JP6462507B2 - Optical fiber cable and optical fiber cable manufacturing method - Google Patents

Description

  The present invention relates to an optical fiber cable composed of a plurality of optical fiber core wires and the like.

  In recent years, with the widespread use of the Internet, FTTH (Fiber To The Home) that realizes a high-speed communication service by directly drawing an optical fiber into a general household is rapidly expanding. In general, an optical fiber cable used for FTTH accommodates a collection of optical fibers so as to be compatible with large-capacity data communication.

  As such an optical fiber cable, an optical fiber cable that does not use a slot rod and is covered with a jacket provided with two tension members has been proposed. For example, a yarn (polyester fiber, aramid fiber, PP fiber, or the like) is gathered as a buffer material on the outer periphery of the optical fiber ribbon, and a sheath is coated on the outer periphery (Patent Document 1).

  In addition, there is an optical fiber cable in which a press-wound tape is vertically attached to the outer periphery of an optical fiber ribbon, and a sheath is coated on the outer periphery (Patent Document 2).

JP 2006-337581 A JP 2001-343571 A

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

  When the bending direction of the optical fiber cable is determined in this way, the optical fiber located near the neutral axis when the optical fiber cable is bent and the optical fiber located far away from the neutral axis are Different strains on the fiber. For this reason, the transmission characteristics when the optical fiber cable is bent are different.

  As described above, when the optical fiber cable is bent, the optical fiber located near the center of the neutral axis has a small distortion and a small increase in loss, but the optical fiber located away from the neutral axis does not have tensile strain or Loss increases due to compression distortion. This increase in loss becomes particularly noticeable 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 or the like that can suppress an increase in loss when bent.

In order to achieve the above-described object, the first invention provides an optical fiber unit composed of a plurality of optical fiber cores and a cross section perpendicular to the longitudinal direction of the optical fiber cores, on the outer peripheral side of the plurality of optical fiber units. a tension member provided, the envelope provided so as to cover the tension member and the optical fiber unit, comprising a plurality of said optical fiber unit, at least, a plurality of optical fiber unit near the center of the cross section The optical fiber unit disposed in the inner layer, divided into a plurality of layers, the optical fiber unit disposed in the formed inner layer and the optical fiber unit disposed in the outer layer formed on the outer peripheral side of the inner layer and an optical fiber disposed unit the outer layer can be in contact with each other, in the cross section, the in the inner layer Than the space factor of fiber occupied, an optical fiber cable, characterized in that the lower the space factor occupied by the optical fiber in the outer layer.

  The plurality of optical fiber units may be divided into a plurality of layers of three or more layers, and the space factor occupied by the optical fiber core in each layer may decrease from the inner layer to the outermost layer.

The optical fiber core is formed by aligning a plurality of optical fiber strands, and adjacent optical fiber strands are intermittently bonded to the longitudinal direction of the optical fiber strand. It is desirable that It is desirable that the optical fiber units of each of the plurality of layers are separately twisted together.

  According to the first invention, the optical fiber unit is formed in a plurality of layers from the center side of the optical fiber cable, and the space factor occupied by the optical fiber core in the outer layer is larger than the space factor occupied by the optical fiber core in the inner layer. Is lower. For this reason, compared with an inner layer, the clearance gap between optical fiber core wires of an outer layer is large, and an optical fiber core wire moves easily within a layer. As a result, when tensile strain or compressive strain accompanying bending is applied, the stress can be relieved by moving the optical fiber core wire. In addition, since the space factor of the inner layer is high compared to the case where the overall space factor is reduced, it is possible to minimize a decrease in the space factor.

  Even if there are three or more layers, the same effect can be obtained by reducing the space factor toward the outer layer.

  Further, if the optical fiber core is an optical fiber tape and each optical fiber is intermittently bonded to the longitudinal direction, the optical fiber can freely move in the non-bonded portion. Can do. Therefore, the shape of the optical fiber core wire can be easily changed.

The second invention includes a step of twisting a plurality of optical fiber units or a plurality of optical fiber cores forming an inner layer at a central portion with a predetermined tension, and a plurality of the optical fibers forming an outer layer on the outer peripheral side of the inner layer. A step of twisting a unit or a plurality of optical fiber core wires with a predetermined tension, a step of winding a pressing member around the outer periphery of the plurality of optical fiber units or the plurality of optical fiber core wires of the outer layer, and the optical fiber core wire And arranging a tension member on the outer circumferential side of the presser winding member and providing a jacket so as to cover the tension member and the presser winding member in a cross section perpendicular to the longitudinal direction of The outer layer is formed more than the tension when the plurality of optical fiber units to be formed or the plurality of optical fiber cores are twisted together. The space factor occupied by the optical fiber core in the inner layer in a cross section perpendicular to the longitudinal direction of the optical fiber core is reduced by reducing the tension of twisting a plurality of the optical fiber units or the plurality of optical fiber cores Rather, the space factor occupied by the optical fiber in the outer layer is lowered.

  ADVANTAGE OF THE INVENTION According to this invention, the optical fiber cable etc. which can suppress the loss increase at the time of bending can be provided.

1 is a cross-sectional view showing an optical fiber cable 1; The perspective view which shows the optical fiber core wire 3. FIG. The conceptual diagram which shows the process in which the optical fiber unit 5 is twisted together. (A) is the sectional view on the AA line of FIG. 2, (b) is the sectional view on the BB line of FIG. Sectional drawing which shows the optical fiber cable 1a. 2 is a cross-sectional view showing an optical fiber cable 30. FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing an optical fiber cable 1. The optical fiber cable 1 is a slotless type optical fiber cable that does not use a slot, and includes a plurality of optical fiber cores 3, a presser winding 7, a tension member 9, a tear string 11, a jacket 13, and the like. In the following description, an assembly of a plurality of optical fiber cores 3 is simply referred to as an optical fiber unit 5, and for example, a plurality of optical fiber cores 3 may be bundled by a bundle material. The optical fiber core wires may be simply twisted together without having a material.

  On the outer periphery of the optical fiber unit 5, a presser winding 7 is provided. The presser winding 7 is disposed so as to collectively cover the plurality of optical fiber units 5 by vertical auxiliary winding. That is, the longitudinal direction of the presser winding 7 is substantially coincident with the axial direction of the optical fiber cable 1, and is vertically attached to the outer periphery of the optical fiber unit 5 so that the width direction of the presser winding 7 is the circumferential direction of the optical fiber cable 1. The

  A jacket 13 is provided on the outer periphery of the presser winding 7. The jacket 13 is a layer for covering and protecting the optical fiber cable 1. In the cross section perpendicular to the longitudinal direction of the optical fiber cable 1, a pair of tension members 9 are provided inside the jacket 13 at positions facing each other with the optical fiber unit 5 interposed therebetween. Further, a tear string 11 is provided in a direction substantially perpendicular to the opposing direction of the tension member 9 so as to face each other with the presser winding 7 interposed therebetween. The tension member 9 and the tear string 11 are embedded in the jacket 13.

  The optical fiber unit 5 is arranged in a plurality of layers. Specifically, in the cross section perpendicular to the longitudinal direction of the optical fiber cable 1, the inner side of the inner layer circumscribed circle 15 is the inner layer 15 a, the outer side of the inner layer circumscribed circle 15, and the inner surface side of the presser winding 7 is the outer layer. 17a. In other words, the plurality of optical fiber units 5 are stacked in a plurality of layers so as to be divided into an optical fiber unit 5 disposed in the inner layer 15a and an optical fiber unit 5 disposed in the outer layer 17a. The number of optical fiber units 5 arranged in each layer is not limited to the illustrated example, and it is sufficient that at least one optical fiber unit 5 is arranged in each layer.

  The inner layer circumscribed circle 15 is a circumscribed circle of a bundle of optical fiber units 5 constituting the inner layer 15a. The inner layer 15 a and the outer layer 17 a are configured by separately twisting the optical fiber units 5. Details of the twisting process of the optical fiber unit 5 will be described later.

  In the present invention, the space factor of the optical fiber core wire 3 in the outer layer 17a is lower than the space factor of the optical fiber core wire 3 in the inner layer 15a. That is, the distance between the optical fiber cores 3 in the outer layer 17a is wider than the distance between the optical fiber cores 3 in the inner layer 15a. For this reason, compared with the optical fiber core wire 3 in the inner layer 15a, the optical fiber core wire 3 in the outer layer 17a is more easily moved in the outer layer 17a.

  In addition, in order to make movement of the optical fiber core wire 3 in each layer easier, it is desirable that the optical fiber core wire 3 is a tape core wire joined intermittently.

  FIG. 2 is a perspective view showing the optical fiber core wire 3. The optical fiber core 3 is configured by bonding optical fiber strands 2a, 2b, 2c, and 2d in parallel. Note that the number of optical fiber strands constituting the optical fiber core wire 3 is not limited to the illustrated example.

  As shown in FIG. 2, in the present invention, it is desirable that the adjacent optical fiber wires 2 a, 2 b, 2 c, and 2 d are intermittently bonded to each other with a bonding portion 6 at a predetermined interval. Moreover, it is desirable that the bonding portion 6 between the adjacent optical fiber strands is disposed so as to be shifted with respect to the longitudinal direction of the optical fiber core wire 3. For example, it is desirable that the adhering portions 6 adjacent to each other be formed with a half-pitch shift in the longitudinal direction of the optical fiber core wire 3. In addition, the length and pitch of the adhesion part 6 are not restricted to the illustrated example.

  In this way, by disposing the bonding portion 6 intermittently with respect to the longitudinal direction of the optical fiber core wire 3, the adjacent optical fiber strands 2 a, 2 b, 2 c, and 2 d are connected to each other in the non-bonding portion. The fiber strands 2a, 2b, 2c, and 2d can be easily folded (folded) in the parallel direction. For this reason, the optical fiber core wire 3 can move easily in each layer.

  The space factor of the inner layer 15a is the ratio of the sum of the cross-sectional areas of all the optical fiber cores 3 constituting the inner layer 15a to the area of the inner layer circumscribed circle 15. Similarly, the space factor of the outer layer 17a is an outer layer circumscribed circle (inner peripheral surface of the presser winding 7), and all optical fibers constituting the outer layer 17a with respect to the area of the donut portion obtained by subtracting the area of the inner layer 15a. This is the ratio of the sum of the cross-sectional areas of the core wire 3.

  Next, the twisting process of the optical fiber unit 5 will be described. FIG. 3 is a conceptual diagram showing a process of twisting the optical fiber unit 5 together. In addition, although the example shown below demonstrates the method of twisting together the some optical fiber unit 5, when each layer is comprised not with several optical fiber units but with several optical fiber core wires ( That is, in the case of a single optical fiber unit), a plurality of optical fiber cores may be similarly twisted together. First, the optical fiber unit 5 is manufactured by twisting the optical fiber core wires 3 in advance and bundling them with a bundle material or the like as necessary. The obtained optical fiber unit 5 is wound around, for example, a bobbin.

  Next, the optical fiber unit 5 is twisted to form the inner layer 15a. FIG. 4A is a cross-sectional view taken along line AA in FIG. The inner layer 15a is formed by twisting each other with a predetermined tension while supplying a plurality of optical fiber units 5 from the bobbin. At this time, the circumscribed circle of the twisted optical fiber unit 5 becomes the inner layer circumscribed circle 15.

  Next, the outer periphery of the twisted inner layer 15a is twisted together with a predetermined tension while supplying a plurality of optical fiber units 5 from the bobbin. FIG. 4B is a cross-sectional view taken along line BB in FIG. Thereby, the outer layer 17a is configured. At this time, the circumscribed circle of the twisted optical fiber unit 5 becomes the outer layer circumscribed circle 17. When the optical fiber unit 5 has a two-layer structure of the inner layer 15a and the outer layer 17a, the outer layer circumscribed circle 17 substantially coincides with the inner surface of the presser winding 7 wound around the outer periphery of the outer layer 17a.

  Here, the space factor in the outer layer 17a can be made smaller than the space factor in the inner layer 15a by weakening the tension in twisting the outer layer 17a rather than the tension when twisting the inner layer 15a. That is, the space factor of each layer can be controlled by appropriately setting the tension when the optical fiber units 5 constituting each layer are twisted together.

  As described above, according to the present embodiment, the space factor of the outer layer 17a is lower than the space factor of the inner layer 15a. For this reason, the optical fiber core wire 3 of the outer layer 17a is easy to move in the cross section. As a result, even when a tensile stress or a compressive stress is generated in the optical fiber core wire 3 when the optical fiber cable 1 is bent, the stress can be relaxed by the movement of the optical fiber core wire 3.

  Further, the space factor of the inner layer 15a is sufficiently high, and in particular, the stress of the outer layer 17a that increases the tensile stress and the compressive stress is relieved, so that the loss when the optical fiber cable 1 is bent can be reduced efficiently. It is possible to suppress a decrease in the overall space factor.

  Next, a second embodiment will be described. FIG. 5 is a diagram showing the optical fiber cable 1a. In the following description, components having the same functions as those of the optical fiber cable 1 are denoted by the same reference numerals as those in FIG. In FIG. 5, for the sake of simplicity, the illustration of the optical fiber core wire 3 (optical fiber unit 5) is omitted.

  The optical fiber cable 1a has substantially the same configuration as the optical fiber cable 1, but differs in that the optical fiber unit 5 (not shown) has a three-layer structure. That is, the optical fiber unit 5 is arranged in three layers of the inner layer 15a, the middle layer 19a, and the outer layer 17a in order from the center side.

  The inner layer 15a is inside the inner layer circumscribed circle 15, the middle layer 19a is inside the middle layer circumscribed circle 19 and excludes the inner layer 15a, and the outer layer 17a is inside the presser winding 7 and is inner layer. This is a portion excluding 15a and the middle layer 19a.

  In this case, the space factor of the optical fiber core wire 3 in the middle layer 19a is lower than the space factor of the optical fiber core wire 3 in the inner layer 15a. Moreover, the space factor of the optical fiber core wire 3 in the outer layer 17a is lower than the space factor of the optical fiber core wire 3 in the middle layer 19a. That is, the space factor decreases as going to the outer peripheral side of the optical fiber cable 1a.

  In order to change the space factor in this way, the tension at the time of twisting the middle layer 19a is weakened than the tension at the time of twisting the inner layer 15a, and further, the outer layer 17a is What is necessary is just to weaken the tension at the time of twisting together. As described above, in the present invention, with respect to the optical fiber unit twisted in a plurality of layers, the decrease in the overall space factor is suppressed by decreasing the space factor of each layer from the center toward the outside. However, an increase in loss when the optical fiber cable is bent can be suppressed.

  According to the second embodiment, an effect similar to that of the first embodiment can be obtained. Thus, in the present invention, the number of layers of the optical fiber unit is not limited.

  Next, a third embodiment will be described. FIG. 6 is a diagram illustrating the optical fiber cable 30. The optical fiber cable 30 has substantially the same configuration as the optical fiber cable 1, but is different in that a support line 31 is provided. The optical fiber cable 30 is a self-supporting optical fiber cable, and the support line 31 and the cable portion are connected via a neck portion. The support wire 31 is, for example, a steel wire or the like, and is configured integrally with the cable portion (the same configuration as the optical fiber cable 1) by the jacket 13.

  Also in the optical fiber cable 30, the space factor of the optical fiber core wire 3 in the outer layer 17a is lower than the space factor of the optical fiber core wire 3 in the inner layer 15a. That is, the distance between the optical fiber cores 3 in the outer layer 17a is wider than the distance between the optical fiber cores 3 in the inner layer 15a. For this reason, compared with the optical fiber core wire 3 in the inner layer 15a, the optical fiber core wire 3 in the outer layer 17a is more easily moved in the outer layer 17a. Also in the optical fiber cable 30, the number of layers of the optical fiber unit 5 is not limited to the illustrated example.

  According to the third embodiment, the same effect as that of the first embodiment can be obtained. Thus, in the present invention, the cross-sectional structure of the optical fiber cable is not limited.

  Actually, an optical fiber cable was prepared and the space factor of each layer and the increase in loss during bending were evaluated. First, an optical fiber cable having a two-layer structure was manufactured by twisting two optical fiber units in which five pieces of four-fiber intermittent optical fiber ribbons were bundled in the inner layer and eight units in the outer layer. In addition, after twisting together the optical fiber units of each layer with a predetermined tension, the optical fiber cable shown in FIG. 1 is wound with a non-woven fabric, a polyester twisted yarn as a tear string, and a φ0.7 mm steel wire as a tension member. Manufactured. The outer diameter was 12 mm.

  Similarly, an optical fiber having a three-layer structure in which ten optical fiber units in which eight optical fiber ribbons are bundled, is twisted by 4 units for the inner layer, 9 units for the outer layer, and 12 units for the outer layer. A cable was manufactured. In addition, after twisting together the optical fiber unit of each layer with a predetermined tension, it is wound with a nonwoven fabric, the polyester twisted yarn is used as a tear string, the φ0.7 mm steel wire is used as a tension member, and the optical fiber cable shown in FIG. Manufactured. The outer diameter was 23 mm.

  Table 1 shows the space factor of each layer and the results of evaluation of increase in loss during bending.

  The space factor of each layer was adjusted by changing the tension when twisting the optical fiber unit. The increase in loss was determined by performing a bending test specified in JIS C 6851, and indicating that an increase in loss was observed as x, and the case where there was no increase in loss as ◯. The bending diameter was a bending test by winding an optical fiber cable around a circular member having a diameter shown in the table.

  No. Nos. 1 and 2 are the above-described two-layer optical fiber cables. Reference numerals 3 and 4 denote the above-described three-layer optical fiber cables. No. No. 1 has a total space factor of 52%. No. 2 has a total space factor of approximately 52%. Is equivalent to 1. No. No. 3 has a total space factor of 50%. No. 4 has a total space factor of about 50%. Is equivalent to 3.

  From the results, it can be seen that an increase in loss during bending can be suppressed by reducing the space factor on the outer layer side. At this time, since the space factor of the inner layer is high, an increase in loss can be prevented without reducing the overall space factor.

  As mentioned above, although embodiment of this invention was described referring an accompanying drawing, the technical scope of this invention is not influenced by embodiment mentioned above. It is obvious for 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 these are naturally within the technical scope of the present invention. It is understood that it belongs.

1, 1a, 30 ... Optical fiber cables 2a, 2b, 2c, 2d ... Optical fiber 3 ... Optical fiber core 5 ... Optical fiber unit 6 ... Adhesive 7 ... Presser winding 9 ... Tension member 11 ... Tear string 13 ... Outer jacket 15 ... Inner layer circumscribed circle 15a ... Inner layer 17 ... Outer layer circumscribed circle 17a ... ... Outer layer 19 ... ... Middle layer circumscribed Circle 19a ……… Middle layer 31 ………… Support line

Claims (5)

An optical fiber unit comprising a plurality of optical fiber cores;
In a cross section perpendicular to the longitudinal direction of the optical fiber core wire, tension members provided on the outer peripheral side of the plurality of optical fiber units;
A jacket provided to cover the tension member and the optical fiber unit;
Comprising
The plurality of optical fiber units are disposed at least in the optical fiber unit disposed in the inner layer formed of the plurality of optical fiber units in the vicinity of the center in the cross section and in the outer layer formed on the outer peripheral side of the inner layer. The optical fiber unit is divided into a plurality of layers,
The optical fiber unit arranged in the inner layer and the optical fiber unit arranged in the outer layer can contact each other,
In the cross section, the space factor occupied by the optical fiber core in the outer layer is lower than the space factor occupied by the optical fiber core in the inner layer. The plurality of optical fiber units are divided into a plurality of layers of three or more layers,
2. The optical fiber cable according to claim 1, wherein a space factor occupied by the optical fiber in each layer decreases from the inner layer to the outermost layer. The optical fiber core wire is formed by aligning a plurality of optical fiber strands,
The optical fiber cable according to claim 1 or 2, wherein adjacent optical fiber strands are optical fiber tape core wires bonded intermittently with respect to the longitudinal direction of the optical fiber strands. . The optical fiber cable according to any one of claims 1 to 3, wherein the optical fiber units of each of the plurality of layers are individually twisted together. A step of twisting a plurality of optical fiber units or a plurality of optical fiber cores forming an inner layer of the central portion with a predetermined tension;
Twisting together a plurality of the optical fiber units or a plurality of optical fiber cores forming an outer layer on the outer peripheral side of the inner layer with a predetermined tension;
Winding a holding member around the outer circumference of the plurality of optical fiber units or the plurality of optical fiber cores of the outer layer;
In a cross section perpendicular to the longitudinal direction of the optical fiber core wire, a tension member is disposed on the outer peripheral side of the presser winding member, and a jacket is provided so as to cover the tension member and the presser winding member;
Comprising
The tension for twisting the plurality of optical fiber units or the plurality of optical fiber cores forming the outer layer is higher than the tension for twisting the plurality of optical fiber units or the plurality of optical fiber cores forming the inner layer. By making it smaller, the space factor occupied by the optical fiber core in the outer layer is smaller than the space factor occupied by the optical fiber core in the inner layer in a cross section perpendicular to the longitudinal direction of the optical fiber core. The manufacturing method of the optical fiber cable characterized by making low.

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