Sensing optical cable

Abstract

To provide an optical cable for sensing which is easily bent and suppresses deformation of a cross-sectional shape when being bent and pulled.SOLUTION: A sensing optical cable (1) includes a shape-retaining cylindrical body (21) and at least one sensing optical fiber (22), the shape-retaining cylindrical body (21) including a cylindrical woven fabric including a plurality of warps along a cylindrical axis direction and a plurality of wefts spirally woven with respect to the warps and having a self-shape retaining property due to at least some of the plurality of wefts being yarns having bending resilience, the at least one sensing optical fiber (22) being spirally wound around an outer peripheral surface of the shape-retaining cylindrical body (21).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an optical cable for sensing that includes an optical fiber for sensing. [Background technology]

[0002] Optical fibers are used for a variety of purposes. Conventionally, sensing optical cables containing optical fibers for measuring temperature, strain, and the like have been known. Light is incident from the end of the optical fiber, and the temperature, strain, and other such parameters are sensed by reading the scattered light that is the reflected light. For example, the sensing optical cable (optical fiber-embedded prestressing steel member 10) described in Patent Document 1 has a configuration in which an optical fiber is spirally wound around a prestressing steel strand made of twisted prestressing steel members.

[0003] Patent Document 2 discloses a flexible optical communication cable in which an optical fiber is spirally wound around the outer periphery of a flexible elastic body. It describes that the elastic body is a braided body made of elastic threads or a coil spring. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2017-078617 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-054312 Summary of the Invention [Problem to be solved by the invention]

[0005] The sensing optical cable (optical fiber-embedded prestressing steel member 10) described in Patent Document 1 is primarily composed of prestressing steel strands, resulting in low flexibility and difficulty in bending. Sensing optical cables are required to be easily bendable to ensure a certain degree of freedom in placement. If the structure disclosed in Patent Document 2, in which an optical fiber is spirally wound around an elastic body made of a braid or coil spring, were applied to a sensing optical cable, the sensing optical cable would be easily bendable. However, if the elastic body is a braid, the cross-sectional shape of the sensing optical cable would deform when the sensing optical cable is bent. Furthermore, if the elastic body is a braid or coil spring, the sensing optical cable stretches when pulled, causing the cross-sectional shape of the sensing optical cable to deform and become smaller. Deformation of the cross-sectional shape of the sensing optical cable may reduce sensing accuracy.

[0006] An object of the present invention is to provide an optical cable for sensing that is easy to bend and that is less likely to deform in cross-sectional shape when bent or pulled. [Means for solving the problem]

[0007] (1) The sensing optical cable of the present invention includes a tubular woven fabric consisting of a plurality of warp threads aligned along the tubular axis and a plurality of weft threads woven spirally around the warp threads, and is equipped with a shape-retaining tubular body having self-shape retention due to at least some of the plurality of weft threads being threads with bending resilience, and at least one sensing optical fiber wound spirally around the outer peripheral surface of the shape-retaining tubular body.

[0008] According to this configuration, the sensing optical cable is easily bendable because it has a structure in which the optical fiber is spirally wound around a shape-retaining tubular body including a tubular woven fabric. Furthermore, the tubular woven fabric of the shape-retaining tubular body has a configuration in which multiple weft yarns, including weft yarns with bending resilience, are woven helically around multiple warp yarns along the cable's longitudinal direction. When an appropriate tensile force is applied to the sensing optical cable, the weft yarns with bending resilience are fixed in place by the woven structure with the warp yarns along the cable's longitudinal direction in a helical wound state. This allows the shape-retaining tubular body to easily maintain its circular shape, and the cross-sectional shape of the shape-retaining tubular body is less likely to deform. Therefore, even when the sensing optical cable is bent, the cross-sectional shape of the shape-retaining tubular body is less likely to deform. Furthermore, because the tubular woven fabric of the shape-retaining cylinder has warp threads aligned in the axial direction of the cylinder, the shape-retaining cylinder is less likely to stretch when the optical sensing cable is pulled, and is less likely to deform so that its cross-sectional shape becomes smaller, compared to when the shape-retaining cylinder is configured from an elastic body made of a braided body or coil spring as described in Patent Document 2. Since the cross-sectional shape of the shape-retaining cylinder is less likely to deform when the optical sensing cable is bent or pulled, this prevents a decrease in the accuracy of sensing by the optical fiber wound around the outer peripheral surface of the shape-retaining cylinder and provides a countermeasure for tension when the optical sensing cable is pulled into a narrow space.

[0009] (2) The optical cable for sensing of (1) above preferably includes a protective member that covers the shape-retaining cylindrical body and the optical fiber.

[0010] According to this configuration, the optical fiber can be protected by the protective member when the sensing optical cable is arranged and in the environment in which the sensing optical cable is arranged.

[0011] (3) In the optical cable for sensing of (1) or (2) above, it is preferable that the optical fiber is integrated into the shape-retaining cylindrical body.

[0012] This configuration prevents the optical fiber from moving relative to the shape-retaining tubular body when the sensing optical cable is bent, ensuring the accuracy of the optical fiber's position and improving sensing accuracy. Furthermore, if a coil spring included in the elastic optical communication cable described in Patent Document 2 were used instead of the shape-retaining tubular body, a large tensile force acting on the sensing optical cable could cause the coil spring to stretch significantly, potentially damaging the optical fiber. In contrast, in the present invention, the shape-retaining tubular body integrated with the optical fiber has warp threads aligned along the cable longitudinal direction. Therefore, when the sensing optical cable is pulled, the warp threads are subjected to a tensile load, thereby preventing damage to the optical fiber due to tension.

[0013] (4) In the optical cable for sensing of any one of the above (1) to (3), it is preferable that the outer peripheral surface of the shape-retaining tubular body has irregularities formed by the tubular woven fabric.

[0014] According to this configuration, when the optical fiber is wound around the shape-retaining cylinder during manufacturing of the optical cable for sensing, the unevenness of the outer surface of the shape-retaining cylinder can prevent the optical fiber from shifting in position. By increasing the accuracy of the position of the optical fiber, the accuracy of sensing can be improved.

[0015] (5) In any of the sensing optical cables (1) to (4) above, the number of the optical fibers may be multiple, and the multiple optical fibers may be arranged spirally in the axial direction of the tube at predetermined intervals, and may be integrated into a single tape wound spirally around the outer surface of the shape-retaining tube.

[0016] According to this configuration, when manufacturing the optical sensing cable, a tape integrated with multiple optical fibers is wound around a shape-retaining cylindrical body. This allows the multiple optical fibers to be easily wound around the shape-retaining cylindrical body while ensuring accurate spacing between the multiple optical fibers. High accuracy in the positional relationship between the multiple optical fibers improves sensing accuracy. Furthermore, when three or more optical fibers are wound helically in a line at a predetermined interval in the cylindrical axial direction, it is possible to sense physical quantities such as strain in three dimensions.

[0017] (6) In any of the sensing optical cables (1) to (4) above, the number of the optical fibers may be multiple, and the multiple optical fibers may be arranged spirally in the axial direction of the tube at predetermined intervals, and may be individually integrated into multiple tapes that are all wound spirally in the same direction on the outer surface of the shape-retaining tube.

[0018] According to this configuration, when manufacturing the optical cable for sensing, by winding a tape integrated with one optical fiber around a shape-retaining cylinder, the optical fiber can be easily wound around the shape-retaining cylinder while ensuring the accuracy of the position of the optical fiber, compared to when only the optical fiber is wound around the shape-retaining cylinder. The high accuracy of the position of each optical fiber also improves the accuracy of the positional relationship between multiple optical fibers, thereby improving sensing accuracy. Furthermore, because the optical fibers are integrated into the tape one by one, it is easy to change the number of optical fibers used in the sensing optical cable when manufacturing it. Furthermore, when three or more optical fibers are wound helically in a line at a predetermined interval in the axial direction of the tube, it is possible to sense physical quantities such as strain in three dimensions.

[0019] (7) In the optical cable for sensing of (5) or (6) above, it is preferable that the tape is adhered to the outer circumferential surface of the shape-retaining cylindrical body.

[0020] According to this configuration, when the sensing optical cable is bent, the optical fiber can be prevented from moving relative to the shape-retaining cylindrical body, so that the accuracy of the position of the optical fiber can be ensured and the accuracy of sensing can be improved.

[0021] (8) In any of the sensing optical cables (5) to (7) above, the tape integrated with at least one of the optical fibers may be stacked in multiple layers in the thickness direction, and two adjacent layers of the tape among the multiple stacked layers may be wound spirally in opposite directions on the outer surface of the shape-retaining cylindrical body.

[0022] This configuration allows more sensing to be performed with one optical sensing cable. Also, when three or more optical fibers are wound spirally in a line at a predetermined interval in the axial direction of the tube, multiple types of physical quantities can be sensed three-dimensionally with one optical sensing cable.

[0023] (9) In the optical cable for sensing according to any one of (5) to (8) above, at least one tension member disposed along the optical fiber may be integrated with the tape.

[0024] With this configuration, when manufacturing an optical cable for sensing, the tape, which integrates both the optical fiber and the tension member, is pulled while being wound around the shape-retaining cylinder. Because the tension member receives the tensile load, it is possible to apply a high tensile force while minimizing damage to the optical fiber and stretching of the tape. This makes it possible to easily wind the optical fiber while ensuring the accuracy of its position. Furthermore, when the sensing optical cable is pulled, the tension member arranged along the optical fiber receives the tensile load, thereby reducing the tensile load acting on the optical fiber and suppressing breakage of the optical fiber due to tension.

[0025] (10) In any of the sensing optical cables (1) to (9) above, a central cord in which at least one sensing optical fiber and at least one tension member are integrated may be arranged inside the shape-retaining cylindrical body.

[0026] According to this configuration, more sensing can be performed using one optical sensing cable.

[0027] (11) In the optical cable for sensing described in (2) above, the protective member may include a tubular woven fabric consisting of a plurality of warp threads aligned along the tubular axis direction and a plurality of weft threads woven spirally around the warp threads, and at least some of the plurality of weft threads may be threads having bending resilience, thereby providing self-shape retention.

[0028] According to this configuration, the protective member covering the shape-retaining cylinder and the optical fiber includes a tubular woven fabric having the same configuration as the shape-retaining cylinder and has self-retaining shape like the shape-retaining cylinder. Therefore, the cross-sectional shape of the protective member is less likely to deform when the sensing optical cable is bent. This makes it possible to suppress deformation of the cross-sectional shape of the shape-retaining cylinder due to inward deformation of the protective member. This makes it possible to suppress a decrease in the accuracy of sensing by the optical fiber wound around the shape-retaining cylinder. [Effects of the Invention]

[0029] According to the present invention, it is possible to provide an optical cable for sensing that is easy to bend and in which deformation of the cross-sectional shape when bent or pulled is suppressed. [Brief explanation of the drawings]

[0030] [Figure 1] 1A and 1B are diagrams illustrating the structure of an example of an optical cable for sensing according to a first embodiment of the present invention. [Figure 2] 1 is a schematic cross-sectional view of an example of an optical cable for sensing according to a first embodiment of the present invention. [Figure 3]FIG. 6 is a schematic diagram illustrating the structure of an example of an optical cable for sensing according to a second embodiment of the present invention. [Figure 4] FIG. 1(a) is a schematic cross-sectional view of an example of an optical cable for sensing according to a third embodiment of the present invention, and FIG. 1(b) is a schematic cross-sectional view of an example of an optical cable for sensing according to a fourth embodiment of the present invention. [Figure 5] FIG. 10 is a schematic diagram illustrating the structure of an example of an optical cable for sensing according to a fifth embodiment of the present invention. [Figure 6] FIG. 10 is a schematic cross-sectional view of an example of an optical cable for sensing according to a sixth embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0031] [First embodiment] A sensing optical cable 1 according to a first embodiment of the present invention will be described with reference to Figures 1 and 2. The sensing optical cable 1 according to this embodiment is buried underground alongside an underground object such as a power line, and is used to monitor the ground around the underground object by sensing the amount of ground displacement, etc. The sensing optical cable 1 according to this embodiment may also be used to monitor bridges, tunnels, roads, etc. However, the situations in which the sensing optical cable of the present invention is used are not limited to these.

[0032] The sensing optical cable 1 includes a shape-retaining cylindrical body 21, a plurality of sensing optical fibers 22, one tape 23, and a protective member 31.

[0033] The shape-retaining tubular body 21 includes a tubular woven fabric made of multiple warp threads along the cable longitudinal direction and multiple weft threads woven helically around the warp threads. The cable longitudinal direction is the tubular axial direction of the tubular woven fabric. At least a portion of the multiple weft threads are made of yarns with bending resilience. This gives the shape-retaining tubular body 21 self-shape retention. More specifically, the shape-retaining tubular body 21 maintains a circular cross-sectional shape. The bending resilience yarns may be, for example, metal wires or synthetic fiber monofilaments. The warp threads are synthetic fiber yarns. It is preferable to use fibers that are resistant to stretching for the warp threads. It is more preferable to use high-strength, low-elongation fibers, such as aramid fiber, for the warp threads. If only a portion of the weft threads constituting the tubular woven fabric are made of yarns with bending resilience, the remaining weft threads are synthetic fiber yarns.

[0034] In addition to the tubular woven fabric, the shape-retaining tubular body 21 may include a coating layer of rubber or synthetic resin that covers at least one of the inner and outer peripheral surfaces of the tubular woven fabric. The thickness of the coating layer provided on the outer peripheral surface of the tubular woven fabric may be such that the irregularities formed by the tubular woven fabric appear on the outer peripheral surface of the shape-retaining tubular body 21, or may be such that the irregularities do not appear.

[0035] The inner and outer diameters of the shape-retaining cylindrical body 21 are constant. The outer diameter of the shape-retaining cylindrical body 21 is, for example, 10 to 40 mm, but is not limited to this size.

[0036] A plurality of optical fibers 22 are spirally wound around the outer peripheral surface of the shape-retaining cylindrical body 21. In FIGS. 1 and 2, the number of optical fibers wound around the shape-retaining cylindrical body 21 is three, but it may be three or more. By spirally winding three or more optical fibers 22 around the shape-retaining cylindrical body 21, physical quantities such as strain can be sensed in three dimensions. The plurality of optical fibers 22 are arranged spirally side by side at predetermined intervals in the cable longitudinal direction. The distances from the center of the shape-retaining cylindrical body 21 of the plurality of optical fibers 22 are the same as each other and are constant along the entire length of the shape-retaining cylindrical body 21. The winding angles of the plurality of optical fibers 22 are the same as each other and are constant along the entire length of the shape-retaining cylindrical body 21. In other words, the pitches of the plurality of optical fibers 22 are the same as each other and are constant along the entire length of the shape-retaining cylindrical body 21. It is preferable that the spacing between the multiple optical fibers 22 in the cable longitudinal direction and the winding angle of the multiple optical fibers 22 are set so that the multiple optical fibers 22 are arranged at equal intervals in the circumferential direction in any cross section of the sensing optical cable 1, but this configuration is not limited to this.

[0037] The optical fiber 22 includes at least one core and a cladding covering the at least one core. The optical fiber 22 may include a coating layer covering the outer circumferential surface of the cladding.

[0038] The multiple optical fibers 22 are integrated into one tape 23 that is wound spirally around the outer peripheral surface of the shape-retaining cylindrical body 21. The tape 23 is made of synthetic resin. The tape 23 and the multiple optical fibers 22 are integrated when the tape 23 is extrusion-molded. The tape 23 is adhered to the shape-retaining cylindrical body 21 via an adhesive layer 26 (see FIG. 2 ) made of an adhesive. When manufacturing the sensing optical cable 1, for example, the adhesive layer 26 is provided on one side of the tape 23 that is integrated with the multiple optical fibers 22, and then the tape 23 is wound spirally around the shape-retaining cylindrical body 21. Note that instead of being adhered via the adhesive layer 26, the tape 23 may be directly adhered to the shape-retaining cylindrical body 21 by thermal welding.

[0039] In FIG. 2 , the optical fiber 22 is almost completely embedded in the tape 23 so as to be located at the inner circumferential end of the tape 23 within the tape 23. However, the configuration for integrating the optical fiber 22 with the tape 23 during extrusion molding of the tape 23 is not limited to this. For example, the optical fiber 22 may be partially embedded in the tape 23 so that a portion of the optical fiber 22 is exposed from the inner circumferential surface of the tape 23 (the surface facing the shape-retaining cylindrical body 21). Furthermore, the configuration for integrating the optical fiber 22 with the tape 23 is not limited to extrusion molding of the tape 23. For example, the optical fiber 22 may be bonded to an adhesive layer provided on one side of the tape 23, thereby integrating the optical fiber 22 with the tape 23. In this case, the portion of the adhesive layer on which the optical fiber 22 is not disposed is bonded to the shape-retaining cylindrical body 21. Alternatively, for example, the tape 23 may be composed of two tapes, each having an adhesive layer on one side, and the optical fiber 22 may be disposed between the adhesive layer of one tape and the surface of the other tape where no adhesive layer is provided, thereby integrating the optical fiber 22 and the tape 23. In this case, the adhesive layer of the other tape is adhered to the shape-retaining cylindrical body 21.

[0040] The protective member 31 is cylindrical and covers the shape-retaining cylindrical body 21, the plurality of optical fibers 22, and the tape 23. The outer peripheral surface of the protective member 31 forms the outer peripheral surface of the sensing optical cable 1. The protective member 31 is provided to protect the optical fibers 22 when the sensing optical cable 1 is arranged and in the environment in which the sensing optical cable 1 is arranged.

[0041] Here, the member in which the shape-retaining cylindrical body 21, the plurality of optical fibers 22, and the tape 23 are integrated is referred to as the main member 20 (see FIG. 2). The material and thickness of the protective member 31 are set so that the bendability of the protective member 31 is equal to or greater than that of the main member 20.

[0042] The protective member 31 has the same configuration as the shape-retaining cylindrical body 21. That is, the protective member 31 includes a tubular woven fabric in which at least some of the weft yarns woven spirally around the warp yarns are made of bending-resilient yarns, and has self-shape retention. In addition to this tubular woven fabric, the protective member 31 may also include a coating layer of rubber or synthetic resin that covers at least one of the inner and outer peripheral surfaces of the tubular woven fabric. The thickness of the coating layer provided on the outer peripheral surface of the tubular woven fabric of the protective member 31 may be such that the irregularities formed by the tubular woven fabric appear on the outer peripheral surface of the shape-retaining cylindrical body 21, or may be such that the irregularities do not appear.

[0043] The inner diameter of the protective member 31 is larger than the outer diameter of the above-described main member 20. This allows the main member 20 to be inserted inside the protective member 31 after the protective member 31 and the main member 20 are fabricated when manufacturing the optical cable 1 for sensing.

[0044] According to this embodiment and its modifications, the following effects can be obtained.

[0045] The sensing optical cable 1 is easily bendable because it has a structure in which the optical fiber 22 is spirally wound around the shape-retaining tubular body 21, which includes a tubular woven fabric. Furthermore, the tubular woven fabric of the shape-retaining tubular body 21 is configured such that multiple weft threads, including weft threads with bending resilience, are woven helically around multiple warp threads along the cable's longitudinal direction. When an appropriate tensile force is applied to the sensing optical cable 1, the weft threads with bending resilience are fixed in place by the woven structure with the warp threads along the cable's longitudinal direction in a helical wound state. This allows the shape-retaining tubular body 21 to easily maintain its circular shape, and the cross-sectional shape of the shape-retaining tubular body 21 is less likely to deform. Therefore, even when the sensing optical cable 1 is bent, the cross-sectional shape of the shape-retaining tubular body 21 is less likely to deform. Furthermore, because the tubular woven fabric of the shape-retaining tubular body 21 has warp threads aligned in the cable longitudinal direction, the shape-retaining tubular body 21 is less likely to stretch when the sensing optical cable is pulled, and deformation that reduces the cross-sectional shape of the shape-retaining tubular body 21 is less likely to occur, compared to when the shape-retaining tubular body 21 is configured from an elastic body made of a braided body or coil spring as described in Patent Document 2. Since the cross-sectional shape of the shape-retaining tubular body 21 is less likely to deform when the sensing optical cable 1 is bent or pulled, this prevents a decrease in the sensing accuracy of the optical fiber 22 wound around the outer peripheral surface of the shape-retaining tubular body 21 and provides a measure against tension when the sensing optical cable 1 is pulled into a narrow space.

[0046] Because the optical fiber 22 is integrated with the shape-retaining cylindrical body 21, it is possible to prevent the optical fiber 22 from moving relative to the shape-retaining cylindrical body 21 when the sensing optical cable 1 is bent. This ensures the accuracy of the position of the optical fiber 22, thereby improving sensing accuracy. Furthermore, because the shape-retaining cylindrical body 21 integrated with the optical fiber 22 has warp threads along the cable longitudinal direction, the warp threads receive a tensile load when the sensing optical cable 1 is pulled, which makes it possible to prevent damage to the optical fiber 22 due to tension.

[0047] Because the multiple optical fibers 22 are integrated into one tape 23, when manufacturing the sensing optical cable 1, the tape 23 integrated with the multiple optical fibers 22 is wound around the shape-retaining cylindrical body 21, making it possible to easily wind the multiple optical fibers 22 around the shape-retaining cylindrical body 21 while ensuring precision in the spacing between the multiple optical fibers 22. High precision in the positional relationship between the multiple optical fibers 22 can improve sensing precision.

[0048] The outer peripheral surface of the shape-retaining cylinder 21 has irregularities formed by the tubular woven fabric. Therefore, when the tape 23 integrated with the optical fiber 22 is wound around the shape-retaining cylinder 21 during manufacturing of the sensing optical cable 1, the irregularities on the outer peripheral surface of the shape-retaining cylinder 21 can prevent the tape 23 and the optical fiber 22 from shifting position. This can increase the accuracy of the position of the optical fiber 22, thereby improving sensing accuracy. Note that this effect can also be achieved when a coating layer is provided on the outer peripheral surface of the tubular woven fabric and the thickness of this coating layer is set so that the irregularities formed by the tubular woven fabric appear on the outer peripheral surface of the shape-retaining cylinder 21.

[0049] Because the protective member 31 has the same configuration as the shape-retaining cylindrical body 21, the cross-sectional shape of the protective member 31 is less likely to deform when the sensing optical cable 1 is bent. This makes it possible to suppress deformation of the cross-sectional shape of the shape-retaining cylindrical body 21 due to inward deformation of the protective member 31. This makes it possible to suppress a decrease in the accuracy of sensing by the optical fiber 22 wound around the shape-retaining cylindrical body 21.

[0050] As a modification of the first embodiment, the protective member 31 may include a tubular woven fabric that does not include a weft yarn having bending resilience. In addition to the tubular woven fabric, the protective member 31 may also include a rubber or synthetic resin coating layer covering at least one of the inner and outer circumferential surfaces of the tubular woven fabric. The protective member 31 may also be formed of rubber or synthetic resin. In this case, the protective member 31 may be integrated with the main member 20. For example, the protective member 31 may be integrally molded on the outer circumferential surface of the main member 20 by extrusion molding. The rubber or synthetic resin protective member 31 may be in contact with the outer circumferential surface of the main member 20 over the entire circumference without being integrated with the main member 20, and may have an inner diameter larger than the outer diameter of the main member 20. The protective member 31 may also be formed by spirally winding a tape having an adhesive layer on one side around the outer circumferential surface of the main member 20. The tape used for the protective member 31 may be, for example, a tape made of rubber or synthetic resin, or a tape having a layer made of rubber or synthetic resin and a metal layer such as aluminum. For example, by using polyvinyl chloride tape or waterproof tape for the protective member 31, it is possible to prevent water from penetrating into the sensing optical cable 1 when it is embedded in concrete or the like.

[0051] Second Embodiment With reference to Fig. 3, differences between the sensing optical cable 101 of the second embodiment and the first embodiment will be described. Note that explanations of commonalities between the sensing optical cable 101 and the first embodiment will be omitted. Portions of the sensing optical cable 101 that are given the same reference numerals as those in the first embodiment are commonalities with the first embodiment. The same applies to the explanations of the third to sixth embodiments described later, where explanations of commonalities will be omitted.

[0052] In the first embodiment, a plurality of optical fibers 22 arranged in a spiral shape at predetermined intervals in the cable longitudinal direction are integrated into a single tape 23, whereas in the present embodiment, a plurality of optical fibers 22 arranged in a spiral shape at predetermined intervals in the cable longitudinal direction are individually integrated into a single tape 24. In other words, the plurality of optical fibers 22 are individually integrated into a plurality of tapes 24 that are all wound in a spiral shape in the same direction on the outer peripheral surface of the shape-retaining cylindrical body 21. In FIG. 3, the number of optical fibers 22 is three, but the number may be three or more. The configuration of the tape 24 is the same as the configuration of the tape 23 of the first embodiment, except for the number of optical fibers 22 integrated.

[0053] According to the present embodiment, one optical fiber 22 is integrated into one tape 24. Therefore, when manufacturing the sensing optical cable 101, by winding the tape 24 integrated with one optical fiber 22 around the shape-retaining cylinder 21, the optical fiber 22 can be easily wound around the shape-retaining cylinder 21 while ensuring the positional accuracy of the optical fiber 22, compared to when only the optical fiber 22 is wound around the shape-retaining cylinder 21. The high positional accuracy of each optical fiber 22 also improves the accuracy of the positional relationship between multiple optical fibers 22, thereby improving sensing accuracy. Furthermore, because the optical fibers 22 are integrated into the tape 24 one by one, it is easy to change the number of optical fibers 22 used in the sensing optical cable 101 when manufacturing the sensing optical cable 101.

[0054] [Third and Fourth Embodiments] With reference to Figures 4(a) and 4(b), differences between the sensing optical cable 201 of the third and fourth embodiments and the first embodiment will be described. Figure 4(a) is a cross-sectional view of an example of the sensing optical cable 201 of the third embodiment, and Figure 4(b) is a cross-sectional view of an example of the sensing optical cable 301 of the fourth embodiment.

[0055] The ribbon 23 of the third and fourth embodiments has integrated therein, in addition to a plurality of optical fibers 22 aligned in the cable longitudinal direction, at least one tension member 41 arranged along the plurality of optical fibers 22. In other words, this tension member 41 is wound spirally around the outer circumferential surface of the shape-retaining cylindrical body 21 along the optical fibers 22. The tension member 41 is made of, for example, a metal wire such as a steel wire, a high-strength synthetic fiber thread such as aramid fiber, a carbon fiber thread, or a glass fiber thread.

[0056] In the third embodiment, a cord 40 including one optical fiber 22 and at least one tension member 41 is integrated into a tape 23. In FIG. 4(a), the cord 40 includes two tension members 41, but the cord 40 may include only one or more than two tension members. The cord 40 has a coating layer 42 that covers the optical fiber 22 and at least one tension member 41. The coating layer 42 integrates the optical fiber 22 and at least one tension member 41. The coating layer 42 is made of rubber or synthetic resin.

[0057] In the fourth embodiment, the optical fibers 22 and the tension members 41 are independently integrated into the tape 23. In FIG. 4(b), the same number of tension members 41 as the optical fibers 22 are integrated into one tape 23 so that the tension members 41 and the optical fibers 22 are alternately arranged in the cross section of the sensing optical cable 201, but the fourth embodiment is not limited to this configuration. In the fourth embodiment, the number of tension members 41 integrated into one tape 23 may be more or less than the number of optical fibers 22, and may be, for example, one.

[0058] In the third and fourth embodiments, at least one tension member 41 arranged along the optical fiber 22 is integrated with the tape 23. Therefore, when the tape 23, in which both the optical fiber 22 and the tension member 41 are integrated, is wound around the shape-retaining cylinder 21 while being pulled during manufacturing of the sensing optical cables 201, 301, the tension member 41 receives a tensile load, making it possible to apply a high tensile force while suppressing damage to the optical fiber 22 and elongation of the tape 23. Therefore, the optical fiber 22 can be easily wound while ensuring the accuracy of the position of the optical fiber 22. Furthermore, when the sensing optical cables 201, 301 are pulled, the tension member 41 arranged along the optical fiber 22 receives a tensile load, making it possible to reduce the tensile load acting on the optical fiber 22 and suppress damage to the optical fiber 22 due to tension.

[0059] The third and fourth embodiments may be implemented in combination with the second embodiment. That is, each of the optical fibers 22 arranged in the longitudinal direction of the cable may be individually integrated into one tape 24 (see FIG. 3), and at least one tension member 41 may be integrated into each tape 24. This modification also provides the same effects as the third and fourth embodiments described above.

[0060] Fifth Embodiment With reference to FIG. 5, the differences between the sensing optical cable 401 of the fifth embodiment and the first embodiment will be described.

[0061] In the first embodiment, only one tape 23 is provided, each integrated with a plurality of optical fibers 22 aligned in the cable longitudinal direction. In contrast, in this embodiment, two layers of tape 23, each integrated with a plurality of optical fibers 22 aligned in the cable longitudinal direction, are stacked in the thickness direction, and the two stacked layers of tape 23 (23A, 23B) are wound spirally in opposite directions around the outer peripheral surface of shape-retaining cylindrical body 21. Of the two stacked layers, tape 23B of the outer layer is bonded to tape 23A of the inner layer directly or via an adhesive layer (not shown). In other words, tape 23B of the outer layer is bonded to shape-retaining cylindrical body 21 via at least tape 23A of the inner layer.

[0062] As a modification of the fifth embodiment, two adjacent layers of tape 23 (23A, 23B) may be spirally wound in the same direction.

[0063] As a modification of the fifth embodiment, the tape 23 integrated with the plurality of optical fibers 22 aligned in the cable longitudinal direction may be stacked in three or more layers in the thickness direction. In this case, it is preferable that two adjacent layers of the tape 23 among the three or more layers of the stacked tape 23 are spirally wound in opposite directions.

[0064] The fifth embodiment may be implemented in combination with the second embodiment. That is, each of the optical fibers 22 arranged in the longitudinal direction of the cable may be individually integrated into one tape 24 (see FIG. 3), and the tapes 24 may be stacked in multiple layers in the thickness direction. In this case, it is preferable that two adjacent tapes 24 among the multiple stacked layers are spirally wound in opposite directions.

[0065] The fifth embodiment may be implemented in combination with the third or fourth embodiment. Also, the fifth embodiment may be implemented in combination with the second embodiment and the third or fourth embodiment.

[0066] According to this embodiment and its modifications, a plurality of types of physical quantities can be sensed three-dimensionally using one optical sensing cable 401.

[0067] Sixth Embodiment With reference to FIG. 6, differences between the sensing optical cable 501 of the sixth embodiment and the first embodiment will be described.

[0068] The sensing optical cable 501 includes a central cord 50 arranged inside the shape-retaining cylindrical body 21. The central cord 50 includes at least one sensing optical fiber 51, at least one tension member 52, and a coating layer 53.

[0069] In FIG. 6, the number of optical fibers 51 is one, but it may be multiple. In FIG. 6, the number of tension members 52 is four, but it may be one or multiple numbers other than four. The optical fibers 51 and tension members 52 are arranged along the longitudinal direction of the cable. The optical fibers 51 are used to sense physical quantities such as temperature. The material of the tension members 52 is the same as the material of the tension members 41 described in the third embodiment.

[0070] The covering layer 53 covers at least one optical fiber 51 and at least one tension member 52. The at least one optical fiber 51 and at least one tension member 52 are integrated by the covering layer 53. The covering layer 53 is made of rubber or synthetic resin.

[0071] The inner diameter of the shape-retaining cylindrical body 21 is larger than the outer diameter of the center cord 50. As a result, when manufacturing the optical cable 501 for sensing, the center cord 50 and the shape-retaining cylindrical body 21 can be fabricated first, and then the center cord 50 can be inserted inside the shape-retaining cylindrical body 21.

[0072] As a modification of the sixth embodiment, the center cord 50 may be integrated with the shape-retaining cylindrical body 21. For example, the covering layer 53 may be formed by insert molding in which rubber or synthetic resin is filled inside the shape-retaining cylindrical body 21. Furthermore, as another modification of the sixth embodiment, the center cord 50 may not be integrated with the shape-retaining cylindrical body 21, but may be in contact with the inner circumferential surface of the shape-retaining cylindrical body 21 over the entire circumference.

[0073] The sixth embodiment may be implemented in combination with at least one of the second to fifth embodiments.

[0074] According to this embodiment and its modifications, more sensing can be performed using one optical sensing cable 501.

[0075] The embodiments of the present invention are not limited to the above-described first to sixth embodiments and their modifications, and various changes and modifications are possible within the scope of the invention as defined in the claims. For example, the optical cables for sensing 1, 101, 201, 301, 401, and 501 of the first to sixth embodiments may be modified as follows.

[0076] Instead of the spirally wound tapes 23, 24, a tubular cover layer made of rubber or synthetic resin may be provided on the outer peripheral surface of the shape-retaining cylindrical body 21, covering the plurality of optical fibers 22 spirally wound around the outer peripheral surface of the shape-retaining cylindrical body 21. When manufacturing this optical cable for sensing, the plurality of optical fibers 22 are wound spirally around the shape-retaining cylindrical body 21, and then the cover layer is formed to cover the plurality of optical fibers 22. The cover layer is integrated with the outer peripheral surface of the shape-retaining cylindrical body 21 and the optical fibers 22.

[0077] The protective member 31 may not be provided. In this case, the optical fiber 22 may be protected by increasing the thickness of the cover layer described above.

[0078] The number of optical fibers 22 wound around the shape-retaining cylindrical body 21 may be 2 or 1. The optical fiber 22 wound around the shape-retaining cylindrical body 21 does not have to be integrated with the shape-retaining cylindrical body 21. [Explanation of symbols]

[0079] 1, 101, 201, 301, 401: Optical cables for sensing 21: Shape-retaining cylindrical body 22: Optical fiber 23, 23A, 23B, 24: Tape 26: Adhesive layer 31: Protective material 41: Tension Member 50: Central code 51: Optical fiber of the central cord 52: Central chord tension member

Claims

1. a shape-retaining cylindrical body that includes a cylindrical woven fabric made of a plurality of warp threads along the cylindrical axis direction and a plurality of weft threads woven spirally around the warp threads, and that has self-shape retention because at least a portion of the plurality of weft threads are threads having bending resilience; and at least one optical fiber for sensing wound spirally around the outer circumferential surface of the shape-retaining cylindrical body. Optical cable for sensing.

2. The optical cable for sensing according to claim 1, a protective member for covering the shape-retaining cylindrical body and the optical fiber; Optical cable for sensing.

3. 3. The optical cable for sensing according to claim 1 or 2, The optical fiber is integrated into the shape-retaining cylindrical body. Optical cable for sensing.

4. 3. The optical cable for sensing according to claim 1 or 2, The outer peripheral surface of the shape-retaining cylindrical body has irregularities formed by the cylindrical woven fabric. Optical cable for sensing.

5. The optical cable for sensing according to claim 1, The number of the optical fibers is plural, A plurality of the optical fibers are arranged in a spiral shape at predetermined intervals in the axial direction of the cylinder, and are integrated into one tape wound in a spiral shape around the outer circumferential surface of the shape-retaining cylinder. Optical cable for sensing.

6. The optical cable for sensing according to claim 1, The number of the optical fibers is plural, The optical fibers are arranged in a spiral shape in the axial direction of the cylinder at predetermined intervals, and are individually integrated into a plurality of tapes that are all wound in a spiral shape in the same direction on the outer peripheral surface of the shape-retaining cylinder. Optical cable for sensing.

7. 7. The optical cable for sensing according to claim 5 or 6, The tape is adhered to the outer peripheral surface of the shape-retaining cylindrical body. Optical cable for sensing.

8. 7. The optical cable for sensing according to claim 5 or 6, The tape integrated with at least one of the optical fibers is stacked in a plurality of layers in the thickness direction, and two adjacent layers of the tape among the stacked layers are spirally wound in opposite directions on the outer circumferential surface of the shape-retaining cylindrical body. Optical cable for sensing.

9. 7. The optical cable for sensing according to claim 5 or 6, At least one tension member is integrated into the tape and is disposed along the optical fiber. Optical cable for sensing.

10. 3. The optical cable for sensing according to claim 1 or 2, A central cord, in which at least one optical fiber for sensing and at least one tension member are integrated, is disposed inside the shape-retaining cylindrical body. Optical cable for sensing.

11. The optical cable for sensing according to claim 2, The protective member includes a tubular woven fabric made of a plurality of warp threads aligned along the tubular axis direction and a plurality of weft threads woven spirally around the warp threads, and at least a portion of the plurality of weft threads are threads having bending resilience, thereby having self-shape retention. Optical cable for sensing.

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