JP2011118213A - Optical fiber cable - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical fiber cable in which all tension members can be uniformly clamped and fixed in a closure. <P>SOLUTION: The optical fiber cable includes: a slot core 4 in which optical fibers 2 are housed and held in a slot groove 3; and a sheath 6, which has an uneven thickness sheath structure, for covering the entire slot core including the opening 5 of the slot groove 3. In this optical fiber cable 1, there are installed in the slot core 4 two or more tension members 7A, 7B having the same dimension and the same cross sectional shape. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an optical fiber cable in which an optical fiber is housed in a slot core provided with two or more strength members and covered with a sheath, and in particular, an optical fiber capable of obtaining a stable strength member gripping state with a closure. It relates to the structure of the cable.

  In general, an optical fiber cable is composed of a slot core having a slot groove for accommodating an optical fiber therein, and a sheath having an uneven thickness structure covering the periphery of the slot core. In this optical fiber cable, when the cable is bent due to the uneven thickness structure of the slot groove and the sheath formed in the slot core, the cable is deformed so that it falls down around the inner side bent from the central axis of the cable cross section. . In order to prevent this deformation, two strength members as tension members are embedded in the slot core (for example, described in Patent Document 1).

  This type of optical fiber cable has two tensile strengths taken out from the slot core in a closure, which is a box that protects the connection and extra length between the optical fiber cables from water and external force. It is necessary to stabilize and fix the body. In the closure, for example, as shown in FIG. 5, two strength members 101 and 102 are inserted into the insertion holes 103 and tightened with the fixing screws 104, thereby gripping metal fittings 105 for gripping and fixing these strength members 101 and 102. Is provided.

JP 2008-077687 A

  When the two strength members 101, 102 having different wire diameters (large diameter and small diameter) are used, the large strength material 101 can be fixed with the fixing screw 104, but the diameter The small strength member 102 cannot be fixed due to a gap with the fixing screw 104, or the fixing force is weakened. For this reason, when the strength members 101 and 102 having different diameters are used, they cannot be gripped evenly by the fixing screw 104, and the gripping force varies, and the one strength member 102 cannot be connected to the ground. There are cases where it cannot be done.

  If the two strength members 101 and 102 have different diameters, it is necessary to take care of the direction of the cable when fixing with the fixing screw 104, and when the strength members 101 and 102 are taken out of the slot core. In addition, one tensile member is easy to remove, but the other tensile member is difficult to remove.

  Then, an object of this invention is to provide the optical fiber cable which can hold | grip and fix all the strength bodies uniformly.

  The invention according to claim 1 is an optical fiber cable comprising: a slot core that stores and holds an optical fiber in a slot groove; and a sheath that covers the entire slot core including the opening of the slot groove. The sheath has an uneven thickness structure in which the sheath thickness facing the opening side of the slot groove is thicker than the sheath thickness on the side opposite to the opening side, and the slot core has the same size and the same cross-sectional shape. It is characterized in that at least two or more strength members are provided.

  A second aspect of the present invention is the optical fiber cable according to the first aspect, wherein the strength members are provided close to each other.

  Invention of Claim 3 is the optical fiber cable of Claim 2, Comprising: The thickness of the site | part in which the said tension body of the said slot core is provided was made thinner than the thickness of another site | part. It is a feature.

  According to the optical fiber cable of the present invention, since two or more strength members having the same dimensions and the same cross-sectional shape are provided in the slot core covered with the sheath of the uneven thickness sheath structure having different sheath thickness depending on the site, When these strength members are gripped by the gripping fittings provided in the closure, all the strength members have the same dimensions and the same cross-sectional shape, so that all the strength members can be uniformly gripped and fixed by the gripping fittings. As a result, the troublesome work of considering the direction of the cable at the time of attaching the cable to the gripping metal fitting becomes unnecessary, and all the tensile strength bodies can be securely grounded and the tensile strength from the slot core can be secured. The body can be taken out easily.

FIG. 1 is a perspective view of the optical fiber cable of the present embodiment, with a part of the sheath removed. FIG. 2 is a cross-sectional view of the optical fiber cable of the present embodiment. FIG. 3 is a schematic view showing a state when the optical fiber cable of the present embodiment is linearly connected in the closure. FIGS. 4A and 4B show a state in which the strength member taken out from the optical fiber cable and the optical fiber cable are gripped and fixed by the holding metal fitting provided in the closure, FIG. 4A is a side view thereof, and FIG. 4B is a front view thereof. FIG. 5 is a diagram of a conventional structure showing a state in which two strength members having different diameters are fixed by a gripping metal fitting.

  Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings.

  FIG. 1 is a perspective view of the optical fiber cable of the present embodiment, with a portion of the sheath removed, and FIG. 2 is a cross-sectional view of the optical fiber cable of the present embodiment.

  As shown in FIGS. 1 and 2, the optical fiber cable 1 of the present embodiment includes a slot core 4 that holds and holds the optical fiber 2 in the slot groove 3, and an opening 5 of the slot groove 3. The sheath 6 covers the entire slot core 4.

  As the optical fiber 2, an optical fiber, an optical fiber, an optical fiber tape, or the like is used. The optical fiber strand is an optical fiber coated with an ultraviolet curable resin. The optical fiber core is made by coating a plastic resin on an optical fiber and making its 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. In FIG. 1 and FIG. 2, an optical fiber ribbon is used, and a plurality of (6) optical fiber ribbons are housed in the slot groove 3. An interference material may be interposed between the optical fiber 2 and the slot groove 3, or a gap may be provided.

  The slot core 4 is a holding member that houses and holds the optical fiber 2 therein, and has a slot groove 3 that is a circular arc having a center point at a position shifted from the center point C of the optical fiber cable 1. . The slot core 4 is formed by extrusion molding, and a cross section perpendicular to the longitudinal direction has a C-shaped cross section. The slot core 4 is not uniform in thickness, and gradually increases in thickness from the part where the opening 5 is formed to the part opposite to the opening 5. In other words, the thickness of the slot core 4 gradually decreases from the portion corresponding to the bottom of the slot groove 3 to the portion where the opening 5 is formed.

  Further, the slot core 4 is a tension member 2 in order to prevent the sheath 6 from being thermally contracted by the influence of heat received at the place where the optical fiber cable 1 is laid, and the optical fiber cable itself being deformed. Tensile strength members 7 (7A, 7B) are embedded. The strength member 7 is made of a wire such as a steel wire or FRP. In the present embodiment, the two strength members 7A and 7B have the same dimensions and the same cross-sectional shape. The same dimension defined here includes a slight error (an error of about ± 0.03 mm) in addition to completely the same without any error. Similarly, the same cross-sectional shape includes some errors in addition to the completely same shape. In FIG. 1 and FIG. 2, a steel wire having the same diameter and having a circular cross section is used as the strength member 7. In the present embodiment, the number of strength members 7 is two, but may be three or more if necessary.

  The two strength members 7A and 7B pass through the center point C of the optical fiber cable 1 and are provided close to each other on the same line at a position corresponding to the bottom portion of the slot groove 3. For this reason, the thickness of the portion of the slot core 4 where the strength members 7A and 7B are provided is thinner than the thickness of the other portions. For example, among the portions of the slot core 4, the slot core thickness T1 between the two strength members 7A and 7B, the slot core thickness T2 between one strength member 7A and the slot groove 3, and the other strength member 7B The slot core thickness T3 between the sheaths 6 is considerably thinner than the thickness of other portions.

  The sheath 6 has a thickness variation sheath structure in which the sheath thickness T4 facing the opening 5 side of the slot groove 3 is thicker than the sheath thickness T5 on the opposite side to the opening 5 side. In this embodiment, the sheath thickness T5 in the portion where the two strength members 7A and 7B are provided is the thinnest, and the sheath thickness is gradually increased toward the portion facing the opening 5 of the slot groove 3, The sheath thickness T4 at the portion facing the opening 5 is the largest.

  Such a sheath 6 is formed by extrusion molding so that the entire periphery of the slot core 4 accommodating the optical fiber 2 is covered with polyethylene resin. At the time of molding, a pressing tape 8 for preventing the polyethylene resin from entering the slot groove 3 is attached so as to close the opening 5.

  The optical fiber cable 1 configured as described above has an uneven thickness sheath structure of the slot groove 3 and the sheath 6 formed in the slot core 4, and when the cable is bent, the inner side from the center point C of the cable cross section is further centered. It will bend. In order to prevent this deformation, a difference (line length difference) is provided in the lengths of the two strength members 7A and 7B and embedded in the slot core 4. These two strength members 7A and 7B are embedded at the time of extrusion molding of the slot core while applying tension by making the length of one strength member longer or shorter than the length of the other strength member.

  The optical fiber cable 1 configured as described above has, for example, a tensile strength drawn from the optical fiber cable 1 itself and the slot groove 3 when the optical fibers 2 are connected to each other in the closure 9 shown in FIG. The body 7 is held and fixed by the holding fitting 10. As shown in FIG. 4, the gripping metal fitting 10 includes a cable holding portion 11 that grips and fixes the cable itself, and a strength body gripping portion 12 that grips and fixes the strength body 7.

  The cable holding portion 11 includes a vertical portion 14 that stands vertically from the base portion 13, a horizontal portion 15 that is bent at a right angle from the tip of the vertical portion 14 and is parallel to the base portion 13, and is screwed into the horizontal portion 15. The upper sheath gripping portion 17A attached to the tip of the screw 16 and the lower sheath gripping portion 17B attached to the tip of the screw 18 screwed into the base portion 13.

  The upper sheath gripping portion 17A and the lower sheath gripping portion 17B are provided at the upper and lower opposing positions, and sandwich and hold the sheath 6 portion of the optical fiber cable 1. The upper sheath gripping portion 17A moves up and down in a direction approaching and separating from the other lower sheath gripping portion 17B by turning a screw 16 screwed into the horizontal portion 15. The lower sheath gripping portion 17B moves up and down in a direction approaching and separating from the upper sheath gripping portion 17A by turning a screw 18 screwed into the base portion 13.

  The strength body gripping portion 12 includes a standing portion 19 that stands vertically from the tip of the base portion 13 that extends on the axis of the optical fiber cable 1, a strength body insertion hole 20 that is provided in the standing portion 19, and a strength body insertion hole. And a tightening screw 21 for gripping and fixing the strength member 7 (7A, 7B) inserted into 20.

  The strength member insertion hole 20 is formed through the upstanding portion 19 as an opening having a size capable of inserting at least two strength members 7 (7A, 7B) side by side. A tip end portion 21A of a tightening screw 21 screwed into the tip end of the upright portion 19 is exposed in the strength member insertion hole 20. When the tightening screw 21 is turned, the protruding amount of the tip 21A protruding into the strength member insertion hole 20 increases or decreases. The connection fitting 10 is grounded to a portion (not shown) and is electrically connected to the strength member 7 inserted into the strength member insertion hole 20. Thereby, the strength member 7 is grounded by being held and fixed by the connection fitting 10.

  In order to grip and fix the end portion of the optical fiber cable 1 with the gripping metal fitting 10 thus configured, first, the two strength members 7A and 7B taken out from the slot core 4 are inserted into the strength member insertion hole 20. To do. Further, the upper and lower screws 16 and 18 are rotated to move the upper sheath gripping portion 17A and the lower sheath gripping portion 17B closer to each other, and the sheath 6 is sandwiched between the upper sheath gripping portion 17A and the lower sheath gripping portion 17B.

  By tightly closing the upper and lower screws 16 and 18, the upper sheath holding member 17A and the lower sheath holding member 17B are held and fixed so that the sheath 6 does not rattle. Next, the tightening screw 21 is tightened, and the two strength members 7A and 7B are pressed against the bottom surface 20a of the strength member insertion hole 20 by the tip 21A.

  In this embodiment, since the two strength members 7A and 7B have the same dimensions and the same cross-sectional shape, the distal end portion 21A of the tightening screw 21 uniformly contacts these strength members 7A and 7B. That is, the distal end portion 21A of the tightening screw 21 does not come into contact with either one of the strength members but does not come into contact with the other strength member. Further, the pressing force from the tightening screw 21 is equally applied to both the strength members 7A and 7B.

  According to the optical fiber cable of the present embodiment, two or more strength members 7 (with the same dimensions and the same cross-sectional shape) are provided on the slot core 4 covered with the sheath 6 of the uneven thickness structure having different sheath thicknesses. 7A, 7B), when these strength members 7 are gripped by the gripping metal fitting 10 provided in the closure 9, all strength members 7 (7A, 7B) have the same dimensions and the same cross-sectional shape. All the tensile strength members 7 (7A, 7B) can be uniformly held and fixed by the holding fitting 10. As a result, the troublesome work of considering the direction of the cable at the time of attaching the cable to the gripping metal fitting 10 becomes unnecessary, and the grounding of all the strength members (7A, 7B) can be surely taken.

  Further, according to the optical fiber cable of the present embodiment, since the two strength members 7A and 7B are provided close to each other, the strength members 7A and 7B are inserted into the strength member insertion hole 20 of the holding fitting 10. It becomes easy.

  Further, according to the optical fiber cable of the present embodiment, the thicknesses T1, T2, and T3 of the portions where the strength members 7A and 7B of the slot core 4 are provided are thinner than the thicknesses of other portions. 7A and 7B can be easily pulled out from the slot core 4. That is, the slot core 4 can be easily peeled to take out the strength members 7A and 7B.

As an example, the variation in gripping force by the tightening screw 21 in the closure 9 when the difference in diameter (wire diameter difference) between the two strength members 7A and 7B was reduced and the electrical conductivity were compared. The results are shown in Table 1.

  When the diameter of one tensile strength body is 1.4 mm, the sample is a prototype 1 with a wire diameter difference of -50%, a prototype 2 with a wire diameter difference of -32%, and a wire diameter difference of- Sample 15 was made 15%, and sample 4 was made the same diameter. The gripping force was expressed in kgf, and the continuity was expressed as the number of conductors / test number when the tensile strength body was gripped by the gripping metal 10 times.

  As a result, as the prototype 1 having a larger wire diameter difference, the gripping force varies and the continuity deteriorates, but in the prototype 4 made of the same-strength tensile member, the variation in the gripping force is small and the continuity is good. Results were obtained.

  Although specific embodiments to which the present invention is applied have been described above, the present invention is not limited to the above-described embodiments. For example, in the above description, the strength member 7 of the optical fiber cable 1 is grasped and fixed by the gripping bracket 10 in the closure 9. However, the strength member 7 is gripped by the gripping bracket 10 in the optical termination box used for constructing the optical network. The present invention can also be applied to gripping and fixing.

  The present invention can be used for an optical fiber cable having two or more strength members in a slot core.

DESCRIPTION OF SYMBOLS 1 ... Optical fiber cable 2 ... Optical fiber 3 ... Slot groove 4 ... Slot core 5 ... Opening (opening part of slot groove)
6 ... Sheath 7 (7A, 7B) ... Tensile body 9 ... Closure 10 ... Grip metal fitting 11 ... Cable holding part 12 ... Tensile body gripping part 20 ... Tensile body insertion hole 21 ... Tightening screw

Claims (3)

In an optical fiber cable comprising a slot core that stores and holds an optical fiber in a slot groove, and a sheath that covers the entire slot core including the opening of the slot groove,
The sheath has an uneven thickness sheath structure in which the sheath thickness facing the opening side of the slot groove is thicker than the sheath thickness on the side opposite to the opening side,
The slot core is provided with at least two strength members having the same dimensions and the same cross-sectional shape. The optical fiber cable according to claim 1,
The tensile strength bodies are provided in close proximity to each other. An optical fiber cable according to claim 2,
An optical fiber cable, wherein a thickness of a portion of the slot core where the strength member is provided is made thinner than a thickness of other portions.

Images