JP2003187650A - Optical fiber complex overhead ground wire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical fiber complex overhead ground wire with high reliability even in a long-term use through setting of an optimum depth and width of a spacer groove. <P>SOLUTION: With the optical fiber complex overhead ground wire provided with a spacer 17 with grooves formed along the length direction and optical fibers 16 contained in the grooves 18 of the spacer 17, each groove 18 of the spacer 17 is formed to have an interval between its inner face and the optical fiber 16 in a depth d and a width w within the range of 0.167 to 0.2 mm. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber composite aerial ground wire constructed by accommodating an optical fiber unit inside an aerial ground wire for the purpose of lightning protection, and more particularly to a groove of a spacer of the optical fiber unit. The present invention relates to a spacer-type optical fiber composite overhead ground wire in which tape fibers stacked vertically in multiple stages are housed.

[0002]

2. Description of the Related Art An optical fiber composite overhead ground wire (OPGW) constructed by accommodating an optical fiber (OP) unit inside an overhead ground wire for the purpose of lightning protection, etc. A fiber unit is housed, and a strand of a wire such as an aluminum-covered steel wire is provided as an overhead ground wire on the outer circumference of this protective tube.

The optical fiber unit is known to have a structure in which optical fiber element wires are twisted and housed in each groove of a spacer formed of an aluminum alloy having a plurality of grooves on the outer periphery, and this is generally a spacer. It is called a mold.

Further, as a technique for coping with the increasing number of cores, which is increasingly required with the recent progress of the advanced information society, a spacer type optical fiber using a tape fiber in which a large number of optical fiber element wires are bundled is used. There is a fiber unit.

FIG. 3 is a cross-sectional view of a conventional spacer type optical fiber composite overhead ground wire.

As shown in FIG. 3, the optical fiber composite overhead ground wire comprises an optical fiber unit 1 and an aluminum-covered steel wire 3 twisted on the outside of an aluminum protective tube 2 accommodating the optical fiber unit 1. It is composed of an overhead ground wire section 4.

This optical fiber unit 1 uses, as an optical fiber, a 4-fiber bundle tape fiber in which four optical fiber strands are arranged in parallel on the same plane and the periphery is covered with resin.
A large number of the tape fibers are housed in a state of being stacked in the groove of the spacer, and a press winding is wound around the outer periphery of the spacer so as to close the groove.

[0008]

By the way, in the spacer type optical fiber composite overhead ground wire, due to the difference in thermal expansion coefficient between the spacer and the tape fiber, a slight bending occurs in the tape fiber due to contraction at a low temperature, and the tape fiber is Transmission loss occurs when it is pressed against the inner wall of the protection tube.
Therefore, an appropriate space is required between the tape fiber and the spacer.

However, in the conventional optical fiber composite overhead ground wire, it is not clear how much the gap between the tape fiber and the spacer is required, and there is a concern that the loss due to the pending of the optical fiber may increase.

Therefore, an object of the present invention is to provide an optical fiber composite overhead ground wire which determines the optimum depth and width of the groove of the spacer and has high reliability even in long-term use.

[0011]

In order to solve the above problems, the invention of claim 1 provides a spacer having a groove formed in the longitudinal direction and an optical fiber housed in the groove of the spacer. In the optical fiber composite overhead ground wire having, the groove of the spacer is formed with a depth and a width such that an interval within a range of 0.167 mm to 0.2 mm is provided between the inner surface of the groove and the optical fiber. It is what

According to a second aspect of the present invention, the optical fiber comprises a laminated body in which a plurality of optical fiber core wires are arranged in the same plane and the periphery thereof is coated with a resin, and the tape fibers are laminated in a multistage structure. .

According to the above construction, even if the tape fiber contracts at a low temperature and a slight bend occurs, the radius of curvature of the bend does not reach the radius of curvature that increases the transmission loss.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Next, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows a cross-sectional view of an optical fiber composite overhead ground wire according to the present invention.

As shown in FIG. 1, the optical fiber composite overhead ground wire comprises an optical fiber unit 10 and an aluminum-covered steel wire 11 twisted on the outside of an aluminum protective tube 12 accommodating the optical fiber unit 10. It is composed of an overhead ground wire section 20.

An enlarged cross-sectional view of the optical fiber unit 10 is shown in FIG.

As shown in FIG. 2, the optical fiber unit uses, as an optical fiber, a tape fiber 16 of four cores in which four optical fiber wires 15 are arranged in parallel in the same plane and the periphery is covered with a resin 14. A large number of the tape fibers 16 are stacked in the groove 18 of the spacer 17 and housed therein, and a press winding 19 is wound around the outer periphery of the spacer 17 so as to close the groove 18.

Four grooves 18 of the spacer 17 are formed at four equally spaced positions in the circumferential direction of the spacer 17, and
It is formed in a spiral shape in the longitudinal direction.

The grooves 18 are formed to be slightly larger than the outer shape of the tape fiber 16 in accordance with the outer shape of the tape fiber 16, and the gap (spacing) between the inner surface of the groove 18 and the tape fiber 16 is 0.167 mm to 0. It is formed with a depth d and a width w that fall within the range of 2 mm.

Next, the optimum distance between the inner surface of the groove 18 of the spacer 17 and the tape fiber 16 will be described in detail.

When the four-core tape fiber is housed in the groove of the spacer, the clearance (C) between the inner wall of the protective tube and the tape fiber housed in the uppermost stage and the tape fiber surplus ratio (ε) are important parameters. Become.

The extra length ratio (ε) is the ratio of the length of the tape fiber to the groove length of the spacer, where the spacer groove length is L _T and the tape fiber length is L _R. Is expressed by the following equation.

[0024]

[Number 1] _{ε = (L R -L T)} / L T optical fiber various stresses composite overhead ground wire is subjected, much transmission loss occurring in the tape fiber in particular by shrinkage at a low temperature, fine meanders tape fiber When it occurs, it is considered to be due to the generation of so-called micro / macro bends.

By the way, each groove of the spacer is formed in a spiral shape in the longitudinal direction as described above, and the tape fiber is accommodated along this groove, so that the tape fiber is attached to the inner wall of the protective tube at a low temperature. When it is assumed that a bend (macrobend) causes a collision and a transmission loss, this bend can be expressed by the following formula as a minimum radius of curvature (R _min ).

[0026]

## EQU00002 ## _Rmin = C / 4.epsilon. Here, the radius of curvature at which the macrobend occurs at low temperature T.degree. However, it is known that the distance is usually 15 to 30 mm.

That is, even if a micro / macrobend occurs in the tape fiber in the optical fiber unit, stress is applied by setting the clearance (C) so that the minimum radius of curvature of the tape fiber is 30 mm or more. However, it is possible to prevent an increase in transmission loss.

Here, it is assumed that the stress generated in the optical fiber is the contraction of the optical fiber unit at a low temperature.

Assuming that the temperature change when the optical fiber unit is at a low temperature is ΔT, the linear expansion coefficient (α) of the optical fiber unit is the linear expansion coefficient of the optical fiber compared with the linear expansion coefficient of the protective tube and the spacer. Is extremely small,
It can be regarded as the linear expansion coefficient of the protective tube and spacer,
The shrinkage rate (ΔL) of the optical fiber unit can be approximated by the following equation.

[0030]

## EQU00003 ## .DELTA.L = .DELTA.T.times..alpha. The extra length generated in the tape fiber at the time of low temperature shrinkage is calculated from the sum of the extra length ratio due to the shrinkage of the optical fiber unit and the extra length ratio (.epsilon.) Produced during the optical fiber unit manufacturing it can.

Assuming that the tape fiber is slightly bent in the protective tube due to this extra length, the minimum radius of curvature of the tape fiber at the time of low temperature shrinkage is approximated by the following equation by applying the equation (2). Can be guided.

[0032]

## EQU00004 ## R _min = C / 4 (ΔL + ε) Here, the clearance (C) of the tape fiber when the temperature change is 60 ° C. (20 to -40 ° C.) and the minimum of the tape fiber in the optical fiber unit. Radius of curvature (R
As a result of calculating ( _min ) by the formulas (3) and (4), the following formula can be obtained.

[0033]

C ≧ 0.167 mm (Equation 5) From the expression (5), the lower limit of the groove depth of the spacer was determined to be 0.167 mm depending on the clearance (C) and the stacking dimension of the four-core tape fiber.

The upper limit is the strength of the spacer as a whole with respect to the groove depth of the spacer (strength against elongation and bending strain).
Considering the above, it was determined to be 0.2 mm or less. Next, the operation will be described.

In the optical fiber composite overhead ground wire according to the present invention, when the temperature is low, the tape fiber shrinks and a slight bend occurs in the tape fiber, but the radius of curvature of the bend does not reach the radius of curvature that increases transmission loss. .

Further, according to the present invention, the clearance is 0.2 m.
Since it is m or less, tensile stress that breaks the optical fiber is not applied at the time of pending, and stable and high reliability can be obtained even in long-term use.

[0037]

In summary, according to the present invention, it is possible to provide an optical fiber composite overhead ground wire having excellent transmission loss characteristics and high reliability even after long-term use.

[Brief description of drawings]

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

FIG. 2 is an enlarged cross-sectional view of the optical fiber unit of FIG.

FIG. 3 is a cross-sectional view of a conventional optical fiber composite overhead ground wire.

[Explanation of symbols]

10 Optical fiber unit 11 Aluminum covered steel wire 16 tape fiber 17 Spacer 18 grooves 20 Aerial ground line section

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2H001 BB16 DD06 FF02 KK02 KK06                       KK14 KK19 KK24 MM08                 5G319 HA01 HB03 HC01 HD01 HE04                       HE14 HE22 HE26

Claims (2)

[Claims] 1. An optical fiber composite overhead ground wire comprising a spacer in which a groove is formed along a longitudinal direction and an optical fiber housed in the groove of the spacer, wherein the groove of the spacer is 0.16 between the inner surface and the optical fiber
An optical fiber composite overhead ground wire, characterized in that it is formed with a depth and a width so as to separate an interval within a range of 7 mm to 0.2 mm. 2. The optical fiber comprises a laminated body in which a plurality of optical fiber core wires are arranged in the same plane in parallel and resin-coated tape fibers are laminated in a multi-tiered manner.
Optical fiber composite overhead ground wire described.