JP5568071B2 - Fiber optic cable - Google Patents

Description

  The present invention relates to an optical fiber cable.

  In recent years, there has been a growing demand for thinner diameters, multi-cores, and ease of intermediate branching work, and a cable core in which optical fibers are bundled at the center of an optical fiber cable is mounted, and a pair of lip cords ( A structure in which a tearing string is arranged has been proposed.

  In such an optical fiber cable, when an impact or a side pressure is applied, the lip cord may be peeled off from the jacket and dropped into the cable core. And an optical fiber is inserted | pinched in the clearance gap between a lip cord and a jacket, and it causes the disconnection of an optical fiber and the increase in transmission loss (for example, refer patent document 1 and 2).

  In order to prevent such a lip cord from falling off, a plurality of protective tapes having a width smaller than the outer circumference of the cable core are vertically attached to the outer periphery of the cable core so that the ends of the cable cores overlap each other. A structure has been proposed in which the cable core is wrapped and pressed (see, for example, Patent Document 3).

JP 2002-341212 A JP 2008-292841 A JP 2009-237341 A

  However, in the case of the structure described in Patent Document 3, a device for supplying a plurality of protective tapes is necessary, it is difficult to precisely overlap the ends of the protective tapes, or when the cable is bent In addition, there is a problem in that the position of the protective tape disposed outside the bend is shifted to the inside of the bend, so that the same portion does not play a protective role.

  In view of the above-described problems, the object of the present invention is to prevent the lip cord from falling into the cable core when a side pressure or impact is applied, resulting in an increase in optical fiber breakage and transmission loss. It is to provide an optical fiber cable that can be prevented.

  According to one aspect of the present invention, a cable core in which a plurality of optical fibers are assembled, a pair of lip cords arranged to face each other across the cable core, and a direction orthogonal to a straight line connecting the pair of lip cords A pair of strength members that are placed facing each other across the cable core, and a width that is wider than the circumference of the outer periphery of the cable core and that wraps around the outer circumference of the cable core, and is on a straight line that connects the pair of lip cords An optical fiber cable comprising: a first protective tape having an outer seam at a position different from that of the first protective tape; and an outer periphery of the first protective tape, a pair of strength members, and a jacket covering the pair of lip cords together. Provided.

  In one aspect of the present invention, the joint of the first protective tape may be disposed at a position farthest from both of the pair of lip cords on the outer periphery of the cable core.

  In one aspect of the present invention, the jacket may be formed directly on the first protective tape.

  In one embodiment of the present invention, a slit may be formed in the first protective tape in a direction orthogonal to the length direction of the first protective tape or in an oblique direction.

  In one embodiment of the present invention, the slit may be arranged at 30 ° to 90 ° with respect to the length direction of the first protective tape.

  In one aspect of the present invention, a second protective tape having a width wider than the peripheral length of the outer periphery of the cable core and disposed so as to wrap the outer periphery of the cable core between the first protective tape and the cable core. Furthermore, you may provide.

  According to the present invention, it is possible to prevent the lip cord from falling into the cable core when a side pressure or impact is applied, and to prevent an optical fiber from being disconnected or an increase in transmission loss due to this. A fiber cable can be provided.

It is sectional drawing which shows an example of the optical fiber cable which concerns on embodiment of this invention. It is the schematic of the prototype of the optical fiber cable which concerns on embodiment of this invention. It is a table | surface showing the test result of the side pressure test which concerns on embodiment of this invention. It is a table | surface showing the test result of the impact test which concerns on embodiment of this invention. It is sectional drawing before the repeated bending test of the optical fiber cable which concerns on a comparative example. It is a table | surface showing the test result of the side pressure test after the repeated bending test which concerns on embodiment and comparative example of this invention. It is a table | surface showing the test result of the impact test after the repeated bending test which concerns on embodiment and comparative example of this invention. It is sectional drawing after the repeated bending test of the optical fiber cable which concerns on a comparative example. It is sectional drawing which shows an example of the protective tape which concerns on the 1st modification of embodiment of this invention. It is a table | surface showing the test result of the impact test of the optical fiber cable which concerns on the 1st modification of embodiment of this invention. It is sectional drawing which shows an example of the optical fiber cable which concerns on the 2nd modification of embodiment of this invention.

  Next, embodiments of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic, and the relationship between the thickness and the planar dimensions, the ratio of the thickness of each layer, and the like are different from the actual ones. Therefore, specific thicknesses and dimensions should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

  Further, the embodiments described below exemplify apparatuses and methods for embodying the technical idea of the present invention, and the technical idea of the present invention includes the material, shape, structure, The layout is not specified as follows. The technical idea of the present invention can be variously modified within the scope of the claims.

(Structure of optical fiber cable)
As shown in FIG. 1, an optical fiber cable according to an embodiment of the present invention includes a cable core 1 in which a plurality of optical fibers are gathered, and a pair of lip cords (see FIG. A pair of strength members (tension members) 3a, 3b disposed opposite to each other with the cable core 1 sandwiched in a direction orthogonal to a straight line L1 connecting the pair of lip cords 4a, 4b, and a cable The outer circumference of the core 1 is wider than the outer circumference of the core 1 and is arranged so as to wrap around the outer circumference of the cable core 1 and has an outer joint 5a at a position different from the straight line L1 connecting the pair of lip cords 4a and 4b. A first protective tape 5 and an outer sheath (sheath) 2 that collectively covers the outer periphery of the first protective tape 5, the pair of strength members 3a and 3b, and the pair of lip cords 4a and 4b.

  The cable core 1 may be configured by aggregating a plurality of optical fibers, or may be configured by aggregating a plurality of optical fiber units obtained by aggregating a plurality of optical fibers. As the optical fiber, an optical fiber, an optical fiber, an optical fiber tape, or the like can be used. The diameter of the cable core 1 is about 3 mm, for example.

  The outer cover 2 is directly formed on the protective tape 5 without rough winding (raw winding). As the material of the outer jacket 2, a resin such as high density polyethylene (HDPE) can be used.

  The strength members 3a and 3b are arranged on a straight line L2 orthogonal to the straight line L1 and extend in the longitudinal direction of the cable core 1. As the strength members 3a and 3b, metal wires such as steel wires or fiber reinforced plastics (FRP) can be used.

  The lip cords 4 a and 4 b are partially or entirely embedded on the inner surface side of the jacket 2 so as to extend in the longitudinal direction of the cable core 1. As the lip cords 4a and 4b, a twisted yarn made of polyester, a fiber cord such as an aramid fiber or glass fiber, or the like can be used.

  The protective tape 5 has a width of about 12 mm, for example, and a thickness of about 0.012 mm to 0.100 mm. As a material of the protective tape 5, a thermoplastic resin such as polyethylene (PE), polypropylene (PP), polyester, polybutylene terephthalate (PBT) or nylon, or a thermosetting resin such as epoxy can be used.

  The protective tape 5 has an overlapping portion and is arranged in a cylindrical shape. The outer joint (end) 5a of the protective tape 5 is arranged on a straight line L2 farthest from both the lip cords 4a and 4b on the outer periphery of the cable core 1. In addition, the position of the joint line (end part) 5b inside the protective tape 5 is not particularly limited.

  The ratio (lap ratio) of the area of the overlapping portion to the surface area of the protective tape 5 is not particularly limited. The wrap rate is, for example, greater than 0% and not greater than 25%, preferably greater than 0% and not greater than 10%, and more preferably greater than 0% and not greater than 5%. The lower the wrap rate, the lower the material cost and the better the optical fiber take-out performance in the intermediate post-branching operation.

  According to the optical fiber cable according to the embodiment of the present invention, since the cable core 1 is wrapped with the single protective tape 5, the lip cords 4a and 4b are peeled off from the jacket 2 when a side pressure or an impact is applied. Even in this case, it is possible to prevent the cable core 1 from dropping out due to the protective tape 5 interposed. Further, by arranging the outer joint 5a of the protective tape 5 at a position different from the straight line L1 connecting the pair of lip cords 4a and 4b, the dropped lip cords 4a and 4b are less likely to enter the inner side from the joint 5a. be able to. As a result, it is possible to prevent disconnection of the optical fiber and increase in transmission loss due to the drop of the lip cords 4a and 4b.

  Further, by arranging the outer joint 5a of the protective tape 5 farthest from both the lip cords 4a and 4b on the outer periphery of the cable core 1, the dropped lip cords 4a and 4b enter the inner side from the joint 5a. This can be further prevented.

(Optical fiber cable manufacturing method)
Next, an example of the manufacturing method of the optical fiber cable which concerns on embodiment of this invention is demonstrated.

  First, the cable core 1 is formed by assembling a plurality of optical fibers or a plurality of optical fiber units. Then, the protective tape 5 having a width wider than the outer periphery of the cable core 1 is bent into a cylindrical shape and vertically attached so as to wrap the outer periphery of the cable core 1. At the same time, the outer cover 2 covering the outer periphery of the protective tape 5 enclosing the cable core 1 is formed by extrusion molding. At this time, the lip cords 4 a and 4 b and the strength members 3 a and 3 b are also embedded in the outer cover 2.

  Here, when the protective covering 5 is vertically attached to the cable core 1 and then covered with a jacket, in order to hold the pressed and wound shape until the jacket is formed, rough winding with a nylon thread or the like is performed. (Unwrapped) is required. On the other hand, if the press-winding with the protective tape 5 is performed simultaneously with the formation of the outer cover 2, the rough winding of the outer periphery of the protective tape 5 becomes unnecessary. Therefore, it is possible to prevent an increase in transmission loss due to the cable core 1 being tightened by rough winding.

<Side pressure test>
As an optical fiber cable according to the embodiment of the present invention, an optical fiber cable in which the position of the outer joint 5a of the protective tape 5 was changed was prototyped, and a lateral pressure test based on IEC60794-1 was performed. The cable core 1 was formed by collecting 100 optical fiber strands (equivalent to ITU-T G.657.A) having a diameter of 250 μm, and the diameter was 3.4 mm. High density polyethylene (HDPE) was used as the material of the jacket 2, and the thickness of the jacket 2 was 1.8 mm. As the lip cords 4 a and 4 b, Tetron (registered trademark) yarns were built in the outer jacket 2 so as to be in contact with the protective tape 5. As the strength members 3a and 3b, steel wires having a diameter of 0.7 mm were used. As the protective tape 5, polyethylene terephthalate (PET) having a thickness of 0.05 mm and a width of 12 mm was used. The press winding with the protective tape 5 was performed simultaneously with the formation of the outer cover 2.

  As shown in FIG. 2, the angle formed by the straight line L3 connecting the center C of the cable core 1 and the joint 5a on the outside of the protective tape 5 with respect to the straight line L1 connecting the center C of the cable core 1 and the lip cord 4b. The angle θ1 was changed by moving the joint 5a along the outer periphery of the cable core 1 to θ1. A counterclockwise direction with respect to the center C of the cable core 1 is defined as a positive direction, and a clockwise direction is defined as a negative direction.

  FIG. 3 shows the test results. In the side pressure test, there was no significant difference between the angle θ1 and the side pressure characteristics.

<Impact test>
As the optical fiber cable according to the embodiment of the present invention, the same prototype as that used in the lateral pressure test was prototyped and an impact test based on IEC 60794-1 was performed.

  FIG. 4 shows the test results. It can be seen that the frequency of increase in loss decreases as the absolute value of the angle θ1 increases. This is because the more the seam 5a is in the vicinity of the lip cord 4b, the more easily the lip cord 4b enters from the seam 5a of the protective tape 5 instantaneously when an impact is applied, and the frequency of increase in loss increases. is there.

  Therefore, in order to reduce the occurrence frequency of the loss increase, it is preferable that the joint 5a is positioned far from both the pair of lip cords 4a and 4b on the outer periphery of the cable core 1. In the structure of FIG. 2, the angle θ1 is preferably in the range of 30 ° to 90 ° and −30 ° to −90 °, and the angle θ1 is in the range of 45 ° to 90 ° and −45 ° to −90 °. It is more preferable that the angle θ1 is a position of ± 90 °.

<Repeated bending test>
As the optical fiber cable according to the embodiment of the present invention, the same prototype as that used in the lateral pressure test was prototyped and subjected to a repeated bending test, and then a lateral pressure test and an impact test were performed. In the repeated bending test, bending with the straight line L3 perpendicular to the straight line L1 passing through the center C of the cable core 1 shown in FIG. 2 is repeated 10 times at a bending radius of 240 mm and a bending angle of ± 90 °. It was.

  Further, as a comparative example, as shown in FIG. 5, four protective tapes 105 a, 105 b, 105 c, and 105 d each having a width of 4 mm are attached to the outer periphery of the cable core 101 and vertically wound, and the others This structure was made in the same manner as the prototype according to the embodiment of the present invention. An outer cover 102 is formed outside the protective tapes 105a, 105b, 105c, and 105d. A pair of strength members 103a and 103b and a pair of lip cords 104a and 104b are disposed inside the outer jacket 102. A straight line connecting the pair of strength members 103a and 103b was defined as a cable bending neutral line. In addition, about the comparative example, the side pressure test and the impact test were each implemented with respect to what performed the bending test repeatedly, and what did not.

  6 and 7 show the test results of the lateral pressure characteristics and the impact characteristics after the repeated bending test, respectively. In the optical fiber cable according to the embodiment of the present invention, there is no change in both the side pressure characteristics and the impact characteristics as compared to the side pressure characteristics and the impact characteristics when the repeated bending test shown in FIGS. 3 and 4 is not performed. It was. In addition, when the loss increase shown in FIG. 7 occurred, it was observed that the internal optical fiber was sandwiched between the lip cords 4b in any case.

  On the other hand, in the comparative example, as shown in FIG. 7, the impact characteristics after the repeated bending test deteriorated. When the inside of the optical fiber cable was confirmed, as shown in FIG. 8, the protective tapes 105a, 105b, 105c, and 105d moved in the direction of the cable bending neutral line L4 perpendicular to the straight line connecting the lip cords 104a and 104b. It was observed that portions where the protective tapes 105a, 105b, 105c, and 105d were not present were formed immediately below the cords 104a and 104b, and the lip cords 104a and 104b sandwiched the optical fiber at such portions.

(First modification)
In the optical fiber cable according to the embodiment of the present invention, since the entire outer periphery of the cable core 1 is wrapped with one protective tape 5, the cable core 1 inside the protective tape 5 is configured in the intermediate post-branching operation. It is not easy to take out the optical fiber, and the optical fiber may be damaged at the time of taking out, which may cause an increase in loss.

  Therefore, in the optical fiber cable according to the first modification of the embodiment of the present invention, as shown in FIG. 9, the protective tape 5 is provided with slits (broken line cuts) 7 obliquely with respect to the longitudinal direction. Yes. The angle θ2 formed between the slit 7 and the length direction of the protective tape 5 may be a direction orthogonal to the longitudinal direction or an oblique direction, and more preferably about 30 ° to 90 °. The slits 7 are repeatedly provided at a predetermined interval on the protective tape 5. The slits 7 may be provided over both ends of the protective tape 5 in the width direction, or may be provided in a part of the width direction. Moreover, many fine slits may be provided in the length direction at both ends in the width direction.

  According to the optical fiber cable according to the first modification of the embodiment of the present invention, the protective tape 5 is easily disassembled from the slit 7 as a starting point in the intermediate post-branching operation by forming the slit 7 in the protective tape 5. And the optical fiber can be easily taken out.

  As an optical fiber cable according to the first modification of the embodiment of the present invention, an optical fiber cable having a different angle θ2 formed with the length direction of the protective tape 5 of the slit 7 was prototyped and subjected to an impact test. FIG. 10 shows the test results. In the impact characteristics, the frequency of loss increase depends on the angle θ2, and the loss increase occurred in the sample of 30 ° or less with a small angle θ2. Where the loss increases, the lip cords 4a and 4b and the slit 7 are in the vicinity of the same position. The lip cords 4a and 4b break the slit 7, and the optical fiber is sandwiched between the lip cords 4a and 4b. Has been confirmed.

(Second modification)
As shown in FIG. 11, the optical fiber cable according to the second modification of the embodiment of the present invention has a width wider than the circumference of the cable core 1, and the cable core 1 and the protective tape (first The optical fiber cable according to the embodiment of the present invention is further provided with a cylindrical protective tape (second protective tape) 6 provided so as to wrap the cable core 1 between the optical fiber cable and the protective fiber). Different.

  As the material of the second protective tape 6, the same material as that of the first protective tape 5 can be used. The positions of the outer joint 6a and the inner joint 6b of the second protective tape 6 are not particularly limited.

  According to the optical fiber cable according to the second modification of the embodiment of the present invention, the heat shielding property and the mechanical strength can be enhanced by wrapping with the plurality of protective tapes 5 and 6. Furthermore, by distinguishing each of the plurality of protective tapes 5 and 6, the discriminability of the optical fiber cable can be improved.

  In the second modification of the embodiment of the present invention, the structure having one second protective tape 6 between the cable core 1 and the first protective tape 5 has been described. You may have a protective tape.

(Other embodiments)
As described above, the present invention has been described according to the embodiment. However, it should not be understood that the description and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  For example, in the optical fiber cable shown in FIG. 11, slits may be formed in the first protective tape 5 in a direction orthogonal to the longitudinal direction or in an oblique direction. Further, slits may be formed in the second protective tape 6 in a direction orthogonal to the longitudinal direction or in an oblique direction.

  As described above, the present invention naturally includes various embodiments not described herein. Therefore, the technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the above description.

DESCRIPTION OF SYMBOLS 1 ... Cable core 2 ... Jacket | cover 3a, 3b ... Strength body 4a, 4b ... Lip code 5, 6 ... Protective tape 5a, 5b, 6a, 6b ... Joint 7 ... Slit

Claims (4)

A cable core that aggregates multiple optical fibers;
A pair of lip cords arranged opposite to each other across the cable core;
A pair of strength members disposed opposite to each other across the cable core in a direction perpendicular to a straight line connecting the pair of lip cords;
1st which has a width | variety wider than the perimeter of the outer periphery of the said cable core, is arrange | positioned so that the outer periphery of the said cable core may be wrapped, and has an outer joint at the position different from the straight line which connects a pair of said lip cord Protective tape,
An outer cover that collectively covers the outer periphery of the first protective tape, the pair of strength members, and the pair of lip cords ;
A second protective tape having a width wider than a peripheral length of the outer periphery of the cable core and disposed so as to wrap the outer periphery of the cable core between the first protective tape and the cable core;
An optical fiber cable, wherein both ends of the first protective tape are overlapped to form the seam, and the seam is directly covered with the jacket.   2. The optical fiber cable according to claim 1, wherein a seam of the first protective tape is disposed at a position farthest from both of the pair of lip cords on an outer periphery of the cable core.   3. The optical fiber cable according to claim 1, wherein a slit is formed in the first protective tape in a direction perpendicular to or oblique to a length direction of the first protective tape. 4. . The optical fiber cable according to claim 3 , wherein the slit is disposed at 30 ° to 90 ° with respect to the length direction of the first protective tape.

Images