JP2016004232A - Optical cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical cable that achieves suppression of a decrease in transmission characteristics due to bending of an optical cable while avoiding an increase in manufacturing costs and deterioration of laying workability.SOLUTION: An optical cable 1 comprises multiple optical fiber ribbons 2 each including multiple coated optical fibers 21 arranged in parallel. A sheath material 3 collectively covers the multiple optical fiber ribbons 2. The multiple optical fiber ribbons 2 are stacked in a direction orthogonal to a direction in which the multiple coated optical fibers 21 are arranged in parallel and a lengthwise direction thereof. Assuming that a pull-out force of the multiple optical fiber ribbons from the sheath material is defined as F (N/3 m), a residual stretching strain (%) of the multiple optical fiber ribbons 2 is greater than (3/13000)×F+0.01 and equal to or less than 0.05.

Description

  The present invention relates to an optical cable.

  There is known an optical cable having a structure in which a plurality of tape cores each having a plurality of optical fiber cores are laminated and these are collectively covered with a sheath material (see, for example, Patent Documents 1 to 3).

JP 2003-295011 A JP 2006-251769 A JP 2007-148181 A

  When the optical cable having the above-described configuration is bent due to winding around a bobbin during transportation, the longitudinal direction of the optical fiber positioned in the bending radial direction when viewed in a cross section perpendicular to the longitudinal direction of the optical fiber is measured. Compressive stress is applied. If the tape core meanders in the optical cable due to the stress, the transmission characteristic of the optical cable is deteriorated.

  Although the stress can be dispersed by twisting the tape core along the longitudinal direction, the manufacturing cost increases because additional equipment is required. Moreover, since it is necessary to loosen the twisted tape core wire at the time of use, laying workability | operativity falls.

  Accordingly, an object of the present invention is to suppress a decrease in transmission characteristics due to bending of an optical cable while avoiding an increase in manufacturing cost and a decrease in laying workability.

In order to achieve the above object, one aspect of the present invention is an optical cable,
A plurality of tape cores each including a plurality of optical fiber cores arranged in parallel;
A sheath material for collectively covering the plurality of tape cores;
With
The plurality of tape cores are laminated in a direction perpendicular to the parallel direction and the longitudinal direction of the plurality of optical fiber cores,
When the pulling force of the plurality of tape cores with respect to the sheath material is F (N / 3 m), the residual elongation strain (%) of the plurality of tape cores is:
Greater than (3/13000) × F + 0.01,
0.05 or less.

  According to said structure, the fall of the transmission characteristic by the bending of an optical cable can be suppressed, avoiding the increase in manufacturing cost and the fall of installation workability | operativity.

It is a cross-sectional view showing a configuration of an optical cable according to an embodiment. It is a cross-sectional view which shows the structure of the tape core wire with which said optical cable is provided. It is a table | surface which shows the result of having evaluated the transmission characteristic of the optical cable.

  Embodiments according to the present invention will be listed and described below.

(1): Optical cable,
A plurality of tape cores each including a plurality of optical fiber cores arranged in parallel;
A sheath material for collectively covering the plurality of tape cores;
With
The plurality of tape cores are laminated in a direction perpendicular to the parallel direction and the longitudinal direction of the plurality of optical fiber cores,
When the pulling force of the plurality of tape cores with respect to the sheath material is F (N / 3 m), the residual elongation strain (%) of the plurality of tape cores is:
Greater than (3/13000) × F + 0.01,
0.05 or less.

  According to such a configuration, the residual elongation strain that normally tries to be as close to zero as possible is actively used within the allowable range of quality, and the value of the pulling force of the tape core wire is set appropriately. Thus, the compressive stress acting on the tape core wire located on the radially inner side of the bending can be relieved. Therefore, it is possible to suppress a decrease in transmission characteristics due to bending of the optical cable. Moreover, since it is not necessary to coat | cover several tape core wires with a sheath material in the twisted state, an additional process and installation are unnecessary and it can avoid the increase in manufacturing cost. Furthermore, the operation | work which loosens the twisted several tape core wire is unnecessary, and the fall of installation workability | operativity can be avoided.

(2): The optical cable according to (1),
The residual elongation strain (%) is larger than (3/13000) × F + 0.025.

  According to such a structure, the compressive stress which acts on the tape core wire located inside the bending radial direction can be relieved more. Therefore, it is possible to further suppress a decrease in transmission characteristics due to bending of the optical cable while avoiding an increase in manufacturing cost and a decrease in laying workability.

  A more specific example of an embodiment according to the present invention will be described below in detail with reference to the accompanying drawings. In each drawing used in the following description, the scale is appropriately changed to make each element a recognizable size.

  FIG. 1 is a cross-sectional view illustrating a configuration of an optical cable 1 according to an embodiment. In the present specification, the “cross section” means a section viewed from the longitudinal direction of the optical cable 1.

  The optical cable 1 includes a plurality of tape core wires 2. Each tape core 2 includes a plurality of optical fiber cores 21 arranged in parallel. In the illustrated example, three tape core wires 2 are laminated in a direction perpendicular to the parallel direction of the optical fiber core wires 21 and the longitudinal direction of the optical cable 1. Furthermore, the optical cable 1 includes a total of six tape cores 2 by arranging a set of three tape cores 2 laminated as described above in parallel in the parallel direction of the optical fiber cores 21. ing. The optical cable 1 can be configured to include at least two tape cores 2 laminated in the above-described direction.

  The optical cable 1 includes a sheath material 3. The sheath material 3 covers a plurality of tape core wires 2 at once. The sheath material 3 is made of a thermoplastic resin such as polyvinyl chloride or polyethylene.

  The optical cable 1 includes a pair of tension members 4. Each tension member 4 is covered with a sheath material 3. The pair of tension members 4 extend in the longitudinal direction of the optical cable 1 on both sides of the plurality of tape core wires 2 stacked in the parallel direction of the optical fiber core wires 21. In this example, each tension member 4 is a steel wire having a diameter of 0.7 mm. Each tension member 4 may be composed of fiber reinforced plastic, aramid fiber, or the like.

  FIG. 2 shows a cross section of each tape core wire 2. As described above, each tape core wire 2 includes a plurality of optical fiber core wires 21.

  Each optical fiber core wire 21 includes an optical fiber 21a. The optical fiber 21a is made of, for example, quartz glass or plastic. Although not shown, the optical fiber 21a includes a core and a clad. The core is disposed at the center in the radial direction and has a first refractive index. The clad covers the periphery of the core and has a second refractive index lower than the first refractive index.

  The optical fiber core wire 21 includes a primary coating 21b. The primary coating 21b covers the optical fiber 21a. The primary coating 21b is made of, for example, an ultraviolet curable resin.

  The optical fiber core wire 21 includes a secondary coating 21c. The secondary coating 21c covers the primary coating 21b. The secondary coating 21c is made of, for example, an ultraviolet curable resin that is harder than the primary coating 21b.

  The plurality of optical fiber cores 21 are juxtaposed in a direction orthogonal to the respective longitudinal directions. In this example, the diameter of each optical fiber core wire 21 is 0.25 mm. In this example, four optical fiber core wires 21 are arranged in parallel. However, the number of the optical fiber cores 21 provided in each tape core wire 2 can be appropriately determined as two or more.

  Each tape core wire 2 includes a covering member 22. The covering member 22 covers a plurality of optical fiber core wires 21 at once. The covering member 22 is made of, for example, an ultraviolet curable resin, a thermoplastic resin, or a thermosetting resin.

  The optical cable 1 is wound around a bobbin during transportation. In this example, winding is performed with the surface 3a of the sheath material 3 shown in FIG. 1 facing the radially outer side of the bobbin and the surface 3b of the sheath material 3 facing the radially inner side of the bobbin. At this time, the tape core 2 </ b> A disposed at a position closer to the surface 3 b than the center of the optical cable 1 in the stacking direction of the tape core 2 indicated by the line C is positioned on the radially inner side of the bending of the optical cable 1 accompanying winding. To do. Therefore, compressive stress in the direction along the longitudinal direction of the optical cable 1 is applied to the tape core wire 2A. If the tape core wire 2 </ b> A meanders in the optical cable 1 due to the stress, the transmission characteristic of the optical cable 1 is deteriorated.

  If the sheathing 3 is used in a state where the tape core wire 2 is twisted along the longitudinal direction, the stress can be dispersed. However, additional equipment for twisting is required, which increases the manufacturing cost. Moreover, since it is necessary to loosen the twisted tape core wire at the time of use, laying workability | operativity falls. The inventors have studied a configuration that can suppress a decrease in transmission characteristics due to bending of the optical cable 1 without increasing the manufacturing cost or laying workability.

  In the manufacturing process of the optical cable 1, it is known that residual elongation distortion occurs in the tape core wire 2. From the viewpoint of avoiding breakage of the optical fiber 21a due to excessive tension, the smaller the residual elongation strain, the better. The inventors thought that the compressive stress applied to the tape core wire 2A located on the radially inner side of the bending could be relaxed by positively using the tension generated by this residual elongation strain.

  On the other hand, one of the parameters indicating the characteristics of the optical cable is the pulling force of the tape core wire. The pull-out force means a force with which a plurality of tape cores starts to come out of the sheath material by grasping and pulling the plurality of tape cores covered with the sheath material in a state where the optical cable having a length of 3 m is straightened. . That is, the magnitude of the pull-out force value corresponds to the degree of freedom of displacement of the tape core wire inside the sheath material. The smaller the pull-out force value, the easier the tape core wire is displaced inside the sheath material. it can. When the value of the pulling force is small to some extent, the inventors let the tape core wire 2A release the stress inside the sheath material 3 when a compressive stress is applied to the tape core wire 2A located on the radially inner side of the bending. We thought that it would be possible to perform such displacement.

  Based on the above considerations, the inventors made a plurality of types of optical cables having the configuration shown in FIG. 1 and changing the value of the pulling force, and changing the tension applied in the longitudinal direction to change the residual elongation strain. The transmission characteristics were evaluated while changing. The value of the residual elongation strain was measured using B-OTDR (Brillouin Optical Time Domain Reflectmeter). For evaluation of transmission characteristics, first, light having a wavelength of 1550 nm was incident on an optical cable wound around a mandrel having a diameter of 150 mm and a loop for 24 cores was formed, and transmission loss was measured. When the transmission loss did not exceed 0.1 dB, the same measurement was performed with the mandrel changed to a diameter of 100 mm. The result is shown in FIG.

  In FIG. 3, an optical cable having a transmission loss of 0.1 dB or less when evaluated using a mandrel having a diameter of 150 mm is shown as an example. An optical cable having a transmission loss exceeding 0.1 dB is shown as an example in which the transmission characteristics desired by the inventors could not be maintained, that is, as a comparative example. Furthermore, as a result of evaluation using a mandrel having a diameter of 100 mm, good transmission characteristics were maintained in the optical cables according to Example 1 and Example 2.

Based on the evaluation results of the optical cables according to Examples 1 to 5 when a mandrel having a diameter of 150 mm is used, the inventors have a residual elongation strain ε (%) and a pulling force F (N / 3 m) of the tape core wire 2. In the case where the following relational expression is satisfied, it has been found that the deterioration of the transmission characteristics due to the bending of the optical cable can be suppressed.

ε> (3/13000) × F + 0.01
ε ≦ 0.05

In addition, based on the evaluation results of the optical cables according to Examples 1 and 2 when using a mandrel having a diameter of 100 mm, it was found that the transmission characteristics can be further reduced when the following relational expression is satisfied. .

ε> (3/13000) × F + 0.025
ε ≦ 0.05

  As described above, according to the configuration of the present embodiment, the residual elongation strain that normally tries to be as close to zero as possible is actively used within the allowable range of quality, and the pulling force of the tape core 2 is pulled out. By appropriately setting this value, it is possible to relieve the compressive stress acting on the tape core wire 2A located on the radially inner side of the bending. Therefore, it is possible to suppress a decrease in transmission characteristics due to bending of the optical cable 1. Moreover, since it is not necessary to coat | cover with the sheath material in the state in which the some tape core wire 2 was twisted, an additional process and equipment are unnecessary and it can avoid the increase in manufacturing cost. Furthermore, the operation | work which loosens the twisted several tape core wire 2 is unnecessary, and the fall of installation workability | operativity can be avoided.

  The above embodiment is for facilitating understanding of the present invention, and does not limit the present invention. The present invention can be modified and improved without departing from the spirit of the present invention, and it is obvious that the present invention includes equivalents thereof.

  The shape of each tape core wire 2 is not limited to that shown in FIGS. For example, a part of the covering member 22 located between a plurality of adjacent optical fiber cores 21 may be recessed along the outer peripheral surface of each optical fiber core 21. Further, the plurality of optical fiber cores 21 are intermittently separated from each other in the longitudinal direction, so that a part of each optical fiber core wire 21 can be relatively displaced with respect to the other optical fiber core wires 21. It is good also as the structure currently made.

1: Optical cable 2, 2A: Tape core 3: Sheath material 21: Optical fiber core 21a: Optical fiber 21b: Primary coating 21c: Secondary coating 22: Coating member C: The center of the optical cable in the stacking direction of the tape core Line

Claims (2)

A plurality of tape cores each including a plurality of optical fiber cores arranged in parallel;
A sheath material for collectively covering the plurality of tape cores;
With
The plurality of tape cores are laminated in a direction perpendicular to the parallel direction and the longitudinal direction of the plurality of optical fiber cores,
When the pulling force of the plurality of tape cores with respect to the sheath material is F (N / 3 m), the residual elongation strain (%) of the plurality of tape cores is:
Greater than (3/13000) × F + 0.01,
0.05 or less,
Optical cable. The residual elongation strain (%) is greater than (3/13000) × F + 0.025.
The optical cable according to claim 1.

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