JPH11311730A - Optical fiber cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress an increase in loss at the time of low temp., to enhance handling quality and to make a diameter smaller and a cost lower by providing the circumference of an optical fiber unit with a tension layer consisting of tension fibers and providing the circumference of this tension layer with a sheath. SOLUTION: The optical fiber unit is formed by integrally coating the circumference of an assembly, which is laminated and assembled with plural coated optical fibers 1, with a unit material 2 to form an optical fiber unit 3 of a circular shape in section and forming the tension layer 4 consisting of the tension fibers and a sheath 5. Poly-P-phenylene terephthalamide fibers, glass fibers, carbon fibers, etc., are adequately used as the tension fibers constituting the tension layer 4. Polyethylene, polyvinyl chloride (PVA), etc., are adequately used as the material of the sheath 5. The tension layer 4 and the sheath 5 are formed by extrusion coating of a resin constituting the sheath 5 in the state of placing the tension fibers constituting the tension layer 4 longitudinal around the optical fiber unit 3.

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 fiber cable suitable for a small-fiber cable having 24 or less cores, and more particularly, to a structure in which a plurality of optical fiber cores constituting an optical fiber cable are integrated with a unit material. .

[0002]

2. Description of the Related Art Conventionally, when designing a small-fiber cable having 24 or less cores, a single-core optical fiber core or an optical fiber tape core is inserted into a slot groove formed on the peripheral surface of a rod-shaped rod rod. In many cases, a slot structure in which a wire is accommodated to form a cable, or a loose tube structure in which a single optical fiber or optical fiber tape is accommodated in a tube and jelly is filled.

[0003]

However, in the case of the slot structure, since the slot rod is used, there is an inconvenience that the outer diameter becomes large or the cost becomes high. In the case of a loose tube structure, a single tube is placed at the center,
Although a relatively low cost can be achieved by using a unitube structure having a sheath around the periphery, there is a problem that it is difficult to manage the extra length of the optical fiber core. That is, the optical fiber core wire including the extra length is accommodated in the tube, and the optical fiber core wire is accommodated in a slightly bent state. However, since the optical fiber core has low rigidity, if the extra length is added more than necessary, there is a problem that the optical fiber core is easily buckled due to shrinkage of the tube at a low temperature, and the transmission loss is greatly increased. . Further, when jelly is filled, there is also an inconvenience that the handleability of the core wire at the time of laying is not preferable.

[0004] The present invention has been made in view of the above-mentioned circumstances, and is intended to suppress an increase in loss at a low temperature, have excellent handleability, and make it possible to suitably reduce the diameter and cost. The purpose is to provide fiber cables.

[0005]

An object of the present invention is to provide an optical fiber unit comprising a plurality of optical fiber cores which are collectively covered with a unit material. The problem can be solved by an optical fiber cable having a sheath on the circumference.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
FIG. 1 shows an embodiment of the optical fiber cable of the present invention. In this optical fiber cable, a unit material 2 is collectively coated on the periphery of an aggregate in which a plurality of optical fiber tape cores 1 are stacked and assembled to form an optical fiber unit 3 having a circular cross section. A tensile strength layer 4 and a sheath 5 made of tensile strength fibers are formed. In this embodiment, the optical fiber ribbon 1 has an outer diameter of 250 μm.
An optical fiber having a width of 1.1 mm and a thickness of 0.3 mm obtained by assembling four optical fiber strands of m is used, and three of these are laminated to form an aggregate. The number of optical fibers constituting one optical fiber ribbon 1 can be appropriately set, but the number of optical fibers constituting the optical fiber cable of the present invention is preferably about 2 to 24. is there.

As the material of the unit material 2, besides UV-curable resins such as urethane acrylate and epoxy acrylate, polyethylene, polyvinyl chloride, nylon, silicone resin and the like are preferably used. Is preferable because there is a large possibility that the production linear speed can be increased. The unit material 2 is formed such that its outer shape is circular in cross section. If the breaking strength of the unit material 2 is too low, the mechanical strength becomes insufficient, and the unit may be broken when the optical fiber unit 3 is handled or a cable is formed. On the other hand, if the breaking strength of the unit material 2 is too large, it becomes difficult to take out the optical fiber ribbon from the optical fiber unit or to extract the optical fiber at the time of branching or the like. Therefore, the breaking strength of the unit material 2 is preferably about 0.2 to 60 Mpa. If the Young's modulus of the unit material 2 is too small, the shell effect on the lateral pressure is reduced, so that the lateral pressure characteristics are inferior. Therefore, the Young's modulus of the unit material 2 is preferably about 1 to 100 kg / mm ² . If the unit material 2 is too thin, a plurality of optical fiber ribbons cannot be integrated. If the thickness is too thick, the optical fiber cable becomes thicker. It is not preferable because it becomes difficult to take out. Therefore, the thickness of the unit material 2 is 0.05 to
It is preferably set to be about 0.3 mm, and in this embodiment, the outer diameter is 1.7 mm.

As the tensile strength fiber constituting the tensile strength layer 4, aramid fiber such as poly-p-phenylene terephthalamide fiber (trade name: Kevlar), glass fiber, carbon fiber and the like are preferably used. The amount of these tensile fibers is
If the amount is too large, the optical fiber cable becomes thick, and if the amount is too small, the tensile strength of the optical fiber cable becomes insufficient.
Therefore, depending on the type of fiber and the size and use of the optical fiber cable, for example, when aramid fiber is used, about 10,000 to 100,000 denier, and when glass fiber is used, 20,000 to 30 denier is used. When carbon fibers are used, the density is preferably about 20,000 to 300,000 denier.

The material of the sheath 5 is polyethylene,
Polyvinyl chloride (PVC) is preferably used. If the Young's modulus of the sheath 5 is too small, the lateral pressure characteristics are inferior, and if it is too large, the flexibility is poor. Therefore, the Young's modulus of the sheath 5 is preferably about 5 to 50 kg / mm ² . If the thickness of the sheath 5 is too large, the optical fiber cable becomes thick, and if it is too thin, mechanical properties such as lateral pressure resistance deteriorate. Therefore, the thickness of the sheath 5 is preferably about 1 to 3 mm.

The tensile strength layer 4 and the sheath 5 are formed by extruding and covering the resin forming the sheath 5 in a state where the tensile strength fibers forming the tensile strength layer 4 are vertically attached around the optical fiber unit 3. Alternatively, in a state in which the tensile strength fiber is vertically attached around the optical fiber unit 3, the resin is passed through an appropriate resin solution to apply and impregnate the resin with the tensile strength fiber, and then the resin is cured by an appropriate technique to thereby form a tensile strength layer. 4 may be formed, and the sheath 5 may be extruded and covered on the periphery. In this case, the resin to be impregnated into the tensile strength fiber is, for example, a thermoplastic resin such as polyester or PBT (polybutylene terephthalate), an epoxy-based thermosetting resin, or the like. In the case of using, a UV-curable resin such as urethane acrylate or epoxy acrylate can be suitably used. Further, the resin to be impregnated into the tensile strength fiber is made of the same kind of resin as the sheath 5, so that the impregnating of the tensile strength fiber with the resin and the extrusion coating of the sheath 5 are continuously performed, so that the curing of the tensile strength layer 4 and the sheath 5 can be performed simultaneously.

According to the optical fiber cable having such a configuration, the optical fiber ribbon 1 constituting the optical fiber cable has the form of an optical fiber unit in which a plurality of optical fiber ribbons 1 are collectively covered with resin. Therefore, the rigidity is higher than in the case of the optical fiber ribbon 1. For example, width 1.1mm, thickness 0.3m
m compared to the rigidity of the optical fiber ribbon 1
The rigidity of the optical fiber unit 3 having an outer diameter of 1.7 mm, which is laminated and united with a unit material, is about 50 to 100 times. By using the optical fiber ribbon 1 as a unit as described above, bending of the optical fiber is less likely to occur due to contraction stress of the resin at a low temperature, and an increase in transmission loss is suppressed. Further, since the rigidity of the optical fiber ribbon 1 is increased, it is possible to widen the range of manufacturing conditions such as cooling conditions when manufacturing the optical fiber cable. Further, the optical fiber cable of the present embodiment is excellent in flexibility because the tensile strength fiber is used as the tensile strength member. In addition, since the tensile strength fibers can be arranged all around the optical fiber unit 3, the bending directionality is reduced and the outer diameter can be reduced as compared with a case where one or two tension members are attached, for example. Furthermore, since the optical fiber cable of this embodiment does not have a structure in which the optical fiber ribbon is accommodated in the cable unlike the slot structure or the loose tube structure, it is not necessary to manage the excess length of the optical fiber tape. It is. Further, since a slot rod is not used, it is suitable for reducing the diameter, and cost reduction can be achieved. Furthermore, since jelly is not used unlike the loose tube structure, the handleability of the cable is good.
In this embodiment, the optical fiber ribbon is used as the optical fiber, but a single optical fiber may be used.

[0012]

EXAMPLES Hereinafter, the effects of the present invention will be clarified by showing specific examples. Example 1 An optical fiber unit having the structure shown in FIG. 1 was manufactured. Outer diameter 250μ as optical fiber ribbon 1
An optical fiber having a width of 1.1 mm and a thickness of 0.3 mm obtained by assembling four optical fiber strands of m was used. First, an optical fiber unit 3 having a circular cross section and an outer diameter of 1.7 mm is formed by laminating three optical fiber tape cores 1 to form an aggregate, extruding and coating an ultraviolet curing resin as a unit material 2 on the periphery thereof.
Was prepared. Unit material 2 had a Young's modulus of 10 kg / mm ² and a breaking strength of 20 Mpa. Aramid fibers are vertically attached to the periphery of the optical fiber unit 3 as a tensile strength layer 4, and 20,000 deniers are attached vertically.
Was extruded to obtain an optical fiber cable having an outer diameter of 5 mm. (Example 2) An optical fiber cable was produced in the same manner as in Example 1 except that glass fibers were used instead of aramid fibers as the tensile strength fibers constituting the tensile strength layer 4.

(Test Example) For each of the optical fiber cables obtained in Examples 1 and 2, the loss, loss temperature characteristic, lateral pressure characteristic, and bending characteristic after cable conversion were examined. In the measurement of the loss after the cable was formed, the increase in the transmission loss before and after the cable was formed was measured for the optical fibers constituting the optical fiber ribbon. The measurement of the loss temperature characteristic is performed by using an optical fiber cable with a body diameter of 1
In the state wound around the m-type drum, the transmission loss increase when the ambient temperature was changed from room temperature to −30 ° C. and the transmission loss increase when the ambient temperature was changed from room temperature to + 70 ° C. were measured. The lateral pressure characteristics were measured by measuring the increase in transmission loss when a load of 100 kg was applied to the optical fiber cable 10 cm. The bending characteristics were measured by measuring the optical fiber cable with a body diameter of 100.
The increase in transmission loss when wound around a 1 mm drum was measured. As a result, each of the optical fiber cables of Examples 1 and 2 has a loss and a loss temperature characteristic of 0.0
It was as good as 5 dB / km or less. In addition, no increase in loss was observed in the lateral pressure characteristics and the bending characteristics, and it was recognized that they had excellent mechanical characteristics.

[0014]

As described above, the optical fiber cable according to the present invention has a tensile strength layer made of tensile strength fibers on the periphery of an optical fiber unit in which a plurality of optical fiber cores are collectively covered with a unit material. And a sheath on the periphery of the tensile strength layer. According to the optical fiber cable of the present invention, since the optical fiber cable is in the form of an optical fiber unit in which a plurality of optical fiber cores are integrated with a unit material, the rigidity is higher than in the case of the optical fiber core. I have. Therefore, the optical fiber is unlikely to be deformed by the shrinkage stress of the resin at a low temperature, and an increase in transmission loss is suppressed. Further, since the rigidity of the optical fiber core is high, it is possible to widen the range of manufacturing conditions such as cooling conditions when manufacturing the optical fiber cable. Further, the optical fiber cable of the present invention does not have a structure in which an optical fiber core is loosely accommodated in a cable unlike a slot structure or a loose tube structure, so that it is not necessary to manage the excess length of the optical fiber core. Furthermore, since jelly is not used unlike the loose tube structure, the handleability of the cable is good, and since no slot rod is used, it is suitable for reducing the diameter and cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of an optical fiber cable of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Optical fiber tape core wire, 2 ... Unit material, 3 ... Optical fiber unit 4 ... Tensile layer, 5 ... Sheath

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Katsuyoshi Ishida 1440, Misaki, Sakura City, Chiba Prefecture Inside Fujikura Sakura Plant (72) Inventor Suehiro 1440, Misaki, Sakura City, Chiba Prefecture Inside Fujikura Sakura Plant, Inc.

Claims (1)

[Claims] 1. An optical fiber unit comprising a plurality of optical fiber cores covered with a unit material at a time, a tensile strength layer made of a tensile strength fiber being provided on a circumference of the optical fiber unit, and a sheath being provided on the circumference of the tensile strength layer. Characteristic optical fiber cable.