetting resin such as silicone resin, and 11 is a secondary coating made of a thermoplastic resin such as nylon or polyethylene. Furthermore, as shown in FIG. 5, tensile strength fibers 14 may be longitudinally spliced or braided between the optical fiber 12 and the covering material 3. In this case, it is also possible to carry out the longitudinal application of the tensile strength fibers, the delivery of the tensile strength wires, and the extrusion of the coating material at the same time using manufacturing equipment as shown in FIG.

To explain FIG. 6 in detail, the optical fiber 12
After the tensile strength fibers 14 are longitudinally attached, the fibers are guided to the crosshead 15 of the extruder, and the tensile strength wires 13 are guided to the crosshead 15 in parallel therewith. The resin discharging part of the crosshead 15 is equipped with a die and a nipple as shown in FIG. A self-supporting optical fiber cable 17 is manufactured and wound.

[Brief explanation of the drawing]

Figures 1a and b are examples of cross-sectional views of conventional self-supporting cables, and Figures 2a and b are the cross-sectional structure of a solid die nipple that tightly covers both the tensile strength wire and the optical fiber, the front view of the die, and the tensile strength wire. The cross-sectional structure and die front view of a draw-down type die nipple in which no tightening force is applied by the coating resin on both optical fibers, and Figure 3 shows the cross-sectional structure and die front view of a die nipple according to the present invention in which the tensile strength line side is a solid type and the optical fiber side is a pull-down type. 4 and 5 are cross-sectional views of a coated optical fiber having one or more layers of plastic coating, respectively, and FIG. 6 is an illustration of the manufacturing process. 1 is a tensile strength wire, 2 is a copper wire, 2 ₁ is an optical fiber,
3 is a covering material, 4 is a solid type nipple, 5 is a die, 6 is a retractable type nipple, 7 ₁ , 7 ₂ are nipples according to the present invention, 8 is a die according to the present invention, 9 is a glass fiber, and 10 is a silicone resin. Primary coating with thermosetting resin such as 11, secondary coating with thermoplastic resin such as nylon or polyethylene, 1
2 is an optical fiber, 13 is a tensile strength wire, 14 is a tensile strength fiber, 15 is a crosshead, 16 is a cooling device, 1
7 is a self-supporting optical fiber cable.

Claims (1)

[Scope of Claims] 1. A method for manufacturing a self-supporting optical fiber cable in which one or more tensile strength wires and one or more optical fibers are coated with a thermoplastic resin by batch extrusion, comprising: the batch extrusion coating. Sometimes, the tensile strength wire is coated with the molten thermoplastic resin in close contact with the tensile strength wire in an extruder crosshead, and the optical fiber is coated with the molten thermoplastic resin in a final coat. A method for manufacturing a self-supporting optical fiber cable, which comprises extruding it into a tube shape with a diameter larger than the finished diameter, and then pulling it down to the finished diameter and covering it.