JPH07225330A - Optical unit for optical composite overhead earth wire - Google Patents

Abstract

PURPOSE:To provide an optical unit which is provided with retaining winding and resin coating and which hardly generates microbends in optical fibers. CONSTITUTION:This optical fiber unit is constituted by arranging a GI type optical fiber 1 in a central part and arranging 6-fibers SM type optical fibers 2 around this optical fiber. Heat resistant thin tapes 3 are wound around the optical fiber unit. A side pressure is applied on the optical fiber unit by the heat resistant thin tapes but the SM type optical fibers which exist around the GI type optical fiber and hardly generate the microbends, directly receive the side pressure from the tapes. Then, the SM type optical fibers play the role of buffers and the GI type optical fiber arranged at the center hardly receives the side pressure. The microbends are thus not generated and the increase in transmission loss is not generated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of an optical unit housed in an optical composite overhead ground wire.

[0002]

2. Description of the Prior Art An optical fiber in an optical composite overhead ground wire is constructed as an optical unit, for example, as described in Japanese Utility Model Publication No. 62-147216, and a spiral groove of a spacer formed of aluminum or the like. It is stored in the inside or in an aluminum pipe. As the optical unit, an optical unit in which a plurality of optical fiber strands are twisted together, a heat-resistant thin tape is wound on the strand, or an optical unit coated with a heat-resistant resin is actually used.

FIG. 7 is a sectional view of a conventional optical composite overhead ground wire. In the figure, 11 is an aluminum pipe, 12 is a spacer member, 13 is a spiral groove, 14 is an optical unit, and 15 is a conductor element wire. Around the aluminum pipe 11, a large number of conductor wires 15 such as an aluminum-coated steel wire and an aluminum wire are twisted around the outer circumference of the aluminum pipe 11. A spacer member 12 having a plurality of spiral grooves 13 formed on the circumference is arranged in the aluminum pipe 11, and an optical unit 14 is housed in the spiral groove 13.

FIGS. 8A and 8B are perspective views of an example of the optical unit 14 housed in the spiral groove 13 of the spacer member 12 in the optical fiber composite overhead wire of FIG. FIG. 8A shows, for example, a primary coating layer 1 of a silicone resin on an optical fiber glass 16 having an outer diameter of 125 μm.
A plurality of optical fiber strands 18 having an outer diameter of 0.4 mm, which have been subjected to No. 7, are twisted together, and a heat-resistant thin tape 19 such as a tetrafluoride resin tape having a thickness of 0.075 mm and a width of 6 mm is vertically attached. The tape is wound, and the overlapping portions of the side edges of the tape 19 are joined by an adhesive. Further, FIG. 8B is formed by spirally winding a heat-resistant thin tape 20 such as a polyimide tape having a thickness of 0.0125 mm on a twist of the optical fiber element wires 18 similar to FIG. 8A. However, the winding method may be lap winding, butt winding, or open spiral winding.

As the material of the heat-resistant thin tape,
In accordance with desired heat resistance requirements, thin-walled heat resistant tapes made of engineering plastics such as trifluorinated resin, difluorinated resin, polyphenylene sulfide, and aramid are used.

As described above, such a conventional optical unit twists only the optical fiber strands, uses FRP as the central member, and gathers six optical fiber strands around it. An optical unit is formed by directly winding a heat-resistant thin tape as a press-winding wire or coating a heat-resistant resin on it. Therefore, when an optical fiber with an outer diameter of 0.4 mm coated with a silicone resin or an optical fiber with an outer diameter of 0.25 mm coated with an ultraviolet curable resin is used, the lateral pressure at the time of winding the heat resistant tape,
After laying, it will be subjected to lateral pressure from the shrinkage of the heat resistant resin due to being exposed to high temperatures.

Therefore, in the SM type optical fiber in which the microbend is hard to be generated even if the lateral pressure is applied, the transmission loss does not increase even after the production of the six-core optical unit and the high temperature after the installation of the overhead ground wire, but the lateral pressure is applied. In the GI type optical fiber in which the micro-bend is likely to occur, there is a problem that the 6-core optical unit cannot be formed due to the increase in transmission loss due to the high temperature after the production of the 6-core optical unit and the installation of the overhead ground wire. there were.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides an optical unit in which a microbend is less likely to occur in an optical fiber in an optical unit having a press winding or a resin coating. The purpose is to do.

[0009]

DISCLOSURE OF THE INVENTION The present invention relates to an optical composite overhead ground wire optical unit in which a GI type optical fiber is arranged at the center and a six-core SM type optical fiber is arranged around it. It is characterized by having.

In the above-mentioned optical unit for an overhead optical ground wire, the optical fiber unit may be wound around with a heat-resistant tape, or the optical fiber optical unit may be covered with a heat-resistant resin. It is a thing.

[0011]

According to the present invention, since the GI type optical fiber is housed in the center of the SM type optical fiber 6-core unit, for example, in the case of a structure in which the GI type optical fiber is pressed and wound by a heat resistant thin tape, the GI type optical fiber is used. The SM type optical fiber around the optical fiber in which micro-bending is unlikely to occur is directly subjected to lateral pressure from the tape. Therefore, the SM type optical fiber serves as a cushioning material, and the GI type optical fiber arranged at the center receives almost no lateral pressure, does not generate microbends, and does not increase transmission loss.

Further, even in the case of a structure coated with a heat-resistant resin, even if shrinkage occurs due to exposure to high temperature after installation,
The SM type optical fiber around the GI type optical fiber in which micro-bending is unlikely to occur is directly subjected to the shrinkage of the heat resistant resin. Therefore, the SM type optical fiber serves as a cushioning material, and the GI type optical fiber arranged at the center receives almost no lateral pressure. Therefore, microbends do not occur and transmission loss does not increase.

[0013]

1 is a sectional view of a first embodiment of an optical unit for an optical composite overhead ground wire according to the present invention. In the figure, 1 is a GI type optical fiber, 2 is an SM type optical fiber, and 3 is a heat-resistant thin tape. The GI type optical fiber 1 is arranged in the central portion, and the SM type optical fiber 2 of 6 cores is arranged around it to form an optical fiber unit. SM type optical fiber 2
May be arranged in parallel with the GI optical fiber 1 or may be twisted together. At least a primary coating is applied to each optical fiber. The heat-resistant thin tape 3 is applied on the optical fiber unit by, for example, the method described with reference to FIG. 8, and the material thereof can be, for example, the one described with reference to FIG.

A specific example will be described. GI in the center
The mold optical fiber 1 is coated with a silicone resin,
An outer diameter of 0.4 mm was used. SM type optical fiber 2
Also has a silicon resin coating and an outer diameter of 0.4 mm. A heat-resistant thin tape 3 is wound around the 6-core SM optical fiber as a press winding. Figure 2
Is an optical unit for an optical composite overhead ground wire of a comparative example. In the figure, the same parts as those in FIG. 4 is an FRP. Outer diameter 0.4m arranged in the center
Around the FRP 4 of m, 6 cores of the same 0.4 mm silicon resin-coated GI type optical fiber 1 are arranged,
It has an optical unit structure in which a heat resistant thin tape 3 is wound around it.

FIG. 3 shows the measurement results of the above-mentioned concrete example and comparative example.
Shown in. The central GI optical fiber of FIG. 1 and the GI optical fiber of FIG.
The transmission loss before manufacturing the optical unit and the change in the transmission loss after manufacturing the optical fiber are shown in the figure. For the GI optical fiber in the center of FIG. 1, the transmission loss changes before and after the optical unit structure. However, in the GI type optical fiber of FIG. 2, the transmission loss increases after the optical unit, and it can be said that the optical unit of FIG. 1 realizes a stable structure.

FIG. 4 is a sectional view of a second embodiment of the optical unit for an optical composite overhead ground wire according to the present invention. In the figure, the same parts as those in FIG. 5 is a heat resistant resin coating. The optical fiber unit is the same as that in FIG. 1, and a heat resistant resin coating 5 is applied on it.

In this specific example, similarly to the specific example of the first embodiment, an outer diameter of 0.4 mm is also provided around the GI type optical fiber 1 having a 0.4 mm outer diameter and coated with a silicone resin.
The optical unit structure is formed by assembling 6 cores of the silicon resin-coated SM optical fiber 2 and applying the heat-resistant resin coating 5.

FIG. 5 shows an optical unit for an optical composite overhead ground wire of a comparative example. As in the comparative example of FIG. 2, a 0.4 mm silicon resin is placed around the center of the FRP 4 having an outer diameter of 0.4 mm. An optical unit structure is provided in which 6 cores of the coated GI optical fiber 1 are housed and a heat-resistant resin coating 5 is applied around them.

FIG. 6 shows the change in transmission loss in the heat resistance experiment when the GI optical fiber at the center of the specific example of FIG. 4 and the GI optical fiber of the comparative example of FIG. 5 are used. In the GI type optical fiber at the center of FIG. 4, the change of the transmission loss during the heat resistance test is within 0.1 dB / km, but in the GI type optical fiber of the structure of FIG. 5, the transmission loss is 0.2 dB / km or more. Therefore, it can be said that the optical unit in FIG. 4 realizes a stable structure.

[0020]

As is apparent from the above description, according to the present invention, the GI type optical fiber is housed in the center of the 6-core unit of the SM type optical fiber, so that the tape-wound optical composite overhead ground wire is provided. It is possible to stabilize the transmission loss at the time of manufacturing the GI type optical fiber in the optical unit for optical fiber and the optical unit for an optical composite overhead ground wire coated with a heat resistant resin and after the installation.

By using the optical unit for an optical composite overhead ground wire of the present invention, the following effects are produced. This is an effective means when a high-density optical fiber can be mounted and a multi-core optical composite overhead ground wire is required. As shown in FIG. 9, in a conventional heat-resin-coated optical composite overhead ground wire optical unit using a GI optical fiber, a buffer layer 22 made of silicon resin is provided in order to prevent lateral pressure due to contraction of the heat-resistant resin coating 23. Since it is necessary, the outer diameter becomes large. On the other hand, in the present invention, since it is not necessary to provide the buffer layer, the packaging density can be increased. For example, in the structure of FIG. 9, the outer diameter is about 1.2 mm, and only three GI type optical fibers 21 can be mounted. However, in the tape wound optical composite overhead ground wire optical unit of FIG. Is about 1.25m
With m, a total of 7 fibers of 6 SM type optical fibers and 1 GI type optical fiber can be mounted. This is an effective means when the number of SM type optical fibers is increased by replacing the already installed optical composite overhead ground wire of the GI type optical fiber with a small number of fibers. In the multi-core optical composite overhead ground wire, conventionally, a structure in which a plurality of optical units for a 6-core tape-wound optical composite overhead ground wire as described in FIG. 2 is mounted is used. If you change only at
After the replacement, all the GI type optical fiber transmission devices that have already been used must be changed to SM type optical fiber transmission devices. However, by using the central GI type optical fiber 6-core optical unit of the present invention, the conventional GI type optical fiber transmission device is also used, and in addition, the multi-core S
It is possible to introduce an M-type optical fiber.

[Brief description of drawings]

FIG. 1 is a sectional view of a first embodiment of an optical unit for an optical composite overhead ground wire of the present invention.

FIG. 2 is a cross-sectional view of an optical composite overhead ground wire optical unit of a comparative example.

FIG. 3 is a diagram showing the measurement results of a specific example of the first embodiment and the comparative example of FIG.

FIG. 4 is a sectional view of a second embodiment of the optical unit for an optical composite overhead ground wire of the present invention.

FIG. 5 is a cross-sectional view of an optical composite overhead ground wire optical unit of a comparative example.

FIG. 6 is a diagram showing the measurement results of a specific example of the second embodiment and the comparative example of FIG.

FIG. 7 is a sectional view of a conventional optical composite overhead ground wire.

FIG. 8 is a perspective view of an optical unit housed in the optical fiber composite overhead wire of FIG.

FIG. 9 is a cross-sectional view of a conventional optical unit for an optical composite overhead ground wire using a GI type optical fiber.

[Explanation of symbols]

1 ... GI type optical fiber, 2 ... SM type optical fiber, 3 ... Heat-resistant thin tape, 4 ... FRP, 5 ... Heat-resistant resin coating.

Claims (3)

[Claims] 1. An optical unit for an optical composite overhead ground wire, comprising an optical fiber unit in which a GI type optical fiber is arranged in a central portion, and six SM type optical fibers are arranged around the GI type optical fiber. 2. The optical unit for an overhead optical ground wire according to claim 1, wherein the optical fiber unit is wound with a heat resistant tape. 3. The optical unit for an optical composite overhead ground wire according to claim 1, wherein the optical fiber optical unit is covered with a heat resistant resin.