JP7155617B2 - fiber optic cable - Google Patents

Description

The present invention relates to optical fiber cables.

An optical fiber cable (Patent Documents 1 to 4) has been disclosed that includes an optical fiber core wire, a tensile member, and a jacket covering the optical fiber core wire and the tensile member. Steel wires, fiber-reinforced plastics (FRP) coated with polyethylene, or steel stranded wires or FRP stranded wires are used for the tensile members of these optical fiber cables.

Japanese Patent Application Laid-Open No. 2005-189608 JP 2005-326622 A JP 2006-251769 A Utility Model Registration No. 3166245

Such fiber optic cables may be bent at small diameters (sharp angles) in use.
However, the tensile strength member made of steel wire tends to have a tendency to bend when it is bent with a small diameter, which may hinder its subsequent use. Moreover, the tensile strength member made of FRP may be damaged if it is bent to a small diameter, and the optical fiber cable may lose its tensile strength function.

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical fiber cable that exhibits sufficient tensile strength even when bent with a small diameter.

An optical fiber cable according to one aspect of the present invention comprises:
an optical fiber core;
at least a pair of tensile strength members arranged so as to extend in the same direction as the extending direction of the optical fiber core wire;
A jacket that covers the optical fiber core wire and the pair of tensile strength members,
The tensile strength member is composed of a stranded wire in which a plurality of bundles of high-strength fibers are assembled and twisted together without being solidified with plastic ,
The high-strength fibers are aramid fibers,
The pair of tensile strength members are arranged so as to sandwich the optical fiber core wire in a cable cross section perpendicular to the extending direction,
The strands are configured to bend without resisting compressive forces .

According to the present invention, it is possible to provide an optical fiber cable that has a small diameter and does not develop a bending tendency even when bent and is not damaged.

It is a figure which shows the structure of the cable cross section of the optical fiber cable which concerns on one Embodiment of this invention. It is a figure explaining the state which bent the optical fiber cable shown in FIG. 1 to a small diameter. FIG. 3 is a diagram for explaining stress acting on the optical fiber cable shown in FIG. 2; FIG. 3 is a diagram showing the configuration of a cable cross section of an optical fiber cable having notches; FIG. 5 is a cross-sectional view showing the configuration of an optical fiber cable according to another embodiment; FIG. 6 is a diagram for explaining stress acting on the optical fiber cable shown in FIG. 5; FIG. 3 is a diagram showing the configuration of a cable cross section of an optical fiber cable having notches; It is a figure which shows the structure of the cable cross section of the optical fiber cable which concerns on other one Embodiment. FIG. 3 is a diagram showing the configuration of a cable cross section of an optical fiber cable having notches;

<Overview of Embodiments of the Present Invention>
First, embodiments of the present invention will be listed and described.
(1) An optical fiber cable according to one aspect of the present invention,
an optical fiber core;
at least a pair of tensile strength members arranged so as to extend in the same direction as the extending direction of the optical fiber core wire;
A jacket that covers the optical fiber core wire and the pair of tensile strength members,
The tensile strength member is composed of a stranded wire in which a plurality of bundles of high-strength fibers are assembled and twisted together without being solidified with plastic ,
The high-strength fibers are aramid fibers,
The pair of tensile strength members are arranged so as to sandwich the optical fiber core wire in a cable cross section perpendicular to the extending direction,
The strands are configured to bend without resisting compressive forces .

According to the optical fiber cable having the above configuration, when the optical fiber cable is bent to a small diameter, the tensile member bends without resisting the compressive force on the inner side of the bending strain neutral plane. Since the tensile strength function is exerted on the outer side of the bending, the tensile strength body does not develop a bending habit and is not damaged. As a result, it is possible to provide an optical fiber cable which has a small diameter and is not damaged even when bent.

(2) In the optical fiber cable according to (1) above,
There may be an adhesive layer that secures the strength member to the jacket.

According to the above configuration, the tensile strength member follows the deformation of the outer cover via the adhesive layer, so that the tensile strength member easily exhibits tensile strength. Therefore, an optical fiber cable with high strength can be realized.

(3) In the optical fiber cable according to (1) or (2) above,
The optical fiber core wire includes a glass portion, and the cable cross section is configured in a shape having a lateral direction and a longitudinal direction,
At least a portion of the tensile strength member is arranged at a position at which the distance in the lateral direction from the straight line passing through the center of the cross section of the cable and extending in the lateral direction is greater than the outer diameter surface of the glass portion. good too.

According to the above configuration, the tensile strength member, which constitutes a part of the tensile strength member, is arranged outside the bending strain of the optical fiber from the neutral plane of the bending strain of the cross section of the cable, so that this part exhibits tensile strength. can be done. This reduces strain on the glass surface of the optical fiber cable due to bending of the optical fiber cable, and reduces the risk of breakage and deterioration of reliability.

(4) In the optical fiber cable according to (3) above,
The tensile strength member and the optical fiber core wire are arranged so that their centers are aligned in the longitudinal direction,
The outer dimensions of the strength body may be larger than the outer dimensions of the glass portion.

According to the above configuration, it is possible to suitably realize a structure in which the tensile strength member, which constitutes a part of the tensile strength member, is arranged outside the bending strain of the optical fiber from the neutral plane of the bending strain of the cross section of the cable.

(5) In the optical fiber cable according to (3) above,
Two pairs of the tensile strength members are provided,
one pair of the tensile members located on one side of the imaginary plane including the central axis of the optical fiber core and extending in the longitudinal direction;
The other pair of strength members may be located on the other side of the longitudinally extending imaginary plane containing the central axis of the optical fiber core.

According to the above configuration, it is possible to arrange a pair of tensile strength members in a well-balanced manner on the inner side of the bend and the outer side of the bend of the optical fiber cable. As a result, when bending acts on the optical fiber cable, the tensile strength member on the outer side of the bend exhibits tensile strength, while the tensile strength member on the inner side of the bend bends without resisting the compressive force . Therefore, by moving the center plane of the bending strain of the optical fiber cable to the outside of the bending with respect to the central axis of the optical fiber core wire, the stretching strain on the optical fiber core wire can be reduced.

(6) In the optical fiber cable according to any one of (1) to (5) above,
An adhesive layer may be provided for fixing the optical fiber core wire to the jacket.

According to the above configuration, when the jacket shrinks significantly in a low-temperature environment and the adhesive layer follows the contraction of the jacket, the optical fiber core is compressed in the extending direction (optical axis direction of the optical fiber cable). Although a force is applied, buckling is prevented because there is no gap between the jacket and the optical fiber core wire that causes the optical fiber core wire to meander.

(7) In the optical fiber cable according to any one of (1) to (6) above,
The jacket may have an elliptical outer shape in cross section of the cable.

According to the above configuration, the cross section of the cable can be flattened, and the amount of jacket material used can be reduced.

(8) In the optical fiber cable according to any one of (1) to (7) above,
The optical fiber core wire may be positioned inside the bend relative to the neutral plane of the bending strain in the cross section of the cable.

According to the above configuration, the entire optical fiber core is subjected to stress (compressive stress) on the inner side of the bend, so that it is possible to reduce elongation strain on the surface of the optical fiber core wire, and reduce the risk of breakage and deterioration of reliability.

<Details of the embodiment of the present invention>
A specific example of an optical fiber cable according to an embodiment of the present invention will be described below with reference to the drawings.
The present invention is not limited to these exemplifications, but is indicated by the scope of the claims, and is intended to include all modifications within the scope and meaning equivalent to the scope of the claims.

(First embodiment)
FIG. 1 is a diagram showing the structure of a cable cross section S of an optical fiber cable 1 according to an embodiment of the present invention. As shown in FIG. 1, the cable cross section S of the optical fiber cable 1 has a rectangular shape having a lateral direction A and a longitudinal direction B. As shown in FIG. The cable section S includes an optical fiber core 2 , a pair of strength members 3 and a jacket 4 . Moreover, the optical fiber core wire 2 is provided in the optical fiber cable 1 so as to extend in the extending direction of the optical fiber cable 1 (the direction orthogonal to the cable cross section S).

Four optical fibers 2 are provided in a row in the longitudinal direction B. As shown in FIG.
Each optical fiber core wire 2 has an optical fiber including a glass portion 21 and a coating layer 22 covering the periphery of the optical fiber. The glass portion 21 has a core, a clad having a lower refractive index than the core, and a trench having a lower refractive index than the clad formed near the boundary between the core and the clad. In this example, the optical fiber core 2 is a bend resistant reinforced fiber having a core, a cladding, a trench and a coating layer 22 .
The coating layer 22 is made of, for example, an ultraviolet curable resin (UV resin).

The optical fiber cable 2 may be either single mode fiber (SMF) or multimode fiber (MMF). SMF is a G.I. 652, G. 657 standard is preferred; 657. B2, G. Anything conforming to the 657B standard is even better. The MMF is better if it conforms to the MMF standards of OM1 to OM4. OM1 conforms to IEC 60793-2-10 Ed. 6 A1b, OM2 is IEC 60793-2-10 Ed. 6 A1a. 1, OM3 is IEC 60793-2-10 Ed. 6 A1a. 2, OM4 conforms to IEC 60793-2-10 Ed. 6 A1a. 3. As an example, the diameter of the glass portion 21 of the optical fiber 2 is 125 μm, and the outer diameter of the optical fiber 2 is 250 μm. Note that the outer diameter of the optical fiber core wire 2 is not limited to 250 μm, and may be, for example, 200 μm.

Further, an adhesive layer 24 for fixing the optical fiber core wire 2 to the jacket 4 is provided around the optical fiber core wire 2 . The adhesive layer 24 is made of thermoplastic resin.

The tensile members 3 are provided so as to extend in the direction in which the optical fiber core 2 extends (the direction perpendicular to the cable cross section S), and are provided in pairs within the cable cross section S. As shown in FIG. A pair of tensile members 3 and four optical fibers 2 are arranged so that their centers are aligned in the longitudinal direction B. As shown in FIG. A pair of tensile members 3 are arranged at positions sandwiching the optical fiber core wire 2 in the cable cross section S. As shown in FIG.

Each tensile strength member 3 is composed of a twisted wire obtained by twisting a plurality of high-strength fibers. High-strength fibers are, for example, aramid fibers. In this example, seven bundles 31 to 37 in which a plurality of high-strength fibers (for example, 1680 decitex) are assembled are assembled, and these are twisted in one direction to form one twisted wire (tensile strength body 3). formed. One tensile strength member 3 is formed, for example, to have an outer dimension such that the diameter of the circumscribed circle of the twisted wire is 1.6 mm. The direction of twisting of the high-strength fibers may be either S-twisting or Z-twisting.

The tensile strength member 3 formed in this manner exhibits tensile strength performance when a force in the tensile direction acts, but does not exhibit resistance to compression when a force in the compression direction acts. It is configured to bend without resistance .

Further, an adhesive layer 38 for bonding the tensile member 3 and the outer cover 4 is formed around the tensile member 3 . The adhesive layer 38 is made of thermoplastic resin.

The outer dimension D3 of the tension member 3 is formed to be larger than the outer dimension D4 of the glass portion 21 of the optical fiber core 2 . As a result, from the straight line CL1 extending in the longitudinal direction B passing through the center C of the cable cross section S to at least a portion of the tensile member 3 (for example, the portion indicated by reference numeral 39 in the bundle 32 of FIGS. 1 and 3) When the distance A is D1 and the distance in the lateral direction A from the outer diameter surface 211 of the glass portion 21 to the straight line CL1 is D2, the distance D1 is greater than the distance D2.

The jacket 4 is configured to cover the optical fiber core 2 and the pair of strength members 3 . The jacket 4 is made of, for example, a resin such as polyethylene (PE), flame-retardant polyethylene, PVC (polyvinyl chloride), or the like.

Next, the operation of this embodiment will be described.

Assume that the straight optical fiber cable 1 is bent as shown in FIG. In this case, a tensile force acts on the bent outer side (Out side) of the optical fiber cable 1, and a compressive force acts on the bent inner side (In side). Therefore, the bundles 31, 32, and 33 of the tensile strength members 3 positioned on the outer side of the bend (Out side) exhibit tensile strength by resisting the tensile force, while the bundles of the tensile strength members 3 positioned on the inner side of the bend (In side) 35, 36, 37 will bend without resisting the compressive force. Therefore, as schematically shown in FIG. 3, the neutral plane N of the bending strain in the cable cross section S is displaced to the outside (Out side) of the straight line CL1 passing through the center of the cable cross section S. As a result, the position of the optical fiber core wire 2 in the cable cross section S is located on the bending inner side (In side) of the bending strain neutral plane N, and a tensile force acts on the optical fiber core wire 2. is prevented. As a result, the elongation distortion of the outer diameter surface 211 of the glass portion 21 due to the bending of the optical fiber cable 1 is reduced, and the risk of breakage of the optical fiber cable 1 and deterioration of reliability can be reduced.

As described above, the optical fiber cable 1 according to the present embodiment includes the optical fiber core wire 2 and at least a pair of tensile strength members arranged so as to extend in the same direction as the extending direction of the optical fiber core wire 2. 3, and a jacket 4 that covers the optical fiber core 2 and the pair of tensile members 3, and the tensile member 3 is composed of a twisted wire obtained by twisting a plurality of high-strength fiber bundles 31 to 37, A pair of tensile members 3 are arranged so as to sandwich the optical fiber core 2 in a cable section S perpendicular to the extending direction, and the twisted wires forming the tensile members 3 bend without resisting the compressive force . is formed as

According to the optical fiber cable 1 of this embodiment, when the optical fiber cable 1 is bent to a small diameter, the bundles 35 to 37 of the tensile members 3 are compressed inside the bending strain neutral plane N (In side). The bundles 31 to 33 of the tensile strength members 3 bend without resisting the force, and exert a tensile strength function in the bending outer side (Out side) of the neutral plane N of the bending strain. Therefore, the tensile strength member 3 does not develop a bending habit and is not damaged. As a result, it is possible to provide a highly reliable optical fiber cable 1 that is small in diameter and does not develop curls or break even when bent.

In addition, since the optical fiber cable 1 according to the present embodiment has the adhesive layer 38 for fixing the tensile member 3 to the jacket 4, the tensile member 3 follows the deformation of the jacket 4 via the adhesive layer 38. do. For this reason, the tensile strength body 3 becomes easy to exhibit tensile strength. Therefore, the optical fiber cable 1 with high strength can be realized.

Further, in the optical fiber cable 1 according to the present embodiment, the optical fiber core 2 includes the glass portion 21, the cable cross section S is configured in a shape having a lateral direction A and a longitudinal direction B, and the tensile strength member 3 At least a portion (portion 39) is arranged at a position where the distance D1 in the lateral direction A from a straight line CL1 passing through the center C of the cable cross section S and extending in the longitudinal direction B is greater than the outer diameter surface 211 of the glass portion 21. It is For this reason, a portion (portion 39) of the tensile strength member 3 is arranged on the outside (Out side) of the bending of the optical fiber 2 from the neutral plane N of the bending strain of the cable cross section S, and this portion (portion 39 ) can exhibit tensile strength. This reduces the elongation distortion of the outer diameter surface 211 of the glass portion 21 of the optical fiber cable 2 due to the bending of the optical fiber cable 1, and reduces the risk of breakage of the optical fiber cable 1 and deterioration of reliability.

Further, in the optical fiber cable 1 according to the present embodiment, the tensile strength member 3 and the optical fiber core wire 2 are arranged so that their centers are aligned in the longitudinal direction B, and the outer dimension D3 of the tensile strength member 3 is glass. larger than the outer dimension D4 of the portion 21; Therefore, a structure in which a portion (portion 39) of the tensile strength member 3 is arranged outside the bending strain of the optical fiber core 2 (Out side) from the neutral plane N of the bending strain of the cable cross section S can be preferably realized.

Further, the optical fiber cable 1 according to this embodiment has an adhesive layer 24 that fixes the optical fiber cable 2 to the jacket 4 . In a low-temperature environment, the outer jacket 4 made of resin shrinks significantly, and the adhesive layer 24 also follows the shrinkage of the outer jacket 4 . At this time, a compressive force is applied to the optical fiber core wire 2 in its extending direction (optical axis direction of the optical fiber cable), but the adhesive layer 24 prevents the optical fiber core wire 2 from winding in a meandering manner. and the optical fiber core wire 2. Therefore, the optical fiber cable 2 is prevented from buckling.

In order to facilitate the operation of tearing the jacket 4 by hand and taking out the optical fiber core wire 2, as shown in FIG. good.

(Second embodiment)
Next, a second embodiment of the invention will be described. The same or equivalent parts as those of the first embodiment are denoted by the same reference numerals in the drawings, and descriptions thereof are omitted or simplified.

FIG. 5 is a diagram showing the configuration of a cable cross section S of an optical fiber cable 1B provided with two pairs of tensile members 3A and 3B. As shown in FIG. 5, the tensile strength member 3A is positioned on one side of a virtual plane P extending in the longitudinal direction B including the central axis CL2 of the optical fiber core 2. As shown in FIG. Moreover, the tension body 3B is located on the other side of the imaginary plane P. As shown in FIG. D5 is the external dimension of the tensile strength member 3A, and D6 is the external dimension of the tensile strength member 3B.

Next, the operation of this embodiment will be described.
By arranging the tensile members 3A and 3B as shown in FIG. 5, the tensile members 3A and 3B can be arranged in a well-balanced pair on the inner side of the bend (In side) and the outer side of the bend (Out side) of the optical fiber cable 1B. . As a result, when the straight optical fiber cable 1B is bent as shown in FIG. 2, a tensile force acts on the outside of the bend (Out side) of the optical fiber cable 1B, and a compressive force acts on the inside of the bend (In side). Therefore, the pair of tensile strength members 3A located on the outer side of the bend (Out side) exerts tensile strength, while the pair of tensile members 3B located on the inner side of the bend (In side) bend without resisting the compressive force. . Therefore, as shown in FIG. 6, the neutral plane N of the bending strain of the optical fiber cable 1B moves to the outside (Out side) of the bending relative to the central axis CL2 of the optical fiber cable 2 . At this time, since the entirety of the optical fiber core wire 2 is located on the inner side of the bend (In side), the expansion and contraction strain on the optical fiber core wire 2 can be reduced.

Further, according to the optical fiber cable 1B provided with two pairs of tensile members 3A and 3B, the neutral plane N of bending strain is in the bending strain of the optical fiber cable 1 provided with only one pair of tensile members 3. Compared to the vertical surface N, the cable cross section S tends to move to the outside of the bend (Out side). Therefore, the outer dimension D5 of the tensile strength member 3A and the outer dimension D6 of the tensile strength member 3B are made smaller than the outer dimension D3 (see FIG. 1) of the tensile strength member 3 in the optical fiber cable 1 provided with only a pair of tensile members 3. , and each tensile member of the tensile members 3A and 3B can be thinned. Thereby, cost reduction of the optical fiber cable 1B can be realized.

In addition, as shown in FIG. 7, the optical fiber cable 1C may have a notch 5 formed on the outer circumference of the jacket 4 .

(Third embodiment)
The shape of the jacket of the optical fiber cable is not limited to the shapes shown in FIGS. Modified examples of the shape of the outer cover will be described below. In the drawings, the same reference numerals are given to the same or equivalent parts as those of the first embodiment or the second embodiment, and the description thereof will be omitted or simplified.

As shown in FIG. 8, in the cable section S, the external shape of the jacket 4A of the optical fiber cable 1D is a flat elliptical shape.

Since the external shape of the sheath 4A is elliptical (the cross section of the cable is flattened), the amount of sheath material used can be reduced compared to the conventional optical fiber cable whose cable cross section is a perfect circle. It is possible to reduce the cost of the optical fiber cable 1D.

Incidentally, as shown in FIG. 9, an optical fiber cable 1E having a notch 5 formed on the outer circumference of the jacket 4A may be used.

Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. Further, the number, positions, shapes, etc., of the constituent members described above are not limited to those of the above-described embodiment, and can be changed to suitable numbers, positions, shapes, etc. in carrying out the present invention.

In the above-described embodiment, an example in which four optical fibers 2 are provided has been described, but the number of optical fibers 2 is not limited to four, and may be any number.

Further, in the above-described embodiment, the optical fiber cable 2 having trenches has been described, but the configuration of the optical fiber cable 2 is not limited to the above example. The optical fiber cable 2 may be configured without a trench.

Further, in the above-described embodiment, an example in which each tensile strength member 3 is composed of 7 bundles of high-strength fibers has been described, but the high-strength fibers that constitute the tensile strength member 3 are not limited to 7 bundles, and are composed of other numbers. You may make it

1, 1A, 1B, 1C, 1D, 1E optical fiber cable 2 optical fiber core wire 3, 3A, 3B tensile member 4, 4A jacket 5 notch 21 glass portion 22 coating layer 24 adhesive layer 31, 32, 33, 34, 35, 36, 37 Bundle 38 Adhesive layer 211 Outer surface A Transversal direction B Longitudinal direction C Center CL1 Straight line CL2 Central axis N Neutral plane P Virtual plane S Cable cross section

Claims (8)

an optical fiber core;
at least a pair of tensile strength members arranged so as to extend in the same direction as the extending direction of the optical fiber core wire;
A jacket that covers the optical fiber core wire and the pair of tensile strength members,
The tensile strength member is composed of a stranded wire in which a plurality of bundles of high-strength fibers are assembled and twisted together without being solidified with plastic,
The high-strength fibers are aramid fibers,
The pair of tensile strength members are arranged so as to sandwich the optical fiber core wire in a cable cross section perpendicular to the extending direction,
A fiber optic cable, wherein the strands are configured to bend without resisting compressive forces . 2. The fiber optic cable of claim 1, further comprising an adhesive layer securing said strength member to said jacket. The optical fiber core wire includes a glass portion, and the cable cross section is configured in a shape having a lateral direction and a longitudinal direction,
At least part of the tensile strength member is arranged at a position where the distance in the lateral direction from the straight line passing through the center of the cross section of the cable and extending in the longitudinal direction is greater than the outer diameter surface of the glass portion. The optical fiber cable according to claim 1 or 2. The tensile strength member and the optical fiber core wire are arranged so that their centers are aligned in the longitudinal direction,
4. The fiber optic cable of claim 3, wherein the outer dimension of said strength member is greater than the outer dimension of said glass portion. Two pairs of the tensile strength members are provided,
one pair of the tensile members located on one side of the imaginary plane including the central axis of the optical fiber core and extending in the longitudinal direction;
4. The optical fiber cable of claim 3, wherein the other pair of strength members is located on the other side of the longitudinally extending imaginary plane containing the central axis of the optical fiber core. 6. The optical fiber cable according to any one of claims 1 to 5, comprising an adhesive layer that secures the optical fiber core wire to the jacket. The fiber optic cable according to any one of claims 1 to 6, wherein the jacket has an elliptical profile in the cross section of the cable. 8. The optical fiber cable according to any one of claims 1 to 7, wherein the optical fiber core wire is positioned on the inner side of the bend with respect to the central axis of bending strain in the cross section of the cable.

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