JPS6320323B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in self-supporting optical cables.

An example of a self-supporting cable is one in which the cable body is wrapped around a messenger wire. Since this type of self-supporting cable has a small effective cross-sectional area against the wind and a small wind pressure load, it is possible to suppress the gearropping phenomenon. However, when the cable body is an optical cable body, there is a drawback that when the optical cable passes through a fishing wheel during installation, large lateral pressure is applied to the optical core line due to the unevenness of the cable surface, resulting in deterioration of transmission characteristics or disconnection. be. In particular, since the optical cable main body is usually constructed by twisting a plurality of optical core wires together, if it is subjected to a large lateral pressure, the optical core wires will press against each other, resulting in a significant deterioration of transmission characteristics.

SUMMARY OF THE INVENTION An object of the present invention is to provide a self-supporting optical cable that does not deteriorate transmission characteristics or break, even if large lateral pressure is applied due to surface irregularities when the cable passes through a fishing wheel during installation.

Embodiments of the invention will now be described with reference to the drawings. FIGS. 1 and 2 show a self-supporting optical cable 10 according to the invention, which comprises a messenger wire 12, such as a stranded steel wire, and an optical cable. Main body 1
It consists of 4. As shown in FIG. 2, the messenger wire 12 is formed of a stranded wire 12a with a plastic coating 12b applied thereto.

The optical cable main body 14, as shown in FIG.
A plurality of optical fibers 16A, 16B... each having a plastic coating reinforced with fibers such as glass fiber, that is, a fiber-reinforced plastic coating, and a thermoplastic plastic such as polyethylene coated on these optical fibers 16A, 16B. It consists of a cable jacket 18. The optical fibers 16A and 16B each have a fiber-reinforced plastic coating provided around the optical fiber via a buffer layer. A plurality of optical core wires 16A and 16B are arranged in parallel at intervals without being twisted, and are covered with a cable jacket 18 made of a non-adhesive material to the fiber-reinforced plastic coating. The wires 16A, 16B and the cable jacket 18 can be offset relative to each other.

The optical cable main body 14 is wound around the messenger wire 12 while being twisted at a twist rate of 100% or close to it. Therefore, the relative positional relationship between the optical fibers 16A and 16B within the optical cable main body 14 is approximately the same no matter where they are located around the messenger wire 12. In this way, the optical cable main body 1 is attached to the messenger wire 12 while giving 100% twist to the optical cable main body 14.
4, the optical cable main body 14 will not be twisted during winding. In addition, as already mentioned, the cable jacket 18 is not bonded to the plastic sheath of the optical core wires 16A, 16B and can be moved in the longitudinal direction within the cable jacket 18, so that when the optical cable main body 14 is wound, the optical center Line 16A, 16
No unreasonable stress is applied to B. That is, when the optical cable main body 14 is wound around the messenger wire 12, looking at one side of the cable sheath 18, it moves toward and away from the center line of the messenger wire 12 in the longitudinal direction. Although it expands and contracts, if the cable jacket 18
A, 16B, optical fibers 16A,
16B follows the longitudinal expansion and contraction of the cable sheath 18 and is subjected to unreasonable stress, but the cable sheath 18
If the cable jacket 18 is not bonded to the optical fibers 16A and 16B and can be shifted relative to the optical fibers 16A and 16B, the cable sheath 18
Since the optical fibers 16A, 16B do not follow the expansion and contraction of the optical fibers, no unreasonable stress is applied to the optical fibers 16A, 16B.

According to the present invention, there are the following effects.

(b) During installation, even if an impact force is applied to the cable due to the unevenness of the surface when passing through a fishing wheel, the optical fibers are embedded within the cable jacket at intervals, so the individual light beams are It is possible to disperse the large lateral pressure that acts on the core, and since the optical core has a strong fiber-reinforced plastic coating and is individually embedded within the cable jacket, it can withstand large lateral pressure. This makes it possible to prevent the transmission characteristics of the optical fiber from deteriorating or breaking the optical fiber.

(b) Since the plurality of optical core wires are embedded in the cable jacket in parallel without being twisted together, there is an advantage that an inexpensive optical cable can be constructed by omitting the step of twisting the optical core wires.

(c) Since the individual optical fibers are not bonded to the cable sheath and have a highly rigid fiber-reinforced plastic sheath, the optical cable body can be wrapped around the messenger wire with twisting. Sometimes, even when multiple optical fibers are in parallel, there is a relative misalignment between the optical fibers and the cable sheath, which prevents undue stress from acting on the optical fibers and stabilizes the transmission characteristics. It is possible to construct an optical cable with

[Brief explanation of the drawing]

1 and 2 are a side view and an enlarged cross-sectional view taken along the line A-A in FIG. 1 of a self-supporting optical cable according to the present invention, and FIGS. FIG. 3 is a schematic cross-sectional view showing different positions relative to the wire; 10...Self-supporting optical cable, 12...Messenger wire, 14...Optical cable main body, 16
A, 16B...Optical core wire, 18...Cable jacket.

Claims (1)

[Claims] 1 Consists of a messenger wire and an optical cable main body, the optical cable main body comprising a plurality of fiber-reinforced plastic coated optical core wires arranged in parallel at intervals and a plastic coating of the optical core wires coated on these optical core wires. and a non-adhesive thermoplastic cable sheath, wherein the optical cable is twisted around the messenger wire and wrapped around the messenger wire. .