JP2005308882A - Optical fiber cable - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical fiber cable which prevents water from running along a coated optical fiber even if water penetrates from a cable terminal etc., and suppresses the deterioration of transmission characteristic of an optical fiber due to swelling of a clad of the coated optical fiber and freezed water. <P>SOLUTION: The optical fiber cable is provided with two pieces of single-core coated optical fibers 16 arranged in parallel, water-absorptive yarns 20, 20 arranged on both sides of the part where two pieces of the single-core coated optical fibers 16 are brought into contact with each other between the single-core coated optical fibers 16 and the clad 18 which is extruded and applied just above them. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  TECHNICAL FIELD The present invention relates to an optical fiber cable used for drawing and wiring from an aerial or underground wiring system cable into a general subscriber's house, and in particular, an optical fiber cable that prevents water running due to inundation. About.

  As a so-called optical drop cable for drawing and wiring from an aerial or underground wiring system cable into a general subscriber's house, steel wire or FRP (glass fiber reinforced plastic) on both sides or one side of a single-core optical fiber A tensile body consisting of the following is placed, and these are collectively covered with a thermoplastic resin such as polyethylene (underground optical drop cable), or such cable is further integrated with a support line (aerial optical drop cable) It is known (for example, refer to Patent Document 1).

  FIG. 7 shows an example of an aerial optical drop cable. As shown in the figure, this optical drop cable has two single-core optical fiber cores 1 sandwiched between tensile strength members 2 and 2 above and below them, and a support wire 3 disposed above them. The outer periphery 4 is covered with a resin such as polyethylene at the same time, and the outer cover 4 is provided. 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 the optical drop cable, since the support wire 3 is provided, the aerial laying is possible, and the tensile body 2 is disposed with the optical fiber core wire 1 interposed therebetween. An increase in transmission loss can be prevented. Further, since the neck portion 7 is provided, the cable portion 6 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.

  By the way, as a material for the jacket 4 of such an optical fiber cable, polyethylene that has been flame-retarded without using a halogen-based flame retardant, that is, non-halogen flame-retardant polyethylene has been widely used recently. This is because even if a fire breaks out, it is difficult to burn and there is no risk of generating harmful gases, etc., and there are advantages such as less environmental impact during disposal after disposal.

However, this non-halogen flame-retardant polyethylene has a higher resin viscosity at the time of melting than ordinary polyethylene and the like. Therefore, when extruded to the outer periphery of the optical fiber core 1, it is sufficiently between the optical fiber cores 1. In some cases, the gap 9 was not filled, as shown in FIG. If there is such a gap 9, if water intrudes from a cable end or the like, the water runs due to capillary action, and as a result, the coating of the optical fiber core 1 absorbs water and swells. Alternatively, when the outside air temperature is low, the running water freezes, and as a result, nonuniform stress is applied to the optical fiber, which may impair the optical transmission characteristics.
JP 2002-365499 A

  The present invention has been made in response to the above-described problems of the prior art, and even if water enters from a cable end or the like, water does not run along the optical fiber core wire. An object of the present invention is to provide an optical fiber cable that can prevent the transmission characteristics of the optical fiber from being deteriorated due to swelling of the coating or frozen water.

  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, a water absorbent yarn disposed along the optical fiber core, and an extrusion coating directly thereon. And an outer jacket.

  Further, the optical fiber cable of the invention according to claim 2 is formed by extrusion-coating two optical fiber cores arranged in parallel, a water absorbent yarn arranged between these optical fiber cores, and the above. And a jacket.

The invention according to claim 3 is the optical fiber cable according to claim 1 or 2, wherein the jacket is made of a thermoplastic resin having a melt viscosity of 1.0 × 10 ² Pa · s or more. It is.
Here, the melt viscosity is a value measured in accordance with ISO 11443 under conditions of a temperature of 180 ° C. and a shear rate of 1.0 × 10 ³ / sec.

  The invention according to claim 4 is the optical fiber cable according to claim 3, wherein the thermoplastic resin is a non-halogen flame-retardant polyolefin.

  According to the optical fiber cable of the present invention, since the water-absorbing yarn is disposed along the optical fiber core wire, there is a gap between the optical fiber core wire and the jacket. Even if one water is about to enter, the water-absorbing yarn absorbs water, so that water running into the inside is suppressed. In particular, when a water-absorbing yarn is placed between two optical fiber cores arranged in parallel, where voids are likely to occur when the jacket is formed, the water-absorbing yarn that has absorbed water expands and fills the voids. A better running water prevention effect can be obtained.

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

  FIG. 1 is a cross-sectional view showing a first embodiment of the optical fiber cable of the present invention, and FIG. 2 is an enlarged cross-sectional view showing the main part thereof.

  As shown in FIG. 1, the optical fiber cable 101 of the present embodiment includes a support line portion 11, a cable portion 12, and a connecting portion 13 that connects them. The support wire part 11 is comprised from the support wire 14 which consists of a steel wire etc., and the outer sheath 15 provided in the outer periphery. The cable portion 12 includes two single-core optical fibers 16 arranged in parallel in the vertical direction, and steel wires FRP and FRP arranged in parallel at intervals above and below these single-core optical fibers 16. A tensile strength body 17 made of (fiber reinforced plastic), a high tensile strength fiber (for example, an aramid fiber such as Kevlar (trademark), a polyarylate fiber, a polyparaphenylenebenzbisoxazole fiber, or a polyester fiber such as polyethylene terephthalate fiber); The outer cover 18 is provided on the outer side. A tearing notch 19 is provided in a substantially central portion of both sides of the jacket 18 at a portion where the single-core optical fiber 16 is located. When the cable is connected, the tearing notch 19 is a starting point. By tearing the outer cover 18, the two single-core optical fibers 16 can be easily taken out.

  The jacket 15 of the support wire portion 11, the jacket 18 of the cable portion 12, and the connecting portion 13 are formed by batch extrusion of a thermoplastic resin. In this embodiment, a non-halogen flame retardant polyethylene having a high melt viscosity is used as the thermoplastic resin, and therefore, a portion where the resin is not sufficiently filled is interposed between the two single-core optical fibers 16. 18a remains. And in this space | gap 18a, the two water absorbing yarns 20 and 20 are arrange | positioned along the length direction of a cable.

  Examples of the water-absorbing yarn 20 include adsorbing water-absorbing resin particles to a yarn made of a polyester fiber such as aramid fiber, polyarylate fiber, polyparaphenylene benzbisoxazole fiber, polyethylene terephthalate fiber, or nylon fiber. Or a material obtained by dispersing water-absorbing resin particles in a butyl rubber adhesive or the like and impregnating the yarn made of the fiber. Examples of the water-absorbent resin particles include starch-based, cellulose-based, polyacrylic acid-based, polyvinyl alcohol-based, and polyoxyethylene-based water-absorbent resin particles. It is also possible to use a yarn obtained by mixing such a water-absorbing resin with a resin such as a polyester resin to prevent melting.

  The water absorbent yarn 20 preferably has a thickness of about 500 dtex to 1000 dtex from the viewpoint of the effect of preventing running water and the effect of interposing to assist molding. If the water-absorbing yarn 20 is too thick, the finished outer shape of the cable becomes large. Conversely, if the water-absorbing yarn 20 is too thin, the surroundings may be covered with resin, so that sufficient water absorption performance may not be obtained. Further, in order to obtain a sufficient water running prevention effect, it is preferable to arrange about 1 to 3 (one in the example of the drawing) on both sides of the two single-core optical fibers 16.

  In the present invention, the single-core optical fiber 16 is not particularly limited, and the outer periphery of the optical fiber is coated with a silicone resin, an ultraviolet curable resin, or the like, or the outer periphery is further coated with nylon resin or polybutylene. Examples thereof include those coated with a thermoplastic elastomer such as a naphthalate thermoplastic elastomer and a polybutylene terephthalate thermoplastic elastomer.

In addition, the thermoplastic resin constituting the outer sheath 18 that covers the single-core optical fiber core wire 16, the outer sheath 15 of the support wire portion 11, and the connecting portion 13 is not limited to non-halogen flame-retardant polyethylene, but other general-purpose materials. May be polyolefin (for example, polyethylene, ethylene / ethyl acrylate copolymer, ethylene / vinyl acetate copolymer), aliphatic polyamide (nylon), polyvinyl chloride, and the like. However, when a thermoplastic resin having a high melt viscosity, specifically, a melt viscosity of 1.0 × 10 ² Pa · s or more, such as non-halogen flame-retardant polyethylene, is used, the single-core optical fiber 16 Since the void 18a which is not sufficiently filled in between is likely to occur, a particularly remarkable effect is obtained by the present invention.

  In the optical fiber cable 101 configured as described above, the water absorbent yarn 20 is embedded in the gap 18a formed between the two single-core optical fibers 16 so that water should be supplied from the cable terminal or the like. Even if it penetrates, since the water absorbing yarn 20 absorbs water and swells to fill the gap 18a, water running in the cable length direction can be prevented. As a result, the coating of the single-core optical fiber 16 absorbs water and swells, or when the outside air temperature is low, the water that has run is frozen, and nonuniform stress is applied to the optical fiber. Thus, an increase in transmission loss can be suppressed.

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

  FIG. 3 is a cross-sectional view according to the second embodiment of the present invention, and parts common to FIG.

  The optical fiber cable 102 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, two single-core optical fibers 16, tensile strength members 17 made of steel wires, FRP, high-strength fibers, and the like arranged in parallel above and below these optical fiber cords 16, and these The outer cover 18 made of a thermoplastic resin such as non-halogen flame-retardant polyethylene is provided on the outer side. A tear notch 19 is provided in the center of both sides of the jacket 18 at the position where the two single-core optical fibers 16 are located, and the two single cores in the jacket 18 are provided. Between the optical fiber core wires 16, water-absorbing yarns 20, 20 are embedded along the length direction of the cable.

  Also in the optical fiber cable 102 configured in this way, as in the case of the first embodiment, the water-absorbing yarn along the length direction of the cable at a position where the air gap 18a is likely to occur when the outer sheath 18 is extrusion-coated. 20 is buried, so that even if water may invade from the cable end or the like, the water absorbent yarn 20 absorbs water and swells to fill the gap. Can be prevented. As a result, the coating of the optical fiber core wire 16 absorbs water and swells, or when the outside air temperature is low, the water that has traveled is frozen and non-uniform stress is not applied to the optical fiber. An increase in transmission loss can be suppressed.

  In the present invention, as shown in FIG. 4 as an example, the number of single-core optical fibers 16 may be three or more, and the parallel direction is not particularly limited. The optical fiber cable 103 shown in FIG. 4 is an example in which four single-core optical fibers 16 are arranged in parallel in the vertical direction in the embodiment shown in FIG. 1, and the optical fiber cables 16 are in contact with each other. It has a structure in which water-absorbing yarns 20 and 20 are embedded on both sides along the length of the cable.

  In addition, the present invention provides a particularly remarkable effect when a single-core optical fiber is used as the optical fiber. For example, an optical fiber tape 161 as shown in FIGS. It is also possible to apply to the optical fiber cable 104 used. That is, in the embodiment shown in FIG. 1, the optical drop cable 104 shown in FIG. 5 has two optical fiber strands arranged in parallel instead of the two single-core optical fibers 16, and the outer periphery thereof is collectively covered. The two-fiber optical fiber ribbons 161 are laminated in the thickness direction and disposed on both sides of the portion where the two fiber-optic fiber ribbons 161 are in contact with each other. 20 and 20 are embedded. Further, in the embodiment shown in FIG. 5, the optical drop cable 105 shown in FIG. 6 is obtained by laminating two two-fiber optical fiber ribbons 161 in the width direction, and these two two-fiber optical fibers. It has a structure in which water-absorbing yarns 20 and 20 are embedded on both sides of a portion where the tape core wire 161 is in contact. In any case, the water-absorbing yarns 20 and 20 are buried, so that it is possible to prevent running water when water has entered.

  Next, examples of the present invention will be described, but the present invention is not limited to the following examples.

Example 1
An optical fiber cable having the structure shown in FIG. 1 was manufactured. A single-core UV curable resin-coated optical fiber core wire having an outer diameter of 250 μm is used for the single-core optical fiber core wire 16, and an FRP rod having an outer diameter of 0.4 mm is used for the strength member 17 of the cable portion 12. For No. 14, a single steel wire having an outer diameter of 1.2 mm was used. As the water absorbing yarn 20, Fujilit Aqua (trade name, 800 dtex) manufactured by Okamoto Kasei Co., Ltd. was used.

Two single-core optical fibers 16, two strength members 17, and a support wire 14 are arranged in parallel as shown in FIG. 1 and two water-absorbing yarns 20 are arranged in parallel. Introduced into the extruder along the both sides of the core optical fiber 16 and non-halogen flame retardant polyethylene (trade name NUC9739, melt viscosity 1.0 × 10 ² Pa · s, manufactured by Nihon Unicar) on the outer periphery. Thus, a two-core optical fiber cable having an overall width of about 2 mm and a height of about 5 mm was manufactured.

Example 2
A four-core optical fiber cable having the structure shown in FIG. 4 was manufactured.
The same material as in Example 1 was used except that four single-core optical fibers 16 were juxtaposed and a total of six water-absorbing yarns were placed on both sides of these single-core optical fibers 16. Produced in a similar manner.

  The water running prevention properties of the optical fiber cables obtained in the above examples were evaluated by an L-shaped waterproof test. That is, a test cable having a length of 10 m is cut out from an optical fiber cable, one end of which is watertightly connected to one end of an L-shaped pipe, the pipe is set up vertically, and the pipe is filled with water up to a height of 1 m. The distance traveled during that time was measured. As a result, Example 1 was 0.5 m or less, and Example 2 was 1.0 m or less. When the transmission characteristics were examined, the loss was 0.33 to 0.35 dB / km (λ = 1.31 μm) and 0.19 to 0.22 dB / km (λ = 1.55 μm), and the transmission characteristics were also good.

  As a comparative example, the same characteristics were evaluated for a two-core optical fiber cable manufactured by the same method using the same material as in Example 1 except that the water absorbing yarn 20 was not disposed. The distance reached almost the entire length (10 m) of the test cable, and the loss was 0.33 to 0.35 dB / km (λ = 1.31 μm) and 0.19 to 0.22 dB / km (λ = 1.55 μm).

Sectional drawing which shows 1st Embodiment of the optical fiber cable of this invention. Sectional drawing which expands and shows the principal part of the optical fiber cable shown in FIG. 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. Sectional drawing which expands and shows the principal part of the optical fiber cable shown in FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Support line part, 12 ... Cable part, 13 ... Connection part, 14 ... Support line, 15, 18 ... Outer sheath, 16 ... Single-core optical fiber core, 17 ... Strength member, 18a ... Air gap, 20 ... Water absorption Yarn, 100-105 ... Optical fiber cable, 161 ... Optical fiber ribbon

Claims (4)

  An optical fiber cable comprising: an optical fiber core; a water-absorbing yarn disposed along the optical fiber core; and an outer jacket that is extrusion-coated immediately above.   An optical fiber cable comprising two optical fiber cores arranged in parallel, a water-absorbing yarn disposed between the optical fiber cores, and an outer sheath coated on the top thereof. . 3. The optical fiber cable according to claim 1, wherein the jacket is made of a thermoplastic resin having a melt viscosity of 1.0 × 10 ² Pa · s or more.   4. The optical fiber cable according to claim 3, wherein the thermoplastic resin is a non-halogen flame retardant polyolefin.

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