Optical fiber cable

Abstract

To provide an optical fiber cable capable of suppressing lengthwise movement of a coated optical fiber in a cable core.SOLUTION: A cable core 15 has a nearly circular outer shape and includes a core part 4 composed of a plurality of coated optical fibers 3 and a press-wrapping member 7 wound on an outer periphery of the core part 4. The press-wrapping member 7 is a tape-shaped member, a nonwoven fabric, or the like and is, for example, disposed so as to collectively cover an outer periphery of the core part 4 in a manner of longitudinally-attached winding. Tension members 9 are provided on both sides of the cable core 15 in a sectional view perpendicular to a lengthwise direction of the cable core 15. A sheath 13 is provided to cover the cable core 15, the tension members 9, and the like. A wrinkle 17 is formed on at least a part of the press-wrapping member 7. The wrinkle 17 is formed to be projected on a core part 4 side.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a slottedless optical fiber cable.

Background Art

[0002] In recent years, with the rapid progress of cloud computing technology enabling larger-capacity information processing, there has been a strong demand to increase the density of optical fiber cables connecting data centers (DCs) in these DCs.

[0003] As such an optical fiber cable, for example, an optical fiber unit is formed by twisting intermittent tape cores advantageous for increasing the density of optical fibers, and the optical fiber unit is further twisted to form a cable core, and an outer sheath in which a tension member is embedded is covered on the cable core.

[0004] On the other hand, in such an optical fiber cable, there is a problem of movement of the optical fiber core in the cable core (so-called core movement). If the optical fiber core moves longitudinally in the cable core, there is a risk of the optical fiber core or the cable core protruding.

[0005] In contrast, in order to suppress the axial movement of the optical fiber core in the cable core, a structure has been proposed in which a string-like body coated with an ultraviolet curable resin is interposed between a plurality of optical fiber cores and a pressing tape (Patent Document 1).

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] An optical fiber cable such as Patent Document 1 is a so-called slottedless optical fiber cable, and a plurality of optical fiber cores are accommodated inside a holding member. Therefore, by arranging a string-like body inside this cable core, the longitudinal movement of the optical fiber cores can be suppressed by friction.

[0008] However, if a string-like body is arranged inside the cable core in this way, there are problems such as a decrease in the occupancy rate of the optical fibers in the cable core and an increase in cost due to an increase in the number of parts.

[0009] The present invention has been made in view of such problems, and an object thereof is to provide an optical fiber cable capable of suppressing the longitudinal movement of optical fiber cores in a cable core.

Means for Solving the Problems

[0010] In order to achieve the above-described object, the present invention includes a cable core, tension members provided on both sides of the cable core in a cross section perpendicular to the longitudinal direction of the cable core, and an outer sheath provided so as to cover the tension members and the cable core. The cable core has a core portion composed of a plurality of optical fiber cores and a holding member wound around the outer periphery of the core portion. The holding member is in contact with a part of the core portion, and at least a part of the holding member is formed with wrinkles protruding toward the core portion side, and the wrinkles are formed in a spiral shape with respect to the longitudinal direction of the cable core , a plurality of the optical fiber cores are twisted together to form an optical fiber unit, the core portion is formed by twisting together a plurality of the optical fiber units, the wrinkle is inserted between the optical fiber units, and a part of the excess length portion of the width of the pressing member with respect to the circumference of the core portion is formed to be folded inward It is an optical fiber cable characterized by this.

[0011] It is desirable that the wrinkles are formed in a spiral shape with respect to the longitudinal direction of the cable core.

[0012] It is desirable that the depth of the wrinkles is 0.2 mm or more.

[0013] In a cross-section perpendicular to the longitudinal direction of the cable core at the portion where the wrinkles are formed, it is desirable that the ratio of the cross-sectional area of the concave portion of the wrinkles on the outer surface side of the cable core to the cross-sectional area of the cable core is 0.01% or more.

[0014] It is desirable that the pulling force of the core portion of the cable core is 3.7 kgf or more and 5.7 kgf or less. 。

[0015] According to the present invention, by forming wrinkles protruding to the inner surface side on the pressing winding member constituting the cable core, these wrinkles serve as a resistance to the movement of the core portion in the longitudinal direction of the optical fiber cable, and the movement of the optical fiber in the longitudinal direction can be suppressed. At this time, there is no need to insert other members into the core portion, and the number of parts does not increase compared with a normal optical fiber cable.

[0016] Further, if these wrinkles are formed in a spiral shape with respect to the longitudinal direction of the cable core, the movement of the optical fiber core wire in the longitudinal direction can be suppressed more efficiently.

[0017] Moreover, if the depth of the wrinkles is 0.2 mm or more, the effect of suppressing the movement of the core wire due to the wrinkles can be obtained efficiently.

[0018] In a cross-section perpendicular to the longitudinal direction of the cable core, if the ratio of the cross-sectional area of the concave portion of the wrinkles on the outer surface side of the cable core to the cross-sectional area of the cable core is 0.01% or more, the effect of suppressing the movement of the core wire due to the wrinkles can be obtained efficiently.

[0019] Furthermore, if the pulling force of the core portion of the cable core is 3.7 kgf or more, the unintentional movement of the core portion can be suppressed. Also, by setting the pulling force of the core portion of the cable core to 5.7 kgf or less, it is possible to suppress the excessive increase in the side pressure received by the core portion from the pressing winding member. Therefore, an increase in microbend loss due to the side pressure from the pressing winding member can be suppressed.

Effects of the Invention

[0020] According to the present invention, it is possible to provide an optical fiber cable capable of suppressing the longitudinal movement of the optical fiber core wire within the cable core.

Brief Description of the Drawings

[0021]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0022] Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view of the optical fiber cable 1. The optical fiber cable 1 is a slottedless cable that does not use slots, and is composed of a cable core 15, a tension member 9, an outer sheath 13, and the like.

[0023] The cable core 15 has a substantially circular outer shape, and includes a core portion 4 composed of a plurality of optical fiber core wires 3 and a holding winding member 7 wound around the outer periphery of the core portion 4. The core portion 4 is formed by twisting a plurality of optical fiber units 5. The optical fiber unit 5 is formed by twisting a plurality of optical fiber core wires 3. As the optical fiber core wire 3, for example, an intermittently adhered optical fiber tape core wire that is intermittently adhered in the longitudinal direction can be applied.

[0024] A pressing and winding member 7 is wound around the outer periphery of the core portion 4. The pressing and winding member 7 is a tape-like member, a non-woven fabric, etc., and is arranged, for example, to collectively cover the outer periphery of the core portion 4 by longitudinal winding. That is, the longitudinal direction of the pressing and winding member 7 substantially coincides with the axial direction of the optical fiber cable 1, and the pressing and winding member 7 is longitudinally wound around the outer periphery of a plurality of optical fiber units 5 so that the width direction of the pressing and winding member 7 becomes the circumferential direction of the optical fiber cable 1.

[0025] By the pressing and winding member 7, the internal core portion 4 (optical fiber core wire 3) is appropriately restrained, and the unwinding of the twist of the optical fiber unit 5 is suppressed. Note that a pressing string or the like (not shown) is wound around the outer periphery of the pressing and winding member 7 to suppress the opening of the overlapping portion of the pressing and winding member 7.

[0026] In a cross-sectional view perpendicular to the longitudinal direction of the cable core 15, tension members 9 are provided on both sides of the cable core 15. That is, a pair of tension members 9 are provided at positions facing each other with the cable core 15 interposed therebetween. Also, a tearing string 11 is provided so as to face each other with the cable core 15 interposed therebetween in a direction substantially orthogonal to the facing direction of the tension members 9.

[0027] An outer sheath 13 is provided on the outer periphery of the cable core 15. The tension members 9 and the tearing string 11 are embedded in the outer sheath 13. That is, the outer sheath 13 is provided so as to cover the cable core 15 and the tension members 9 and the like. The outer shape of the outer sheath 13 is substantially circular. The outer sheath 13 is, for example, a polyolefin-based resin.

[0028] Here, wrinkles 17 are formed in at least a part of the pressing and winding member 7. FIG. 2 is an enlarged view of the vicinity of the wrinkles 17. The wrinkles 17 are formed so as to protrude toward the core portion 4 side. That is, the outer peripheral side (outer sheath 13 side) becomes a concave portion. The wrinkles 17 are inserted between the optical fiber units.

[0029] As described above, the pressing and winding member 7 is longitudinally wound around the outer periphery of the core portion 4. Therefore, the width direction of the pressing and winding member 7 corresponds to the circumferential direction of the core portion 4. At this time, with respect to the circumferential length of the core portion 4, the extra length portion of the width of the pressing and winding member 7 becomes the overlapping portion between the ends (see Fig. 1). On the other hand, the wrinkle 17 is formed such that a part of the extra length portion of the width of the pressing and winding member 7 is folded inward instead of all becoming the overlapping portion.

[0030] Here, in a cross-section perpendicular to the longitudinal direction of the cable core 15, it is desirable that the depth of the concave portion of the wrinkle 17 (the distance from the virtual circle of the cable core 15 to the deepest part of the concave portion, which may simply be referred to as the depth of the wrinkle 17) is 0.2 mm or more. If the depth of the wrinkle 17 is 0.2 mm or more, the effect of suppressing the movement of the optical fiber core wire 3 in the longitudinal direction can be obtained more reliably. On the other hand, if the depth of the wrinkle 17 becomes too large, there is a risk of an increase in the lateral pressure on the optical fiber core wire 3. Therefore, for example, it is desirable that the depth of the wrinkle 17 is 2.0 mm or less.

[0031] In addition, in a cross-section perpendicular to the longitudinal direction of the cable core 15 at the portion where the wrinkle 17 is formed, the ratio of the cross-sectional area of the concave portion of the wrinkle 17 on the outer surface side of the cable core 15 to the cross-sectional area of the cable core 15 (the cross-sectional area without considering the wrinkle) is desirably 0.01% or more. Here, if the outer diameter of the pressing and winding member 7 is A (see Fig. 1), the cross-sectional area of the cable core 15 is represented by (A / 2) 2 ·π. Also, if the width of the wrinkle 17 is B and the depth is C (see Fig. 2 respectively), the cross-sectional area of the concave portion due to the wrinkle 17 is approximated by B·C / 2. Therefore, the cross-sectional area ratio of the concave portion of the wrinkle 17 (which may simply be referred to as the cross-sectional area ratio of the wrinkle 17) can be expressed as {B·C / 2} / {(A / 2) 2 ·π}×100%.

[0032] In the portion where the wrinkles 17 are formed, if the cross-sectional area ratio of the wrinkles 17 is 0.01% or more, the effect of suppressing the longitudinal movement of the optical fiber core wire 3 can be obtained more reliably. On the other hand, if the wrinkles 17 become too large, there is a risk of excessive increase in the lateral pressure on the optical fiber core wire 3. For this reason, for example, it is desirable that the cross-sectional area ratio of the wrinkles 17 is 0.8% or less.

[0033] As a method of forming such wrinkles 17, for example, a method of changing the shape and manufacturing conditions of the forming jig used for vertical winding can be mentioned. Usually, when performing vertical winding, a belt-like holding winding member is sent out to the outer periphery of the core portion 4 and passed through the forming jig together with the core portion 4. By the forming jig, the holding winding member 7 is gradually rounded from a flat state, and when passing through the forming jig, the holding winding member 7 is in a state of being completely wound around the outer periphery of the core portion 4.

[0034] At this time, usually, the shape and linear speed of the forming jig are set so that the holding winding member 7 is gently rounded so that wrinkles do not enter the holding winding member 7. In this way, by gradually rounding the holding winding member, it is possible to neatly round it to a circular shape on the outer periphery of the core portion 4.

[0035] On the other hand, for example, if an attempt is made to round the holding winding member 7 rather abruptly, as described above, due to the influence of friction between the overlapping portions at the ends, etc., the holding winding member 7 may not be neatly rounded and wrinkles 17 may be formed partially. At this time, since the outer peripheral side of the holding winding member 7 is pressed by the forming jig, the wrinkles 17 protrude to the inner surface side.

[0036] In this way, in addition to changing the shape of the forming jig, wrinkles can also be formed by increasing the linear speed to increase the forming processing speed of the holding winding member 7. Further, wrinkles can also be formed in the holding winding member 7 by adjusting the tension of the holding string wound around the outer periphery of the holding winding member 7. In this way, the method of forming the wrinkles 17 is not particularly limited.

[0037] FIG. 3(a) is a conceptual diagram showing the cable core 15 after the forming process. Note that the illustration of the holding winding string is omitted. The wrinkles 17 formed in this way tend to be continuously formed straight along a predetermined length in the longitudinal direction. Here, although it is desirable for the wrinkles 17 to be formed over the entire length, they may be formed partially over a predetermined length. That is, the wrinkles 17 may not be formed over the entire length and may be intermittent. Also, in one cross section, the wrinkles 17 may be formed at a plurality of locations.

[0038] Further, after winding the holding winding member 7 in this way, the cable core 15 may be further twisted. By doing so, as shown in FIG. 3(b), the wrinkles 17 can be formed in a spiral shape with respect to the longitudinal direction of the cable core 15. In this way, by forming the wrinkles 17 in a spiral shape with respect to the longitudinal direction of the cable core 15, the movement of the optical fiber core wire 3 in the longitudinal direction can be more reliably suppressed.

[0039] Note that the twisting direction of the cable core 15 may be the same as or opposite to the twisting direction of the core portion 4 (optical fiber unit 5). However, by making them the same direction, the unwinding of the core portion 4 (optical fiber unit) when the cable core 15 is twisted can be suppressed.

[0040] As described above, according to the present embodiment, by forming the wrinkles 17 in the holding winding member 7 and projecting them toward the core portion 4 side, the wrinkles 17 become a resistance, and the movement of the core portion 4 (optical fiber core wire 3) in the longitudinal direction can be suppressed.

[0041] Also, by forming the wrinkles 17 in a spiral shape with respect to the longitudinal direction, a higher resistance is obtained, and the movement of the core portion 4 (optical fiber core wire 3) in the longitudinal direction can be more efficiently suppressed.

[0042] In this way, since the movement of the core portion 4 in the longitudinal direction is suppressed, the pulling force of the core portion 4 of the cable core 15 can be set to 3.7 kgf or more. By doing so, the unintentional protrusion of the core portion 4 can be suppressed.

[0043] If the pull-out force of the core portion 4 of the cable core 15 exceeds 5.7 kgf, there is a risk of an increase in microbend loss occurring due to the large lateral pressure on the core portion 4. For this reason, it is desirable that the pull-out force of the core portion 4 of the cable core 15 be 3.7 kgf or more and 5.7 kgf or less. EXAMPLES

[0044] An optical fiber cable was fabricated, and the pull-out force was measured when the core part was pulled out from the cable core (holding winding member). The cross-sectional shape of the optical fiber cable was a slotless type cable similar to that shown in Figure 1.

[0045] First, a core section with 6912 cores was formed. After twisting the core sections together, a pressure winding member was rolled and vertically wrapped around it using a forming jig, and a nylon pressure thread was wound around the outer circumference of the pressure winding member to create a cable core. At this time, several types of cable cores were formed by changing the forming jig and manufacturing conditions. The cable core thus created, a pair of tension members, and a ripping string for ripping the jacket were sheathed into a cylindrical shape with the jacket material to create an optical fiber cable.

[0046] The obtained optical fiber cable was cut into 2 m, and the outer sheath was removed within a range of 10 cm on both ends of the optical fiber cable to expose the cable core. Furthermore, the holding winding member of the cable core at one end was peeled off, and the holding winding member was fixed to the outer sheath with tape.

[0047] Next, the pressure winding material of the cable core at the other end was peeled off, the core portion was bundled and pulled in the axial direction of the cable, and the pull-out force at the start of the movement was measured with a spring scale. A pull-out force of less than 3.7 kgf was deemed to be a failure (×) because the pull-out force was too small and the core portion was likely to slip out of the pressure winding material, and a pull-out force of 3.7 kgf or more was deemed to be a pass (◯). The results are shown in Table 1.

[0048] [Table 1]

[0049] After finishing the measurement of the pulling force, all the jackets of the optical fiber cable were removed, and the outer diameter of the cable core and, at a position with generally large wrinkles, the width and depth of the wrinkles were measured. The widths of the wrinkles in Examples 1 to 6 were all 0.5 mm to 3 mm. Also, the maximum value of the length of the wrinkles in the longitudinal direction was measured.

[0050] Note that the cross-sectional area ratio of the wrinkles was calculated based on the cross-sectional area of the recesses of the wrinkles on the outer surface side of the pressing member with respect to the cross-sectional area of the circle calculated from the outer diameter of the pressing member. The cross-sectional area of the recess was calculated as the width of the recess × depth / 2.

[0051] As shown in Table 1, in Examples 1 to 6 in which wrinkles were formed on the pressing member, the pulling force of the core part was 3.7 kgf or more in all cases. On the other hand, in Comparative Example 1 in which no wrinkles were formed on the pressing member, the pulling force was small and it was unqualified.

[0052] As described above, the embodiments of the present invention have been described with reference to the accompanying drawings, but the technical scope of the present invention is not limited by the above-described embodiments. It is obvious that those skilled in the art can conceive of various modification examples or correction examples within the scope of the technical idea described in the claims, and it is naturally understood that those also belong to the technical scope of the present invention.

Explanation of Reference Numerals

[0053] 1.........Optical fiber cable 3.........Optical fiber core wire 4.........Core part 5.........Optical fiber unit 7.........Pressing member 9.........Tension member 11.........Tearing string 13.........Jacket 15.........Cable core 17.........Wrinkles

Claims

1. A cable core, In a cross-section perpendicular to the longitudinal direction of the cable core, tension members provided on both sides of the cable core, An outer sheath provided so as to cover the tension members and the cable core, Comprising, The cable core has a core portion composed of a plurality of optical fiber cores and a pressing member wound around the outer periphery of the core portion, The pressing member is in contact with a part of the core portion, At least a part of the pressing member has wrinkles protruding toward the core portion side, The wrinkles are formed in a spiral shape with respect to the longitudinal direction of the cable core, A plurality of the optical fiber cores are twisted to form an optical fiber unit, and the core portion is formed by twisting a plurality of the optical fiber units, The wrinkles are inserted between the optical fiber units and are formed such that a part of the extra length portion of the width of the pressing member with respect to the circumference of the core portion is folded inward. An optical fiber cable characterized by this.

2. The optical fiber cable according to claim 1, characterized in that the depth of the wrinkles is 0.2 mm or more.

3. In a cross-section perpendicular to the longitudinal direction of the cable core at the portion where the wrinkles are formed, the ratio of the cross-sectional area of the concave portion of the wrinkles on the outer surface side of the cable core to the cross-sectional area of the cable core is 0.01% or more. The optical fiber cable according to claim 1 or claim 2, characterized by this.

4. The optical fiber cable according to any one of claims 1 to 3, characterized in that the pulling force of the core portion of the cable core is 3.7 kgf or more and 5.7 kgf or less.

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