JP3920252B2 - Fiber optic cable - Google Patents

Description

  The present invention relates to an optical fiber cable used for lead-in wiring from a distribution cable installed in an aerial or underground to a general subscriber's house.

  The concept of spreading the optical fiber communication network to the homes of subscribers such as ordinary houses and buildings is progressing concretely, and accordingly, development of various optical fiber cables necessary for the construction of such a communication network is continued.

  Among these, as a so-called optical drop cable for wiring from an aerial or underground wiring system cable to a general subscriber's house, steel wire or FRP (glass fiber reinforced) is installed on both sides or one side of the single-core optical fiber. Plastic (strength materials) are placed, and these are collectively covered with a resin such as polyethylene (underground optical drop cable), or such cables are further integrated with support lines (aerial optical drop cable). It is known (for example, refer to Patent Document 1).

  FIG. 6 shows an example of an aerial optical drop cable. As shown in the figure, this optical drop cable has single-strand optical fiber core 1 sandwiched between tensile strength members 2 and 2 above and below it, and support wire 3 on top of them, and the outer periphery thereof. It has a structure in which a jacket 4 is provided by batch extrusion coating of a resin such as polyethylene. Between the support wire 3 and the strength member 2 of the cable, a neck portion (connecting portion) 7 for dividing the cable into the support wire portion 5 and the cable portion 6 is provided. The notches 8 and 8 for tearing are provided in the part which the single-core optical fiber core wire 1 is located in both sides.

  In such an optical drop cable, since the support wire 3 is provided, the aerial laying is possible, and the tensile strength member 2 is disposed with the optical fiber core wire 1 interposed therebetween. An increase in the transmission loss of the fiber can be prevented. Further, since the neck portion 7 is provided, the cable portion 8 can be easily separated from the support wire portion 5 and wired indoors after the cable is drawn into the subscriber's house. Further, since the notch 8 for tearing is provided, it is possible to easily take out the optical fiber core wire 1 by tearing the jacket 4 in the width direction of the cable at the time of cable end processing or the like.

However, in such a conventional optical fiber cable, the outer diameter of the single-core optical fiber core 1 is very thin (usually 250 μm), although it is excellent in the ability to take out the core wire as described above. There is a problem that if the cord 1 is bent carelessly when it is taken out, it is easily broken. For this reason, it is necessary for the operator to take out the core wire with great care, which is a heavy burden.
There is also a problem that transmission loss is likely to occur particularly in a low-temperature environment (about −30 ° C. or lower).
JP 2001-337255 A

  The present invention has been made to solve the above-described problems of the prior art, and the optical fiber core wire is not broken even if an inadvertent bending or the like is applied when the optical fiber core wire is taken out. An object of the present invention is to provide an optical fiber cable that can obtain stable optical transmission characteristics even in a low-temperature environment of about 30 ° C. or less and that is excellent in handling properties and transmission characteristics.

In order to achieve the above object, an optical fiber cable according to the first aspect of the present invention includes an optical fiber core wire, a tensile body arranged in parallel to the optical fiber core wire, and an outer periphery thereof collectively. In an optical fiber cable having an outer sheath coated with extrusion , at least one of a polyether / polybutylene naphthalate thermoplastic elastomer and a polyether / polybutylene terephthalate thermoplastic elastomer is provided on the outer periphery of the optical fiber core wire. In addition, a coating having a thickness of 0.05 mm to 0.35 mm made of a polyester-based thermoplastic elastomer having a flexural modulus (ASTM D 790) of 60 MPa to 250 MPa is provided.

The invention according to claim 2, in the optical fiber cable of claim 1, wherein the optical fiber has an outer diameter of 0.25mm or less following single-core optical fiber or width 0.66 mm, a height of less than 0.38mm It is characterized by being a 2-fiber ribbon.

According to a third aspect of the present invention, in the optical fiber cable of the first or second aspect , the jacket is made of a polyolefin resin or a vinyl chloride resin.

  According to the optical fiber cable of the present invention, the handleability of the optical fiber core wire is improved, and it is possible to prevent the breakage when the optical fiber core wire is taken out. In addition, stable optical transmission characteristics can be obtained even in a low temperature environment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a cross-sectional view schematically showing an embodiment of the optical fiber cable of the present invention.
As shown in FIG. 1, the optical fiber cable 100 according to the present embodiment includes a support line portion 11, a cable portion 12, and a connecting portion 13 that connects them. The support wire portion 11 is configured by providing a jacket 15 on the outer periphery of a support wire 14 made of a steel wire or the like. In addition, the cable portion 12 sandwiches two single-core optical fiber cores 16 arranged in parallel in the vertical direction, with steel wires, FRP (glass fiber reinforced plastic), high tensile strength fibers (Kevlar ( A tensile strength body 17 made of aramid fiber (such as a trademark), polyester fiber, etc.) is disposed in parallel, and an outer cover 18 is provided on the outside thereof. The outer sheath 15 of the support wire portion 11, the outer sheath 18 of the cable portion 12, and the connecting portion 13 are formed by batch extrusion of a thermoplastic resin such as polyethylene or polyvinyl chloride. The notch 19a, 19b for tearing is provided in the part where the single-core optical fiber core wire 16 is located at the approximate center of both sides of the jacket 18 of the cable part 12, and these are connected during cable connection work. By tearing the jacket 18 starting from the tearing notches 19a and 19b, the inner single-core optical fiber 16 can be easily taken out.

  In the present embodiment, a coating 20 made of a polyester-based thermoplastic elastomer is provided on the outer periphery of each single-core optical fiber core wire 16.

  Examples of the polyester-based thermoplastic elastomer used here include polybutylene naphthalate-based thermoplastic elastomers and polybutylene terephthalate-based thermoplastic elastomers. These may be used alone or in combination of two or more.

  The polyester-based thermoplastic elastomer preferably has a flexural modulus (ASTM D 790) in the range of 60 MPa to 250 MPa, and more preferably in the range of 100 MPa to 200 MPa. If the flexural modulus is less than 60 MPa, the outer sheath 18 is in close contact with each other, and the take-out property of the optical fiber core wire 16 may be deteriorated. In particular, when the jacket 18 is made of a polyolefin-based thermoplastic resin, it is easy to adhere. Moreover, there is a possibility that the optical transmission characteristics in a low temperature environment cannot be sufficiently improved. On the other hand, when the flexural modulus exceeds 250 MPa, the optical fiber core wire 16 protrudes from the coating 20, and there is a possibility that problems such as disconnection of the core wire or peeling of the coating may occur when a connector is attached to the tip. . Further, as in the case where the flexural modulus is less than 60 MPa, the effect of improving the optical transmission characteristics in a low temperature environment may not be sufficiently obtained.

  Further, the thickness of the coating 20 made of the polyester thermoplastic elastomer is preferably in the range of 0.05 μm to 0.35 μm, more preferably in the range of 0.125 μm to 0.33 μm. When the thickness of the coating 20 is less than 0.05 μm, the effect of improving the light transmission characteristics in a low temperature environment is reduced. If the thickness exceeds 0.35 μm, it is difficult to coat the optical fiber core wire 16 with the coating 20 without being eccentric (the thickness balance of the jacket 18 is lost due to the eccentricity, and the optical fiber core wire 16 is bent). Occurs.)

  The coating 20 made of polyester thermoplastic elastomer may be blended with a colorant in order to identify the single-core optical fiber core wires 16 from each other.

  In the optical fiber cable 100 configured as described above, by providing the coating 20 made of a polyester-based thermoplastic elastomer on the outer periphery of the optical fiber core wire 16, the handleability of the optical fiber core wire 16 is improved (so-called The optical fiber cord 16 can be handled.) If the optical fiber core wire 16 is taken out, the optical fiber core wire 16 will not be broken even if careless bending is applied. Thereby, both the operator and the burden are reduced. Moreover, compared with the conventional optical fiber cable, the optical transmission characteristic in a low temperature environment is improved, and a good and stable optical transmission characteristic can be obtained in a wide temperature range.

  Next, another embodiment of the present invention will be described.

  FIG. 2 is a cross-sectional view according to the second embodiment of the present invention, and parts common to FIG.

  The optical fiber cable 101 according to the present embodiment is generally used as a so-called underground drop cable wired underground, and does not have the support line portion 11 and the connecting portion 13. The configuration is the same as that of the first embodiment.

  That is, sandwiching two single-core optical fibers 16 arranged in parallel vertically, the tensile strength members 17 made of steel wires, FRP, high-strength fibers, etc. are arranged in parallel at intervals above and below them. An outer cover 18 made of a thermoplastic resin such as polyethylene or polyvinyl chloride is provided on the outside. Then, tearing notches 19a and 19b are provided in the center of both sides of the jacket 18 at the portion where the optical fiber core wire 16 is located, and on the outer periphery of each single-fiber optical fiber core 16, A coating 20 made of a polyester-based thermoplastic elastomer is provided.

  Also in the optical fiber cable 101 configured in this manner, as in the case of the first embodiment, the coating 20 made of a polyester-based thermoplastic elastomer is provided on the outer periphery of the optical fiber core wire 16, thereby providing an optical fiber core. The handling property of the wire 16 is improved (so-called optical fiber cord can be handled), and the optical fiber core wire 16 may be broken even if careless bending is applied when the optical fiber core wire 16 is taken out. There will be no such thing. Thereby, both the operator and the burden are reduced. Moreover, compared with the conventional optical fiber cable, the optical transmission characteristic in a low temperature environment is improved, and a good and stable optical transmission characteristic can be obtained in a wide temperature range.

  In the present invention, for example, as shown in FIG. 3, the number of single-core optical fibers 16 may be one, or may be three or more. The optical fiber cable 102 shown in FIG. 3 has a single optical fiber core wire 16 arranged in the first embodiment.

  For example, as shown in FIG. 4, one or a plurality of optical fiber ribbons 161 may be used instead of the single-fiber ribbon 16. The optical fiber cable 103 shown in FIG. 4 has four optical fiber strands arranged in parallel instead of the two single-core optical fibers 16 in the first embodiment, and the outer periphery is collectively covered. One optical fiber ribbon 161 is disposed.

  Furthermore, in the example described above, each of the two strength members 17 is disposed in parallel with a space between the upper and lower sides of the single optical fiber core wire 16 or the optical fiber tape core wire 161. You may make it arrange | position only in any one of the upper and lower sides of the optical fiber core wire 16 or the optical fiber tape core wire 161. An optical fiber cable 104 shown in FIG. 5 is an example thereof, and in the first embodiment, one strength member 17 is disposed only on the opposite side of the support wire 14.

  The single-core optical fiber 16 or the optical fiber tape 161 used in the present invention is not particularly limited, but the single-core optical fiber 16 has an outer diameter of 0.25 mm or less, The effect of the present invention is particularly remarkable when the optical fiber ribbon 161 is a two-fiber ribbon having a width of 0.66 mm or less and a height of 0.38 mm.

  EXAMPLES Next, although this invention is described in an Example, this invention is not limited to a following example at all.

Example and Comparative Example An optical fiber cable having the structure shown in FIG. 1 was manufactured. The single-core optical fiber core 16 uses a single-core optical fiber core wire with an outer diameter of 250 μm, the tensile body 17 of the cable body 12 uses an FRP rod with an outer diameter of 0.4 mm, and the support wire 14 has an outer A single steel wire with a diameter of 1.2 mm was used.

  First, the material shown in Table 1 was extrusion-coated on the outer periphery of the single-core optical fiber 16 by a first extruder to form a coating having a thickness shown in Table 2. Next, two single-core optical fibers 16, strength members 17 and support wires 14 are arranged in parallel as shown in FIG. 1 and introduced into the second extruder, and non-halogenated on the outer periphery thereof. Flame retardant polyethylene (trade name NUC9739 manufactured by Nippon Unicar Co., Ltd.) was collectively extrusion coated to produce an optical fiber cable having a total width of about 2 mm and a height of about 5 mm.

About the optical fiber cable obtained by each said Example and each comparative example , the heat cycle test (-40 degreeC-+85 degreeC, 10 cycles) was done, and the maximum transmission loss increase amount was investigated. In addition, the single-core optical fiber 16 was actually taken out from the coating 18 and the lead-out property was evaluated. Further, the eccentricity (axial misalignment) of the coating 20 with respect to the single-core optical fiber core 16 and the amount of protrusion of the single-core optical fiber core 16 from the coating 20 were examined. These results are shown in Tables 2 and 3 together with the structure of the coating 20 (flexural modulus, thickness, outer diameter).

As is clear from the above results, the optical fiber cables of Examples 1 to 6 in which the coating 20 having a thickness of 0.05 μm to 0.35 μm is provided using a polyester-based thermoplastic elastomer having a flexural modulus of 60 MPa to 250 MPa. Both the temperature characteristics and the core wire take-out property were good, and the eccentricity of the coating 20 and the protrusion of the optical fiber core wire 16 were less than 50 μm and less than 0.5 μm, respectively.

Sectional drawing which shows 1st Embodiment of the optical fiber cable of this invention. Sectional drawing which shows 2nd Embodiment of the optical fiber cable of this invention. Sectional drawing which shows other embodiment of the optical fiber cable of this invention. Sectional drawing which shows other embodiment of the optical fiber cable of this invention. Sectional drawing which shows other embodiment of the optical fiber cable of this invention. Sectional drawing which shows an example of the conventional optical fiber cable.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Support wire part, 12 ... Cable part, 13 ... Connection part, 14 ... Support wire, 15, 18 ... Outer sheath, 16 ... Single-core optical fiber core, 17 ... Strength member, 19a, 19b ... Notch for tearing, 20 ... covering 101-104 ... optical fiber cable, 161 ... optical fiber ribbon

Claims (3)

In an optical fiber cable comprising an optical fiber core, a tensile body arranged in parallel with the optical fiber core, and a jacket that is extrusion-coated collectively on the outer periphery thereof,
At least one of a polyether / polybutylene naphthalate-based thermoplastic elastomer and a polyether / polybutylene terephthalate-based thermoplastic elastomer on the outer periphery of the optical fiber core , and a flexural modulus (ASTM D 790) of 60 MPa to An optical fiber cable having a thickness of 0.05 mm to 0.35 mm made of a polyester-based thermoplastic elastomer of 250 MPa. Wherein the optical fiber has an outer diameter of 0.25mm or less following single-core optical fiber or width 0.66 mm, the optical fiber according to claim 1, characterized in that the height 0.38mm following two fiber ribbons cable. The optical fiber cable according to claim 1 or 2 , wherein the jacket is made of polyolefin resin or vinyl chloride resin.

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