JP2002090594A - Optical fiber cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the shape of an outer sheath of an optical fiber cable which is a constituent element of aerial multiple drop cables into a shape with which a cicada cannot lay eggs near a coated optical fiber or hardly lays eggs. SOLUTION: In an optical fiber, a coated optical fiber 1 located at the center of the cable and two tension members 2 disposed at both sides of and parallel to the fiber 1 are covered en block with an outer sheath 3 having a nearly rectangular cross section so that the fiber 1 and the members 2 are included in the same plane. The cable is further provided with notches 4 in the surface of the outer sheath 3 and just above and just below the fiber 1, respectively, and the notches 4 are extended in the longitudinal direction parallel to the fiber 1, and each notch has a shape of a rhombus, a lens form or the like which forms a nearly closed slit 41 at the outer sheath surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in an optical fiber cable which is a constituent element of an overhead aggregate drop cable which is installed between telephone poles immediately before drawing an optical fiber to a subscriber's house.

[0002]

2. Description of the Related Art An aerial collective drop cable is formed by assembling and twisting an optical fiber cable (hereinafter referred to as an optical element) as a constituent element around a plurality of support wires. A notch having a V-shaped cross-section extending continuously in the longitudinal direction is provided at the center of the outer skin having a substantially rectangular cross-section of the optical element, and the V-shaped apex is close to the optical fiber. The optical fiber inside can be taken out of this notch by hand without using a tool.

However, an investigation into the cable breakage accident of this cable that occurred in the summer revealed that a cicada pierced the ovipositor tube into this notch, possibly damaging the optical fiber inside. This is presumed to be because the cicada recognized the optical element as an object that is easy to lay eggs from the dimensions of the ovipositor tube and the notch.

[0004] The structure of a conventional overhead collection drop cable will be described with reference to FIG. FIG. 3A is a cross-sectional view of the optical element 10, wherein 1 is an optical fiber core coated with an optical fiber, 2 is a tension member, and 3 is an outer sheath. A notch 4 having a V-shaped cross section extending in the longitudinal direction is provided at the center of the outer cover 3, and the optical fiber core 1 can be taken out by tearing the notch by hand.

The dimensions of the optical element are about 3.0 mm in width and about 1.6 mm in thickness, and the outer cover 3 is made of plastic such as polyvinyl chloride or polyethylene. A steel wire having a diameter of 0.4 mm is used for the tension member, and the optical fiber core wire 1 usually has an outer diameter of 0.25 mm coated with an ultraviolet curing resin (UV resin). .

FIG. 3B is a cross-sectional view showing the overall structure of an aerial assembly drop cable, in which a plurality of optical elements 10 shown in FIG. 3A are assembled in a state of being twisted around a support wire 20. I have. The supporting wire 20 is composed of a steel wire 5 and a coating 6 therearound. The diameter of the steel wire 5 is about 2.6 mm. The material of the coating 6 is plastic such as polyvinyl chloride or polyethylene, and its outer diameter is It is about 3.5 mm.

[0007] The entire cable shown in (B) is in a stage before being wired to the subscriber's house, and is erected between telephone poles in an overhead state. Each subscriber has a support line 20 of the optical element 10.
The optical element 10 is wired by unwinding the wire.

After the wiring, the optical fiber core 1 in the optical element 10 is connected to the home equipment. At this time, the sheath 3 is torn by hand from the notch 4 to take out the optical fiber core. Due to the presence of the notch, no special tool is required and the optical fiber can be taken out.

The disconnection accident caused by the spawning of the cicada was found to be caused by the notch 4 of the optical element 10 pierced by the spawning tube of the cicada in the state of being erected between telephone poles in the state of FIG. ing. The cicada's ovipositor has a diameter of about 0.4mm, a length of about 10mm, and a pointed tip. The notch has an entrance width of about 0.5mm and a depth of about 0.5mm, and the ovipositor just fits It is a dimensional shape.

[0010] Cicada usually lays eggs on dead trees instead of live trees,
It is said that a hole is made in a dead branch at the tip of a hard ovipositor to lay eggs. Investigation of the cable breakage accident of this cable that occurred in the summer described above showed that cicada illusioned this cable with a dead tree branch suitable for spawning, traumatizing the optical fiber core wire while piercing the ovipositor tube at the notch, Suggested that it was thought to have led to the fiber break.

[0011]

SUMMARY OF THE INVENTION The present invention provides an optical fiber cable, which is a constituent element of an imaginary aggregate drop cable, by providing a notch shape in which a cicada cannot lay eggs or is difficult to lay eggs, and the fiber is damaged by a cicada laying tube. The purpose is to provide a highly reliable optical fiber cable that is not affected by the problem.

[0012]

SUMMARY OF THE INVENTION According to the present invention, a single optical fiber cable at the center of a cable and two tension members arranged in parallel on both sides thereof are collectively covered so as to be included in the same plane. Of a substantially rectangular outer cross-section, directly above and below said optical fiber core on a surface parallel to said plane,
In an optical fiber cable provided with a notch extending in the longitudinal direction parallel to the optical fiber core, the cross section of the notch is almost closed on the outer surface and a sharp cavity on the optical fiber core side. The cicada does not notice the existence of the notch, and prevents the cicada from piercing the oviposition tube into the notch and spawning near the optical fiber.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to FIG. In FIG. 1, the same parts as those in FIG. In the present invention, the entrance portion of the notch 4, that is, the outer skin surface portion of the notch is closed, and the slit 41 is formed there. Since the notch is almost closed on the outer skin surface, there is no gap at the entrance, making it difficult for the cicada to notice the notch and lay eggs. Is equivalent to

According to the present invention, any shape may be used as long as a cavity having a substantially closed notch entrance is formed and the optical fiber side of the cavity is sharp. As shown in FIG. 2, in addition to the one shown in FIG.
(B) lens shape, (C) turnip shape, etc. are also possible. Regardless of the shape, if the outer surface of the notch is almost closed and a hollow portion with a sharp optical fiber side is formed, spawning of the cicada is prevented, and at the same time, the optical fiber core wire has the same tearability as conventional.

The optical element shown in FIGS. 1 and 2 can be obtained by continuously extruding an outer cover made of polyvinyl chloride or polyethylene using a specially shaped die.

[0016]

According to the present invention, since the cicada does not lay eggs at the notch portion of the optical fiber cable, the optical fiber has an effect of preventing an accident in which the optical fiber is broken due to a traumatic injury caused by the oviposition tube of the cicada.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of an optical fiber cable of the present invention.

FIG. 2 is a sectional view showing another embodiment of the optical fiber cable of the present invention.

FIG. 3 is a sectional view showing another embodiment of the conventional optical fiber cable.

[Explanation of symbols]

1: Optical fiber core wire 2: Tension member 3: Outer skin 4: Notch 41: Slit 5: Steel wire 6: Steel wire coating 10: Optical fiber cable (optical element) as element 20: Support wire

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masayoshi Yamano 1 Tayacho, Sakae-ku, Yokohama-shi, Kanagawa Prefecture Inside the Yokohama Works, Sumitomo Electric Industries, Ltd. (72) Inventor Kimio Ando 2-3-1 Otemachi, Chiyoda-ku, Tokyo No. Nippon Telegraph and Telephone Corporation (72) Inventor Shinji Nagasawa 2-3-1 Otemachi, Chiyoda-ku, Tokyo F-Term (in reference) 2H001 BB15 DD06 DD21 KK17

Claims (1)

[Claims] An outer sheath having a substantially rectangular cross section formed by covering one optical fiber core wire at the center of a cable and two tension members arranged in parallel on both sides thereof in a lump. In an optical fiber cable provided with a notch extending in the longitudinal direction parallel to the optical fiber core just above and immediately below the optical fiber core on the surface parallel to the plane,
An optical fiber cable characterized in that the cross-sectional shape of the notch is substantially closed on the outer surface and forms a sharp cavity on the optical fiber core side.