JP2003302560A - Optical fiber cable - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve utilization efficiency of coated optical fibers in post- branching optical fibers in the intermediate part of installation. <P>SOLUTION: In the optical fiber cable (11) in which a cable core composed of a plurality of coated optical fibers is stored in a pipe like sheath (17), with buffer layers (15) installed between the cable core and the pipe-like sheath (17); the cable core is constituted of more than one unit (14) which is structured by bundling every plurality of single-coated optical fibers (12) with a thread like fiber (13). <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of an optical fiber cable in which an optical fiber core wire is formed into a cable.

[0002]

2. Description of the Related Art FIG. 3 shows an example of a conventional optical fiber cable. In FIG. 3, in the optical fiber cable 31, the outer periphery of a cable core made of a laminated body of a plurality of four-fiber optical fiber ribbons 32 is twisted and covered in one direction by a buffer layer 35 made of a plastic yarn. Together with the strength member 36 arranged on the outside, a sheath 37 made of a thermoplastic resin or the like is collectively covered. In the case of this conventional optical fiber cable, when post-branching the optical fibers of several cores at the intermediate portion of the installation due to the occurrence of demand after installation, strip off the sheath and buffer layer of the relevant part, cut the optical fiber tape,
Generally, it is connected to the core wire at the branch destination. In such a conventional optical fiber cable, if the required number of post-branching cores is less than the number of cores of the optical fiber tape, if the optical fiber tape is cut, the cores that do not need to be cut are also cut. Since it cannot be used at the lower part of the branch point, there is a problem that the efficiency of using the core wire is poor.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to improve the utilization efficiency of the optical fiber core wire when the optical fiber is branched at the intermediate portion for installation.

[0004]

As a result of intensive studies to solve the above-mentioned problems, the present inventors have decided to use an optical fiber single core wire instead of an optical fiber tape for a cable core, and It has been found that it is possible to improve the use efficiency of the core wire at the time of branching in the middle part of the installation. Furthermore, by bundling this optical fiber single-core wire every several fibers, it prevents the optical fiber single-core wire from jumping out into the buffer layer and causing an increase in loss, and the optical fiber single-core wire is entangled with the buffer layer at the time of branching The present invention has been completed by finding that they can be easily separated without the need.

That is, according to the present invention, (1) an optical fiber in which a cable core composed of a plurality of optical fiber cores is housed in a pipe-shaped sheath and a buffer layer is provided between the cable core and the pipe-shaped sheath. In the fiber cable, the cable core is composed of a plurality of units, and the unit is configured by bundling a plurality of optical fiber single-core wires with a filament fiber, ( 2) The optical fiber cable according to item (1), characterized in that the color of the single fiber of the optical fiber in the unit is matched with the color of the filament fiber used in the bundle.
(3) The optical fiber cable according to item (1) or (2), wherein the buffer layer is made of a string-shaped fiber.
(4) The buffer layer is twisted around the cable core by unidirectional twisting or SZ twisting in which the twisting direction changes periodically. (1) to (3) (5) The optical fiber cable according to item (5), wherein the plurality of units are twisted by unidirectional twisting or SZ twisting in which the twisting direction changes periodically (1) to (4). An optical fiber cable according to any one of the above items is provided.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is an optical fiber cable in which a cable core composed of a plurality of optical fiber core wires is housed in a pipe-shaped sheath and a buffer layer is provided between the cable core and the pipe-shaped sheath. In the above, the cable core is composed of a plurality of units, and the unit is configured by bundling a plurality of single optical fiber cores with a filament fiber.

The present invention applies to glass optical fibers and plastic optical fibers. In the present invention, since the cable core is composed of an optical fiber single core wire instead of an optical fiber tape, it is possible to improve the utilization efficiency of the core wire when the optical fiber cable is branched at the intermediate portion of the installation. .

Further, by bundling a plurality of optical fiber single-core wires in each bundle, it is possible to prevent the optical fiber single-core wires from jumping out into the buffer layer and causing an increase in loss. It can be easily separated without being entangled with the layers. The number of optical fibers to be bundled is not limited, but is preferably 2 or more, more preferably 4 to 12. The bundling is performed at intervals of 20 mm or more, preferably at intervals of 30 to 120 mm. The fineness of the filamentous fibers used for the bundle is 100 to 500 dtex, preferably 20.
It is 0 to 400 dtex.

[0009] In order to be able to satisfy the optical fiber discriminating property concerned by using the single-core wire instead of the optical fiber tape, the color of the single-core fiber and the thread shape used in the bundle It is preferable to match the color of the fibers. For example, the color of one of the single fibers of the optical fiber and the color of the thread-like fiber used for the bundle may be matched with each other. Synthetic resins such as polyester, polypropylene, nylon, polyaramid, etc. are used for the filamentous fibers, and polyester spinning is preferably used.

In the present invention, the buffer layer is provided between the cable core formed of a plurality of optical fiber cores and the pipe-shaped sheath. Synthetic resins such as polyvinyl chloride, polyethylene, nylon, and fluorinated ethylene propylene are used for the sheath, and polyethylene is preferably used. Further, a string-shaped fiber is used for the buffer layer, and a synthetic resin such as polypropylene, nylon, or polyester is used as the material thereof, and it may be made of a plastic yarn having easy handling and an appropriate buffering effect. preferable.

In order to prevent the cable core from being exposed through the gap of the buffer layer and directly contacting the sheath to cause an increase in loss, the buffer layer is unidirectionally twisted around the cable core, or
It is preferable to be twisted by SZ twist in which the twist direction changes periodically. In order to alleviate the compressive or tensile strain applied to the optical fiber cores located inside or outside the bend when the cable is bent, the unit is unidirectionally twisted or SZ twisted in which the twisting direction is periodically changed. It is preferably twisted. Further, it is not easy to remove the buffer layer from the unit if the buffer layer is inserted between the units, so it is preferable that the units are united together.

[0012]

FIG. 1 is a sectional structural view of a preferred embodiment of the present invention.
Shown in. In the optical fiber cable 11 of FIG. 1, the outer circumference of four single-core optical fiber cores (outer diameter 0.25 mm) 12 is 10 by polyester spinning (fineness 300 dtex) 13.
The unit 14 bundled at 0 mm intervals has an inversion angle of 36.
10 strands of SZ are twisted at 0 ° and a reversal pitch of 500 mm, and a polypropylene yarn (fineness 4400 dtex) 15 is covered as a buffer layer around the SZ twist at a reversal angle of 360 ° and a reversal pitch of 500 mm. Rustproof treated steel wire (outer diameter 0.7 mm) 16 and polyethylene sheath (outer diameter 10 mm) 17
It is the one covered with. Although a gap is shown between the buffer layers 15 in FIG. 1, the buffer layer 15 is actually filled between the sheath 17 and the bundle of the optical fiber units 14 without any gap. The color of the core wire and the color of the bundle thread in the unit in the unit 14 are as shown in Table 1.

[0013]

[Table 1]

Another embodiment of the present invention is shown in the sectional structural view of FIG. The optical fiber cable 21 shown in FIG. 2 is formed by polyester spinning (fineness 300 dtex) 23 around the outer circumference of four single-core optical fibers (outer diameter 0.25 mm) 22.
The unit 24 bundled at an interval of
Twisted into 10 SZ with an inversion pitch of 500 mm,
Polypropylene yarn (fineness 4
400dtex) 25, reversal angle 360 °, reversal pitch 5
A rustproof steel wire (outer diameter 0.7 mm) 26, which is covered with SZ twist at 00 mm and arranged as a tensile strength body on the outside,
A rustproof steel stranded wire (7 strands with an outer diameter of 1.4 mm) 28 arranged as a support wire for aerial installation is intermittently provided in the longitudinal direction of the cable with a polyethylene connecting portion (length 40 m).
m) A sheath 27 made of polyethylene is collectively covered so as to be connected at 29. Although a gap is shown between the buffer layers 25 in FIG. 2, the buffer layer 25 is actually a sheath 27 and an optical fiber unit 24.
It is filled with no gap between the bundle and. In this embodiment, the cable main body is intermittently connected to the supporting wire 28 for aerial installation in the longitudinal direction of the cable by the connecting portions 29, and the cable main body has an extra length with respect to the supporting wire. It is a cable.

The optical fiber cable 11 of the above embodiment,
As a result of evaluating general transmission characteristics and mechanical characteristics required for the optical fiber cable for No. 21, it was confirmed that there was no problem in practical use. In addition, regarding the discriminating property of the optical fiber after the intermediate post-branching, it was possible to easily discriminate, and it was possible to improve the use efficiency of the core wire without cutting the optical fiber which does not need to be cut. .

[0016]

As described above, since the unit is constructed by bundling a plurality of single optical fibers with the filament fibers, there is an excellent effect that the use efficiency of the optical fibers is improved. Also, by bundling every few pieces,
There is an excellent effect that the optical fiber single-core wire is prevented from jumping out into the buffer layer to cause an increase in loss and the optical fiber single-core wire can be easily separated from the buffer layer without being entangled at the time of post branching. Further, since the buffer layer is twisted around the cable core in one direction or SZ twist in which the twisting direction changes periodically, the cable core is exposed from the gap of the buffer layer and directly contacts the sheath. It has an excellent effect of preventing an increase in loss. Furthermore, since the unit is twisted in one direction or SZ twist in which the twisting direction changes periodically, the excellent effect of alleviating the strain applied to the optical fiber core when the cable is bent There is.

[Brief description of drawings]

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

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

FIG. 3 is a sectional structural view showing an example of a conventional optical fiber cable.

[Explanation of symbols]

11, 21, 31 Fiber Optic Cable 12, 22 Single-core optical fiber 32 optical fiber tape 13,23 Filamentous fiber 14, 24 Optical fiber unit 15, 25, 35 Buffer layer 16, 26, 36 Strength member 17, 27, 37 sheath 28 Support line 29 Connection

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Masami Hara             2-6-1, Marunouchi, Chiyoda-ku, Tokyo             Kawa Electric Industry Co., Ltd. (72) Inventor Moto Yamamoto             2-3-1, Otemachi, Chiyoda-ku, Tokyo             Inside Telegraph and Telephone Corporation F-term (reference) 2H001 BB04 BB12 BB22 DD06 DD09                       DD10 DD11 DD15 DD22 HH02

Claims (5)

[Claims] 1. An optical fiber cable in which a cable core composed of a plurality of optical fiber cores is housed in a pipe-shaped sheath and a buffer layer is provided between the cable core and the pipe-shaped sheath. Is composed of a plurality of units, and the unit is configured by bundling a plurality of single optical fiber cores with a filament fiber. 2. The optical fiber cable according to claim 1, wherein the color of the single fiber of the optical fiber in the unit is matched with the color of the thread-like fiber used in the bundle. 3. The optical fiber cable according to claim 1, wherein the buffer layer is made of a string-shaped fiber. 4. The buffer layer is twisted around the cable core by unidirectional twisting or SZ twisting in which the twisting direction is periodically changed. The optical fiber cable described in. 5. The light according to claim 1, wherein the plurality of units are twisted by unidirectional twisting or SZ twisting in which the twisting direction is periodically changed. Fiber cable.