JP5009262B2 - Spacer type optical cable - Google Patents

Description

  The present invention relates to a spacer-type optical cable in which an upper tape is wound around the outer surface of a grooved spacer that accommodates a plurality of optical fiber ribbons, and the outside is covered with an extruded sheath.

  With the recent expansion of broadband services such as video distribution, IP telephony, and data communications, the number of subscribers to home-use data communications services (FTTH: Fiber To The Home) using optical fibers is increasing. In this FTTH, a drop optical cable is used to drop a subscriber's house or the like from an aerial or underground laying trunk optical cable. As the trunk optical cable, a spacer type optical cable in which a plurality of optical fiber tape cores (hereinafter referred to as tape cores) is stored in a grooved spacer is often used.

  As shown in FIG. 3A, the spacer-type optical cable 1 has, for example, a resin rod having a tensile strength body 3 at the center and a plurality of fiber storage grooves 4 formed in an SZ shape or a spiral shape. A spacer 2 (also referred to as a slot) is used. A plurality of multi-fiber optical fiber ribbons 5 are stacked and accommodated in the fiber housing groove 4, and an upper tape 6 (also referred to as a presser winding) is wound around the outer periphery of the spacer 2 to cover the optical fiber ribbon 5. ing. And the thing of the shape which coat | covered the outer side of the upper winding tape 6 with the sheath 7 (it is also called a jacket) formed by extrusion molding is common.

As the conventional slot-type optical cable 1, cables of various shapes have been proposed in accordance with usage patterns. For example, Patent Document 1 discloses that a deep groove is formed between the fiber storage grooves 4 so that the spacers can be easily separated into segments including the fiber storage grooves and the optical fiber can be easily taken out. ing. Further, Patent Document 2 discloses that apart from the fiber storage groove 4, a small groove for storing an optical fiber for water immersion detection is formed.
JP-A-1-213612 JP 2003-66293 A

  The sheath 7 of the spacer-type optical cable 1 is usually extruded from an extruder while being heated and melted at a temperature of 160 ° C. to 200 ° C. and molded into a tube shape on the outer periphery of the spacer. . The extruded sheath 7 contracts by cooling. FIG. 3B shows the state at this time, and a portion 7 a of the sheath 7 is extended (or dropped) into the opening portion of the optical fiber housing groove 4 so that the upper tape 6 is pushed into the fiber housing groove 4. Included). As a result, the upper winding tape 6 and the sheath 7 may press the uppermost tape core wire 5 to apply a lateral pressure to the optical fiber, which may deteriorate the transmission characteristics of the optical fiber.

  In order to avoid the influence of the tape core wire 5 protruding into the housing groove 4 of the extruded sheath 7, a method of removing the cooling by reducing the cooling rate at the time of extrusion molding of the sheath 7 can be considered. However, this method is not practical because it reduces the production line speed and increases costs. In addition, the clearance C from the outermost tape core wire 5 and the outer surface of the spacer 2 may be sufficient, but the storage rate as an optical cable is lowered, and as a result, the cable outer diameter is increased. However, in particular, as an optical cable for underground laying, it is desired to reduce the diameter of the cable from the viewpoint of laying space, and it is difficult to adopt a solution that involves increasing the diameter of the cable.

  The present invention has been made in view of the above-described circumstances, and it is an object of the present invention to provide a spacer-type optical cable that can reduce the sheath overhanging the fiber housing groove of the spacer and can increase the housing ratio of the tape core wire. To do.

The spacer type optical cable according to the present invention is an optical cable in which an upper tape is wound around the outer surface of a grooved spacer containing a plurality of optical fiber ribbons, and the outside is covered with a sheath by extrusion molding. From the opening width of the fiber storage groove, which reduces the extension of the sheath and the upper winding tape into the fiber storage groove due to the shrinkage of the extruded sheath on the surface between the fiber storage grooves that store the optical fiber ribbon of the spacer A recess having a wide opening width is provided in parallel with the fiber storage groove.

The cross section of the recess is formed in an arc shape or a polygonal shape. The spacer type optical cable according to the present invention is useful when the clearance between the uppermost optical fiber tape core housed in the groove of the spacer and the outer surface of the spacer is 0.3 mm to 0.6 mm.

  According to the present invention, when the sheath is cooled after being molded, the inward sheath overhang due to the sheath contraction is absorbed by the recessed portion, and the amount of the sheath overhang into the fiber storage groove can be reduced, and the uppermost tape There is no need to increase the clearance between the core wire and the outer surface of the spacer. As a result, the accommodation rate of the tape core wire in the spacer can be increased, and an increase in the cable diameter can be suppressed.

  Embodiments of the present invention will be described with reference to the drawings. 1A shows a cross section of a spacer type optical cable, FIG. 1B shows an outline of the spacer, and FIGS. 2A to 2C show examples of the shape of the recesses of the spacer. In the figure, 11 is a spacer type optical cable, 12 is a spacer, 13 is a tensile body, 14 is a fiber storage groove, 15 is an optical fiber tape core (tape core), 16 is an upper winding tape, 17 is a sheath, 17a and 17b are The overhang portions 18, 18 a, 18 b and 18 c indicate dents.

  As shown in FIG. 1A as an example, the spacer type optical cable 11 according to the present invention has a tensile strength member 13 (also referred to as a tension member) such as a steel wire at the center, and is formed in a plurality of SZ shapes or spiral shapes. This is an optical cable using a spacer 12 (also referred to as a slot) made of a resin rod provided with a fiber storage groove 14 of a strip. A plurality of multi-fiber optical fiber ribbons 15 (hereinafter referred to as tape cores) are stacked and stored in the fiber storage groove 14. The tape core wire 15 is, for example, one having 4 cores (thickness 0.3 mm, width 1.1 mm) or 8 cores (thickness 0.3 mm, width 2.1 mm).

  On the outer periphery of the spacer 12, an upper winding tape 16 (also referred to as a presser winding) is wound to cover the tape core wire 15. For example, a non-woven fabric woven with polyester, polyethylene, and polypropylene fibers is used as the upper tape 16, and a tape having a tape width of about 20 mm to 30 mm is spirally wound. The upper tape 16 holds the tape core 15 so that it does not jump out of the fiber housing groove 14, and the heat of the resin when forming the sheath 17 (also referred to as the jacket) affects the tape core 15. It can be made to function as heat insulation for suppressing the occurrence of water, and further as water absorption for water stoppage in the cable.

  The sheath 17 is formed by molding a thermoplastic resin such as polyethylene, flame retardant polyethylene or the like with a thickness of about 1.5 mm to 2.0 mm and a heating temperature of 160 ° C. to 200 ° C. with an extruder. The sheath 17 formed by extrusion shrinks due to cooling and hardening. By this contraction, the inner surface of the sheath 17 resists the winding tension of the upper winding tape 16 and pushes the upper winding tape 16 into the fiber accommodation groove 14. Put out (or get depressed). As a result, if the clearance between the uppermost tape core wire 15 and the outer surface of the spacer 12 is small in the fiber housing groove 14, the tape core wire 15 receives a pressing force due to the overhang of the sheath 17, and the loss increases. Will be.

  In the present invention, in addition to the fiber accommodation groove 14 that accommodates the tape core wire 15 in the spacer 12, a recess 18 is provided on the spacer surface between the fiber accommodation grooves 14. As shown in FIG. 1B, the recess 18 is provided so as to be parallel to the fiber storage groove 14, and the depth thereof is shallow, and the opening-side width D is wider than the opening-side width S of the fiber storage groove 14. It is desirable to be formed. When the sheath 17 is cooled and hardened and contracts, the overhanging portion 17b of the sheath 17 overhangs in the recess 18 in the same manner as the overhanging portion 17a of the sheath 17 overhangs into the fiber housing groove 14.

  That is, a part of the amount of the sheath 17 contracted by the cooling and hardening and projecting into the fiber housing groove 14 can be projected to the recess 18 side, and the overhang on the fiber housing groove 14 side can be reduced. In addition, since the overhanging portion 17b is generated in the recess 18 due to the contraction of the sheath 17, the upper winding tape 16 is pushed into the recess 18, and the entire winding tension of the upper winding tape 16 is increased, so that the inside of the fiber accommodating groove 14 is increased. This also suppresses the sheath overhang.

  Further, by making the width D on the opening side of the recess 18 wider than the width S on the opening side of the fiber storage groove 14, it is possible to make the sheath overhang into the recess 18 more easily than the fiber storage groove 14. . As a result, the amount of sheath extension into the fiber storage groove 14 is reduced, the clearance C between the tape core wire 15 and the outer surface of the spacer 12 can be reduced, and the storage density of the tape core wire 15 can be increased. The diameter of the cable can be reduced.

  Since the thickness of the tape core 15 is about 0.3 mm, the clearance C is preferably secured as at least one tape core as a sheath overhang. Further, a clearance of 0.3 mm for one tape core wire is added as a clearance that allows some margin so that the upper winding tape 16 does not contact the tape core wire 15, and the clearance C is 0.6 mm or less. I just need it. Therefore, it is desirable that the tape core wire 15 is accommodated so that the clearance C is about 0.3 mm to 0.6 mm.

  FIG. 2 is a diagram illustrating various cross-sectional shape examples of the above-described recess 18. The recess 18a in FIG. 2A is formed in an arc shape, and is a shape suitable for the overhanging form of the sheath 17, and has a shape that is easy to manufacture without waste in the recess cross-sectional area. The recess 18b shown in FIG. 2B has a triangular shape, can have a large opening side width, and can have a simple die shape when the sheath 17 is formed. The recess 18c in FIG. 2C has a trapezoidal shape, can have a large recess volume, and can reduce the depth of the recess compared to the examples of FIGS. 2A and 2B. is there.

  In any example of the shape of the dent, it is not necessary to form the dent deeply, as long as the dent 17 has a dent volume that can absorb the amount of sheath extension when the sheath 17 is cooled and cured and contracts. In addition, as long as the opening side of the dent is wider than the fiber housing groove, it is sufficient that the sheath is easily extended.

It is a figure explaining the outline of the present invention. It is a figure which shows the structural example of the dent in this invention. It is a figure explaining the prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Spacer type optical cable, 12 ... Spacer, 13 ... Tensile body, 14 ... Fiber accommodation groove, 15 ... Optical fiber tape core wire (tape core wire), 16 ... Top wound tape, 17 ... Sheath, 17a, 17b ... Overhang part, 18, 18a, 18b, 18c ... dent.

Claims (3)

A spacer-type optical cable in which an upper tape is wound around the outer surface of a grooved spacer containing a plurality of optical fiber ribbons, and the outside is covered with a sheath by extrusion molding,
On the surface between the fiber receiving groove for accommodating the optical fiber ribbon of the spacer, of the fiber storage groove to reduce the overhang of the sheath and the first volume tapes to the fiber storage groove due to shrinkage of the sheath is extruded A spacer-type optical cable, wherein a recess having an opening width wider than the opening width is provided in parallel with the fiber housing groove. The spacer type optical cable according to claim 1 , wherein the recess has an arc shape or a polygonal cross section. According to claim 1 or 2, wherein the clearance between the outer surface of the uppermost ribbon optical fiber and the spacer accommodated in the fiber receiving groove of the spacer is 0.3 Mm～0.6Mm Spacer type optical cable.

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