JP6719175B2 - Fiber optic cable - Google Patents

Description

The present invention relates to an optical fiber cable including a plurality of optical fiber core wires.

2. Description of the Related Art In recent years, with the spread of the Internet, FTTH (Fiber To The Home), which directly brings an optical fiber into a general household to realize a high-speed communication service, is rapidly expanding. In general, an optical fiber cable used for FTTH accommodates an aggregate of optical fibers in order to support large-capacity data communication.

As such an optical fiber cable, there has been proposed an optical fiber cable which does not use a slot rod and is covered with an outer jacket provided with two tension members. For example, there is one in which yarns (polyester fiber, aramid fiber, PP fiber, etc.) are gathered as a cushioning material on the outer circumference of the optical fiber ribbon, and the outer circumference is covered with a sheath (Patent Document 1).

Further, there is an optical fiber cable in which a press-winding tape is vertically attached to the outer circumference of an optical fiber tape core wire, and the outer circumference is covered with a sheath (Patent Document 2).

JP, 2006-337581, A JP 2001-343571 A

An optical fiber cable having two tension members without using such a slot rod has bending directionality of the optical fiber cable. That is, the optical fiber cable can be easily bent in the bending direction with the line connecting the two tension members as the neutral axis. On the other hand, the optical fiber cable cannot be bent on the side orthogonal to it, and if the optical fiber cable is forcibly bent, the tension member may break through the outer cover. This is because the tension member has a high rigidity and cannot be extremely compressed or stretched.

In this way, when the bending direction of the optical fiber cable is fixed, the optical fiber that is near the neutral axis of the bend when the optical fiber cable is bent and the optical fiber that is largely off the neutral axis The strain on the fiber is different. Therefore, the transmission characteristics when the optical fiber cable is bent are different.

In this way, when the optical fiber cable is bent, the optical fiber located near the center of the neutral axis has a small strain and a small loss increase, but the optical fiber located far from the neutral axis has a tensile strain or Compressive strain is added and loss increases. This increase in loss becomes more remarkable as the distance from the neutral axis increases.

The present invention has been made in view of such a problem, and an object thereof is to provide an optical fiber cable capable of suppressing an increase in loss when bent.

In order to achieve the above-mentioned object, the present invention provides a plurality of optical fiber cores of 200 cores or more and a position facing each other with the optical fiber cores interposed in a cross section perpendicular to the longitudinal direction of the optical fiber cores. A pair of tension members, and an outer cover provided so as to cover the optical fiber core wire and the tension member, and the plurality of optical fiber core wires are intermittently joined to each other. A plurality of tape core wires, the inner diameter of the jacket is 8 mm or more with respect to the facing direction of the tension member, in an arbitrary cross section perpendicular to the longitudinal direction of the optical fiber core wire , and the facing direction of the tension member. The inner diameter of the jacket is smaller than the inner diameter of the jacket with respect to the direction perpendicular to the opposing direction of the tension member, and in any cross section perpendicular to the longitudinal direction of the optical fiber core wire, the outer shape of the jacket is substantially a true circle, the outer a subject of the inner surface shape, Ri space flat shape der a plurality of the optical fiber which is supported by the support winding is held, the opposing direction of the pair of tension members in a direction substantially orthogonal, straps tear in opposite directions via the pressing winding is an optical fiber cable, characterized in Rukoto provided.

In a cross section perpendicular to the longitudinal direction of the optical fiber core wire, the outer shape of the outer cover is a substantially perfect circle, is the inner surface shape of the outer cover, and holds the optical fiber core wire which is pressed by a press winding. The space may have a flat shape.

The inner surface shape of the outer cover may be substantially rectangular.

The inner surface shape of the outer cover may be substantially elliptical.

According to the present invention, when an optical fiber cable is bent in a bending direction having a line connecting the tension members as a neutral axis (hereinafter, simply referred to as an easy bending direction of the optical fiber cable), it is farthest from the neutral axis of bending. The distance to the optical fiber core becomes shorter than the distance from the neutral axis to the furthest optical fiber core when bent in a direction perpendicular to this. Therefore, the stress applied to the optical fiber core wire can be relaxed when a tensile strain or a compressive strain is applied due to the bending of the optical fiber cable in the easy bending direction. Further, since the inner diameter of the jacket is sufficiently large in the direction perpendicular to the easy-bend direction of the optical fiber cable, it is possible to minimize the decrease in the space factor of the optical fiber core wire.

Further, by making the outer shape of the outer cover substantially circular, manufacturability is good. At this time, if the inner surface shape of the outer cover is substantially rectangular, a high space factor can be secured. Further, if the inner surface shape of the outer cover is substantially elliptical, the manufacturability is good.

According to the present invention, it is possible to provide an optical fiber cable capable of suppressing an increase in loss when bent.

Sectional drawing which shows the optical fiber cable 1. Sectional drawing which shows the optical fiber cable 1a. Sectional drawing which shows the optical fiber cable 1b. Sectional drawing which shows the optical fiber cable 1c.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view showing an optical fiber cable 1. The optical fiber cable 1 is a slotless type optical fiber cable that does not use slots, and includes a plurality of optical fiber core wires 3, a press winding 7, a tension member 9, a tear string 11, an outer jacket 13, and the like. In addition, in the following description, an assembly of a plurality of optical fiber core wires 3 is simply referred to as an optical fiber unit 5.

A press winding 7 is provided on the outer circumference of the optical fiber unit 5. The press winding 7 is arranged so as to collectively cover the plurality of optical fiber units 5 by vertical attachment winding. That is, the longitudinal direction of the press winding 7 is substantially aligned with the axial direction of the optical fiber cable 1, and the press winding 7 is longitudinally wound around the optical fiber unit 5 so that the width direction thereof is the circumferential direction of the optical fiber cable 1. It

An outer jacket 13 is provided on the outer circumference of the press winding 7. The jacket 13 is a layer for covering and protecting the optical fiber cable 1. In a cross section perpendicular to the longitudinal direction of the optical fiber cable 1, inside the jacket 13, a pair of tension members 9 are provided at positions facing each other with the press winding 7 interposed therebetween. Further, a tear string 11 is provided in a direction substantially orthogonal to the facing direction of the tension member 9 so as to face each other with the press winding 7 interposed therebetween. The tension member 9 and the tear cord 11 are embedded in the outer cover 13.

In the cross section perpendicular to the longitudinal direction of the optical fiber cable 1, the inner surface of the outer cover 13 has an elliptical shape. That is, the space in which the optical fiber core wire 3 pressed by the press winding 7 is held is formed in a substantially elliptical shape. If the inner surface shape of the outer cover 13 is substantially elliptical, manufacturability is good.

More specifically, rather than the inner diameter (A in the figure) of the jacket 13 in the opposing direction of the tension member 9 (the horizontal direction in the figure), the outside in the direction orthogonal to the opposing direction of the tension member 9 (the vertical direction in the figure). The inner diameter of the object 13 (B in the figure) is small. That is, the inner surface of the outer cover 13 has a flat shape that bulges toward the tension member 9.

Further, the outer shape of the outer cover 13 is a substantially perfect circular shape (it is a substantially perfect circular shape as a whole, and a convex portion or a concave portion may be formed). Therefore, the thickness of the outer cover 13 in the facing direction of the tension member 9 (left-right direction in the drawing) is larger than the thickness of the outer cover 13 in the direction orthogonal to the facing direction of the tension member 9 (up-down direction in the drawing).

Here, as described above, when the optical fiber cable 1 is bent, it is easy to bend so that the line connecting the tension members 9 becomes the neutral axis. Therefore, when the optical fiber cable 1 is bent in the easy bending direction, the optical fiber core wire located farther from the line connecting the tension members 9 receives a larger tensile stress or compressive stress.

In the present invention, the inner diameter of the jacket 13 is small in the direction perpendicular to the line connecting the tension members 9. That is, in the present invention, the distance from the line connecting the tension members 9 to the optical fiber core wire 3 is relatively short in the direction perpendicular to the line connecting the tension members 9. Therefore, when the optical fiber cable 1 is bent in the easy-to-bend direction, a large tensile stress or compressive stress is generated even in the optical fiber core wire 3 which is the farthest from the line connecting the tension members 9. Can be suppressed. Therefore, it is possible to suppress an increase in loss when the optical fiber cable 1 is bent.

On the other hand, the inner diameter of the outer cover 13 is large in the opposing direction of the tension member 9. That is, the distance from the line connecting the tear cords 11 to the optical fiber core wire 3 is relatively long. Therefore, when the optical fiber cable 1 is bent in a direction perpendicular to the easy bending direction, a large tensile stress or compressive stress is generated in the optical fiber core wire 3 at the position farthest from the line connecting the tear cords 11 to each other. However, due to the rigidity of the tension member 9, bending in this direction hardly occurs. Therefore, even if the length from the line connecting the tear cords 11 to the optical fiber core wire 3 at the farthest position becomes long, it is possible to suppress an increase in loss when the optical fiber cable 1 is bent. ..

In order to reduce the stress applied to the optical fiber core wire 3, it is desirable that the optical fiber core wire 3 is a tape core wire that is intermittently joined. For example, it is desirable that adjacent optical fiber strands be intermittently bonded with a bonding portion at a predetermined interval. In addition, it is desirable that the bonding portion between the adjacent optical fiber element wires be displaced from the longitudinal direction of the optical fiber core wire 3. For example, it is desirable that the adhesive portions adjacent to each other be formed with a half pitch shift in the longitudinal direction of the optical fiber core wire 3.

In this way, by arranging the bonded portion intermittently in the longitudinal direction of the optical fiber core wire 3, adjacent optical fiber element wires can be easily folded (bent) in the non-bonded portion. .. Therefore, the optical fiber core wire 3 can be easily moved, and the stress is relieved.

It should be noted that the present invention is not limited to the example in which the inner surface shape of the outer cover 13 is elliptical like the optical fiber cable 1 shown in FIG. For example, as in the optical fiber cable 1a shown in FIG. 2, the inner surface shape of the outer cover 13 may be substantially rectangular.

Even in this case, rather than the inner diameter (A in the drawing) of the jacket 13 with respect to the facing direction of the tension member 9 (the horizontal direction in the drawing), the direction orthogonal to the facing direction of the tension member 9 (the vertical direction in the drawing). The inner diameter (B in the figure) of the jacket 13 is small. That is, the inner surface of the outer cover 13 has a flat shape that bulges toward the tension member 9.

By making the inner surface shape of the outer cover 13 substantially rectangular, it is possible to further increase the space in which the optical fiber core wire 3 is arranged. Therefore, the space factor can be further improved.

In the present invention, as described above, as long as the inner surface shape of the outer cover 13 can be made flat, it may be a rhombus like the optical fiber cable 1b shown in FIG. 3, or another shape. May be

Further, in the present invention, as in the optical fiber cable 1c shown in FIG. 4, the outer shape of the outer cover 13 may be a substantially elliptical shape according to the inner surface shape. In this case, the thickness of the outer cover 13 is substantially constant. As described above, according to the present invention, the direction orthogonal to the facing direction of the tension member 9 (the vertical direction in the drawing), rather than the inner diameter (A in the drawing) of the jacket 13 with respect to the facing direction (the horizontal direction in the drawing) of the tension member 9. It suffices that the inner diameter (B in the figure) of the jacket 13 with respect to is smaller.

As described above, according to the present embodiment, when the optical fiber cable having the bending directivity is bent in the easy bending direction, the optical fiber core wire 3 ( By making the distance to the inner surface of the jacket 13 shorter than the distance from the neutral axis of bending to the furthest optical fiber core wire 3 (the inner surface of the jacket 13) when bent in a direction perpendicular to this. It is possible to suppress the tensile stress and the compressive stress applied to the optical fiber core wire 3 when the optical fiber cable is bent. Therefore, it is possible to suppress an increase in transmission loss when the optical fiber cable is bent.

At this time, if the outer shape of the outer cover 13 is a substantially perfect circle, manufacturability is good. If the inner surface of the outer cover 13 has a substantially elliptical shape, the manufacturability is good. Further, if the inner surface of the outer cover 13 has a substantially rectangular shape, more optical fiber core wires 3 can be accommodated. Further, the outer shape of the outer cover 13 and the inner surface shape of the outer cover 13 are made flat so that the thickness of the outer cover 13 can be made substantially constant.

In fact, we made an optical fiber cable and evaluated the increase in loss during bending. First, a 200-fiber unit in which 50 pieces of 4-fiber intermittent optical fiber ribbons are twisted together is pressed and wound with a non-woven fabric, a polyester twisted yarn is used as a tear string, and a φ0.7 mm steel wire is used as a tension member to form an optical fiber cable. Two types were manufactured.

At this time, the inner surface shape of the outer cover of one of the optical fiber cables was a circle having an inner diameter of 5.5 mm. Further, the inner surface shape of the outer cover of the other optical fiber cable was an elliptical shape of 3.0 mm×8.0 mm (A=8.0 mm in FIG. 1, B=3.0 mm in FIG. 1). Polyethylene was used as the material for the outer cover. The outer diameter of the optical fiber cable was 12 mm.

Similarly, a 1000-fiber unit in which 125 8-fiber intermittent tapes are twisted together is pressed and wound with a non-woven fabric, a polyester twisted yarn is used as a tear string, and a φ1.8 mm steel wire is used as a tension member, and two types of optical fiber cables are used. Manufactured.

At this time, the inner surface shape of the outer cover of one of the optical fiber cables was a circle having an inner diameter of 12.0 mm. The inner surface shape of the outer cover of the other optical fiber cable was an elliptical shape of 8.0 mm×14.0 mm (A=14.0 mm in FIG. 1, B=8.0 mm in FIG. 1). Polyethylene was used as the material for the outer cover. The outer diameter of the optical fiber cable was 19 mm.

The bending test shown in JIS C 6851 was performed on the manufactured optical fiber cable. The bending direction of the optical fiber cable was the easy bending direction described above. At this time, the case where the increase in loss was recognized was marked with “X”, and the case where the increase in loss was not recognized was marked with “◯”. The results are shown in Tables 1 and 2.

From the results, when the inner surface shape of the outer cover was elliptical, no increase in loss was observed when bent. On the other hand, when the inner surface shape of the outer cover was circular, an increase in loss was confirmed as the bending diameter decreased.

Although the embodiments of the present invention have been described above with reference to the accompanying drawings, the technical scope of the present invention is not affected by the above-described embodiments. It is obvious to those skilled in the art that various modifications or modifications can be conceived within the scope of the technical idea described in the claims, and naturally, those modifications are also within the technical scope of the present invention. It is understood that it belongs.

1, 1a, 1b, 1c ......... optical fiber cable 3 ... optical fiber core wire 5 ... optical fiber unit 7 ... presser winding 9 ... tension member 11 ... tearing string 13 ... Jacket

Claims (3)

A plurality of optical fiber cores of 200 cores or more; a pair of tension members provided at positions facing each other with the optical fiber cores being sandwiched in a cross section perpendicular to the longitudinal direction of the optical fiber cores; And a jacket provided to cover the wire and the tension member, wherein the plurality of optical fiber core wires are a plurality of tape core wires in which a plurality of optical fiber core wires are intermittently joined, In an arbitrary cross section perpendicular to the longitudinal direction of the optical fiber core wire, the inner diameter of the jacket in the facing direction of the tension member is 8 mm or more, and the tension is more than the inner diameter of the jacket in the facing direction of the tension member. The inner diameter of the jacket is small with respect to the direction orthogonal to the facing direction of the members, and in any cross section perpendicular to the longitudinal direction of the optical fiber core wire, the outer shape of the jacket is a substantially perfect circle, and the inner surface of the jacket is a shape, Ri space flat shape der a plurality of the optical fiber which is supported by the support winding is retained in the opposite direction in a direction substantially perpendicular to the pair of tension members, across said presser winding in an optical fiber cable, characterized in Rukoto tear cord is provided to face. The optical fiber cable according to claim 1, wherein the inner surface of the outer cover has a substantially rectangular shape. The optical fiber cable according to claim 1, wherein the inner surface of the outer cover has a substantially elliptical shape.

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