JP2002090593A - Fiber optic cable - Google Patents

Abstract

(57) [Problem] To provide an optical fiber cable, which is a constituent element of an imaginary aggregate drop cable, in a shape in which a cicada cannot or does not easily lay eggs near an optical fiber core. SOLUTION: An outer sheath 3 having a substantially rectangular cross section formed by simultaneously covering one optical fiber core wire 1 at the center of a cable and two tension members 2 arranged in parallel on both sides thereof so as to be included in the same plane. Of the notch 4, which is provided above and below the optical fiber core wire on the surface parallel to the plane and extends in the longitudinal direction parallel to the optical fiber core wire, is shifted from the position of the optical fiber core wire, and There is no optical fiber core in the outer skin, so that even if a cicada ovipositor is pierced into the notch, the ovipositor does not damage the optical fiber core.

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. 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 is composed of a steel wire 5 and a coating 6 around the steel wire, and 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 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]

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. In an optical fiber cable having a notch extending in a longitudinal direction parallel to the optical fiber core on the upper and lower portions of the optical fiber core on a surface parallel to the plane of the outer skin having a substantially rectangular cross section, Since the optical fiber core is not located in the outer skin just below the apex by shifting it from the position of the fiber core, even if the cicada's ovipositor is pierced into the notch, the ovipositor may damage the optical fiber. There is no.

[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 position of the apex of the notch 4 is shifted from the center so that there is no optical fiber core wire in the outer skin immediately below the apex. Strictly speaking, there is a certain distance a between the leg of a perpendicular line lowered from the apex of the notch to the straight line connecting the center of the optical fiber core and the center of the tension member, and the center of the optical fiber core wire. . In other words, since there is no optical fiber core 1 at the end of the apex, the egg-laying tube of the cicada does not hit the optical fiber core wire directly.

Since the thickness of the ovipositor tube is about 0.4 mm in diameter and the thickness of the optical fiber core is about 0.25 mm, in order for the cicada ovipositor to directly hit the optical fiber core, a Needs to be greater than 0.325 mm. Also, a
If the size is too large, the tearability of the notch deteriorates. From this point of view, it was confirmed through experiments that if a was smaller than 0.75 mm, no problem of tearing would occur. Therefore, in order to sufficiently exert the effects of the present invention, it is necessary to satisfy 0.325 mm ≦ a ≦ 0.75 mm. In this case, the function to take out the optical fiber core wire by tearing the notch by hand is almost the same as before,
It can protect the optical fiber from the spawning tube of cicada.

FIG. 2 shows another embodiment of the present invention. In this example, the shape of the notch 4 itself is asymmetrical,
The definition of the deviation amount a of the notch vertex and the effective range of a are exactly the same as those shown in FIG.

An optical element shown in FIG. 1 was experimentally manufactured. Polyethylene was continuously extruded with a die having a shape corresponding to FIG. 1 to provide an outer cover, and a was set to 0.4 mm. The prototype had good initial characteristics and good core wire take-out property by tearing the notch.

[0017]

According to the present invention, since there is no optical fiber at the tip of the notch apex, it is possible to prevent an accident in which the optical fiber is broken due to a traumatic injury caused by the oviduct 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 shell 4: Notch 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 Shinsuke Niiyama 1-chome, Tayacho, Sakae-ku, Yokohama-shi, Kanagawa Prefecture Sumitomo Electric Industries, Ltd. Yokohama Works (72) Inventor Kimio Ando 2-3-3 Otemachi, Chiyoda-ku, Tokyo No. 1 Within 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 DD06 DD21 PP01 2H038 CA64

Claims (2)

[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 in which a notch extending in the longitudinal direction parallel to the optical fiber core is provided above and below the optical fiber core on the surface parallel to the plane, the notch apex is shifted from the position of the optical fiber core. An optical fiber cable characterized in that there is no optical fiber core wire in the outer sheath immediately below the apex. 2. A distance a between a leg of a perpendicular line lowered from the apex of the notch to a center line of the optical fiber core and a center line of the optical fiber core and a tension member center is 325 m.
2. The structure according to claim 1, wherein m ≦ a ≦ 0.75 mm.
An optical fiber cable according to claim 1.