JP2002090595A - Optical fiber cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the shape of the envelope of an optical fiber cable which is the constituent element of an aerial concentric drop cable into the shape with which a cicada cannot oviposit near a coated optical fiber or hardly oviposit. SOLUTION: One coated optical fiber 1 at the center of the cable and two tension members 2 disposed at both sides of and in parallel to the fiber 1 are covered in bloc with the outer sheath 3 with a nearly rectangular cross section so that the fiber 1 and the members 2 are included in the same plane. Notches 4 extended in the longitudinal direction in parallel with the fiber 1 are provided on the surface, parallel to the above plane, of the sheath 3 and just above and just below the sheath 3. A plurality of notches are further provided in parallel with the notches 4. Thereby, the possibility that a cicada oviposits in notches at the central part is reduced.

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 presumably 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, 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. As the tension member, a steel wire having a diameter of 0.4 mm is used, and the optical fiber core wire 1 usually has an outer diameter of 0.25 mm covered with an ultraviolet curable 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 giving an outer shell 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]

According to the present invention, a single optical fiber in 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. An optical fiber cable having a notch extending in a longitudinal direction parallel to an optical fiber core line at a position directly above and immediately below an optical fiber core line on a surface parallel to the plane and having a substantially rectangular cross section. By providing two or more notches on the upper surface and the lower surface of the outer skin, respectively, another notch reduces the probability that the cicada pierces the ovipositor tube at the central notch and damages 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, a plurality of notches 4 are provided on the upper surface and the lower surface of the coating, respectively. In the case of FIG. 1, the notch is 4a,
Five notches 4b, 4c, 4d, and 4e are provided on the upper and lower surfaces. By doing so, the insertion point of the oviposition tube of the cicada is dispersed, the possibility of spawning at the notch 4c immediately above and below the optical fiber is reduced, and the probability of an optical fiber disconnection accident can be reduced. Even in this case, the function of taking out the optical fiber core by tearing the central notch 4c by hand is equivalent to that of the conventional one.

In the present invention, a plurality of notches 4 are provided on the upper surface and the lower surface of the coating, respectively, and the number and shape of the notches 4 may be arbitrary. In addition to the one shown in FIG. 1, as shown in FIG. 2, the notch 4 may have a wide width to eliminate the flat portions on the upper surface and the lower surface to form a saw-tooth shape. If a notch is secured immediately above and below the optical fiber, the optical fiber will be prevented from breaking due to the spawning of the cicada, and at the same time, the optical fiber core will have 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, in order to reduce the probability that the cicada lays eggs in the notch portion immediately above and below the optical fiber core of the optical fiber cable, the optical fiber is disconnected due to injury caused by the cicada's oviposition tube. Has the effect of preventing.

[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 shell 4: Notch 5: Steel wire 6: Steel wire coating 10: Optical fiber cable (optical element) as element 20: Support wire

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Nobuhiro Akasaka 1 Tayacho, Sakae-ku, Yokohama-shi, Kanagawa Prefecture Sumitomo Electric Industries, Ltd. Yokohama Works (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 within Nippon Telegraph and Telephone Corporation (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 two or more plural notches are further provided on the upper surface and the lower surface of the outer cover, respectively, and another notch parallel to the notch is further provided.