JPS636846B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to fiber optic cables.

When forming fiber optic cables, it is important that the transmission properties of the optical fibers are not impaired during manufacturing, installation, and use, and that the optical fibers do not break under these conditions.

Optical fibers are sensitive to stretching. For this reason, conventionally, in order to prevent tension from being applied to the optical fiber (the optical fiber has a protective coating such as plastic on the outer periphery), the optical fiber was wound around the outer periphery of a long tensile strength body, etc. They were either attached and fixed, or housed in a protective pipe with extra length.

However, forming an optical fiber cable with a long tensile strength member, etc. to prevent it from stretching requires the use of a high tensile strength member, which increases the cable diameter, increases the cable weight, increases the cost, and increases the cost. It has the disadvantage of poor flexibility.

In addition, it is technically very difficult to insert the optical fiber core into a long protection pipe with an appropriate amount of extra length.

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical fiber cable that does not adversely affect the optical fiber core even when stretched, and allows for easy provision of extra length to the optical fiber core.

The optical fiber cable of the present invention is characterized in that it has a rubber-like elastic elongated body having a spiral groove on its outer periphery, and an optical fiber core wire accommodated in the spiral groove of the rubber-like elastic body. When tension is applied to the rubber-like elastic elongate body and the rubber-like elastic elongate body stretches, the diameter of the rubber-like elastic elongate body becomes thinner as it stretches, and the optical fiber core wire also decreases accordingly. Since the optical fiber can be stretched, the optical fiber is prevented from being adversely affected by elongation due to tension or lateral pressure.

Embodiments of the present invention will be described in detail below with reference to the drawings. 1 and 2 show a first embodiment of an optical fiber cable according to the present invention.
As shown in the figure, the optical fiber cable of this example is
For example, a rubber-like elastic elongate body 1 with a circular cross section made of rubber, elastomer, etc. having an elongation rate of 200% or more
has. A plurality of spiral grooves 2 are provided on the outer periphery of this rubber-like elastic elongated body 1, and a cored optical fiber 3 is accommodated in each of these spiral grooves 2.
The depth and width of each helical groove 2 are such that even when the optical fiber cable is at its maximum elongation, the optical fiber core 3
The diameter is selected so that it is not less than the outer diameter of the A metal tape 4 is placed around the outer circumference of the rubber-like elastic elongate body 1 without tightening the rubber-like elastic elongate body 1.
A and a thin plastic layer 4B laminated around its outer periphery
A metal-plastic laminate tape 4 consisting of is longitudinally applied and coated, a plastic sheath 5 is extruded and coated on the outer periphery, and the plastic sheath 5 is fused to the plastic thin layer 4B to provide a laminate cable sheath 6.

In such an optical fiber cable, when tension is applied to the rubber-like elastic elongate body 1 and the rubber-like elastic elongate body 1 is stretched, the rubber-like elastic elongate body 1 becomes thinner, and the rubber-like elastic elongate body 1 becomes thinner. Spiral groove 2 from the center of body 1
The radius to the bottom of the optical fiber 3 becomes smaller, and as the radius decreases, the optical fiber core 3 also has more room to stretch.
The optical fiber core wire 3 can be protected from tension. When the tension applied to the rubber-like elastic elongate body 1 is removed, the rubber-like elastic elongate body 1 is restored to its original length, and the optical fiber core 3 is also locally stretched within the space of the groove 2. It is restored to its original state without receiving lateral pressure.

If it is necessary to increase the strength of the cable sheath in the above-described structure, a tension member layer made of, for example, polyamide fibers may be provided around the outer periphery of the laminate sheath 5, and a plastic sheath may be further applied to the outer periphery of the tension member layer.

3 and 4 show a second embodiment of the optical fiber cable according to the present invention. In the optical fiber cable of this embodiment, a plurality of optical fiber cable units 8 are wound around the outer periphery of a tension member 7 made of glass fiber reinforced plastic, etc., a pressure winding layer 9 is provided on the outer periphery of the tension member 7, and a pressure winding layer 9 is provided on the outer periphery of the tension member 7. The structure includes a plastic sheath 10 made of. As shown in FIG. 4, the optical fiber cable unit 8 has a rubber-like elastic elongate body 1 with a circular cross section, and a plurality of spiral grooves 2 are provided on the outer periphery of the body. A fiber core 3 is accommodated therein. At the entrance of each spiral groove 2, in order to prevent the optical fiber core 3 from escaping from the groove 2, a fiber escape prevention member 11 is integrally formed and protrudes from one side wall of the groove. The rubber-like elastic elongated body 1 having such a shape can be formed by spiral extrusion, in which extrusion is performed while rotating a die.

Even with such an optical fiber cable, the same effects as in the first embodiment can be obtained. In this case as well, if it is necessary to increase the strength of the cable sheath, a tension member layer made of, for example, polyamide fibers may be provided around the outer periphery of the plastic sheath 10, and a plastic sheath may be further applied around the outer periphery of the tension member layer.

In the case of the optical fiber cable shown in FIG. 1, the rubber-like elastic elongated body 1 may have a structure as shown in FIG. 4.

In addition, in the case of the optical fiber cable shown in FIG. 3, the optical fiber cable unit 8 has a rubber-like elastic elongate body 1 itself which is not provided with a core wire escape prevention member, as shown in FIG. A core wire escape prevention member 1 made of a pipe is placed on the outer periphery of the elastic elongated body 1.
1 can also be used. With this structure, the rubber-like elastic elongated bodies 1 do not come into direct contact with each other, and
The rubber-like elastic body 1 can be expanded and contracted favorably. The wire escape prevention member 11 made of a pipe can be formed, for example, by extruding a pipe of plastic or the like.

Example 1 Four spiral grooves each having a width of 1.5 mm and a depth of 1.5 mm were provided at a pitch of 200 mm on a rubber-like elastic body made of vulcanized rubber having an outer diameter of 4 mmφ and an elongation property of about 300%. A cored optical fiber was housed in each spiral groove. Each optical fiber core was made by coating a glass fiber with an outer diameter of 125 μm with a primary coat of silicone rubber and a buffer layer of silicone rubber to give an outer diameter of 0.4 mmφ. On the outer periphery of the rubber-like elastic body, the inner diameter is 4.5
An aluminum-polyethylene laminate sheath with a thickness of 0.75 mm was applied so that the outer diameter was 6 mmφ. The outer circumference of this laminate sheath is covered with 20 twisted polyamide fibers of 1140 denier, and the outer circumference is covered with 1.2
An optical fiber cable with an outer diameter of 11 mmφ was constructed by covering it with a mm-thick polyethylene sheath.

Although this optical fiber cable was stretched by 4%, no breakage of the optical fiber was observed.

Example 2 A 4-core optical fiber cable unit with an outer diameter of 6 mmφ and a laminated sheath configured as described above was
Six pieces are twisted together around the circumference of a tension member with an outer diameter of 6 mmφ, and a pressure wrapping layer of non-woven fabric is applied to the outer circumference to make the outer diameter 19 mmφ.A 1.2 mm thick aluminum-polyethylene laminate sheath is applied to the outer circumference. A 21.5mmφ optical fiber cable was constructed. The tension member used was made by twisting seven glass fiber reinforced plastic wires each having an outer diameter of 1 mmφ and applying a polyethylene sheath around the outer periphery to make the outer diameter 6 mmφ.

Although this optical fiber cable was stretched by 4%, no breakage of the optical fiber was observed.

As explained above, in the optical fiber cable according to the present invention, the optical fiber core wire is accommodated in the spiral groove on the outer periphery of the rubber-like elastic body, so that when the rubber-like elastic body stretches under tension and becomes thinner, the optical fiber It is possible to give the core wire some room for elongation, and it is possible to protect the optical fiber core wire from tension. Therefore, according to the present invention, it is possible to provide an optical fiber cable with excellent breaking life. Furthermore, according to the present invention, providing an extra length to protect the optical fiber from tension is very simple because it is sufficient to simply insert the optical fiber into the spiral groove of the rubber-like elastic elongated body. be. Therefore, according to the present invention, it is possible to easily manufacture an optical fiber cable with excellent breaking life.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a first embodiment of an optical fiber cable according to the present invention, FIG. 2 is a perspective view of a rubber-like elastic elongated body used in the present invention, and FIG. 3 is a cross-sectional view of a first embodiment of an optical fiber cable according to the present invention. FIG. 4 is a cross-sectional view of the second embodiment of the fiber cable, FIG. 4 is a cross-sectional view of the optical fiber cable unit used in this embodiment, and FIG. 5 is a cross-sectional view of another example of the optical fiber cable unit. be. DESCRIPTION OF SYMBOLS 1... Rubber-like elastic elongate body, 2... Spiral groove, 3... Optical fiber core wire, 4... Laminate tape, 5... Plastic sheath, 6... Laminate sheath, 7... Tension member, 8... Optical fiber cable unit, 9 ...Pressure winding layer, 10...Plastic sheath, 11... Core wire escape prevention member.

Claims (1)

[Claims] 1. An optical fiber cable characterized in that an optical fiber core wire is accommodated in a spiral groove provided on the outer periphery of a rubber-like elastic elongated body.