JPH11174288A - Self supporting optical fiber cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical fiber cable in which the branching is easy in the middle of the cable at a low price. SOLUTION: A laminated body 2 is made by laminating plural tape-like optical fiber core wires 1 in which the plural optical fiber core wires 1a are made parallel and batch coating 1b is performed, an intertwined body 4 is made by intertwining the laminated body 2 and a buffer cord 3 and a potbelly type plastic coating 6 is provided on a supporting wire 5 so that the supporting wire is positioned at a potbelly head part. Thus, the intertwined body 4 is made to meander and housed inside a tubular void 6a in parallel to the supporting wire formed at the position of a potbelly body part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aerial self-supporting optical fiber cable mainly used for subscribers.

[0002]

2. Description of the Related Art As a self-supporting optical fiber cable for a subscriber, a cable having a cross section as shown in FIG. 2 is known. FIG. 2A shows a cross section of this self-supporting optical cable. A housing 12 made of a plastic resin such as polyethylene having a spiral groove 12a is provided around a strength member 11 such as a steel wire or FRP. A tape-shaped optical fiber core 13 is stacked and stored therein, and an upper winding 14 made of a plastic tape or the like is wound into a cable core 15, and the cable core 15 and a tensile strength member 16 such as a steel stranded wire are made parallel to each other. It is provided with a ball-shaped plastic coating 17.

The tape-shaped optical fiber core 13 is shown in FIG.
It has a cross-section shown in (B), in which a plurality of optical fiber core wires 13a arranged in parallel are provided with a collective coating 13b made of an ultraviolet curable resin.

[0004] In such a cable according to the prior art,
Elongation of the cable due to the tension applied at the time of laying the cable and elongation of the cable due to the temperature change of the environment occur.To prevent the elongation of the cable from causing an unacceptable elongation strain to the optical fiber core, It is devised.

[0005] That is, in applying the ball-shaped plastic coating 17 with an extruder, the coating is applied in a state where a large tension is applied to the tensile strength wire 16 to give an elongation, and the tension is released to compress the cable core 15 toward the cable core 15. Give distortion. Then, the cable elongation due to the cable laying and the temperature change does not directly become the elongation of the cable core, and the elongation of the cable core does not occur until the above-mentioned compressive strain is eliminated. Therefore, in that case, the elongation strain of the optical fiber core does not exceed the value when the cable core was manufactured.

As another method, as shown in FIG. 2 (C), the connection of the ball-shaped plastic coating 17 by the neck portion 17a is discontinuous in the longitudinal direction of the cable, and a short connection portion 17b and a long non-connection portion 17c are formed. There is a method in which the cable core 15 side is slackened by the unconnected portion 17c so that the length of the cable core 15 is longer than the length of the support wire 16 side. In this way, even if the cable is stretched due to laying or temperature change, the stretching does not reach the cable core, so that no extra stretching strain is applied to the optical fiber core.

[0007] However, these cables use a plastic housing having a spiral groove around the strength member, so that there is a problem that the cable price is high. Further, since a spiral groove is usually provided with four or more grooves, it is optimal as a cable having a number of cores of about 100 or more, but there is a problem that a cable having a small number of cores is expensive. On the other hand, as a subscriber cable, if you go near the subscriber, you do not need too many cores,
About 10 to 50 cores are required.

When a part of the core wire is to be branched in the middle of the cable, the support wire portion and the cable core portion of the ball-shaped plastic coating are separated at the middle portion of the cable by a knife or the like. Removing the plastic coating and exposing the cable core, the tape-shaped optical fiber core will be taken out from the spiral groove,
Since the tape-shaped optical fibers are stacked and housed in the groove, it is not easy to take them out. When branching the entire core of one groove, it is sufficient to pull out the entire core from the groove, cut it, and connect it to the branch cable.However, it is usually impossible to take out only a part of the core at the bottom of the groove. is there.

[0009]

The present invention does not require a special storage body having a spiral groove as described above,
It is an object of the present invention to provide an optical fiber cable which can be provided at a low price and is suitable for a request for a small number of fibers such as 0 to 50 fibers and which can be easily branched in the middle of the cable.

[0010]

A self-supporting optical fiber cable according to the present invention is formed by laminating a plurality of tape-shaped optical fiber cores in which a plurality of optical fiber cores are parallel-coated and collectively coated. The laminated body and the shock-absorbing string are twisted into a stranded body, and the support wire is formed on the daruma abdomen by providing a daruma-type plastic coating on the support wire so that the daruma head is located at the daruma head. The twisted body is housed in a tube-shaped cavity parallel to the support wire in a meandering manner.

Also, in order to make the twisted body meander in the cavity sufficiently, it is desirable that the inner diameter of the cavity be 1.5 times or more the envelope outer diameter of the twisted body.

[0012]

FIG. 1A is a sectional view of an embodiment of a self-supporting optical fiber cable according to the present invention. FIG. 1B is a cross-sectional view of a tape-like optical fiber used in the cable.

As shown in FIG. 1B, a plurality of optical fiber cores 1a each formed by coating a glass fiber with an ultraviolet-curable resin or the like are arranged in parallel, and are collectively coated 1b. It consists of what was done.

As shown in FIG. 1 (A), a plurality of tape-shaped optical fibers 1 are laminated to form a laminated body 2, and the laminated body 2 and the buffer string 3 are twisted to form a stranded body 4. .
In addition, as the buffering cord 3, when the tape-like optical fiber is stretched and tension is applied to straighten it, it is deformed in the cross-sectional direction or stretches itself to give a large lateral pressure to the tape-like optical fiber. You need to choose a material that does not.

Accordingly, a string made of a plastic foam which is easily stretched and easily deformed, and a string of plastic fibers which are deformed into various shapes in the cross-sectional direction are used as the buffer string. It is more preferable that a string obtained by bundling plastic fibers such as polyester fibers has a considerable tension by itself when twisted with a laminate, and can be deformed into various shapes in a cross-sectional direction when a lateral pressure is applied.

When a laminated body is formed by laminating six tape-shaped optical fiber cords each having a size of 1.1 mm × 0.3 mm, a buffer string having a diameter of about 1.8 mm is used. used. The twisting pitch between the twisted body and the buffer string is about 200 mm.

The laminated body 2 of the tape-shaped optical fiber cores 1 can be provided with an appropriate coarse winding 2a such as a thin fiber.
The laminate 2 is twisted with the laminate 2 and the buffer string 3.
If the lamination state does not collapse stably, the coarse winding 2a on the laminate 2 can be omitted.

The stranded body 4 is made of steel wire, steel stranded wire, FR
In parallel with the supporting wire 5 made of P or the like, a daruma-shaped plastic coating 6 is put on the outside thereof. The daruma-type plastic covering 6 is put on the daruma abdomen so that the support wire 5 is located on the daruma head. Further, the support wire 5 and the plastic coating are brought into close contact with each other, and the side of the twisted body 4 is formed with a cavity 6a in the plastic coating 6, and the twisted body 4 is housed in the cavity 6a in a meandering manner. Extruder point when extruding Daruma type plastic coating, like
Adjust the die.

The meandering of the twisted body 4 in the cavity 6a is performed as follows. When extruding the plastic with the Daruma-type plastic coating 6 applied around the support wire 5 and the twisted body 4 with an appropriate tension applied to the support wire 5, the tension is released after the extrusion and the support wire 5 is released. Since the plastic coating shrinks, the twisted body 4 accommodated in the cavity 6a of the plastic coating 6 has a meander corresponding to the shrinkage. In addition,
By adjusting the tension applied to the support wire, the degree of this meandering is adjusted. The required degree of meandering varies depending on the place where the cable is used, etc., but generally, the length of the twisted body 4 is about 0.06 to 0.15% longer than the length of the support wire 5. What should I do?

Assuming that the size of the tape-shaped optical fibers constituting the twisted body 4 is 1.1 mm × 0.3 mm, that is, 6 pieces, the outer diameter of the buffer string is 1.8 mm, and the twisting pitch is 200 mm. The length of the optical fiber ribbon is about 0.04% longer than the length of the twisted body.

Therefore, the length of the optical fiber ribbon is about 0.1 to 0.2% longer than the length of the supporting wire. If the cable is stretched due to the tension applied during cable laying or a temperature change after the cable is laid, first, the meandering of the twisted body in the cavity is stretched. Since the laminated body pushes the buffer string and straightens in the mating body to cope with it, the tape-shaped optical fiber core itself does not extend.

When it is necessary to perform a branching operation or the like in the middle part of the cable, the covering of the part where the twisted body of the Daruma type plastic covering is stored is peeled off, and the cushioning cord and the coarse winding are cut. In this case, since the lamination of the tape-shaped optical fibers can be easily separated, any tape-shaped optical fiber can be easily taken out.

[0023]

The self-supporting type optical fiber cable of the present invention is obtained by twisting a laminated body of a tape-shaped optical fiber core and a buffering cord into a stranded body, and positioning the supporting wire at the head of the daruma and twisting it. Position the body on the belly abdomen, apply a daruma type plastic coating on the support wire and the twisted body, make the support wire and the plastic coating adhere closely, and place the twisted body in a tubular cavity in the plastic coating. Since the cable is housed and the twisted body is meandering in the cavity, the elongation of the cable due to the tension at the time of laying the cable or the elongation of the cable due to the temperature change after the laying is eliminated. It is absorbed by the displacement of the tape-shaped optical fiber core in the twisted body and does not reach the tape-shaped optical fiber core.

Accordingly, the characteristic of the optical fiber is not deteriorated by the tension at the time of installation or the temperature change after the installation. In addition, since a housing having a spiral groove is not used, cable cost can be reduced. Further, even in the middle part of the cable, any tape-like optical fiber can be easily taken out by removing the plastic coating and cutting the cushioning cord, which is suitable for branching work.

[Brief description of the drawings]

FIG. 1A is a cross-sectional view of a self-supporting optical fiber cable according to an embodiment of the present invention, and FIG. 1B is a cross-sectional view of a tape-shaped optical fiber used in the embodiment.

FIG. 2A is a cross-sectional view of a self-supporting optical fiber cable according to the related art, and FIG. 2B is a cross-sectional view of a tape-shaped optical fiber used for the same. FIG. 1C is a perspective view of a self-supporting cable of a buckle type having a discontinuous neck.

[Explanation of symbols]

 1: tape-shaped optical fiber core 1a: optical fiber core 1b: batch coating 2: laminated body 3: buffer string 4: twisted body 5: support wire 6: plastic coating

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Hideyuki Iwata 3-19-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo Nippon Telegraph and Telephone Corporation

Claims (3)

[Claims] 1. A plurality of tape-shaped optical fibers coated in parallel with a plurality of optical fibers being laminated in parallel to form a laminated body, and the laminated body and a buffer string are twisted and twisted. Body, the support line is located at the head of the daruma, and the daruma-type plastic coating is provided on the support line. A self-supporting optical fiber cable, wherein a twisted body is housed in a meandering manner. 2. An inner diameter of the cavity is 1.5 times or more of an outer diameter of an envelope of the twisted body.
2. The self-supporting optical fiber cable according to item 1. 3. The self-supporting type optical fiber cable according to claim 1, wherein the buffer string is a string obtained by bundling fibers made of plastic.