JP2848766B2 - Optical composite ground wire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical composite ground wire in which a protective tube contains an optical fiber.

[0002]

2. Description of the Related Art As an optical composite ground wire in which an optical fiber is combined with an overhead ground wire, there is known an optical composite ground wire in which an optical fiber is housed in a central member, as described in Japanese Utility Model Application Laid-Open No. 64-16021. Have been.

FIG. 5 shows an optical composite ground wire described in the above publication. In the figure, 11 is a central tensile strength line, 12 is an optical fiber, 13 is a heat resistant thin tape, 14 is a central tensile strength member,
Reference numeral 15 denotes a silicone resin, 16 denotes a heat-resistant tape, 17 denotes a protective tube, and 18 denotes a conductor strand. A plurality of optical fibers 12,
For example, six wires are twisted around the outer periphery of the central tensile strength wire 11,
The heat-resistant thin tape 13 is vertically wrapped or wound thereon to form an optical fiber assembly. This optical fiber assembly is divided into a plurality of, for example, four
The outer periphery of the optical cable is coated with a thermosetting silicone resin 15 by a method such as a coating die and then cured, wound around a heat-resistant tape 16 and stored in a protective tube 17 made of aluminum or the like. Is configured. An optical composite ground wire is formed by twisting the conductor wires 18 around the optical cable.

As the optical fiber 12, an optical fiber in which a glass fiber having an outer diameter of 125 μm and a silicon resin coated to an outer diameter of 400 μm has been used. The optical composite ground wire is required to have the same outer diameter as the overhead wire due to the problem of the strength of the installed steel tower. Therefore, when trying to combine more optical fibers with the overhead ground wire,
Due to the limited storage space, they need to be stored at high density. To this end, it is effective to reduce the outer diameter of the optical fiber itself.However, when the glass diameter is reduced, the fiber is easily bent, so that microvent loss is likely to occur,
Further, when the coating diameter of the silicone resin is reduced, the coating becomes fragile against external damage, and the strength is reduced.

To solve this problem, an outer diameter of 250 μm
Although it is effective to use an optical fiber coated with the ultraviolet curing resin described above, the thin coating makes the cushion effect poor and the external force is easily transmitted to the glass fiber. Then, microbend loss is likely to occur. Therefore, in the conventional optical fiber unit structure using an optical fiber having a coating outer diameter of 250 μm, it is necessary to provide a sufficient buffer layer for protecting the optical fiber from external force, and as a result, the storage density cannot be improved. was there.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems. By providing a small-diameter optical fiber unit used for an optical composite ground wire, a large number of optical fibers can be provided. It is an object of the present invention to realize an optical composite ground wire containing a fiber core.

[0007]

According to a first aspect of the present invention, there is provided an optical composite ground wire in which an optical fiber is accommodated in a protective tube, and a plurality of optical fibers coated with a urethane acrylate ultraviolet curing resin. Are twisted around a central material that does not melt at 150 ° C., and a plurality of optical fiber aggregates on which a primary coating made of a synthetic resin such as a thermoplastic resin or an ultraviolet curable resin and having a stress relaxing effect is applied. Is twisted around a tensile strength member coated with a resin having a Young's modulus of 40 kg / mm ² or less, and the outer periphery thereof is pressed and wound with a thin heat-resistant tape having a thickness of 30 μm or less, and a small diameter with no outer coating thereon. An optical fiber unit is housed in the protective tube.

According to a second aspect of the present invention, in the optical composite ground wire according to the first aspect, the center material is formed by coating a FRP with a urethane acrylate ultraviolet curing resin. It is.

[0009]

[0010]

[0011]

[0012]

FIG. 2 is a graph comparing the life of an optical fiber coated with a urethane acrylate UV curable resin and an optical fiber coated with a silicone resin. The abscissa represents the outer diameter of the coating, and the ordinate represents the relative life value of a silicon-coated optical fiber having an outer diameter of 400 μm as 1. As can be seen from FIG.
An optical fiber coated with a urethane acrylate-based ultraviolet curable resin can have a longer breaking life even with a smaller diameter than an optical fiber coated with a silicon resin. for that reason,
The storage density can be improved.

The central member located at the center of the optical fiber aggregate is integrated with the optical fiber by the primary coating, thereby preventing the individual optical fibers from moving in the axial direction and preventing random bending. doing. Therefore,
The optical fiber does not cause an increase in loss due to bending. However, it is desirable that the surface of the center member be covered with a smooth material in order to effectively produce the above-mentioned action. This is because if the central material has irregularities, the optical fiber may be slightly bent when integrated by temporary coating.

The primary coating has a stress relaxing effect. Stress is applied in the radial direction of the optical fiber aggregate by the thin tape, but since the cross-sectional shape of the optical fiber aggregate is not deformed by providing the primary coating, the stress is hardly transmitted to the optical fiber. . From this viewpoint, the primary coating is made of a synthetic resin such as a thermoplastic resin or an ultraviolet curing resin, and the product of the Young's modulus and the coating thickness is 6 kg / m.
m or more, and desirably a cylindrical shape whose cross section is not deformed by a pressure of 30 g / mm ² .

The tensile strength member prevents the aggregate from moving in the axial direction and shares the axial stress, thereby preventing an optical fiber from being stretched and broken. When FRP is used for the tensile strength member, the material is hard, so that the radial stress caused by the thin heat-resistant tape is easily transmitted to the optical fiber aggregate having the primary coating. As described above, since the primary coating has a stress relaxation effect, the optical fiber hardly causes an increase in loss. However, an ultraviolet curable resin, a thermoplastic resin, or a thermosetting resin having a Young's modulus of 40 kg / mm ² or less is formed on the FRP. As described above, when a resin coating capable of being formed uniformly in the axial direction is applied, it is effective against stress. FIG. 3 is a diagram showing the relationship between the Young's modulus of the coating material of the strength member and the pressure applied to the optical fiber assembly. When the Young's modulus is 40 kg / mm ² or less,
The pressure applied to the optical fiber assembly is reduced, which is more effective.

The thin heat-resistant tape makes it difficult for the heat generated by the current flowing through the overhead ground wire to be transmitted to the optical fiber in the event of a lightning or power transmission line accident, and at the same time tightens the primary coated optical fiber assembly around the tensile strength member. It has the function of improving the storage density. An appropriate thickness of the thin heat-resistant tape is 30 μm or less. FIG. 4 is a diagram showing the relationship between the thickness of the thin heat-resistant tape and the loss increase. Tape thickness 12μm, 20μm, 30μm, 40μm, 50μ
A similar unit was manufactured using a polyimide tape of m and the loss was measured. In order to make the loss increase almost zero, the tape thickness is desirably 30 μm or less. Further, when the tape thickness is 30 μm or more, not only does the outer diameter of the optical fiber unit increase, but also when the thin heat-resistant tape is circulated, the tape is not easily deformed. The contact area becomes small, and partial stress is applied. It is considered that the loss increases due to the partial stress.

[0017]

FIG. 1 is a sectional view for explaining an embodiment of a thin optical fiber unit for an optical composite ground wire according to the present invention.
FIG. 1A is a cross-sectional view of the optical fiber unit, and FIG.
FIG. 3 is a sectional view of an optical fiber assembly. In the figure, 1 is an optical fiber, 2 is a center material, 3 is a primary coating, 4 is an optical fiber assembly, 5 is a tensile strength member, 6 is a coating, and 7 is a thin heat-resistant tape.

The optical fiber 1 is coated with a urethane acrylate ultraviolet curing resin. This optical fiber 1
Are twisted around the center member 2 and are integrated at a high density with the primary coating 3 to form the optical fiber aggregate 4.
The primary coating 3 protects the optical fiber 1 in the optical fiber aggregate 4 from external force. The center member 2 prevents the optical fiber 1 from moving in the axial direction. However, since the surface is smooth, even when a radial external force is applied to the optical fiber assembly 4, the optical fiber is less likely to bend slightly. I have. The optical fiber aggregate 4 is twisted around the strength member 5. The tensile members 5 prevent the optical fiber aggregate 4 from moving in the axial direction, share the stress in the axial direction, and prevent the optical fiber 1 from being stretched and broken. Since the coating 6 applied to the strength member 5 is softer than the core material of the strength member 5, the coating 6 is deformed by a radial force to reduce the stress transmitted to the optical fiber assembly 4. The heat-resistant thin tape 7 radially pulls the aggregate of the optical fiber aggregate 4 and the tensile strength member 5 to improve the storage density. Since the thin tape itself is thin, it hardly contributes to the increase in the outer diameter of the optical fiber unit.

A specific example of the embodiment shown in FIG. 1 will be described. As the optical fiber 1, a single mode optical fiber coated with a urethane acrylate ultraviolet curing resin was used. The core diameter is about 9 μm, the cladding diameter is 125 μm,
The relative refractive index difference between the core and the clad is about 0.35%, and the coating diameter is 250 μm. In this specific example, all of the optical fiber aggregates are made of optical fibers. However, if the center material 2 or other one core is changed to a string having a smooth surface, the primary coating 3 can be torn by the string or the like. Therefore, workability of terminal processing is improved. When the center member 2 is used, the outer diameter 2
A resin obtained by applying a urethane acrylate-based ultraviolet curable resin to FRP of 00 μm can be used. The center material 2 is
It has been confirmed that similar properties can be obtained with thermoplastic materials such as nylon, FEP, PFA, ETFE and the like having a melting temperature of 150 ° C. or higher. When a thermoplastic material is used for the center member 2, if the melting temperature is not higher than 150 ° C., a rise in temperature during energization may cause a problem in that the center member is melted and deformed. Therefore, as a temperature characteristic of the center material, it is necessary that the core material does not melt at 150 ° C. Center material 2
It is not necessary to limit the core material to FRP. For example, the same effect can be obtained by using an optical fiber, and there is an advantage that the storage density of the optical fiber is improved.

The primary coating 3 has a Young's modulus of 60 kg / mm.
^2. Nylon with a coating thickness of 125 μm was used. Similar characteristics were obtained with thermoplastic materials such as PBT, polyetherimide, and polycarbonate. Also, a urethane acrylate-based ultraviolet curable resin is preferable as a material used for the primary coating if the product of the Young's modulus and the coating thickness is 6 kg / mm or more. Further, any material whose cross section is not deformed from a cylindrical shape by a force of 30 g / mm ² equivalent to the pressure from a thin heat-resistant tape is similarly desirable as a material used for the primary coating.

The tensile member 5 is made of FRP having an outer diameter of 1.35 mm.
Was coated with a coating 6 having an outer diameter of 1.6 mm. For the coating 6, FEP resin was used. Young's modulus is 40 kg / mm ²
The following urethane acrylate ultraviolet curable resins, elastomers, thermoplastic resins such as FEP and PFA, and thermosetting resins such as silicone resins are also suitable as coating materials for the tensile strength member.

The thin heat-resistant tape 7 has a thickness of 1 in this example.
A 2.5 μm, 15 mm wide polyimide tape was wrapped around in 1/2 lap. A thin tape made of PET or PPS may be used. Further, when the film was wound around with a polyimide tape having a thickness of 50 μm, a loss increase of 0.18 dB / km was observed. Then, tape thickness 20μm, 30μm, 4
When a similar optical fiber unit was manufactured using a 0 μm polyimide tape and loss was measured, the relationship shown in FIG. 4 was obtained between the tape thickness and the loss increase, and the loss increase was almost zero. In order to achieve this, it was found that the tape thickness was desirably 30 μm or less.

[0023]

As is clear from the above description, the optical fiber unit for an optical composite ground wire according to the present invention has a higher optical fiber storage density than the conventional optical fiber unit. The overhead ground wire can store more cores. Therefore, it is effective to apply to a path requiring a larger number of hearts.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of one embodiment of a thin optical fiber unit for an optical composite ground wire according to the present invention.

FIG. 2 is a diagram comparing the lifetimes of an optical fiber coated with a urethane acrylate-based ultraviolet curable resin and an optical fiber coated with a silicone resin.

FIG. 3 is a diagram showing a relationship between a Young's modulus of a coating material of a tensile strength member and a pressure applied to an optical fiber assembly.

FIG. 4 is a graph showing the relationship between the thickness of a thin heat-resistant tape and the amount of increase in loss.

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical fiber 2 Core material 3 Primary coating 4 Optical fiber assembly 5 Strength member 6 Coating 7 Thin heat-resistant tape

Continued on the front page. (72) Inventor Satoshi Kuno 1st Tayacho, Sakae-ku, Yokohama-shi, Kanagawa Prefecture Sumitomo Electric Industries, Ltd. Inside the Yokohama Works (72) Inventor Yuichi Mami 1st, Tayacho, Sakae-ku, Yokohama-shi, Kanagawa Sumitomo Electric Industries, Ltd. Inside Yokohama Works (72) Inventor Takashi Saito Kanagawa Prefecture, Yokohama City, Yokohama, 1st Tayacho Sumitomo Electric Industries, Ltd. Yokohama Works (72) Inventor Yuji Kume 3-2-2 Nakanoshima, Kita-ku, Osaka-shi, Osaka Kansai Electric Power Company In-company (72) Inventor Yoshinaga Kashiwara 3-2-2 Nakanoshima, Kita-ku, Osaka-shi, Osaka Kansai Electric Power Co., Inc. (56) References JP-A-62-216946 (JP, A) JP-A-5-163318 ( JP, A) JP-A-60-156025 (JP, A) JP-A-2-44305 (JP, A) JP-A-60-57305 (JP, A) JP-A-62-91904 (JP, A) Pp. 64-16021 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) G02B 6/44 366

Claims (2)

(57) [Claims] 1. An optical composite ground wire in which an optical fiber is housed in a protective tube, a plurality of optical fibers coated with a urethane acrylate-based ultraviolet curable resin are twisted around a center material which does not melt at 150 ° C. A plurality of optical fiber aggregates, which are made of a synthetic resin such as a thermoplastic resin and an ultraviolet curable resin and have a primary coating having a stress relaxation effect, are coated thereon with a resin having a Young's modulus of 40 kg / mm ² or less. Twisted around the tensile strength body
An optical composite ground wire comprising a thin optical fiber unit, which is wound down with a thin heat-resistant tape having a thickness of 0 μm or less, and a thin optical fiber unit, which is not covered, is accommodated in the protective tube. 2. The optical composite ground wire according to claim 1, wherein the center material is formed by coating a FRP with a urethane acrylate-based ultraviolet curable resin.