Optical fiber supported resin tube

Abstract

To provide an optical fiber carrying resin tube which is usable as a sensor for measuring distortion of a structure and temperature change, can dissolve molding shrinkage and can reduce signal loss.SOLUTION: An optical fiber carrying resin tube 10 has a cylindrical shape and 4 or more optical fibers 12 in a cylinder wall 11A, wherein the optical fiber 12 extends in a tube axis O1 direction, the cylinder wall 11A is formed from a polyolefin resin composition containing a resin (A), density of the resin (A), which is measured according to ISO 1183-1:2019, is 0.920 g / cm3 or more and 0.940 g / cm3 or less, a melt flow rate (MFR) of the resin (A), which is measured according to a method A in ISO 1133 at 190°C and a load of 2.16 kg, is 0.1 g / 10 min. or more and 1.3 g / 10 min. or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to a resin tube for supporting optical fibers. [Background technology]

[0002] Conventionally, a connector having optical fibers has been used as a sensor capable of monitoring the displacement of a structure using optical fibers. This connector has a cylindrical inner tube, an optical fiber mounting layer arranged in a cylindrical shape to cover the outer circumference of the inner tube, and four or more optical fibers laid spirally at a predetermined pitch on the optical fiber mounting layer and attached so as to deform along with the deformation of the inner tube (see, for example, Patent Document 1).

[0003] Furthermore, as an optical fiber sensor that minimizes residual compressive stress in the resin after molding and suppresses noise (signal loss) in the measurement data, a resin belt is known that is made of a water-absorbing, expandable resin that can eliminate molding shrinkage due to cooling after heat molding and can be assembled into a cylindrical shape (see, for example, Patent Document 2). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Patent No. 5851630 [Patent Document 2] Patent No. 3929378 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, in the sensor described in Patent Document 1, there was a problem in that the optical fiber mounting layer peeled off from the optical fiber, preventing the deformation of the inner tube from being transmitted to the optical fiber, as the inner tube was laid spirally at the pitch of the inner tube. Furthermore, the optical fiber sensor described in Patent Document 2 had the problem that, in the resin belt described above, stress was generated due to uneven moisture absorption of the resin, resulting in noise in the measurement data.

[0006] The present invention has been made in view of the above circumstances, and aims to provide an optical fiber-supported resin tube that can be used as a sensor capable of measuring structural distortion and temperature changes, can eliminate molding shrinkage, and can reduce signal loss. [Means for solving the problem]

[0007] To solve the above problems, the present invention has the following aspects. [1] A cylindrical tube having four or more optical fibers within its wall, the optical fibers extending in the direction of the tube axis, the wall being formed of a polyolefin resin composition containing resin (A), the density of which is 0.920 g / cm³ as measured in accordance with ISO 1183-1:2019 3 More than 0.940g / cm 3 A resin tube for supporting optical fibers, wherein the melt flow rate (MFR) of the resin (A) is 0.1 g / 10 min. to 1.3 g / 10 min., measured according to ISO 1133 Method A at 190°C and a load of 2.16 kg. [2] The polyolefin resin composition comprises resin (B), the density of which is 0.940 g / cm³ as measured in accordance with ISO 1183-1:2019. 3 More than 0.970g / cm 3 The optical fiber supporting resin tube described in [1], wherein the melt flow rate (MFR) of the resin (B) is 0.03 g / 10 min. to 0.1 g / 10 min., measured in accordance with Method A of ISO 1133 at 190°C and a load of 2.16 kg. [3] The optical fiber supporting resin tube according to [2], wherein the polyolefin resin composition has a content ratio of resin (A) to resin (B) (resin (A) / resin (B)) of 0.1 or more and 1.5 or less by mass ratio. [4] The wall thickness of the cylindrical wall is 2.5 mm or more and 10 mm or less, and the optical fiber-carrying resin tube according to any one of [1] to [3]. [5] The outer diameter is 20 mm or more and 50 mm or less, and the optical fiber-carrying resin tube according to any one of [1] to [4]. [6] The four or more optical fibers are arranged at rotationally symmetric positions with respect to each other in a cross section perpendicular to the tube axis direction, and the optical fiber-carrying resin tube according to any one of [1] to [5]. [7] The optical fiber is spirally embedded in the cylindrical wall at an inclination angle of more than 0 degrees and less than 90 degrees from the tube axis direction toward the circumferential direction, and the optical fiber-carrying resin tube according to any one of [1] to [6]. [8] The spiral pitch of the optical fiber is 10 mm or more and 600 mm or less, and the optical fiber-carrying resin tube according to [7]. [Advantages of the Invention]

[0008] According to the present invention, it is possible to provide an optical fiber-carrying resin tube that can be used as a sensor for measuring the distortion and temperature change of a structure, can eliminate molding shrinkage, and can reduce signal loss. [Brief Description of the Drawings]

[0009] [Figure 1] It is a perspective view showing an optical fiber-carrying resin tube according to an embodiment of the present invention. [Figure 2] It is a perspective view showing an optical fiber-carrying resin tube according to an embodiment of the present invention. [Modes for Carrying Out the Invention]

[0010] [Optical Fiber-Carrying Resin Tube] As the optical fiber-carrying resin tube of the present embodiment, for example, the one shown in FIG. 1 can be mentioned. The optical fiber-carrying resin tube 10 shown in FIG. 1 is a cylindrical long resin tube. The optical fiber-carrying resin tube 10 has a cylindrical resin tube 11 and an optical fiber 12 extending in the direction of the axis (tube axis) O1 of the resin tube 11 within the cylindrical wall 11A of the resin tube 11.

[0011] As shown in FIG. 1, at least two optical fibers 12 embedded in the cylindrical wall 11A of the resin tube 11 are provided to detect bending displacement, and preferably four or more optical fibers are provided to detect torsion and flat displacement. Further, in order to ensure the mechanical strength of the resin tube 11, the number of optical fibers 12 is preferably 20 or less. The optical fiber 12 is preferably located within 25% from the position bisecting in the thickness direction of the cylindrical wall 11A toward the surface. Thereby, when the optical fiber-carrying resin tube 10 is installed and constructed, the surface of the resin tube is scraped, and it is possible to suppress the optical fiber 12 from being exposed to the outside of the resin tube 11 and damaged.

[0012] As shown in FIG. 1, the four optical fibers 12 are preferably arranged at rotationally symmetric positions with respect to each other in a cross section perpendicular to the tube axis O1 direction in the cylindrical wall 11A of the resin tube 11. That is, in FIG. 1, the optical fibers 12 are preferably arranged at intervals of 90° in a cross section perpendicular to the tube axis O1 direction in the cylindrical wall 11A of the resin tube 11. Even when there are five or more optical fibers 12, the five or more optical fibers 12 are preferably arranged at rotationally symmetric positions with respect to each other in a cross section perpendicular to the tube axis O1 direction in the cylindrical wall 11A of the resin tube 11.

[0013] The thickness of the cylindrical wall 11A is preferably 2.5 mm or more and 10 mm or less, and more preferably 3 mm or more and 5 mm or less. If the thickness of the cylindrical wall 11A is less than the lower limit value, the cylindrical wall 11A may be damaged during construction and the optical fiber may be exposed from the cylindrical wall. If the thickness of the cylindrical wall 11A exceeds the upper limit value, the bending rigidity of the resin tube 11 increases, and it becomes difficult to follow the displacement of the structure. When the polyolefin resin composition forming the cylindrical wall 11A contains the resin (A) described later and when the polyolefin resin composition forming the cylindrical wall 11A contains the resin (A) and the resin (B) described later, the more resin (A) there is compared to resin (B), the greater the tendency for the thickness of the cylindrical wall 11A to be larger.

[0014] The outer diameter of the cylinder wall 11A is preferably 20 mm or more and 50 mm or less, and more preferably 30 mm or more and 40 mm or less. If the outer diameter of the cylinder wall 11A is less than the lower limit value, signal interference occurs between the optical fibers. If the outer diameter of the cylinder wall 11A exceeds the upper limit value, the bending rigidity of the resin tube 11 increases and it becomes difficult to follow the displacement of the structure.

[0015] The cylinder wall 11A is formed of a polyolefin resin composition containing resin (A). The density of resin (A) contained in the polyolefin resin composition forming the cylinder wall 11A is a value measured in accordance with ISO 1183-1:2019 "Plastics - Methods for measuring the density of non-foamed plastics - Part 1: Immersion method, liquid pycnometer method and titration method" is 0.920 g / cm 3 or more and 0.940 g / cm 3 or less, and preferably 0.925 g / cm 3 or more and 0.939 g / cm 3 or less, and more preferably 0.930 g / cm 3 or more and 0.938 g / cm 3 or less. If the density of resin (A) is less than the lower limit value, rigidity cannot be obtained. If the density of resin (A) exceeds the upper limit value, molding shrinkage increases and signal loss increases.

[0016] In a conventional optical fiber-carrying resin tube, the density of the resin composition forming the cylinder wall is a value measured in accordance with ISO 1183-1:2019 "Plastics - Methods for measuring the density of non-foamed plastics - Part 1: Immersion method, liquid pycnometer method and titration method" is 0.940 g / cm 3 or more and 0.960 g / cm 3 or less. In a conventional optical fiber-carrying resin tube, since the purpose is to obtain rigidity, the density of the resin composition forming the cylinder wall is within the above range.

[0017] The melt flow rate (MFR) of the resin (A) contained in the polyolefin resin composition forming the cylindrical wall 11A is measured according to Method A of ISO 1133 "Mass flow rate and volume flow rate of plastics" at 190°C and a load of 2.16 kg, and is preferably 0.1 g / 10 min. to 1.3 g / 10 min., more preferably 0.2 g / 10 min. to 0.8 g / 10 min., and more preferably 0.2 g / 10 min. to 0.6 g / 10 min.

[0018] In conventional optical fiber-supported resin tubes, the MFR of the polyolefin resin composition forming the tube wall was measured according to Method A of ISO 1133 "Mass flow rate and volume flow rate of plastics" and was between 0.01 g / 10 min. and 0.1 g / 10 min. In conventional optical fiber-supported resin tubes, the objective is to obtain rigidity, so the MFR of the polyolefin resin composition forming the tube wall was kept within the above range.

[0019] Examples of the resin (A) described above include polyolefin resins such as polyethylene, polypropylene, polybutene, ethylene-vinyl acetate copolymer, and ethylene-α-olefin copolymer. Polyolefin resins may be used individually or in combination of two or more types.

[0020] A specific example of resin (A) is one with a density of 0.938 g / cm³. 3 Furthermore, medium-density polyethylene with a melt flow rate (MFR) of 0.2 g / 10 min. is preferred.

[0021] The content of resin (A) in the polyolefin resin composition forming the tube wall 11A is preferably 40% to 90% by mass, and more preferably 60% to 90% by mass, of the total amount (100% by mass) of the resin composition. If the content of resin (A) is below the lower limit, molding shrinkage increases and signal loss increases. If the content of resin (A) exceeds the upper limit, the tube dimensions become unstable.

[0022] The polyolefin resin composition forming the cylindrical wall 11A preferably further contains resin (B). The statement that the polyolefin resin composition forming the cylindrical wall 11A contains resin (A) in addition to resin (B) means that the cylindrical wall 11A is formed of a polyolefin resin composition containing resin (A) and resin (B). The polyolefin resin composition forming the cylindrical wall 11A is a uniform mixture (dispersion) of resin (A) and resin (B). Furthermore, resin (B) is added for the purpose of increasing rigidity.

[0023] The density of resin (B) was measured according to ISO 1183-1:2019 "Plastics - Methods for determining the density of non-foamed plastics - Part 1: Immersion method, liquid pycnometer method and titration method" and was 0.940 g / cm³. 3 More than 0.970g / cm 3 Preferably, it is 0.940 g / cm³. 3 More than 0.960g / cm 3 It is more preferable that the following is the case: 0.940 g / cm³ 3 More than 0.950g / cm 3 The following conditions are even more preferable: If the density of resin (B) is below the lower limit, the pipe dimensions will not be stable. If the density of resin (B) exceeds the upper limit, molding shrinkage will increase and signal loss will increase.

[0024] The specific method for measuring the density of resin (B) in accordance with ISO 1183-1:2019 "Plastics - Methods for determining the density of non-foamed plastics - Part 1: Immersion method, liquid pycnometer method and titration method" is the same as the method for measuring the density of resin (A).

[0025] The melt flow rate (MFR) of resin (B) is preferably 0.03 g / 10 min. to 0.1 g / 10 min., measured according to Method A of ISO 1133 "Mass flow rate and volume flow rate of plastics" at 190°C and a load of 2.16 kg. If the MFR of resin (B) falls below the lower limit or exceeds the upper limit, the moldability becomes unstable.

[0026] The specific method for measuring the MFR of resin (B) in accordance with Method A of ISO 1133 "Mass flow rate and volume flow rate of plastics" is the same as the method for measuring the MFR of resin (A).

[0027] Examples of the resin (B) described above include polyolefin resins such as polyethylene, polypropylene, polybutene, ethylene-vinyl acetate copolymer, and ethylene-α-olefin copolymer. Polyolefin resins may be used individually or in combination of two or more types.

[0028] A specific example of resin (B) is one with a density of 0.952 g / cm³. 3 Furthermore, high-density polyethylene with a melt flow rate (MFR) of 0.02 g / 10 min. is preferred.

[0029] The content of resin (B) in the polyolefin resin composition forming the tube wall 11A is preferably 10% by mass or more and 60% by mass or less of the total amount (100% by mass) of the polyolefin resin composition. If the content of resin (B) is below the lower limit, the tube dimensions will not be stable. If the content of resin (B) exceeds the upper limit, molding shrinkage will increase and signal loss will increase.

[0030] Other components besides resin (A) and resin (B) in the polyolefin resin composition that forms the cylindrical wall 11A include, for example, polyolefin resins such as polypropylene, polybutene, ethylene-vinyl acetate copolymer, and ethylene-α-olefin copolymer.

[0031] The optical fiber 12 used has a core, cladding, and a coating layer, and when discontinuous pump light such as laser light is incident on the core, scattered light originating from the core's strain, temperature, etc., such as Brillouin scattering and Raman scattering, is generated. The optical fiber 12 is used as an optical fiber for strain measurement or an optical fiber for temperature measurement. A suitable optical fiber 12 for this purpose is one composed of a core and a cladding. The core and cladding materials can include plastic or quartz glass.

[0032] Examples of optical fibers include optical fiber strands with a primary coating on the outer circumference of the cladding, optical fiber cores with a secondary coating on the outer circumference of the primary coating, and optical fiber cords with a reinforcing material and an outer sheath covering the outer circumference of the secondary coating.

[0033] Examples of primary coating materials include UV-curing resins, nylon, fluororesins, polyimide, and polyethylene. Examples of materials for the secondary coating include flame-retardant polyester elastomer and polyimide. Examples of materials used for reinforcement include glass fiber, carbon fiber, and aramid fiber. Examples of materials for the outer covering include flame-retardant polyolefins such as flame-retardant polyethylene, flame-retardant crosslinked polyolefins such as flame-retardant crosslinked polyethylene, and heat-resistant vinyl.

[0034] Among these, a material with high heat resistance is preferable to reduce signal loss caused by deformation of the coating resin due to molding heat. Here, high heat resistance means that there is no melting point or glass transition temperature, or it is preferably 200°C or higher, and more preferably 250°C or higher. Suitable materials for this purpose include polyimide, fluororesin, high heat-resistant nylon, and curable resins. If the material does not have very good heat resistance, molding methods such as localized insulation may be applied.

[0035] The types of optical fibers used for strain measurement and temperature measurement are not particularly limited and can be selected according to the method of measuring strain and temperature, the type of scattered light used during measurement, etc. For example, it is preferable to use at least one type of optical fiber selected from the group consisting of single-mode optical fibers, multimode optical fibers, and polarization-maintaining optical fibers as the optical fiber for strain measurement and the optical fiber for temperature measurement. The optical fiber used for strain measurement and the optical fiber used for temperature measurement may be of the same type, or they may be of different types.

[0036] Furthermore, the optical fiber-supported resin tube 10 of this embodiment can have one or more optical fibers each for strain measurement and temperature measurement, depending on the measurement method, etc. Therefore, for example, different types of optical fibers or two or more of the same type of optical fiber can be used as strain measurement optical fibers, and the same applies to temperature measurement optical fibers.

[0037] In particular, when performing measurements, Brillouin scattered light or Rayleigh scattered light can be preferably used as the scattered light, and since a sharp peak can be obtained, it is preferable to use a single-mode optical fiber as the optical fiber for strain measurement. Furthermore, when performing temperature measurements, Raman scattered light can be preferably used as the scattered light, and since a high peak intensity can be obtained, it is preferable to use a multi-mode optical fiber as the optical fiber for temperature measurement. In this way, by selecting an optical fiber suitable for the scattered light used for measurement, strain and temperature can be measured with high accuracy.

[0038] The outer diameter of the optical fiber 12 is preferably 125 μm or more and 2000 μm or less, and more preferably 150 μm or more and 1000 μm or less. If the outer diameter of the optical fiber 12 is less than the lower limit, it will break even with a small load, making it difficult to handle during the manufacturing process. If the outer diameter of the optical fiber 12 exceeds the upper limit, it is difficult to strip the coating during measurement.

[0039] The optical fiber-supported resin tube 10 of this embodiment is cylindrical and has four or more optical fibers 12 within the tube wall 11A, the optical fibers 12 extending in the direction of the tube axis O1, the tube wall 11A is formed of a polyolefin resin composition containing resin (A), and the density of resin (A) is 0.920 g / cm³ as measured in accordance with ISO 1183-1:2019. 3 More than 0.940g / cm 3The following conditions are met, and the melt flow rate (MFR) of resin (A) is measured according to ISO 1133 Method A at 190°C and a load of 2.16 kg, with a value of 0.1 g / 10 min. to 1.3 g / 10 min. Therefore, signal loss transmitted through the optical fiber 12 is suppressed, and measurements over long distances can be performed with greater accuracy.

[0040] [Manufacturing method for optical fiber-supported resin tubes] The method for manufacturing the optical fiber-supported resin tube of this embodiment will now be described. A polyolefin resin composition containing only the above-mentioned resin (A), or a polyolefin resin composition containing the above-mentioned resin (A) and resin (B), along with an optical fiber 12, was supplied to a mold. The extruded molded body, in which the resin tube and the optical fiber 12 were integrally molded, was taken up using a take-up machine installed downstream of the mold to obtain the optical fiber-supported resin tube 10 shown in Figure 1.

[0041] <Other Embodiments> However, the present invention is not limited to the embodiments described above.

[0042] For example, a modified optical fiber-supported resin tube 20 as shown in Figure 2 may be used. The optical fiber-supported resin tube 20 shown in Figure 2 is a long, cylindrical resin tube. The optical fiber-supported resin tube 20 comprises a cylindrical resin tube 21 and an optical fiber 22 that is spirally embedded within the cylindrical wall 21A of the resin tube 21 at an inclination angle of more than 0 degrees and less than 90 degrees from the axial direction (tube axis) O2 of the resin tube 21 toward the circumferential direction.

[0043] As shown in Figure 2, there are at least four optical fibers 22 embedded in the cylindrical wall 21A of the resin tube 21, and there may be five or more to increase the sensitivity for detecting strain changes, etc. Furthermore, in order to ensure the mechanical strength of the resin tube 21, it is preferable that there be 20 or fewer optical fibers 22. It is preferable that the optical fiber 22 is located within 25% of the distance from the point where the thickness of the tube wall 11A is bisected at its center toward the surface. This prevents the optical fiber 22 from being exposed to the outside of the resin tube 21 and being damaged when the optical fiber-supported resin tube 20 is bent.

[0044] The helical pitch P of the optical fiber 22 shown in Figure 2 is preferably 10 mm or more and 600 mm or less, more preferably 100 mm or more and 500 mm or less, and even more preferably 300 mm or more and 400 mm or less. If the helical pitch of the optical fiber 22 is below the lower limit, the measurement accuracy does not change, but more optical fibers 22 are required, and the cost increases. If the helical pitch of the optical fiber 22 exceeds the upper limit, the measurement accuracy decreases.

[0045] The resin tube 21 has the same configuration as the resin tube 11, and the optical fiber 22 has the same configuration as the optical fiber 12.

[0046] While embodiments of this invention have been described in detail with reference to the drawings above, these embodiments are merely illustrative examples of the invention. Therefore, this invention is not limited to the configurations of the embodiments, and any design changes, etc., that do not depart from the gist of this invention are also included. Furthermore, for example, if each embodiment includes multiple configurations, it goes without saying that possible combinations of these configurations are included, even if not specifically stated. Also, if multiple examples or variations are disclosed as part of this invention within an embodiment, it goes without saying that possible combinations of configurations spanning these are included, even if not specifically stated. Moreover, configurations depicted in the drawings are included, even if not specifically stated. Furthermore, where the term "etc." is used, it means that equivalent items are included. [Examples]

[0047] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0048] [Example 1] Medium-to-low density polyethylene and polyimide-coated optical fibers were supplied to a mold, and the extruded body, in which the resin tube and the polyimide-coated optical fiber were integrally molded, was pulled up while twisting in the circumferential direction using a rotary take-up machine installed downstream of the mold to obtain an optical fiber-supported resin tube as shown in Figure 2. In the resulting optical fiber-supported resin tube, four or more optical fibers are arranged within the tube wall, and these optical fibers are positioned in a rotationally symmetrical manner in a cross-section perpendicular to the tube axis direction of the optical fiber-supported resin tube within the tube wall. For polyethylene, the density measured according to ISO 1183-1:2019 "Plastics - Methods for determining the density of non-foamed plastics - Part 1: Immersion method, liquid pycnometer method and titration method" was 0.938 g / cm³. 3 In accordance with Method A of ISO 1133 "Mass flow rate and volume flow rate of plastics," a melt flow rate of 0.2 g / 10 min. was measured at 190°C and under a load of 2.16 kg.

[0049] [Example 2] A resin composition containing medium- and low-density polyethylene and high-density polyethylene, along with a polyimide-coated optical fiber, was supplied to a mold. The extruded body, in which the resin tube and the polyimide-coated optical fiber were integrally molded, was then pulled up using a rotary take-up machine installed downstream of the mold, twisting it circumferentially to obtain an optical fiber-supported resin tube as shown in Figure 2. In the resulting optical fiber-supported resin tube, four or more optical fibers are arranged within the tube wall, and these optical fibers are positioned in a rotationally symmetrical manner in a cross-section perpendicular to the tube axis direction of the optical fiber-supported resin tube within the tube wall. For medium- and low-density polyethylene, the density measured according to ISO 1183-1:2019 "Plastics - Methods for determining the density of non-foamed plastics - Part 1: Immersion method, liquid pycnometer method and titration method" is 0.938 g / cm³. 3 In accordance with Method A of ISO 1133 "Mass flow rate and volume flow rate of plastics," a melt flow rate of 0.2 g / 10 min. was measured at 190°C and under a load of 2.16 kg. For high-density polyethylene, the density measured according to ISO 1183-1:2019 "Plastics - Methods for determining the density of non-foamed plastics - Part 1: Immersion method, liquid pycnometer method and titration method" was 0.952 g / cm³. 3 They used what is.

[0050] [Comparative Example] High-density polyethylene and polyimide-coated optical fibers were supplied to a mold, and the extruded body, in which the resin tube and the polyimide-coated optical fiber were integrally molded, was pulled up while twisting in the circumferential direction using a rotary take-up machine installed downstream of the mold to obtain an optical fiber-supported resin tube as shown in Figure 2. In the resulting optical fiber-supported resin tube, four or more optical fibers are arranged within the tube wall, and these optical fibers are positioned in a rotationally symmetrical manner in a cross-section perpendicular to the tube axis direction of the optical fiber-supported resin tube within the tube wall. For high-density polyethylene, the density measured according to ISO 1183-1:2019 "Plastics - Methods for determining the density of non-foamed plastics - Part 1: Immersion method, liquid pycnometer method and titration method" was 0.952 g / cm³. 3 They used what is.

[0051] "Method for evaluating signal loss" We evaluated the signal loss of the optical fiber by irradiating it with pulsed light of very short wavelength into an optical fiber supported by a resin tube. The signal loss in optical fibers was evaluated using the Optical Time Domain Reflectometer (OTDR) method, which measures the power of backscattered and reflected light generated in the optical fiber, and the LSPM method, which measures the amount of attenuation using a light source and a power meter. A dummy cord was placed between the fiber optic-supported resin tube and the signal loss measuring instrument. The exposed fiber optic cable was connected to the dummy cord, and after connecting the dummy cord to the measuring instrument, the signal loss in the fiber optic-supported resin tube was measured. The criteria for determining signal loss were as follows. The results are shown in Table 1. <Criteria for determining signal loss> "○" indicates a signal loss of 5 dB / km or less, and "×" indicates a signal loss exceeding 5 dB / km.

[0052] [Table 1]

[0053] The results in Table 1 confirm that the optical fiber-supported resin tubes of Examples 1 and 2 can reduce signal loss. [Explanation of symbols]

[0054] 10,20 Fiber optic cable supporting resin tube 11,21 Resin pipe 11A,21A Cylinder wall 12,22 Optical Fibers

Claims

1. It is cylindrical and has four or more optical fibers inside the cylindrical wall. The optical fiber extends having a component along the direction of the tube axis, The cylindrical wall is formed of a polyolefin resin composition containing resin (A), The density of the aforementioned resin (A) was measured in accordance with ISO 1183-1:2019 and was 0.920 g / cm³. ３ 0.940g / cm or more ３ The following: Furthermore, the melt flow rate (MFR) of the resin (A) was measured according to Method A of ISO 1133 at 190°C and a load of 2.16 kg, and was between 0.1 g / 10 min. and 1.3 g / 10 min. The optical fiber is embedded in the cylindrical wall in a spiral shape at an angle such that the angle between the direction in which the optical fiber extends and the axis of the cylindrical wall is greater than 0 degrees and less than 90 degrees. A resin tube for supporting optical fibers, wherein the helical pitch of the optical fiber is 10 mm or more and 600 mm or less.

2. The polyolefin resin composition comprises resin (B), The density of the aforementioned resin (B) was measured in accordance with ISO 1183-1:2019 and was 0.940 g / cm³. ３ 0.970g / cm or more ３ The following: Furthermore, the melt flow rate (MFR) of the resin (B) was measured according to Method A of ISO 1133 at 190°C and a load of 2.16 kg, and was between 0.03 g / 10 min. and 0.1 g / 10 min. The optical fiber supporting resin tube according to claim 1, wherein the melt flow rate (MFR) of the resin (B) is 0.03 g / 10 min. to 0.1 g / 10 min. as measured in accordance with ISO 1133 Method A at 190°C and a load of 2.16 kg.

3. The optical fiber supporting resin tube according to claim 2, wherein the content ratio of resin (A) to resin (B) (resin (A) / resin (B)) in the polyolefin resin composition is 0.1 or more and 1.5 or less by mass ratio.

4. The optical fiber supporting resin tube according to any one of claims 1 to 3, wherein the thickness of the tube wall is 2.5 mm or more and 10 mm or less.

5. An optical fiber supporting resin tube according to any one of claims 1 to 4, wherein the outer diameter is 20 mm or more and 50 mm or less.

6. The optical fiber-supported resin tube according to any one of claims 1 to 5, wherein the four or more optical fibers are arranged in positions that are rotationally symmetrical with respect to each other in a cross section perpendicular to the tube axis.

7. The optical fiber supporting resin tube according to any one of claims 1 to 6, wherein the helical pitch of the optical fiber is 100 mm or more and 500 mm or less.

Images