JP7704583B2 - Fiber optic cable - Google Patents

Description

The present invention relates to a slotless type optical fiber cable.

In recent years, rapid advances in cloud computing technology have made it possible to process larger volumes of information, and there is a strong demand for higher density optical fiber cables connecting data centers (DCs) that process this information.

One example of such an optical fiber cable is one in which an optical fiber unit is formed by twisting together intermittent ribbon cores, which are advantageous for increasing the density of optical fibers, and the optical fiber unit is then twisted further to form a cable core, which is then covered with an outer jacket containing an embedded tension member.

However, such optical fiber cables have a problem with the movement of the optical fiber core within the cable core (so-called core movement). If the optical fiber core moves longitudinally within the cable core, there is a risk that the optical fiber core or the cable core will protrude.

In response to this, a proposal has been made to place a string-like body coated with ultraviolet curable resin between multiple optical fiber cores and the pressure winding tape in order to suppress axial movement of the optical fiber cores within the cable core (Patent Document 1).

JP 2014-139609 A

The optical fiber cable described in Patent Document 1 is a so-called slotless type optical fiber cable, in which multiple optical fiber cores are housed inside the pressure winding member. Therefore, by disposing a string-like body inside this cable core, it is possible to suppress longitudinal movement of the optical fiber cores by friction.

However, placing a string-like body inside the cable core in this way poses problems such as a decrease in the space factor of the optical fiber in the cable core and an increase in costs due to an increase in the number of parts.

The present invention was made in consideration of these problems, and aims to provide an optical fiber cable that can suppress longitudinal movement of the optical fiber core within the cable core.

In order to achieve the above-mentioned object, the present invention provides an optical fiber cable comprising 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 to cover the tension members and the cable core, the cable core having a core portion consisting of a plurality of optical fiber cores, and a pressure winding member wound around the outer periphery of the core portion, the pressure winding member contacts a portion of the core portion, at least a portion of the pressure winding member has wrinkles that protrude toward the core portion, the wrinkles are formed in a spiral shape in the longitudinal direction of the cable core, an optical fiber unit is formed by twisting together the plurality of optical fiber cores, the core portion is formed by twisting together the plurality of optical fiber units, the wrinkles are inserted between the optical fiber units, and a portion of the excess portion of the width of the pressure winding member relative to the circumferential length of the core portion is folded inward .

It is preferable that the wrinkles are formed in a spiral shape relative to the longitudinal direction of the cable core.

It is desirable for the wrinkles to have a depth of 0.2 mm or more.

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

It is desirable that the pull-out force of the core portion of the cable core is 3.7 kgf or more and 5.7 kgf or less .

According to the present invention, by forming wrinkles that protrude on the inner surface of the pressure winding member that constitutes the cable core, these wrinkles provide resistance to the movement of the core portion in the longitudinal direction of the optical fiber cable, thereby suppressing the movement of the optical fiber in the longitudinal direction. In this case, there is no need to insert other members into the core portion, and the number of parts does not increase compared to a normal optical fiber cable.

Furthermore, if the wrinkles are formed in a spiral shape in the longitudinal direction of the cable core, the movement of the optical fiber core in the longitudinal direction can be more efficiently suppressed.

In addition, if the wrinkle depth is 0.2 mm or more, the wrinkles can efficiently suppress the movement of the core wire.

In a cross section perpendicular to the longitudinal direction of the cable core, if the cross-sectional area of the concave portion of the wrinkles on the outer surface of the cable core accounts for 0.01% or more of the cross-sectional area of the cable core, the wrinkles can be used to efficiently suppress core wire movement.

In addition, if the pull-out force of the core portion of the cable core is 3.7 kgf or more, unintended movement of the core portion can be suppressed. In addition, by setting the pull-out force of the core portion of the cable core to 5.7 kgf or less, it is possible to prevent the lateral pressure that the core portion receives from the pressure winding member from becoming excessively large. This makes it possible to suppress an increase in microbend loss due to the lateral pressure from the pressure winding member.

The present invention provides an optical fiber cable that can suppress longitudinal movement of the optical fiber core within the cable core.

FIG. An enlarged view of wrinkle 17. 1A is a diagram showing a state in which wrinkles 17 are formed straight in the longitudinal direction of a cable core 15, and FIG. 1B is a diagram showing a state in which wrinkles 17 are formed spirally in a cable core 15. FIG.

The following describes an embodiment of the present invention with reference to the drawings. Fig. 1 is a cross-sectional view of an optical fiber cable 1. The optical fiber cable 1 is a slotless type cable that does not use slots, and is composed of a cable core 15, a tension member 9, an outer jacket 13, etc.

The cable core 15 has a generally circular outer shape, and includes a core portion 4 made of multiple optical fiber cores 3, and a pressure winding member 7 wound around the outer circumference of the core portion 4. The core portion 4 is formed by twisting together multiple optical fiber units 5. The optical fiber unit 5 is also formed by twisting together multiple optical fiber cores 3. The optical fiber cores 3 can be, for example, intermittently bonded optical fiber ribbon cores that are intermittently bonded in the longitudinal direction.

A pressure winding member 7 is wound around the outer periphery of the core portion 4. The pressure winding member 7 is a tape-like member or nonwoven fabric, and is arranged, for example, by vertical wrapping to cover the outer periphery of the core portion 4 as a whole. In other words, the longitudinal direction of the pressure winding member 7 is approximately aligned with the axial direction of the optical fiber cable 1, and the width direction of the pressure winding member 7 is aligned with the circumferential direction of the optical fiber cable 1, and the pressure winding member 7 is vertically wrapped around the outer periphery of the multiple optical fiber units 5.

The internal core 4 (optical fiber 3) is appropriately restrained by the pressure winding member 7, suppressing untwisting of the optical fiber unit 5. A pressure string (not shown) is wound around the outer circumference of the pressure winding member 7 to suppress opening of the overlapping portion of the pressure winding member 7.

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 in between. In addition, tear cords 11 are provided in a direction approximately perpendicular to the facing direction of the tension members 9 so as to face each other with the cable core 15 in between.

An outer sheath 13 is provided around the outer periphery of the cable core 15. The tension members 9 and the tear cord 11 are embedded in the outer sheath 13. In other words, the outer sheath 13 is provided so as to cover the cable core 15, the tension members 9, etc. The outer shape of the outer sheath 13 is approximately circular. The outer sheath 13 is, for example, a polyolefin-based resin.

Here, wrinkles 17 are formed in at least a portion of the pressure winding member 7. Figure 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. In other words, the outer peripheral side (the outer jacket 13 side) becomes a recess. The wrinkles 17 are inserted between the optical fiber units.

As described above, the pressure winding member 7 is wound vertically around the outer periphery of the core portion 4. Therefore, the width direction of the pressure winding member 7 corresponds to the circumferential direction of the core portion 4. In this case, the excess width of the pressure winding member 7 relative to the circumferential length of the core portion 4 becomes an overlapping portion of the ends (see FIG. 1). In contrast, the wrinkles 17 are formed when the excess width of the pressure winding member 7 does not entirely overlap, but is partially folded inward.

Here, in a cross section perpendicular to the longitudinal direction of the cable core 15, it is desirable that the depth of the recess of the wrinkle 17 (the distance from the imaginary circle of the cable core 15 to the deepest part of the recess, 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 longitudinal movement of the optical fiber core 3 can be more reliably obtained. On the other hand, if the depth of the wrinkle 17 is too large, there is a risk of an increase in lateral pressure on the optical fiber core 3. For this reason, for example, it is desirable that the depth of the wrinkle 17 is 2.0 mm or less.

In a cross section perpendicular to the longitudinal direction of cable core 15 at the portion where wrinkles 17 are formed, the proportion of the cross-sectional area of the concave portion of wrinkles 17 on the outer surface side of cable core 15 to the cross-sectional area of cable core 15 (cross-sectional area without considering wrinkles) is desirably 0.01% or more. Here, the cross-sectional area of cable core 15 is expressed as (A/2) ² ·π, where A is the outer diameter of pressure winding member 7 (see FIG. 1). Furthermore, the cross-sectional area of the concave portion of wrinkles 17 is approximated as B·C/2, where B is the width of wrinkles 17 and C is the depth (see FIG. 2). Therefore, the cross-sectional area ratio of the concave portion of wrinkles 17 (sometimes simply referred to as the cross-sectional area ratio of wrinkles 17) can be expressed as {B·C/2}/{(A/2) ² ·π}×100%.

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

One method for forming such wrinkles 17 is, for example, to change the shape or manufacturing conditions of the forming jig used for vertical wrapping. Normally, vertical wrapping is performed by sending a strip-shaped pressure winding member to the outer periphery of the core part 4 and passing it through the forming jig together with the core part 4. The forming jig gradually rolls the pressure winding member 7 from a flat state, and when it passes through the forming jig, the pressure winding member 7 is completely wrapped around the outer periphery of the core part 4.

At this time, the shape of the forming jig and the line speed are usually set so that the pressure winding member 7 is rolled gently to prevent wrinkles from forming in the pressure winding member 7. By gradually rolling the pressure winding member in this way, it is possible to roll it into a neat circle around the outer periphery of the core portion 4.

In contrast, for example, if one tries to roll the pressure winding member 7 rather abruptly, as described above, the pressure winding member 7 may not be rolled neatly due to friction between the overlapping ends, and wrinkles 17 may form in parts. In this case, because the outer periphery of the pressure winding member 7 is held down by the forming jig, the wrinkles 17 protrude toward the inner surface.

In this way, in addition to changing the shape of the forming jig, wrinkles can also be formed by increasing the line speed and thereby increasing the speed of the forming process of the pressure winding member 7. Wrinkles can also be formed in the pressure winding member 7 by adjusting the tension of the pressure string that is wrapped around the outer periphery of the pressure winding member 7. In this way, the method of forming wrinkles 17 is not particularly limited.

Figure 3(a) is a conceptual diagram showing the cable core 15 after forming. Note that the holding winding string is not shown. The wrinkles 17 formed in this way tend to be formed continuously and straight for a predetermined length in the longitudinal direction. Here, it is preferable that the wrinkles 17 are formed over the entire length, but they may also be formed partially for a predetermined length. In other words, the wrinkles 17 do not have to be formed over the entire length, but may be intermittent. Furthermore, the wrinkles 17 may be formed in multiple places in one cross section.

Furthermore, after winding the pressure winding member 7 in this manner, the cable core 15 may be further twisted. In this manner, the wrinkles 17 can be formed in a spiral shape in the longitudinal direction of the cable core 15, as shown in FIG. 3(b). In this manner, by forming the wrinkles 17 in a spiral shape in the longitudinal direction of the cable core 15, the movement of the optical fiber core 3 in the longitudinal direction can be more reliably suppressed.

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). By twisting them in the same direction, untwisting of the core portion 4 (optical fiber unit) can be suppressed when the cable core 15 is twisted.

As described above, according to this embodiment, by forming wrinkles 17 in the pressure winding member 7 and protruding toward the core portion 4, the wrinkles 17 provide resistance, suppressing the movement of the core portion 4 (optical fiber core 3) in the longitudinal direction.

In addition, by forming the wrinkles 17 in a spiral shape in the longitudinal direction, it becomes more resistant and can more efficiently suppress the movement of the core portion 4 (optical fiber 3) in the longitudinal direction.

In this way, the movement of the core portion 4 in the longitudinal direction is suppressed, so the pull-out force of the core portion 4 of the cable core 15 can be set to 3.7 kgf or more. In this way, unintended protrusion of the core portion 4 can be suppressed.

If the pull-out force of the core portion 4 of the cable core 15 exceeds 5.7 kgf, the lateral pressure on the core portion 4 is large, which may cause an increase in microbending loss. 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.

An optical fiber cable was created, and the pull-out force was measured when pulling the core part out of 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.

First, a core section with 6912 cores was formed. After twisting the core sections together, the pressure winding member was rolled and vertically wrapped with a forming jig, and 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 outer jacket were sheathed into a cylindrical shape with the outer jacket material to create an optical fiber cable.

2 m of the resulting optical fiber cable was cut out, and the outer sheath was removed over a range of 10 cm on both ends of the optical fiber cable to expose the cable core. In addition, the pressure winding member on one end of the cable core was peeled off, and the pressure winding member was fixed to the outer sheath with tape.

Next, the holding down winding member 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 (x) because the pull-out force was too small and the core portion was likely to slip out of the holding down winding member, and a pull-out force of 3.7 kgf or more was deemed to be a pass (o). The results are shown in Table 1.

After completing the pull-out force measurements, the entire outer sheath of the optical fiber cable was removed, and the outer diameter of the cable core and the width and depth of the wrinkles in the areas with the largest wrinkles were measured. The width of the wrinkles in Examples 1 to 6 was 0.5 mm to 3 mm. The maximum length of the wrinkles in the longitudinal direction was also measured.

The cross-sectional area ratio of the wrinkles was calculated as the cross-sectional area of the recesses of the wrinkles on the outer surface of the pressing and winding member relative to the cross-sectional area of the circle calculated from the outer diameter of the pressing and winding member. The cross-sectional area of the recesses was calculated as the width of the recesses x the depth / 2.

As shown in Table 1, in Examples 1 to 6, in which wrinkles were formed in the pressure winding member, the pull-out force of the core portion was 3.7 kgf or more. In contrast, in Comparative Example 1, in which wrinkles were not formed in the pressure winding member, the pull-out force was small and the sample was rejected.

Although the embodiment of the present invention has been described above with reference to the attached drawings, the technical scope of the present invention is not limited to the above-mentioned embodiment. It is clear that a person skilled in the art can come up with various modified or revised examples within the scope of the technical ideas described in the claims, and it is understood that these also naturally fall within the technical scope of the present invention.

1... Optical fiber cable 3... Optical fiber core 4... Core portion 5... Optical fiber unit 7... Presser winding member 9... Tension member 11... Tear string 13... Outer jacket 15... Cable core 17... Wrinkles

Claims (4)

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;
an outer sheath provided to cover the tension member and the cable core;
Equipped with
The cable core has a core portion formed of a plurality of optical fiber cores and a pressure winding member wound around an outer periphery of the core portion,
The pressure winding member is in contact with a part of the core portion,
A wrinkle protruding toward the core portion is formed in at least a part of the pressure wrapping member,
The wrinkles are formed in a spiral shape relative to the longitudinal direction of the cable core ,
A plurality of the optical fiber cores are twisted together to form an optical fiber unit, and the core portion is formed by twisting together a plurality of the optical fiber units,
The optical fiber cable is characterized in that the wrinkles are inserted between the optical fiber units and are formed by folding inward a portion of the excess width of the pressure winding member relative to the circumferential length of the core portion . The optical fiber cable according to claim 1, characterized in that the wrinkles have a depth of 0.2 mm or more. The optical fiber cable according to claim 1 or 2, characterized in that in a cross section perpendicular to the longitudinal direction of the cable core at the portion where the wrinkles are formed, the cross-sectional area of the recesses of the wrinkles on the outer surface side of the cable core accounts for 0.01% or more of the cross-sectional area of the cable core. The optical fiber cable according to any one of claims 1 to 3, characterized in that the pull-out 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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