JPH041529Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Background and Purpose of the Invention] The present invention relates to a self-supporting overhead optical cable, and particularly to a self-supporting overhead optical cable suitable for use in long-span installation.

Self-supporting overhead optical cables conventionally come in various types, such as the stand-up type (SSD), wrapped type (SSS), and latching type (SSF), all of which have a hanging wire part and an optical cable part molded separately. The cross-sectional shapes of the hanging wire part and the optical cable part are each circular. An example is shown in FIG. In Figure 5,
1 is a hanging wire, 2 is a tension member of an optical cable,
Reference numeral 3 indicates an optical fiber placed around the outer periphery of the tension member 2, and numeral 4 indicates a covering material placed around the outer periphery of the hanging wire 1 and the optical fiber 3.

Therefore, the ideal conditions required for optical cables installed over long spans (several hundred meters) are: (1) use of materials with high tensile strength for the suspension wires, (2) use of cables with equivalent cable strength to prevent increases in tension due to wind pressure. There are three points to consider: reducing the outer diameter (3) withstanding the compressive force generated in the cable during cable extension, but conditions (2) and (3) above are contradictory conditions. Conventionally, in order to increase the number of fibers in a self-supporting overhead optical cable and install it over a long span, it is necessary to increase the outer diameter of the cable part and increase the size of the hanging wire part so that it can withstand the increased wind pressure load. It was getting bigger. In particular, if the self-supporting overhead optical cable is made of non-metallic material, it is necessary to use a non-metallic material with high tensile strength for the suspension wire. / ^mm2 ), and the Young's modulus of nonmetal high tensile strength materials is about 1/25 to 1/35 of that of ordinary steel. I had no choice but to make it bigger.

The present invention was developed as a result of various studies in consideration of the above points, and its purpose is to reduce the equivalent outer diameter of the cable in order to prevent the increase in tension due to wind pressure, and to reduce the cable extension. The cable can withstand the compressive force generated in the cable during wiring, and is also highly effective in preventing snow from accreting.
It is an object of the present invention to provide a self-supporting overhead optical cable that is particularly suitable for use with non-metallic cables.

[Summary of the invention] In order to achieve the above object, the present invention provides a self-supporting overhead optical cable in which a plurality of flat optical cables are wound around the outer periphery of a tensile suspension wire. The cable is characterized by being provided with a protrusion extending in the longitudinal direction of the cable.

[Example] Hereinafter, the present invention will be explained based on an embodiment shown in FIGS. 1 and 2. FIG. 1 is a front view of a self-supporting overhead optical cable according to the present invention, and FIG. A partially enlarged view of the figure is shown in which 1 is a suspension wire made of a non-metallic material such as glass fiber reinforced plastic or Keppra (trade name) fiber reinforced plastic; 4 is a covering material applied to the outer periphery of the suspension wire 1; When used for long span construction, the outer diameter of the hanging wire 1 is suitably about 10 mmφ. Reference numeral 5 denotes a flat optical cable with protrusions wound around the outer periphery of the suspension wire 1. The flat optical cable 5 with protrusions includes a covering material 6 having protrusions 6a at both ends of the surface that does not come into contact with the hanging wire 1;
It is composed of a tension member 2 buried in the projections 6a at both ends thereof, and a plurality of optical fibers 3 buried approximately in the center of the covering material 6. Six flat optical cables 5 with projections are wound around the outer periphery of the hanging wire 1.

The present invention has the above-mentioned configuration, and the self-supporting overhead optical cable according to the present invention is different from conventional cables of this type, in which the cross-sectional shapes of the hanging wire part and the cable part are circular, and the cross-sectional shapes are circular, and the cable parts are not molded separately. Since the flat optical cable is directly wound around the outer periphery of the tensile suspension wire, the equivalent outer diameter of the self-supporting overhead optical cable can be made smaller than before, and an increase in tension due to wind pressure can be effectively prevented.
In addition, in the cable of the present invention, since the protrusion 6a is provided on the side of the covering material 6 in which the optical fiber 3 is embedded, which does not come into contact with the hanging wire 1, compression occurs in the cable when the cable is stretched. Not only can the protrusions 6a of the sheathing material 6 be sufficiently resistant to the force, but they also serve as so-called hard-to-snow points that prevent snow from gradually encircling the entire surface of the cable and growing larger. But it has a big effect.

3 and 4 show other embodiments of the present invention, with FIG. 3 corresponding to FIG. 1 and FIG. 4 corresponding to FIG. 2, respectively. In the embodiments shown in FIGS. 1 and 2, the projections 6a are provided at both ends of the sheathing material 6 constituting a part of the flat optical cable 5. However, in the embodiments shown in FIGS. shows a case where a protrusion 6a is provided at one end of the covering material 6. Alternatively, a protrusion may be provided at the center of the cross section of the flat optical cable to form a convex flat optical cable (not shown).

In the illustrated embodiment, a case is illustrated in which a plurality of flat optical cables 5 are wound around the outer periphery of the suspension wire 1, but according to this configuration, the optical fiber 3 is arranged in units of small fibers (for example, every 5 to 6 fibers). Even in the middle of the cable installation route, optical fibers can be branched in small units without affecting other optical fibers. In the illustrated embodiment, the tension member 2 is buried in one or both ends of the sheathing material 6, but the tension member 2 is attached to the optical fiber 3 when the flat optical cable 5 is wound around the hanging wire 1. If it is buried to prevent stretching, and the twisting degree when winding the flat optical cable 5 around the suspension wire 1 is loose, it may be omitted. By doing so, the compression resistance of the covering material protrusion 6a during cable extension may be reinforced. Furthermore, the flat optical cable 5 may be wound around the suspension wire 1 by unidirectional winding or by winding by SZ twisting, and in the case of winding by SZ twisting, the strand boundary part is made of plastic material. You can fix it with etc.

In addition, JP-A-49-18338, JP-A-50-
When a flat optical cable having protrusions extending in the longitudinal direction of the cable on both sides is wound around the outer periphery of a suspension wire as disclosed in Publication No. 125752, the appearance of the cable is reduced by the gap created between the suspension wire and the flat optical cable. The outer diameter of the upper part becomes larger and the wind pressure load increases. In addition, since the covered part in which the optical fiber is buried does not come into contact with the support element and is in a floating state, the floating covered part easily deforms when subjected to compressive load due to cable extension, etc. Not only will transmission loss increase, but there is also a very high risk that the optical fiber will break. For these reasons, the present invention does not provide protrusions on the surface of the flat optical cable that comes into contact with the suspension wire, but provides protrusions only on the surface that does not come into contact with the suspension wire.

[Effects of the invention] The invention is as described above, and as is clear from the explanation of the illustrated embodiments, according to the invention, the equivalent outer diameter of the cable can be reduced in order to prevent an increase in tension due to wind pressure. Moreover, when extending the cable,
It is possible to obtain a self-supporting overhead optical cable that is particularly suitable for use in non-metallic cables, which can sufficiently withstand the compressive force generated in the cable, and which has a large snow-repellent effect.

[Brief explanation of the drawing]

Fig. 1 is a front view showing one embodiment of the self-supporting aerial optical cable according to the present invention, Fig. 2 is a partially enlarged view of Fig. 1, and Fig. 3 is a front view showing another embodiment of the cable of the present invention. 4 is a partially enlarged view of FIG. 3, and FIG. 5 is a front view of a self-supporting overhead optical cable that has been put into practical use in the past. 1... Hanging wire, 2... Tension member, 3...
Optical fiber, 4... sheathing material, 5... flat optical cable with protrusion, 6... sheathing material, 6a... protrusion.

Claims (1)

[Scope of utility model registration request] In a self-supporting overhead optical cable in which multiple flat optical cables are wrapped around the outer circumference of a tensile suspension wire,
A self-supporting overhead optical cable, characterized in that a protrusion extending in the longitudinal direction of the cable is provided only on the surface of the flat optical cable that does not come into contact with the tensile suspension wire.