JPH0243289B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in optical cables, particularly optical cables used in optical composite overhead ground wires.

Recently, optical fiber cables can transmit large amounts of information, and because they are low-loss, non-inductive insulators, they can be used in combination with power transmission lines, making them more convenient than traditional power line transportation and microwave communications. is also attracting attention because it can reliably transmit large amounts of data.

In the case of power transmission lines, considering various circumstances, optical fibers are incorporated into overhead ground wires and used for purposes such as transmitting information between substations, transmitting information on power transmission lines, and countermeasures against television interference. However, it is being considered that optical cables used for this purpose may be incorporated into the internal cavity of the overhead ground wire.

By the way, in the event of a failure such as a break in the overhead optical cable or an increase in loss, it would be difficult to replace the entire overhead ground wire.
It is preferable to run a new optical cable through the overhead ground wire.

When carrying out such a pull-through, if a large tension is applied, the optical fiber will break, so
It is required that the frictional resistance between the optical fiber cable jacket and the inner surface of the overhead ground wire be small, and that the load distributed to the optical fiber be small. In addition, if the temperature becomes high due to lightning or unbalanced current, it can withstand this high temperature and
Moreover, it is desired that the transmission characteristics of the optical fiber are not adversely affected.

This invention is in response to these demands.
An optical cable is provided in which a wear-resistant braid is applied to the outside of a sheath of the optical cable, and a thermoplastic resin linear body is interposed between the sheath and the wear-resistant braid.

Here, as the wear-resistant braid, a wear-resistant metal or synthetic fiber such as steel wire or polyaramid fiber (trade name: Kevlar, manufactured by DuPont) is applied.
The structure of optical cables that are coated with such wear-resistant braids is the same as before, for example:
In addition to optical cables that have a cable core made of optical fiber and tensile strength wires and a silicone polymer sheath with excellent heat resistance as the outer sheath, by providing a non-adhesive intermediate layer between the optical fiber and the sheath, Optical cables with reduced buckling are applied.

Next, the present invention will be explained with reference to the drawings. Fig. 1 is a cross-sectional view showing an embodiment of the optical cable of the present invention, which has a tensile strength line 1 at the center and silicone polymer 3 around it. Optical fiber 2 coated with
The six cores are twisted together, a silicone polymer sheath 5 is applied to the outer periphery via a non-adhesive intermediate layer 4, and a heat-resistant material made of, for example, a polyethylene string is applied on the silicone polymer sheath 5 by vertically wrapping or spirally winding. A plastic resin linear body 7 is placed, and a wear-resistant braid 6 is applied thereon to constitute the optical composite optical cable of the present invention.

Although silicone resin has excellent heat resistance and elasticity, it expands by about 5% at 250°C. Abrasion-resistant braids, if made of metal wires or polyaramid fibers, therefore have little expansion. Therefore, when the overhead ground wire becomes hot due to a lightning strike, etc., the thermoplastic resin linear body 7 melts, flows into the gap between the sheath and the braid, becomes flat, or leaks to the outside through the gap in the braid. Even if the wear-resistant braid hardly expands, the silicone polymer sheath 5 made of silicone resin can expand, and no stress is applied to the optical fiber.

As described above, in the cable of the present invention, since the outermost layer is provided with the abrasion-resistant braid 6 such as metal wire or polyaramid fiber, the abrasion-resistant braid 6 can be pulled to easily draw the cable. Since the braid is made of wear-resistant metal or synthetic fiber such as metal wire or polyaramid fiber, there is little frictional resistance with the inner surface of the overhead ground wire, so the pulling tension is small and the load on the optical fiber is low. Since the load is small, there is little risk of the optical fiber breaking.

Furthermore, since the thermoplastic resin linear body is interposed between the wear-resistant braid and the outer sheath, the thermoplastic resin linear body will not melt even if the overhead ground wire becomes hot due to a lightning strike or unbalanced current. Since the outer sheath is allowed to expand by leaking to the outside, stress is not applied to the optical fiber core and the properties of the optical fiber are not deteriorated.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of the optical composite overhead ground wire optical cable of the present invention. 2: Optical fiber, 5: Sheath, 6: Wear-resistant braid, 7: Thermoplastic resin linear body.

Claims (1)

[Claims] 1. An optical composite optical cable for an overhead ground line, characterized in that a thermoplastic resin linear body is interposed between a sheath made of silicone polymer of the optical cable and a wear-resistant braid provided on the outside thereof.