Optical fiber cable

Abstract

To provide an optical fiber cable having excellent laying working efficiency and handling properties.SOLUTION: An optical fiber cable 1 is for example a slotless type cable without using any slots, and is constituted of a core 3, tension members 5, a covering 7, and the like. The core 3 comprises multiple optical fiber conductors. Multiple tension members 5 are provided around the core 3. The tension member 5 bears tension of the optical fiber cable 1. The covering 7 is provided in the outer periphery of the core 3 and the core 3 is covered with the covering 7. Multiple recesses 9 are formed nearly at an equal interval in a circumferential direction on an outer peripheral surface of the covering 7 on a section vertical to the axial direction of the optical fiber cable 1. The recesses 9 are formed intermittently relative to the axial direction of the optical fiber cable 1.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an optical fiber cable comprising a plurality of optical fiber core wires. [Background technology]

[0002] In order to efficiently lay optical fiber cables in ducts, etc., development of blown cables for pressure feeding is progressing. Such blown cables lay optical fiber cables in ducts by feeding the optical fiber cable into the duct with a pushing unit while sending compressed air into the duct.

[0003] For such optical fiber cables, a method has been proposed in which multiple protrusions are provided on the outer surface of the jacket to reduce the contact area with the inner surface of the duct and thereby reduce frictional resistance (Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2021-018338 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the shape of the convex portion of a conventional optical fiber cable, a corner portion is formed at the boundary between the concave portion and the convex portion (the base of the convex portion).

[0006] 14 is a diagram showing a conventional optical fiber cable 100. In the optical fiber cable 100, the core 103 and the tension members 105 are covered with the jacket 107, and as described above, the convex portions 111 and the concave portions 109 are formed alternately in the circumferential direction on the outer periphery of the jacket 107. In other words, the concave portions 109 are formed between the convex portions 111.

[0007] Here, the recess 109 excluding the protrusion 111 is substantially circular, and the protrusion 111 is formed to protrude from the outer periphery of this circle. Therefore, a corner (X in the figure) is formed at the boundary between the protrusion 111 and the recess 109 (the base of the protrusion 111). At such a corner (the intersection of curves in different directions, the concave direction and the convex direction, or a portion with a large change in curvature), stress is likely to concentrate when the optical fiber cable is bent. Therefore, if corners are continuous in the longitudinal direction, they can cause damage to the optical fiber cable.

[0008] The present invention has been made in view of the above problems, and has as its object to provide an optical fiber cable that is easy to install and handle. [Means for solving the problem]

[0009] In order to achieve the above-mentioned object, the present invention provides an optical fiber cable comprising a core consisting of a plurality of optical fiber core wires, an outer sheath covering the core, and a tension member that bears tension, wherein a plurality of recesses or protrusions are formed circumferentially on the outer surface of the outer sheath, and the recesses or protrusions are formed intermittently in the axial direction of the optical fiber cable.

[0010] A plurality of recesses may be formed on the outer peripheral surface of the outer jacket, and the ratio of the total surface area of ​​the recesses to the outer surface area of ​​the outer jacket when the outer jacket is unfolded may be 35% or more and 75% or less.

[0011] In this case, it is desirable that the depth of the recess is greater than 0.2 mm and the minimum thickness of the jacket at the recess is greater than 1.0 mm.

[0012] In a cross section perpendicular to the axial direction of the optical fiber cable, it is desirable that the circumferential spacing between the plurality of recesses is 0.3 mm or more and 1 / 3 or less of the cable diameter in areas other than the recesses.

[0013] The recesses are preferably arranged discontinuously on a straight line in the axial direction of the optical fiber cable, and the distance between the recesses in the axial direction of the optical fiber cable is preferably 5 mm or more and 30 mm or less.

[0014] In a cross section perpendicular to the axial direction of the optical fiber cable, the recesses are preferably arranged at approximately equal intervals in the circumferential direction.

[0015] A plurality of the protrusions may be formed in the circumferential direction on the outer peripheral surface of the outer jacket, and the ratio of the total surface area of ​​the protrusions to the outer surface area of ​​the outer jacket when the outer jacket is unfolded may be 25% or more and 65% or less.

[0016] In this case, it is desirable that the height of the protrusion be greater than 0.1 mm.

[0017] In a cross section perpendicular to the axial direction of the optical fiber cable, it is desirable that the circumferential spacing between the multiple convex portions is 0.1 mm or more and 1 / 4 or less of the cable diameter in areas other than the convex portions.

[0018] It is desirable that the convex portions are arranged discontinuously on a straight line with respect to the axial direction of the optical fiber cable, and that the distance between the convex portions in the axial direction of the optical fiber cable is 5 mm or more and 30 mm or less.

[0019] In a cross section perpendicular to the axial direction of the optical fiber cable, the protrusions are preferably arranged at approximately equal intervals in the circumferential direction.

[0020] A plurality of dimple-shaped recesses may be formed at predetermined intervals over the entire outer peripheral surface of the jacket.

[0021] In this case, it is desirable that the depth of the recess be 0.1 mm or more.

[0022] The optical fiber may be an intermittently bonded optical fiber ribbon in which a plurality of optical fibers are arranged in parallel and intermittently bonded in the longitudinal direction.

[0023] According to the present invention, since a plurality of recesses or protrusions are formed in the circumferential direction, the contact area with the duct or the like is reduced, and the same effect as that of a conventional optical fiber cable with protrusions can be obtained. Furthermore, since the recesses or protrusions are formed intermittently in the axial direction of the optical fiber cable, the corners as described above are not continuous in the longitudinal direction of the optical fiber cable. Therefore, damage to the optical fiber cable during installation or handling can be suppressed.

[0024] In addition, when multiple recesses are formed on the outer surface of the outer jacket, efficient pumping can be achieved by setting the ratio of the total surface area of ​​the recesses to the outer surface area of ​​the outer jacket when the outer jacket is unfolded to be 35% or more and 75% or less.

[0025] Furthermore, by making the depth of the recess greater than 0.2 mm and making the minimum thickness of the outer jacket at the recess greater than 1.0 mm, it is possible to prevent an increase in the contact area due to deformation of areas other than the recess during pumping, which would otherwise cause an increase in frictional resistance, while also ensuring the strength of the outer jacket.

[0026] Furthermore, by making the circumferential spacing between multiple recesses 0.3 mm or more in a cross section perpendicular to the axial direction of the optical fiber cable and making it 1 / 3 or less of the cable diameter in areas other than the recesses, deformation in areas other than the recesses can be suppressed, and the contact area can be efficiently reduced, thereby reducing frictional resistance.

[0027] In addition, by arranging the recesses intermittently in a straight line in the axial direction of the optical fiber cable and setting the spacing between the recesses arranged in the longitudinal direction to be 5 mm or more and 30 mm or less, the contact area can be efficiently reduced, thereby reducing frictional resistance.

[0028] Furthermore, by arranging the recesses at approximately equal intervals in the circumferential direction in a cross section perpendicular to the axial direction of the optical fiber cable, the contact area can be efficiently reduced, thereby reducing frictional resistance.

[0029] Furthermore, when multiple protrusions are formed circumferentially on the outer peripheral surface of the outer jacket, efficient pumping can be achieved by setting the ratio of the total surface area of ​​the protrusions to the outer surface area of ​​the outer jacket when unfolded to be 25% or more and 65% or less.

[0030] Furthermore, by making the height of the convex portions greater than 0.1 mm, it is possible to suppress an increase in the contact area due to deformation of the convex portions during pumping, which in turn suppresses an increase in frictional resistance.

[0031] Furthermore, by making the circumferential spacing between multiple convex portions 0.1 mm or more in a cross section perpendicular to the axial direction of the optical fiber cable and making it 1 / 4 or less of the cable diameter in areas other than the convex portions, deformation of the convex portions can be suppressed and the contact area can be efficiently reduced, thereby reducing frictional resistance.

[0032] In addition, by arranging the convex portions intermittently in a straight line in the axial direction of the optical fiber cable and setting the spacing between the convex portions arranged in the longitudinal direction to 5 mm or more and 30 mm or less, the contact area can be efficiently reduced, thereby reducing frictional resistance.

[0033] Furthermore, by arranging the protrusions at approximately equal intervals in the circumferential direction in a cross section perpendicular to the axial direction of the optical fiber cable, the contact area can be efficiently reduced, thereby reducing frictional resistance.

[0034] The same effect can also be achieved by forming a plurality of dimple-shaped recesses at predetermined intervals over the entire outer peripheral surface of the jacket.

[0035] In this case, by making the depth of the recesses 0.1 mm or more, it is possible to suppress an increase in the contact area due to deformation of parts other than the recesses during pumping, and an increase in frictional resistance. [Effects of the Invention]

[0036] According to the present invention, an optical fiber cable that is excellent in laying workability and handling ability can be provided. [Brief explanation of the drawings]

[0037] [Figure 1] FIG. 1 is an external view of an optical fiber cable 1. [Figure 2] 1 is a cross-sectional view of an optical fiber cable 1. FIG. [Figure 3] FIG. [Figure 4] 2 is a development view of the jacket 7 of the optical fiber cable 1. FIG. [Figure 5] FIG. 10 is a diagram showing another arrangement of the recesses 9. [Figure 6] FIG. 2 is an external view of an optical fiber cable 1a. [Figure 7] FIG. 2 is a cross-sectional view of the optical fiber cable 1a. [Figure 8] FIG. [Figure 9] FIG. 2 is a development view of the jacket 7 of the optical fiber cable 1a. [Figure 10] 10 is a development view of the jacket 7 of another optical fiber cable. [Figure 11] FIG. [Figure 12] 1 is a schematic diagram showing a method for performing a pressure test on an optical fiber cable 15. FIG. [Figure 13] FIG. 3 is a diagram showing the shape of a pipe 13. [Figure 14] 1 is a diagram showing the shape of a conventional optical fiber cable 100. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0038] Hereinafter, an embodiment of the first invention will be described with reference to the drawings. Fig. 1 is an external view of an optical fiber cable 1, and Fig. 2 is a cross-sectional view perpendicular to the axial direction of the optical fiber cable 1 (cross-sectional view taken along line AA in Fig. 1). The optical fiber cable 1 is, for example, a slotless cable that does not use slots, and is composed of a core 3, a tension member 5, an outer jacket 7, etc.

[0039] The core 3 is made up of a plurality of optical fiber cores. More specifically, a plurality of optical fiber cores are twisted together to form an optical fiber unit, and a plurality of optical fiber units are further twisted together to form the core 3. The optical fiber core may be, for example, an intermittently bonded optical fiber ribbon in which a plurality of optical fibers are arranged in parallel and bonded intermittently in the longitudinal direction.

[0040] A pressure winding member is provided on the outer periphery of the core 3. The pressure winding member is a tape-like member, a nonwoven fabric, or the like, and is wound longitudinally around the outer periphery of the core 3 so that, for example, its width direction coincides with the circumferential direction of the optical fiber cable 1. The pressure winding member is not necessarily required, and the core 3 may include the pressure winding member.

[0041] In a cross section perpendicular to the longitudinal direction of the optical fiber cable 1, tension members 5 are provided at locations facing each other with the core 3 at the center. The tension members 5 bear the tension of the optical fiber cable 1. There are no particular restrictions on the material of the tension members 5, but examples that can be used include fiber-reinforced plastics (FRP) made from aramid fiber, glass fiber, etc.

[0042] An outer sheath 7 is provided on the outer periphery of the core 3, and the core 3 is covered by the outer sheath 7. Note that tear cords (not shown) are provided at circumferential positions different from the tension members 5, facing each other across the core 3. In other words, the outer sheath 7 is provided so as to cover the core 3, the tension members 5, the tear cords, etc.

[0043] In a cross section perpendicular to the axial direction of the optical fiber cable 1, a plurality of recesses 9 are formed at approximately equal intervals in the circumferential direction on the outer peripheral surface of the jacket 7. As shown in Fig. 1, the recesses 9 are formed intermittently in the axial direction of the optical fiber cable 1. Note that the number and cross-sectional shape of the recesses 9 are not limited to the example shown, but for example, approximately 6 to 20 recesses 9 are formed in the circumferential direction. Furthermore, the shape of the recesses 9 may be, for example, approximately rectangular as shown in the figure, or may be arc-shaped.

[0044] The material of the outer jacket 7 is not particularly limited, but may be, for example, a polyolefin resin, such as LDPE (low density polyethylene) or HDPE (high density polyethylene). Considering the strength of the protrusions 11, the protrusions 11 may be made of a resin with an elastic modulus of 1000 MPa or more, and the material of the outer jacket 7 may be, for example, PP (polypropylene) or (PBT) polybutylene terephthalate.

[0045] 3 is an enlarged cross-sectional view of the recess 9. The circumferential width (C in the figure) of the recess 9 is preferably about 1.5 to 4.0 mm, for example. The range of the recess 9 is the range surrounded by the boundary of an imaginary circle (dotted line portion) that circumscribes the area other than the recess 9.

[0046] Furthermore, it is desirable that the depth of the recess 9 (the maximum depth from the aforementioned imaginary circle to the bottom surface of the recess 9, D in the figure) be greater than 0.2 mm. If the depth of the recess 9 is 0.2 mm or less, the effect of providing the recess 9 will be small and manufacturability will be impaired. It is also desirable that the minimum thickness of the outer jacket 7 at the recess 9 (E in the figure) be greater than 1.0 mm. If the minimum thickness of the outer jacket 7 is 1.0 mm or less, the strength of the outer jacket 7 will be insufficient and there is a risk of breakage.

[0047] 4 is a development view of the jacket 7 of the optical fiber cable 1. That is, it is a plan view of the state in which the surface of the optical fiber cable 1 is cut in the axial direction and opened into a flat surface. That is, the up-down direction in FIG. 4 (G in the figure) corresponds to the circumferential direction of the optical fiber cable 1, and the left-right direction in FIG. 4 (H in the figure) corresponds to the axial direction of the optical fiber cable 1.

[0048] As shown in the figure, the recesses 9 are arranged at approximately equal intervals in the circumferential direction. In this case, it is desirable that the circumferential interval between the plurality of recesses 9 (F in the figure) is 0.3 mm or more. If the distance between the recesses 9 is too narrow, deformation of the corresponding portion is likely to occur. Furthermore, it is desirable that the circumferential interval between the plurality of recesses 9 (F in the figure) is 1 / 3 or less of the cable diameter (B in Figure 2) in the portion other than the recesses 9. If the interval between the recesses 9 is too wide, the effect of reducing the contact area is reduced, and there is a risk that the pumping distance will decrease.

[0049] Furthermore, each recess 9 is arranged intermittently at a predetermined interval in a straight line with respect to the axial direction of the optical fiber cable 1. In this case, the longitudinal length of the recess 9 (J in the figure) is not particularly limited, but is, for example, 10 mm or more and 50 mm or less. Furthermore, it is desirable that the distance between the recesses 9 in the axial direction of the optical fiber cable 1 (I in the figure) be 5 mm or more and 30 mm or less. In this way, the pumping distance can be efficiently extended and the influence of the corners described above can be reduced.

[0050] Furthermore, it is desirable that the ratio of the total surface area of ​​the recesses 9 to the outer surface area of ​​the jacket 7 when it is unfolded be 35% or more and 75% or less. For example, if the recesses 9 are repeatedly formed at a predetermined pitch in the axial direction of the optical fiber cable 1, it is desirable that the ratio of the total area of ​​the recesses 9 (hatching L in the figure) to the outer surface area of ​​the jacket 7 in one period (hatching K+L in the figure) be 35% or more and 75% or less.

[0051] By setting the shape of the recess 9 in this way, a sufficient pumping distance can be ensured.

[0052] 4, all of the recesses 9 that are adjacent in the circumferential direction are arranged at the same position in the axial direction of the optical fiber cable 1. That is, all of the recesses 9 are arranged in the range indicated by J in the figure, and no recesses 9 are formed in the circumferential direction in the range indicated by I in the figure.

[0053] In contrast, Fig. 5 is a development view of a state in which the recesses 9 are arranged in a staggered pattern in the longitudinal direction. In this case, for example, the recesses 9 may be arranged so that there is always a recess 9 at any position in the axial direction of the optical fiber cable 1. Even in this case, it is desirable that the ratio of the total area of ​​the recesses 9 (hatching L in the figure) to the outer surface area of ​​the jacket 7 (hatching K+L in the figure) in one cycle of the repeated arrangement of the recesses 9 be 35% or more and 75% or less. Note that the recesses 9 may also be arranged randomly without any regularity.

[0054] The recesses 9 formed intermittently can be formed, for example, by contacting the outer peripheral surface of the outer jacket 7 with a roller having protrusions of a predetermined length corresponding to the recesses immediately after the outer jacket 7 is extruded. Alternatively, the recesses 9 can be formed intermittently by using a die having multiple movable claws arranged in parallel in the circumferential direction, passing the outer jacket 7 through the die immediately after the outer jacket 7 is extruded, pressing the claws against the outer jacket 7 to form the recesses 9, and opening the claws at predetermined intervals to stop contact with the outer jacket 7. In this way, the method of forming the recesses 9 is not particularly limited.

[0055] As described above, according to this embodiment, by forming multiple recesses 9 on the outer surface in a cross section perpendicular to the longitudinal direction of the optical fiber cable 1, the contact area with the inner surface of the duct can be reduced when laying the optical fiber cable in a duct, etc., thereby reducing the resistance to wiring.

[0056] Furthermore, since the recesses 9 are arranged intermittently in the longitudinal direction of the optical fiber cable 1, the corners of the recesses 9 do not continue for more than a predetermined length in the longitudinal direction of the optical fiber cable 1. Therefore, even when the optical fiber cable 1 is bent, damage to the jacket 7 can be suppressed, and the strength of the optical fiber cable 1 can be ensured.

[0057] Furthermore, by optimizing the size, arrangement, and area ratio of the recesses 9, it is possible to more reliably perform long-distance pressure feeding.

[0058] Next, a second embodiment will be described. Fig. 6 is an external view showing an optical fiber cable 1a according to the second embodiment, and Fig. 7 is a cross-sectional view perpendicular to the axial direction of the optical fiber cable 1a (cross-sectional view taken along line MM in Fig. 6). In the following description, components that have the same functions as those in the first embodiment are denoted by the same reference numerals as in Figs. 1 to 5, and redundant description will be omitted.

[0059] The optical fiber cable 1a has a configuration substantially similar to that of the optical fiber cable 1, but has protrusions 11 formed in place of the recesses 9. That is, in a cross section perpendicular to the axial direction of the optical fiber cable 1, a plurality of protrusions 11 are formed at substantially equal intervals in the circumferential direction on the outer circumferential surface of the jacket 7. Also, as shown in FIG. 6 , the protrusions 11 are formed intermittently in the axial direction of the optical fiber cable 1.

[0060] The number and cross-sectional shape of the protrusions 11 are not limited to the example shown in the figure, and are set in the same manner as the recesses 9.

[0061] 8 is an enlarged view of the protrusion 11. The circumferential width (T in the figure) of the protrusion 11 is preferably, for example, about 2.0 to 5.0 mm. The range of the protrusion 11 is the range surrounded by the boundary of an imaginary circle (dotted line portion) that circumscribes the parts other than the protrusion 11.

[0062] Furthermore, it is desirable that the height of the protrusions 11 (the height from the aforementioned imaginary circle to the outer surface of the protrusions 11, U in the figure) be greater than 0.1 mm. If the height of the protrusions 11 is 0.1 mm or less, the effect of providing the protrusions 11 will be small and manufacturability will also be impaired.

[0063] Fig. 9 is a development view of the jacket 7 of the optical fiber cable 1a similar to Fig. 4. That is, the up-down direction in Fig. 9 (G in the figure) corresponds to the circumferential direction of the optical fiber cable 1a, and the left-right direction in Fig. 4 (H in the figure) corresponds to the axial direction of the optical fiber cable 1a.

[0064] As shown in the figure, the protrusions 11 are arranged at approximately equal intervals in the circumferential direction. In this case, it is desirable that the circumferential interval (N in the figure) between the multiple protrusions 11 is 0.1 mm or more. If the interval between the protrusions 11 is too narrow, the effect of reducing the contact area will be reduced due to deformation of that area. In addition, it is desirable that the circumferential interval (N in the figure) between the multiple protrusions 11 is ¼ or less of the cable diameter (S in Figure 7) in areas other than the protrusions 11. If the interval between the protrusions 11 is too wide, the effect of reducing the contact area will be reduced, and there is a risk of the pumping distance decreasing.

[0065] Furthermore, each of the protrusions 11 is arranged intermittently at a predetermined interval in a straight line in the axial direction of the optical fiber cable 1a. In this case, the longitudinal length of the protrusions 11 (P in the figure) is not particularly limited, but is, for example, 10 mm or more and 50 mm or less. Furthermore, it is desirable that the distance between the protrusions 11 in the axial direction of the optical fiber cable 1 (O in the figure) be 5 mm or more and 30 mm or less. In this way, the pumping distance can be efficiently extended and the influence of the corners described above can be reduced.

[0066] Furthermore, it is desirable that the ratio of the total surface area of ​​the protrusions 11 to the outer surface area of ​​the jacket 7 when it is unfolded be 25% or more and 65% or less. For example, if the protrusions 11 are repeatedly formed at a predetermined pitch in the axial direction of the optical fiber cable 1, it is desirable that the ratio of the total area of ​​the protrusions 11 (hatching R in the figure) to the outer surface area of ​​the jacket 7 in one period (hatching Q+R in the figure) be 25% or more and 65% or less.

[0067] A sufficient pumping distance can be ensured by setting the shape of the protrusions 11 in this way. As a method for intermittently forming the protrusions 11, for example, as described above, the protrusions 11 can be formed by pressing a roller having a recess of a predetermined length against the outer peripheral surface of the outer jacket 7 immediately after the outer jacket 7 is extruded.

[0068] 9, all of the circumferentially adjacent convex portions 11 are arranged at the same position in the axial direction of the optical fiber cable 1. That is, all of the convex portions 11 are arranged in the range indicated by P in the figure, and no convex portions 11 are formed in the circumferential direction in the range indicated by O in the figure. In contrast to this, the convex portions 11 may be arranged in a staggered manner in the longitudinal direction, as in the case shown in FIG. 5, or the convex portions 11 may be arranged randomly without any regularity.

[0069] According to the second embodiment, the same effects as those of the first embodiment can be obtained. That is, since the protrusions 11 are arranged discontinuously in the longitudinal direction, the corners of the protrusions 11 do not continue for more than a predetermined length in the longitudinal direction of the optical fiber cable 1a. Therefore, even when the optical fiber cable 1a is bent, damage to the jacket 7 can be suppressed, and the strength of the optical fiber cable 1a can be ensured.

[0070] Furthermore, by optimizing the size, arrangement, and area ratio of the protrusions 11, it is possible to more reliably perform long-distance pressure feeding.

[0071] Next, a third embodiment will be described. Fig. 10 is a development view of an optical fiber cable according to the third embodiment. In this embodiment, a large number of small, approximately circular recesses 9a are formed on the outer peripheral surface of the jacket 7. For example, in the illustrated example, the recesses 9a are arranged in a staggered pattern in the longitudinal and circumferential directions.

[0072] 11 is an enlarged cross-sectional view of the recessed portions 9a. The recessed portions 9a are hemispherical, and a plurality of dimple-shaped recessed portions 9a are formed at predetermined intervals over substantially the entire outer peripheral surface of the jacket 7. That is, the recessed portions 9a are arranged at predetermined intervals and intermittently in the longitudinal direction. In order to efficiently obtain the effect of forming the recessed portions 9a, it is desirable that the depth of the recessed portions 9a be 0.1 mm or more.

[0073] In place of the recesses 9a, protrusions may be formed with the same size and arrangement as the recesses 9a shown in the figure. That is, a plurality of hemispherical protrusions may be formed on the outer surface of the jacket 7. [Example]

[0074] A number of optical fiber cables were fabricated and subjected to a pressure-feeding test. Figure 12 is a conceptual diagram showing the method of the pressure-feeding test. First, a prototype optical fiber cable 15 is inserted into the conduit 13 from the pressure-feeding head 17 via a pair of caterpillar (registered trademark)-shaped propulsion units 19. While feeding high-pressure air into the propulsion head 17 (arrow D in the figure), the optical fiber cable 15 is sent out by the propulsion units 19, thereby enabling the optical fiber cable 15 to be pressure-fed into the conduit 13 (arrow C in the figure).

[0075] Figure 13 is a schematic diagram showing the route of the pipeline 13. The straight section E in the figure is approximately 9 m long, and the straight section F in the figure is approximately 38 m long. The curved section R1 in the figure has a radius of approximately 12 m. The straight section E and the straight section F are smoothly connected by two quarter circles with a radius R2 = 1 m in the figure.

[0076] The length of one lap of the pipe 13 is approximately 200 m, and the pipes 13 in the form shown in FIG. 13 are connected in a continuous coil shape, with 10 laps making up a total length of 2000 m.

[0077] First, Table 1 shows the shapes of the optical fiber cables 15 having recesses formed on the surface of the jacket 7 and the results of the pressure feeding test.

[0078] [Table 1]

[0079] Each optical fiber cable was made by twisting the same number of ribbon fibers together to form an optical fiber unit, and then wrapping a pressure winding member around the outer periphery of a predetermined number of optical fiber units to form a core. A tension member was placed around the core and an outer jacket was extruded to cover it.

[0080] In the table, "intermittent" recesses mean that the recesses are not continuous in the longitudinal direction of the optical fiber cable but are formed intermittently, while "continuous" means that the same cross-sectional shape is continuous over the entire length in the longitudinal direction. Note that the arrangement of the recesses is such that recess-formed areas and non-formed areas are alternately formed in the longitudinal direction, as shown in Figure 4.

[0081] The total recess area / surface area of ​​the outer shell is, for example, the value of L / (K+L) in the example shown in Fig. 4. The recess depth is, for example, the depth D in Fig. 3, and the number of circumferential recesses is the number of circumferential recesses in a cross section perpendicular to the longitudinal direction.

[0082] The longitudinal length of the recess and the longitudinal spacing of the recess correspond to J and I in Fig. 4, respectively, the circumferential width of the recess corresponds to C in Fig. 3, and the circumferential spacing of the recess corresponds to F in Fig. 4. Example 8 in Table 1 is an embodiment with a dimple shape as shown in Fig. 11, and *1 in the table indicates that the value is unknown because no clear measurement was performed.

[0083] In assessing strength, those in which the corners between the convex and concave portions as described above were formed continuously in the longitudinal direction were rated as failing (×) as they were considered to be continuous stress concentration areas and could be prone to breakage, while those in which the corners between the convex and concave portions were intermittent were rated as passing (○).

[0084] In addition, in the pressure feeding test, those that were able to pump 2000m were rated as passing (○), those that were unable to pump the optical fiber cable 15 along the way and the pumping distance was less than 2000m but 600m or more were rated as (△), and those that were less than 600m were rated as failing (×).

[0085] From the results in Table 1, Examples 1 to 8 and Comparative Examples 1, 3, and 4 all had continuous corners and were therefore rated as passing. On the other hand, Comparative Example 2 had continuous corners and was therefore rated as failing in terms of strength.

[0086] On the other hand, Comparative Example 1, in which no recesses were formed, had a large frictional resistance and failed the pumping test (×). In Comparative Examples 3 and 4, recesses were formed intermittently, but the ratio of the total area of ​​the recesses to the surface area of ​​the outer jacket was less than 35% or more than 75%, so the pumping test was △.

[0087] Next, in addition to Table 1, Table 2 shows the shapes of the optical fiber cables 15 having convex portions formed on the surface of the jacket 7 and the results of the pressure feeding test. The optical fiber cables used were the same as those in the previous examples.

[0088] [Table 2]

[0089] The configurations in Table 2 are the same as those in Table 1, except that the recesses are replaced with protrusions. Example 15 in Table 2 is an embodiment of the dimpled shape shown in Fig. 11, in which the recesses are replaced with protrusions, and *2 in the table indicates that the numerical value is unknown because no clear measurement was performed.

[0090] From the results in Table 2, Examples 9 to 15 and Comparative Examples 5, 7, and 8 all had continuous corners and were therefore rated as passing. On the other hand, Comparative Example 6 had continuous corners and was therefore rated as failing in terms of strength.

[0091] On the other hand, Comparative Example 5, in which no convex portions were formed, had a large frictional resistance and failed the pumping test (×). Furthermore, Comparative Examples 7 and 8, in which convex portions were formed intermittently, the ratio of the total area of ​​the convex portions to the surface area of ​​the outer coating was less than 25% or more than 65%, so the pumping test was △.

[0092] Although the embodiments of the present invention have been described above with reference to the accompanying drawings, the technical scope of the present invention is not limited to the above-described embodiments. It is clear that those skilled in the art can conceive of various modifications and alterations within the scope of the technical ideas described in the claims, and it is understood that these modifications and alterations also fall within the technical scope of the present invention. [Explanation of symbols]

[0093] 1, 1a....Optical fiber cable 3...Core 5...Tension member 7……Outer cover 9, 9a...recess 11....Convex part 13……Pipeline 15....Optical fiber cable 17... Pumping head 19……Promotion Department 100....Optical fiber cable 103...Core 105...Tension member 107……Outer cover 109...recess 111....Convex part

Claims

1. a core consisting of a plurality of optical fiber cores; an outer jacket covering the core; A tension member that bears tension, Equipped with An optical fiber cable characterized in that a plurality of recesses or protrusions are formed circumferentially on the outer surface of the outer jacket, and the recesses or protrusions are formed intermittently in the axial direction of the optical fiber cable.

2. 2. The optical fiber cable according to claim 1, characterized in that a plurality of recesses are formed on the outer surface of the outer jacket, and when the outer jacket is unfolded, the ratio of the total surface area of ​​the recesses to the outer surface area of ​​the outer jacket is 35% or more and 75% or less.

3. 3. The optical fiber cable according to claim 2, wherein the depth of the recess is greater than 0.2 mm, and the minimum thickness of the jacket at the recess is greater than 1.0 mm.

4. An optical fiber cable as described in claim 2, characterized in that in a cross section perpendicular to the axial direction of the optical fiber cable, the circumferential spacing between multiple recesses is 0.3 mm or more and is 1 / 3 or less of the cable diameter in areas other than the recesses.

5. The optical fiber cable according to claim 2, characterized in that the recesses are arranged intermittently in a straight line with respect to the axial direction of the optical fiber cable, and the axial spacing between the recesses of the optical fiber cable is 5 mm or more and 30 mm or less.

6. 3. The optical fiber cable according to claim 2, wherein the recesses are arranged at approximately equal intervals in the circumferential direction in a cross section perpendicular to the axial direction of the optical fiber cable.

7. The optical fiber cable of claim 1, characterized in that a plurality of the convex portions are formed circumferentially on the outer surface of the outer jacket, and when the outer jacket is unfolded, the ratio of the total surface area of ​​the convex portions to the outer surface area of ​​the outer jacket is 25% or more and 65% or less.

8. 8. The optical fiber cable according to claim 7, wherein the height of the projection is greater than 0.1 mm.

9. An optical fiber cable as described in claim 7, characterized in that in a cross section perpendicular to the axial direction of the optical fiber cable, the circumferential spacing between multiple convex portions is 0.1 mm or more and is 1 / 4 or less of the cable diameter in areas other than the convex portions.

10. The optical fiber cable according to claim 7, characterized in that the convex portions are arranged intermittently in a straight line with respect to the axial direction of the optical fiber cable, and the axial spacing between the convex portions of the optical fiber cable is 5 mm or more and 30 mm or less.

11. 8. The optical fiber cable according to claim 7, wherein the protrusions are arranged at approximately equal intervals in the circumferential direction in a cross section perpendicular to the axial direction of the optical fiber cable.

12. 2. The optical fiber cable according to claim 1, wherein a plurality of dimple-shaped recesses are formed at predetermined intervals over the entire outer peripheral surface of the jacket.

13. 13. The optical fiber cable according to claim 12, wherein the depth of the recess is 0.1 mm or more.

14. 2. The optical fiber cable according to claim 1, wherein the optical fiber is an intermittently bonded optical fiber ribbon in which a plurality of optical fibers are arranged in parallel and intermittently bonded in the longitudinal direction.

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