JP2013054219A - Loose tube optical fiber cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a loose tube optical fiber cable which, when an external load acts on the cable, can suppress crushing and cracking of a loose tube and protect an optical fiber in the tube by relaxing an impact load of the loose tube to a tensile strength body.SOLUTION: In a loose tube optical fiber cable 1, a plurality of loose tubes 6 each storing optical fibers 3 in a tube 5 together with jelly 4 are disposed so as to enclose around a tensile strength body 2, and the tensile strength body 2 and the loose tubes 6 are covered with a sheath 7. The tensile strength body 2 comprises a tensile strength body main body 8 which is provided in the longitudinal direction of the cable, and an impact relaxing layer 9 which relaxes impact applied to the surface 8a of the tensile strength body main body 8 from the loose tubes 6.

Description

  The present invention relates to a loose tube type optical fiber cable.

  A loose tube type optical fiber cable has a structure in which a plurality of loose tubes containing optical fibers in a tube together with jelly are arranged so as to surround the periphery of the tensile strength body, and the tensile strength body and the loose tube are covered with a sheath. (For example, described in Patent Document 1).

  2. Description of the Related Art In recent years, with the trend toward cost reduction, cable diameter reduction and cable weight reduction with cable diameter reduction are required for loose tube type optical fiber cables. In response to these requirements, there are concerns about compression (side pressure) characteristics, impact characteristics, tensile characteristics, and temperature characteristics when the tube diameter is reduced, the sheath is thinned, and the tensile strength is reduced. .

  In the loose tube type optical fiber cable described in Patent Document 1, waterproofness and compression characteristics are improved by arranging a circular water absorbing member between the loose tubes.

Japanese Patent No. 3920240

  However, in the loose tube type optical fiber cable described in Patent Document 1, when an external load is applied to the cable (including a load at the time of an impact test), the sheath of the portion where the external load is applied and the center of the cable If the loose tube between the provided strength members is crushed or broken, the internal optical fiber may be damaged.

  Therefore, when an external load is applied to the cable, the present invention reduces the impact load of the loose tube between the sheath of the portion where the external load is applied and the strength member, and prevents the loose tube from being crushed or cracked. An object of the present invention is to provide a loose tube type optical fiber cable that can suppress and protect the optical fiber in the tube.

  A first invention is a loose tube type in which a plurality of loose tubes in which an optical fiber is housed in a tube together with a jelly are arranged so as to surround the tensile strength body as a center, and the tensile strength body and the loose tube are covered with a sheath. In the optical fiber cable, the strength member includes a strength member main body provided in the longitudinal direction of the cable, and an impact relaxation layer that relaxes an impact received from the loose tube on the surface of the strength body main body.

  According to a second invention, in the first invention, the impact relaxation layer is an ethylene ethyl acrylate copolymer resin having a Young's modulus of 0.01 to 0.1 GPa.

  A third invention is characterized in that, in the first or second invention, the strength body is made of a fiber reinforced plastic.

  A fourth invention is characterized in that, in the first or second invention, the strength member body is made of a steel wire.

  According to the loose tube type optical fiber cable of the present invention, when an external load is applied to the cable, the loose tube is pushed and comes into contact with the tensile body arranged at the center of the cable, but provided on the surface of the tensile body. The impact relaxation layer absorbs the load and prevents the loose tube from being crushed or cracked. Therefore, according to this invention, the damage to the optical fiber accommodated in the tube of the loose tube can be avoided.

FIG. 1 is a cross-sectional view of the loose tube type optical fiber cable of the present embodiment.

Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings.
FIG. 1 shows a cross-sectional view of the loose tube type optical fiber cable of the present embodiment. The loose tube type optical fiber cable 1 has a plurality of loose tubes 6 in which the optical fiber 3 is accommodated in the tube 5 together with the jelly 4 so as to surround the strength member 2 as a center. The tube 6 is covered with a sheath 7.

  The strength member 2 includes a strength body main body 8 provided in the longitudinal direction of the cable, and an impact relaxation layer 9 that reduces the impact received from the loose tube 6 on the surface 8a of the strength body main body 8.

  The strength body 8 is made of a wire material such as glass fiber reinforced plastic (GFRP), glass fiber, aramid fiber, aramid FRP, or steel wire, and is a cable having a circular cross section. In particular, if fiber reinforced plastic is used, the weight of the cable is reduced. The strength body 8 may be used without being twisted in the longitudinal direction, or may be used by twisting in the circumferential direction as necessary.

  The impact relaxation layer 9 functions to alleviate the impact received from the loose tube 6 when an external load is applied to the cable (including a load during an impact test). For example, an ethylene ethyl acrylate copolymer resin (EEA) having a Young's modulus of 0.01 to 0.1 GPa can be used for the impact relaxation layer 9. By setting the Young's modulus within the above range, the role of the impact relaxation layer 9 as a cushion becomes the most optimal, and the collapse of the loose tube 6 and the damage of the internal optical fiber 2 can be suppressed. This range will be described in an example described later.

  The loose tube 6 includes an optical fiber 3, a jelly 4 and a tube 5. The optical fiber 3 is an optical fiber, an optical fiber, an optical fiber tape, or the like. The optical fiber is a quartz glass fiber coated with an ultraviolet curable resin. The optical fiber core is a silica glass fiber coated with a plastic resin and has a diameter larger than that of the optical fiber. The optical fiber ribbon is made of several optical fiber strands arranged in parallel and covered with an ultraviolet curable resin.

  The tube 5 is made of, for example, a cylindrical polybutylene terephthalate (PBT) resin, and accommodates the optical fiber 3 together with the jelly 4 therein. In FIG. 1, a plurality of optical fiber strands are bundled to form an optical fiber 2, and the bundle of optical fibers 2 fills the jelly 4 and is accommodated in a tube 5. The jelly 4 is made of a jelly compound that protects the optical fiber 3 from external impacts and also has a function of stopping water that enters the loose tube 6.

  The loose tube 6 is disposed so as to surround the periphery of the strength member 2. In FIG. 1, six loose tubes 6 are arranged around the strength member 2. Of course, the number of loose tubes 6 may not be six. In this embodiment, the loose tube 6 has an SZ twisted structure in which the left and right are alternately twisted in the circumferential direction. Of course, the loose tube 6 may not be SZ twisted.

  The sheath 7 is formed by extrusion molding so as to cover the entire outer periphery of the strength member 2 and the loose tube 6. For the sheath 7, for example, a resin such as polyethylene (PE) or polyolefin (PO) is used.

  Several types of loose tube type optical fiber cables were manufactured under the following conditions, and their impact characteristics, lateral pressure characteristics, tensile characteristics, and temperature characteristics were examined. Three types of strength bodies were produced by coating the surface of the strength body with ethylene ethyl acrylate copolymer (EEA), low density polyethylene (LDPE), and polyurethane in a thickness of 0.15 mm. Then, six loose tubes are twisted around the strength member, covered with a sheath made of 1.2 mm-thick linear low density polyethylene (LLDPE), and a loose tube type optical fiber having an outer diameter of 7.4 mm. Got the cable.

  Then, an impact test, a side pressure test, a tensile test, and a temperature test were performed on each loose tube type optical fiber cable obtained. The impact test was performed based on IEC60794-1-2 E4 Impact. In this impact test, the impact striking surface had a radius of 10 mm and an impact force of 3J was applied to each of three locations. Then, the loss variation after the test at 1550 nm of each optical fiber is 0.1 dB / core or less, and there is no damage to the sheath or the cable constituting material (the hitting surface trace is not regarded as damage). A value exceeding 10 dB / heart and damage was judged as rejected (x).

  The side pressure test was performed based on IEC60794-1-2 E3 Crush. Using a 100 mm flat plate, a load of 1500 N was applied for 1 minute, and after releasing the load, the amount of fluctuation in loss was 0.05 dB or less, and the amount of fluctuation in loss during the application of 750 N load for 10 minutes was 0.05 dB or less, and No damage to the sheath or cable constituting material (the plate mark is not considered to be damaged) passes (◯), exceeds 0.05 dB, and damage is rejected (x).

  The tensile test was performed based on IEC60794-1-2 E1 Tensile performance. When a tensile load equivalent to the cable weight per 1 km is applied to the cable, the strain applied to the optical fiber is 60% or less of the fiber proof level, and the sheath or cable constituent material is not damaged (O), exceeds 60%. , And damage is rejected (x).

  The temperature test was performed based on IEC60794-1-2 F1 Temperature cycling. When a cable with a cable length of 1000 m or more is subjected to a temperature cycle of −45 ° C. to + 80 ° C. × 2 cycles to the cable, the amount of loss fluctuation is 0.05 dB / Km or less compared to normal temperature (◯), 0.05 dB / Km, but rejected (x).

The test results are shown in Table 1. In Table 1, “−” is used for items that have not been evaluated.

  As can be seen from these results, it was confirmed that the loose tube type optical fiber cable using EEA for the impact relaxation layer satisfies the evaluation criteria in all of the impact characteristics, the lateral pressure characteristics, the tensile characteristics, and the temperature characteristics. In addition, in terms of impact characteristics, a loose tube type optical fiber cable coated with EEA having a Young's modulus of 0.01 to 0.1 GPa as a buffer layer that absorbs impact when a weight is dropped as a coating material on the surface of the strength body. Satisfies the evaluation criteria.

  According to the loose tube type optical fiber cable of the present embodiment, when an external load (including a load by an impact test) is applied to the cable, the portion between the sheath 7 and the strength member 2 where the external load is applied. The impact load of the loose tube 6 is absorbed by the impact relaxation layer 9 provided on the surface 8a of the strength body 8 and the collapse or cracking of the loose tube 6 is suppressed. Therefore, according to the present invention, damage to the optical fiber 2 housed in the tube 5 of the loose tube 6 can be avoided. Thereby, the transmission loss of the optical fiber 3 can be suppressed.

  In addition, according to the loose tube type optical fiber cable of the present embodiment, the impact relaxation layer 9 is made of ethylene ethyl acrylate copolymer resin having a Young's modulus of 0.01 to 0.1 GPa. Evaluation criteria can be satisfied for all of properties, tensile properties and temperature properties.

  Moreover, according to the loose tube type optical fiber cable of this embodiment, since the strength body 8 is made of fiber reinforced plastic, the cable itself can be reduced in weight. In addition, since the tensile strength body 8 is made of fiber reinforced plastic, it becomes a non-dielectric material (no electricity flows).

  Further, according to the loose tube type optical fiber cable of the present embodiment, since the strength body 8 is made of a steel wire, the tensile strength can be increased even with a small diameter in addition to being inexpensive.

  The present invention can be used for a loose tube type optical fiber cable.

DESCRIPTION OF SYMBOLS 1 ... Optical fiber cable 2 ... Strength body 3 ... Optical fiber 4 ... Jerry 5 ... Tube 6 ... Loose tube 7 ... Sheath 8 ... Strength body main body 9 ... Impact relaxation layer

Claims (4)

In a loose tube type optical fiber cable in which a plurality of loose tubes in which optical fibers are housed in a tube together with a jelly are arranged so as to surround the strength member as a center, and the strength members and the loose tube are covered with a sheath,
The loose-strength optical fiber cable comprising: a tensile-strength body provided in a longitudinal direction of the cable; and an impact-relief layer that relaxes an impact received from the loose tube on a surface of the tensile-strength body. . The loose tube type optical fiber cable according to claim 1,
The loose tube type optical fiber cable, wherein the impact relaxation layer is an ethylene ethyl acrylate copolymer resin having a Young's modulus of 0.01 to 0.1 GPa. The loose tube type optical fiber cable according to claim 1 or 2,
The loose-strength optical fiber cable is characterized in that the tensile body is made of fiber reinforced plastic. The loose tube type optical fiber cable according to claim 1 or 2,
The loose-strength optical fiber cable is characterized in that the tensile body is made of steel wire.

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