JPS62170921A - Optical fiber cable - Google Patents

Abstract

PURPOSE:To prevent individual optical fibers from partial concentration of tensile load or side pressure by storing a flat type optical fiber cable stranded in the longitudinal direction in a protection tube. CONSTITUTION:The optical fiber cable 1 is arranged on the approximately center part of an overhead earth-wire constituted of a stranded wire 2, a pair of half-divided spacer pipes 3a, 3b divided into two parts like half-pipes are combined to from a protection pipe, and the stranded flat type optical fiber cable 1 is stored in a hollow part 3c formed inside the combined spacer pipe. The half-divided spacer pipes 3a, 3b are made of a metallic material such as a zinc-plated steel pipe and an aluminum alloy pipe or a hard plastic material such as FRP and the outside of the spacers 3a, 3b is coated with an outer casing type made of aluminium e.g. to prevent both the half-divided spacer pipes 3a, 3b from being shifted or distorted. Consequently, tensile load or side pressure to be applied to respective optical fibers can be uniformed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical fiber cable that is effective when installed in an electric power cable or an overhead space 11 attached to the electric power cable.

[Prior art] Optical fibers for communication or control have traditionally been incorporated into power cables or overhead ground wires attached to power cables, but this type of optical fiber is With the increasing sophistication, multi-core cables are required, and in response to this demand, flat type optical fiber cables in which a plurality of optical fibers are arranged side by side and integrally coated have recently begun to be used.

However, this type of flat optical fiber cable is
When an optical fiber cable is bent into a bend called microbending when there is not enough room in the length, the elongation and lateral pressure on each optical fiber vary greatly depending on the direction of bending, so tensile loads may be applied directly to the optical fiber depending on the location. There are problems such as disconnection or increased transmission loss due to lateral pressure.

[Object of the invention] The object of the present invention is to improve the above-mentioned problems,
Even if the flat fiber optic cable is bent,
An object of the present invention is to provide an optical fiber cable that reduces the influence of bending direction and prevents tensile loads and lateral pressures from being locally concentrated on individual optical fibers.

[Summary of the invention] The gist of the present invention is to achieve the above objects.

This optical fiber cable is characterized in that a flat optical fiber cable twisted in the longitudinal direction is built into a protective tube.

[Embodiments of the invention] The present invention will be explained in detail based on illustrated embodiments.

FIG. 1 is a sectional view showing an example of an optical fiber composite overhead ground wire incorporating a flat type optical fiber cable 1. As shown in FIG. 1st
In the figure, 2 is a twisted wire made of a conductor constituting the overhead ground wire, and for example, an aluminum coated wire, an aluminum alloy wire, etc. are used. The optical fiber cable l is arranged approximately at the center of the overhead ground wire made up of these strands 2, and is divided into a pair of half-tubular spacer tubes 3a, 3.
b are combined to form a protective tube, and the flat optical fiber cable 1 is housed in the hollow portion 3C formed inside the protective tube in a twisted state as shown in FIG.

The half spacer tubes 3a and 3b are made of a metal material such as a galvanized steel pipe or an aluminum alloy tube, or a hard plastic material such as FRP. A jacket tube 4 made of, for example, aluminum is coated to prevent it from coming apart. However, if the two half spacer tubes 3a and 3b are joined by welding or the like, the mantle tube 4 can be omitted, and instead of the mantle tube 4, a metal tape such as aluminum, an insulating tape such as plastic, or a Heat-resistant tape or the like may be wrapped around the halved spacer tubes 3a, 3b, or may be placed vertically along the seam.

As shown in Fig. 2, the flat type optical fiber cable 1 consists of a plurality of parallel optical fibers 1a coated with a common rubber or plastic layer 1b, and because its structure is flat, it can be stored in a normal state. In this case, as mentioned above, depending on the bending direction due to microbending, some parts may be subject to large elongation or lateral pressure, and others may not be. However, if the optical fiber located on the outside is bent in a direction parallel to the flat surface as shown in Figure 4, it will not cause much of a problem.
A large tensile force is applied to the inner optical fiber 1a''', and a large compressive force is applied to the optical fiber 1a''' located on the inside.

In order to reduce the influence of such bending direction, in the present invention, the flat optical fiber cable 1 is housed in a twisted state as shown in FIG. By twisting in this way, even if the mantle tube 4 is bent, the optical fiber cable l will have a length margin, and will not be bent as shown in Figure 4, but will remain flat as shown in Figure 3. Since the direction perpendicular to the plane is bent, no tensile force or compressive force is applied to the individual optical fibers 1a.

Further, even when the flat optical fiber cable 1 is pulled, if it is not twisted, a tensile load is directly applied to each optical fiber 1a, but as in the present invention, the optical fiber cable 1 is twisted. In some cases, recovery of torsion can provide considerable relief from the tensile load.

However, when this optical fiber 1 is incorporated into an overhead ground wire, assuming that the instantaneous heat resistance temperature of the overhead ground wire is 400°C, the maximum strain will be 1.0% and the equivalent load strain will be about 0.4%. Therefore, the usage conditions are very strict. In order to absorb such elongation of the optical fiber cable 1, for example, as illustrated in FIG. It may also have a structure in which they are twisted together.

In this case, each flat optical fiber cable 1 may be stored in a twisted state within each half spacer tube 3a, 3b, but even if it is stored in a normal state, the half spacer tube 3a, By twisting the cables 3b together, the flat I-type optical fiber/to cable 1 is placed under the same conditions as if it were twisted.

In this case, since the optical fiber cable 1 does not necessarily need to be twisted within each protection tube, it may be wired without twisting using a normal protection tube.

Furthermore, in order to make the optical fiber cable 1 incorporated into an overhead ground wire etc. multicore, for example, as shown in FIG. The structure may be such that the half spacer tubes 3a, 3b and the mantle tube 4 are twisted together.In this case, each flat optical fiber cable 1 is stored in the respective half spacer tubes 3a, 3b in a twisted state. You can also
Furthermore, even when stored in a normal state, the same conditions as in a twisted state can be achieved by twisting.

[Effects of the Invention] As explained above, according to the optical fiber cable according to the present invention, since the flat optical fiber cable is laid in a twisted state, when the optical fiber cable is bent, each optical fiber The applied tensile load, lateral pressure, etc. can be equalized, and there are effects such as preventing disconnection accidents and reducing transmission loss.

[Brief explanation of drawings]

The drawings show an embodiment of the optical fiber cable according to the present invention, and FIG. 1 is a cross-sectional view of an overhead ground wire incorporating a flat optical fiber cable, and FIG. 2 is a wiring state of the flat optical fiber. 3 and 4 are action explanatory views, FIG. 5 is a perspective view of another embodiment, and FIG. 6 is a sectional view of still another embodiment. Symbol l is a flat optical fiber cable, 2 is a stranded wire,
3a and 3b are half spacer tubes, 4 is a mantle tube, and 5 is a reinforcing wire. Patent applicant: Dainichi Nippon Electric Cable Co., Ltd. Figure 1 Figure 2 b Figure 3 Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] 1. An optical fiber cable characterized in that a flat optical fiber cable twisted in the longitudinal direction is built into a protective tube. 2. The optical fiber cable according to claim 1, wherein a plurality of protective tubes containing the optical fiber cable are twisted together. 3. The optical fiber cable according to claim 1, wherein the protective tube is a combination of a pair of halved spacer tubes.