JP3949677B2 - Fiber optic cable - Google Patents

Description

  The present invention relates to an optical fiber cable installed inside and outside a building and inside and outside a home.

With the progress of the construction of optical subscriber line networks, optical fiber cables (including indoor / drop optical cables / optical cords) have been used inside and outside office buildings and ordinary households.
In recent years, a drop optical fiber cable has been developed in which a plurality of optical fiber single fibers are accommodated in the cable (for example, Patent Document 1).

    A typical drop optical fiber cable is shown in FIG. In the drop optical fiber cable of FIG. 1, tension members 2 are arranged on both sides of a core assembly 1 ′ in which two optical fiber single cores 1 are arranged on the assembly center line 20, and the tension member 2 is further provided. The support wires 3 are arranged on one outer side of the two, and these are integrally covered with a sheath 4 via a neck portion 8 to form a rectangular shape. At this time, the centroid 21 (see FIG. 3) in the cross-sectional shape of the core assembly 1 ′ and the centroid 22 in the cross-sectional shape of the tension member 2 are arranged on the sheath center line 23. Further, V-shaped notches 6 are formed on both surfaces of the outer surface of the sheath 4.

On the other hand, in order to prevent the cicada from mistakenly inserting the laying tube into the cable during spawning and damaging the optical fiber under the notch bottom, a cable with no notch on the long side of the sheath has been developed and studied.
Such a drop optical fiber cable is shown in FIG. In the drop optical fiber cable 5 ′, a tension member 2 is arranged on both sides of two optical fiber single cores 1, and a support wire 3 is arranged on one outer side of the tension member 2, and these are separated by a sheath 4. It is integrally formed and formed into a rectangular shape. At this time, the centroid 21 (see FIG. 3) in the cross-sectional shape of the core assembly 1 ′ and the centroid 22 in the cross-sectional shape of the tension member 2 are arranged on the sheath center line 23. A notch is not formed on the surface of the sheath 4 of the cable.

These drop optical fiber cables tend to bend in a direction perpendicular to the sheath center line 23 as shown in FIG. In order to relieve the stress applied to the optical fiber single core wire 1 when bent in this way, the assembly center line 20 and the sheath center line 23 are arranged to overlap each other, that is, between the assembly center line 20 and the sheath center line 23. The conventional technology level is to make the angle to be 0 degree.
JP 2002-365499 A

    A state in which the optical fiber cable configured by embedding a plurality of optical fiber single core wires in the sheath as described above is torn will be described below. FIG. 5 is a diagram showing a state in which an optical fiber cable 5 having, for example, two optical fiber single-core wires 1 is torn. When the optical fiber single fiber 1 is taken out from the optical fiber cable 5, if there is a notch 6, the notch 6 is used as a trigger. A notch-shaped tear groove 9 (see FIG. 6) is retrofitted on the top, and the sheath 4 of the optical fiber cable 5 is cut into two by using the tear groove 9 to expose the single optical fiber 1. However, in this case, a part of the sheath 4 between the two optical fiber single fibers 1 often remains as the protruding portion 15. In this case, the protruding portion 15 becomes an obstruction factor and it is difficult to take out the optical fiber single core wire 1. In particular, when the sheath is stiff in a low temperature environment, the optical fiber single core wire 1 may be disconnected at the time of extraction.

    In recent years, in order to cope with the cicada spawning as described above, an optical fiber cable without a notch is required, or an optical fiber single-core wire is not only at the terminal part of the optical fiber cable but also at the intermediate part. Since it is required to be able to be taken out, a higher level of the taking-out property of the optical fiber single core wire is being demanded.

The present invention has been made as a result of intensive studies in view of the above points, and the optical fiber cable according to claim 1 is a core disposed on an assembly center line in which a plurality of optical fiber single fibers are one straight line. A notch formed on both outer surfaces of the sheath, the wire assembly and one or more tension members being covered with a sheath, and passing through the core assembly and substantially perpendicular to the sheath center line, or An optical fiber cable in which the sheath is cut along a slit groove formed later on both outer surfaces of the sheath, and each optical fiber single fiber is taken out from the sheath, in the cross-sectional shape of the core assembly The centroid and the centroid in the cross-sectional shape of the tension member are arranged on a sheath centerline that is a straight line, and the sheath has a flat shape that is long in the direction along the sheath centerline, Serial each optical fiber single fiber is arranged embedded directly the sheath, respectively, the angle of the sheath centerline and the assembly centerline is equal to or less than 90 degrees 24 degrees.

The optical fiber cable according to claim 2 is further characterized in that an angle formed by the assembly center line and the sheath center line is not less than 45 degrees and not more than 90 degrees.

The optical fiber cable according to claim 3 is further characterized in that an angle formed by the assembly center line and the sheath center line is less than 90 degrees.

Since the angle formed by the assembly center line and the sheath center line is not less than 24 degrees and not more than 90 degrees in the optical fiber cable according to claim 1, when the sheath is cut into two as shown in FIG. Since the two cracks extending into the wire assembly run on different optical fiber single cores, for example, in the case of a two-core cable, when a part of the sheath between the two cores protrudes as shown in FIG. In addition, the protruding portion 15 remains only at one location on both sides of the sheath that has been split into two, and the take-out property of the optical fiber single-core wire is improved.

Furthermore, the optical fiber cable according to claim 1 is particularly effective when a single optical fiber is taken out at an optical fiber cable terminal portion of an optical fiber cable having no notch. That is, since the angle formed by the assembly center line and the sheath center line is 24 degrees or more, the sheath of the optical fiber cable at the terminal is cut into two by using a notch-like tear wound attached on the sheath with a tool or the like, In the operation of exposing the optical fiber single core wire, the core wire can be taken out without disconnection under a general aerial environment of −30 ° C. to 70 ° C.

A fiber optic cable according to claim 2, especially for the type of optical fiber cables without notches, in the optical fiber cable intermediate portion, is effective when taking out the optical fiber single fibers. That is, since the angle formed by the assembly center line and the sheath center line is 45 degrees or more, in the operation of taking out the optical fiber single fiber at the intermediate portion of the optical fiber cable, as shown in FIG. A conventional aerial environment of -30 ° C to 70 ° C using a conventional intermediate sheath tearing tool that has a function of splitting the wedge-shaped member into two directions on the surface of the sheath central portion on the surface of the sheath. The core can be taken out without disconnection below.

    For example, as shown in FIG. 9, when the optical fiber cable is sandwiched along the long side direction, it is preferable that the sandwiching direction does not coincide with the direction of the assembly center line 20. This is because when the sandwiching direction and the direction of the assembly center line 20 coincide, the optical fiber single-core wires 1 may be pressed against each other by the sandwiching force and may be damaged. Therefore, as in the optical hiber cable described in claim 4, it is preferable that the angle formed by the assembly center line and the sheath center line is less than 90 degrees.

The best mode recognized by the inventors for carrying out the present invention will be described below.
In FIG. 10, reference numerals 1 to 5 denote an optical fiber single core wire, a tension member, a support wire, a sheath, and an optical fiber cable, respectively, similarly to the case shown in FIG.

  The optical fiber single core wire 1 is coated on a glass fiber of 0.125 mmφ so as to be 0.25 mmφ with UV resin, the tension member 2 is made of 0.5 mmφ aramid FRP, and the support wire 3 is The sheath 4 is made of non-halogen flame retardant polyethylene. Further, the optical element portion 7 has a rectangular long side (width direction) of 3.1 mm and a short side (thickness) of 2.0 mm. The two optical fiber single core wires 1 are arranged in a straight line on the assembly center line 20 to constitute a core assembly 1 ′. The centroid 21 in the cross-sectional shape of the core wire assembly and the centroid 22 in the cross-sectional shape of the two tension members 2 are arranged on a straight line on the sheath center line 23. The angle α formed by the assembly center line 20 and the sheath center line 23 is 75 degrees.

As an example of the present invention, when the angle α formed by the assembly center line and the sheath center line was changed to various values and the core wire take-out property was evaluated, the results shown in Table 1 were obtained. In order to take out the core wire without disconnecting from the cable end in the range of -30 ° C to 70 ° C, use the tool from the middle part at the angle of the core wire in the range of 24 ° to 90 ° and -30 ° C to 70 ° C. And it was found that 45 degrees or more is enough to take out the core without disconnection.

The optical transmission part of the optical fiber single fiber may be made of any material such as plastic or glass such as quartz. The material of the tension member may be any material such as steel wire, FRP, or fiber. As the sheath material, a thermoplastic resin such as non-halogen flame-retardant polyethylene is generally used in addition to polyethylene, but is not particularly limited. There may or may not be a notch on the cable jacket. Even if there is a notch, the straight line connecting the centers of the single core wires of the core assembly and the sheath long side are not parallel, so that the cracks extending from the bottom of the notch groove to the core portion are different from each other. The same effect can be obtained.

The end view which shows an example of the past. End view showing another conventional example Explanatory drawing which shows the principal part of the said prior art example. Explanatory drawing which shows the bending part of an example in the said prior art example. End view showing the sheath tearing state of the conventional example The end view which shows the state before the sheath tearing of the said prior art example. The end view which shows one Embodiment of this invention. The end view which shows the sheath tearing state of the said embodiment. Explanatory drawing which shows the example of a sheath tearing of the optical fiber cable of this invention. The end view which shows the other embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical fiber single fiber 1 'Core wire assembly 2 Tension member 3 Support line 4 Sheath 5 Optical fiber cable 6 Notch 7 Optical element part 8 Neck part 9 Rupture groove 10 The remainder 11 of the sheath between two cores The sheath extends A portion 12 A crack 13 extending from the sheath surface to the core portion 13 Tool 14 Wedge-shaped member 15 Protrusion portion 20 Aggregate center line 21 Centroid 22 centroid 23 Sheath center line α angle

Claims (3)

A core assembly in which a plurality of optical fiber single cores are arranged on a single center line is covered with a sheath and one or more tension members are covered with the sheath, and the sheath passes through the core assembly. The sheath is cut along notches formed on both outer surfaces of the sheath substantially perpendicular to the center line, or along slit grooves formed later on both outer surfaces of the sheath, and each light from the sheath is cut. An optical fiber cable from which a fiber single fiber is taken out,
The centroid in the cross-sectional shape of the core assembly and the centroid in the cross-sectional shape of the tension member are arranged on a sheath center line that is a straight line,
The sheath has a flat shape that is long in a direction along the sheath centerline,
Each of the optical fiber single core wires is directly embedded in the sheath, respectively,
An optical fiber cable, wherein an angle formed by the assembly center line and the sheath center line is 24 degrees or more and 90 degrees or less . 2. The optical fiber cable according to claim 1 , wherein an angle formed by the assembly center line and the sheath center line is not less than 45 degrees and not more than 90 degrees. The optical fiber cable according to claim 1 or 2, wherein an angle formed by the assembly center line and the sheath center line is less than 90 degrees.

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