JP3662824B2 - Fiber optic cable - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an improvement in an optical fiber cable that is a constituent element of an aerial collective drop cable that is installed between utility poles just before an optical fiber is drawn into a subscriber's house.
[0002]
[Prior art]
An aerial collective drop cable is configured by collecting and twisting a plurality of optical fiber cables (hereinafter referred to as optical elements) as constituent elements around a support line. The optical element has a V-shaped notch extending continuously in the longitudinal direction at the center of the outer shell having a substantially rectangular cross section, and the V-shaped apex is close to the optical fiber. Without using a simple tool, you can tear the cable sheath from this notch by hand and take out the optical fiber inside.
[0003]
However, when the cable breakage accident of this cable that occurred in the summer was investigated, it was found that there was a case where a spear pierced the laying tube into this notch and damaged the optical fiber inside. This is presumed that the moth recognized the optical element as an object that is easy to lay eggs from the dimensions of the laying tube and the size and shape of the notch.
[0004]
The structure of a conventional aerial collective drop cable will be described with reference to FIG. FIG. 3A is a cross-sectional view of the optical element 10, where 1 is an optical fiber core wire, 2 is a tension member, and 3 is an outer skin. A central portion of the outer skin 3 has a notch 4 having a V-shaped cross section extending in the longitudinal direction, and the optical fiber core wire 1 can be taken out by tearing the notch by hand.
[0005]
The dimensions of the optical element are about 3.0 mm in width and about 1.6 mm in thickness, and the outer skin 3 is a plastic such as polyvinyl chloride or polyethylene. A steel wire with a diameter of 0.4 mm is used for the tension member, and the optical fiber core wire 1 is usually used with a coating outer diameter of 0.25 mm coated with an ultraviolet curable resin (UV resin). .
[0006]
FIG. 3B is a cross-sectional view showing the entire structure of the aerial assembly drop cable, in which a plurality of the optical elements 10 shown in FIG. 3A are assembled around the support wire 20 in a twisted state. The support wire is composed of a steel wire 5 and a coating 6 around it, 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 3 mm. About 5 mm.
[0007]
The entire cable shown in (B) is a stage before being wired to the subscriber's house, and is installed in an aerial state between utility poles. Each subscriber is wired in the state of the optical element 10 by unwinding the optical element 10 around the support wire 20.
[0008]
After the wiring, the optical fiber core wire 1 in the optical element 10 is connected to a home appliance. At this time, the outer skin 3 is torn from the notch 4 by hand, and the optical fiber core wire is taken out. The presence of this notch makes it possible to take out the optical fiber without using any special tool.
[0009]
It has been found that the disconnection accident caused by spawning of the spider is that the spawning tube of the spear has been pierced into the notch 4 of the optical element 10 in the state of being laid between the utility poles in the state of FIG. The spawning tube of the moth has a diameter of about 0.4 mm, a length of about 10 mm, and a pointed tip. The notch has a width of about 0.5 mm at the entrance and a depth of about 0.5 mm. Dimensional shape.
[0010]
Spiders are usually said to lay on dead trees instead of raw trees, and to lay holes on dead branches at the tips of hard laying tubes. In the investigation of the fiber breakage accident of this cable that occurred in the summer, the moth illusioned that this cable was a dead tree branch suitable for egg laying, pierced the egg-laying tube into the notch, and damaged the optical fiber core wire. It was suggested that this was thought to have led to a fiber breakage.
[0011]
[Problems to be solved by the invention]
The present invention provides an optical fiber cable, which is a component element of an aerial assembly drop cable, with a shape of a shell that cannot be spawned or hard to spawn, so that the fiber is not damaged by a spawning tube of a spear. The purpose is to provide cables.
[0012]
[Means for Solving the Problems]
The present invention provides an outer sheath having a substantially rectangular cross-section formed by covering a single optical fiber core wire at the center of a cable and two tension members arranged in parallel on both sides so as to be included in the same plane. In the optical fiber cable provided with a notch extending in the longitudinal direction parallel to the optical fiber core on the upper and lower sides of the optical fiber core on the surface parallel to the plane, the apex of the notch is shifted from the position of the optical fiber core, Since the optical fiber core wire is not present in the outer skin directly under the apex, even if the spawning tube of the spider is pierced into the notch, the spawn tube does not damage the optical fiber core wire.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
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 vertex 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 vertex. Strictly speaking, there is a certain distance a between the leg of the perpendicular drawn from the top of the notch to the straight line connecting the center of the optical fiber and the center of the tension member and the center of the optical fiber. . That is, since there is no optical fiber core wire 1 at the tip of the apex, the spawning tube does not hit the optical fiber core wire directly.
[0014]
Since the thickness of the laying tube is about 0.4 mm in diameter and the thickness of the optical fiber core is about 0.25 mm in diameter, in order not to directly hit the optical fiber core, the a is 0. It needs to be larger than 325 mm. On the other hand, if a is too large, the notch tearability deteriorates. From this viewpoint, it was confirmed by experiment that it was found that if a is smaller than 0.75 mm, the problem of tearability does not occur. Therefore, in order to fully demonstrate the effects of the present invention,
0.325mm ≦ a ≦ 0.75mm
It is necessary to. In this case, the function of taking out the optical fiber core wire by tearing the notch by hand can be made almost the same as the conventional one, and the optical fiber core wire can be protected from the spawning tube of the spider.
[0015]
Another embodiment of the present invention is shown in FIG. In this example, the shape of the notch 4 itself is asymmetrical, but the definition of the shift amount a of the vertex of the notch and the effective range of a are exactly the same as those shown in FIG.
[0016]
The optical element shown in FIG. 1 was prototyped. Polyethylene was continuously extruded with a die having a shape corresponding to FIG. 1 to provide an outer skin, and a = 0.4 mm. The prototype had good initial characteristics and good core line pullability after tearing the notch.
[0017]
【The invention's effect】
According to the present invention, since there is no optical fiber core at the tip of the notch, it is possible to prevent an accident in which the optical fiber core is disconnected due to an injury caused by a spawning tube.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an embodiment of an optical fiber cable according to the present invention.
FIG. 2 is a cross-sectional view showing another embodiment of the optical fiber cable of the present invention.
FIG. 3 is a cross-sectional view showing another embodiment of a conventional optical fiber cable.
[Explanation of symbols]
1: Optical fiber core wire 2: Tension member 3: Outer sheath 4: Notch 5: Steel wire 6: Steel wire coating 10: Optical fiber cable as an element (optical element)
20: Support line

Claims (1)

Of generally rectangular outer skin section formed by collectively covering to contain a single optical fiber and the two tension members arranged in parallel on both sides in the same plane in the center of the optical fiber cable, the said plane the top and bottom of the optical fiber of the parallel surfaces, an optical fiber cable provided with a notch extending in the longitudinal direction parallel to the optical fiber, the position vertexes of the notches of the optical fiber offset from, said in the outer skin the optical fiber is rather non perpendicular line drawn from the apex of the notch to a straight line connecting the center with the tension member the center of the optical fiber foot just below the apex, The distance a between the center of the optical fiber core wire is
0.325mm ≦ a ≦ 0.75mm
Optical fiber cables, characterized in that it.

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