Optical fiber cable

Abstract

To provide an optical fiber cable that has fire retardancy while maintaining sufficient strength.SOLUTION: An optical fiber cable comprises a plurality of coated optical fibers and a covering provided on the periphery of the plurality of coated optical fibers. The covering has an inner layer provided on the outside of the plurality of coated optical fibers, and an outer layer provided on the outside of the inner layer. The density of material used for the outer layer is 1.4 g / cm3 or more. The density of material used for the inner layer is less than 1.4 g / cm3. The oxygen index of the material used for the outer layer is 36 or more.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to an optical fiber cable.

Background Art

[0002] Patent Document 1 discloses an optical fiber cable for pneumatic transmission.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in recent years, there has been an increasing demand for cable wiring that can be drawn from the outside to the inside of a building for the purpose of reducing the connection points of optical fiber cables. For outdoor cables, flame retardancy is not very necessary, but for indoor cables, the flame retardancy standards are strict, and there is an increasing demand for optical fiber cables with the flame retardancy required for indoor cables. However, generally, materials with high flame retardancy have a low Young's modulus, and the strength of the outer sheath tends to decrease as the flame retardancy increases.

[0005] An object of the present disclosure is to provide an optical fiber cable having flame retardancy while maintaining sufficient strength.

Means for Solving the Problems

[0006] The optical fiber cable according to one aspect of the present disclosure includes a plurality of optical fiber cores, an outer sheath provided around the plurality of optical fiber cores, and the outer sheath has an inner layer provided outside the plurality of optical fiber cores and an outer layer provided outside the inner layer. The density of the material used for the outer layer is 1.4 g / cm 3 or more, and the density of the material used for the inner layer is 1.4 g / cm 3 less than, and the oxygen index of the material used for the outer layer is 36 or more.

Advantages of the Invention

[0007] According to the present disclosure, it is possible to provide an optical fiber cable having flame retardancy while maintaining sufficient strength.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0009] (Description of Embodiments of the Present Disclosure) First, embodiments of the present disclosure will be listed and described. An optical fiber cable according to one aspect of the present disclosure is (1) a plurality of optical fiber cores, a jacket provided around the plurality of optical fiber cores, and the jacket has an inner layer provided outside the plurality of optical fiber cores and an outer layer provided outside the inner layer, the density of the material used for the outer layer is 1.4 g / cm 3 or more, and the density of the material used for the inner layer is 1.4 g / cm 3 less than, and the oxygen index of the material used for the outer layer is 36 or more. According to such a configuration, the outer layer has a density of 1.4 g / cm 3Since it is formed of a material having an oxygen index of 36 or more, it has high flame retardancy. On the other hand, the inner layer is formed of a material having a density of less than 1.4 g / cm 3 Since it is formed of a material having a density of less than 1.4 g / cm, the entire cable has sufficient strength. Therefore, it is possible to provide an optical fiber cable having flame retardancy while maintaining sufficient strength.

[0010] (2) In the above (1), the average value of the arithmetic mean roughness Ra of the outer layer may be 0.8 μm or less, and the average value of the maximum height roughness Rz of the outer layer may be 6.0 μm or less. According to such a configuration, since the outer layer has high surface smoothness, for example, when pneumatically feeding an optical fiber cable in a duct as cable laying work, the friction between the outer sheath of the optical fiber cable and the duct can be reduced.

[0011] (3) In the above (1) or (2), a plurality of tension members arranged in the inner layer are provided, The storage elastic modulus of the material used for the inner layer at 23°C may be 800 MPa or more. According to such a configuration, since the inner layer in which the tension members are arranged has high strength, for example, when bundling the slack of an optical fiber cable as cable laying work, it is possible to prevent the tension members from breaking.

[0012] (4) In the above (3), the thickness of the inner layer may be 0.1 mm or more larger than the diameter of the tension member and may be half or less of the thickness of the outer sheath. According to such a configuration, it is possible to embed the tension members in the inner layer while achieving both strength and flame retardancy.

[0013] (Details of Embodiments of the Present Disclosure) A specific example of a slotless optical fiber cable according to an embodiment of the present disclosure will be described below with reference to the drawings. It should be noted that the present invention is not limited to these examples, and is defined by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0014] FIG. 1 illustrates the configuration of the optical fiber cable 1 according to the present embodiment. FIG. 1 shows a cross section perpendicular to the length direction of the optical fiber cable 1. In this example, the optical fiber cable 1 is a slottedless type optical fiber cable. The optical fiber cable 1 is used, for example, as an air pressure feeding type optical fiber cable laid in a pressure feeding microduct.

[0015] As illustrated in FIG. 1, the optical fiber cable 1 includes a plurality of optical fiber ribbons 2, a water absorption tape 3, an outer sheath 4, a plurality of tension members 5, and a tear string 6.

[0016] The optical fiber ribbon 2 is formed by connecting a plurality of optical fiber cores 21 in a state where they are arranged in parallel. The optical fiber core 21 is formed of, for example, a glass fiber composed of a core and a cladding, and a coating layer that coats the outer periphery of the glass fiber.

[0017] FIG. 2 shows an example of an intermittently connected type optical fiber ribbon 2. FIG. 2 shows a state in which a plurality of optical fiber cores 21 are opened in the arrangement direction.

[0018] As shown in FIG. 2, in a state where a plurality of optical fiber cores 21 are arranged in parallel, a connecting portion 22 where adjacent optical fiber cores 21 are connected and a non-connecting portion 23 where adjacent optical fiber cores 21 are not connected are provided intermittently in the longitudinal direction. In this example, 12 optical fiber cores 21 are intermittently connected in pairs of two. That is, units in which two optical fiber cores 21 are integrated are intermittently connected by the connecting portion 22 and the non-connecting portion 23. In the connecting portion 22, for example, a connecting resin is applied between the optical fiber cores 21 so that the optical fiber cores 21 are connected to each other. Note that instead of in pairs of two, all adjacent optical fiber cores 21 (one by one) may be intermittently connected.

[0019] The optical fiber ribbon 2 is accommodated in the optical fiber cable 1 in a rounded state. Alternatively, a plurality of optical fiber ribbons 2 may be accommodated in the optical fiber cable 1 in a twisted state. Further, the plurality of optical fiber ribbons 2 may be bundled with a bundling material or the like in a grouped state or a twisted state.

[0020] The water absorption tape 3 is formed so as to cover the periphery of the optical fiber ribbon 2. Specifically, the water absorption tape 3 is wound around the entire periphery of the plurality of optical fiber ribbons 2, for example, in a longitudinal attachment or a spiral winding. The water absorption tape 3 is obtained by subjecting a base fabric made of, for example, polyester or the like to a water absorption process by attaching a water-absorbing powder thereto.

[0021] The outer sheath 4 is provided so as to cover the periphery of the water absorption tape 3. The outer sheath 4 is formed, for example, by extruding a resin onto the plurality of optical fiber ribbons 2 around which the water absorption tape 3 is wound.

[0022] The outer sheath 4 has an inner layer 41 and an outer layer 42. The inner layer 41 is provided so as to cover the periphery of the water absorption tape 3 provided outside the plurality of optical fiber cores 21. The material used for the inner layer 41 has a density of less than 1.4 g / cm 3 less than. The material is not particularly limited as long as the density is less than 1.4 g / cm 3 less than, but as the material used for the inner layer 41, for example, polyethylene or the like is used.

[0023] The outer layer 42 is provided outside the inner layer 41. The material used for the outer layer 42 has a density of 1.4 g / cm 3 or more. The material is not particularly limited as long as the density is 1.4 g / cm 3 or more, but as the material used for the outer layer 42, for example, a flame-retardant polyolefin or the like obtained by blending a substance that enhances flame retardancy with high-density polyethylene as a base material is used.

[0024] The tension member 5 is provided inside the outer sheath 4. Specifically, the tension member 5 is embedded along the longitudinal direction of the optical fiber cable 1 within the inner layer 41 of the outer sheath 4. The tension member 5 is formed of, for example, a fiber-reinforced plastic (FRP) such as aramid FRP, glass FRP, or carbon FRP. Alternatively, the tension member 5 may be formed of metal. In this example, four tension members 5 that are adjacent to each other are grouped together, and four groups are arranged at equal intervals. Note that the number and arrangement of the tension members 5 are not limited to the number and arrangement shown in FIG. 1.

[0025] The thickness of the inner layer 41 is preferably equal to or greater than the diameter of the tension member 5 + 0.1 mm and equal to or less than half of the thickness of the outer sheath 4. As an example, the thickness of the outer sheath 4 is 1.8 mm, the diameter of the tension member 5 is 0.5 mm, the thickness of the inner layer 41 is 0.6 mm, and the thickness of the outer layer 42 is 1.2 mm.

[0026] The tear string 6 is provided inside the outer sheath 4. Specifically, the tear string 6 is embedded along the longitudinal direction of the optical fiber cable 1 within the inner layer 41 of the outer sheath 4. By pulling out the tear string 6 from the outer sheath 4, the outer sheath 4 can be torn in the longitudinal direction, and the optical fiber ribbon 2 can be taken out. The tear string 6 is formed of, for example, a plastic material that is resistant to pulling (e.g., polyester). In this example, two tear strings 6 are provided so as to face each other. Note that the number and arrangement of the tear strings 6 are not limited to the number and arrangement shown in FIG. 1.

[0027] Here, for the purpose of reducing the connection points of the optical fiber cable, the demand for cable wiring that can be drawn from outdoors to indoors is increasing, and the demand for optical fiber cables with flame retardancy required for indoor cables is increasing. When imparting flame retardancy to an optical fiber cable, for example, it is conceivable to form an outer sheath with a flame-retardant material. However, generally, the flame-retardant materials used for the outer sheath have lower tensile strength and Young's modulus compared to non-flame-retardant materials. In particular, they soften more as the temperature rises, which may lead to deterioration in the handleability of the cable during pneumatic feeding (such as straightness, low friction, and cable slack take-up (bundling)), or the cable itself may kink.

[0028] According to the optical fiber cable 1 according to this embodiment, since the material density of the outer layer 42 is 1.4 g / cm 3 or more and it contains a substance that enhances flame retardancy, the outer layer 42 has high flame retardancy. Also, since the material used for the outer layer 42 has an oxygen index of 36 or more, the flame retardancy of the outer layer 42 can be enhanced. Here, the oxygen index is the minimum oxygen concentration required for continuous combustion as defined in JIS K7201.

[0029] On the other hand, the material density of the inner layer 41 is less than 1.4 g / cm 3 but it has reduced flame retardancy, so it has stronger material strength than the outer layer 42. That is, in the optical fiber cable 1, a material with higher strength than flame retardancy is used for the inner layer 41 closer to the inside of the cable, and a material with priority on flame retardancy is used for the outer layer 42 exposed to the outside. Thereby, an optical fiber cable 1 having flame retardancy while maintaining sufficient strength can be provided.

[0030] Also, in the optical fiber cable 1, the material used for the inner layer 41 may have a storage elastic modulus at 23°C of 800 MPa or more. Thereby, the strength of the inner layer 41 can be enhanced, so that, for example, when bundling the slack of the optical fiber cable 1, it is possible to prevent the tension member 5 disposed inside the inner layer 41 from breaking. Here, the storage elastic modulus is a physical property value that can be measured by dynamic viscoelasticity measurement (DMS).

[0031] Further, in the optical fiber cable 1, the average value of the arithmetic mean roughness Ra of the outer layer 42 may be 0.8 μm or less, and the average value of the maximum height roughness Rz of the outer layer 42 may be 6.0 μm or less. According to such a configuration, since the outer layer 42 has high surface smoothness, for example, when pneumatically feeding the optical fiber cable 1 in a duct as cable laying work, the friction between the outer covering of the optical fiber cable 1 and the duct can be reduced.

[0032] Here, the arithmetic mean roughness Ra and the maximum height roughness Rz are defined in JIS B 0601:2013.

[0033] The method for obtaining the average values of the arithmetic mean roughness Ra and the maximum height roughness Rz is not particularly limited. For example, in an arbitrary cross section perpendicular to the longitudinal direction of the optical fiber cable 1, four measurement points are set at equal intervals along the circumferential direction of the outer circumference. Then, the arithmetic mean roughness Ra and the maximum height roughness Rz are respectively measured along the longitudinal direction of the optical fiber cable 1 at each measurement point. And the average value of the measured values at the four measurement points is taken as the average value of the arithmetic mean roughness Ra and the maximum height roughness Rz.

[0034] (Example 1) The flame retardancy and kink resistance of the outer covering 4 combining an inner layer and an outer layer with different material densities, oxygen indices and storage elastic moduli were evaluated. The evaluation results are shown in Table 1. For the flame retardancy, it was evaluated as A (qualified) when passing the riser combustion test (applicable safety standard UL1666), and as B (unqualified) when failing the riser combustion test. For the kink resistance, when the optical fiber cable 1 was formed into a loop with a diameter of φ150 mm and left at 70 °C for 5 minutes without kinking (twisting), it was evaluated as A (qualified), and as B (unqualified) when kinked.

[0035]

Table 1

[0036] From Table 1, in Sample 1, both the flame retardancy and kink resistance were good. In Sample 2, the kink resistance was good. In Sample 3, only the flame retardancy was good.

[0037] That is, from the evaluation results of Sample 1 and Sample 3, when the material density of the outer layer is 1.4 g / cm 3 or more and the oxygen index is 36 or more, it was found that the flame retardancy is good. Also, from the evaluation results of Sample 1 and Sample 2, when the material density of the inner layer is less than 1.4 g / cm 3 and the storage modulus at 23°C of the material used for the inner layer is 800 MPa or more, it was found that the kink resistance is good.

[0038] (Example 2) The surface roughness of the outer sheath was evaluated. The evaluation results are shown in Table 2. Specifically, using a single-layer flame-retardant outer sheath and a non-flame-retardant outer sheath, the average values of the arithmetic mean roughness Ra and the maximum height roughness Rz of each outer sheath were measured. As the flame-retardant outer sheath, an outer sheath with an oxygen index of 36 or more and a material density of less than 1.4 g / cm 3 and an outer sheath with an oxygen index of 36 or more and a material density of 1.4 g / cm 3 or more were used. As the non-flame-retardant outer sheath, an outer sheath with an oxygen index of less than 36 and a material density of 1.4 g / cm 3 or less, which was the same as the outer layer used in Sample 2, was used.

[0039] As described above, for the arithmetic mean roughness Ra and the maximum height roughness Rz, in an arbitrary cross-section perpendicular to the longitudinal direction of the optical fiber cable 1, four measurement points were set at equal intervals along the circumferential direction of the outer circumference, and the measurements were taken along the longitudinal direction of the optical fiber cable 1 at each measurement point. Also, for the arithmetic mean roughness Ra and the maximum height roughness Rz, the average value of the measured values at the four measurement points was obtained.

[0040]

Table 2

[0041] From Table 2, in Sample 4, the average of the arithmetic mean roughness Ra was 0.41 μm, the average of the maximum height roughness Rz was 2.6 μm, and the surface smoothness was good. Whether the surface smoothness was good or not was determined by whether the optical fiber cable 1 could be pneumatically conveyed to the reference distance under the same conditions. In Sample 5, the average of the arithmetic mean roughness Ra was 0.39 μm, the average of the maximum height roughness Rz was 2.9 μm, and the surface smoothness was good. In Sample 6, the average of the arithmetic mean roughness Ra was 1.18 μm, the average of the maximum height roughness Rz was 8.1 μm, and good surface smoothness could not be obtained. That is, it was found that in the jacket having flame retardancy and an average value of the arithmetic mean roughness Ra of 0.8 μm or less and an average value of the maximum height roughness Rz of 6.0 μm or less, the surface smoothness was good.

[0042] As described above, the present invention has been described in detail with reference to specific embodiments. However, it is obvious to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present invention. Also, the number, position, shape, etc. of the constituent members described above are not limited to the above-described embodiments, and can be changed to the number, position, shape, etc. suitable for implementing the present invention.

[0043] In the above embodiment, the tension member 5 is completely embedded in the inner layer 41 of the jacket 4. However, a part of the tension member 5 may be arranged so as to be exposed from the inner layer 41 of the jacket 4. FIG. 3 illustrates the configuration of the slotted optical fiber cable 1 in which a part of the tension member 5 is arranged so as to be exposed from the inner layer 41 of the jacket 4 toward the water absorption tape 3. According to such a configuration, the thickness of the inner layer 41 can be reduced, and as a result, an increase in the cable outer diameter can be suppressed.

[0044] In the above-described embodiment, the plurality of optical fiber cores 21 are arranged in the optical fiber cable 1 in the form of an optical fiber ribbon 2. However, for example, the plurality of optical fiber cores 21 may be arranged in the optical fiber cable 1 in a single-core state, bundled or twisted together. In this case, the plurality of single-core optical fiber cores 21 that are bundled or twisted together may be bundled with a bundling material or the like. Alternatively, a part of the plurality of optical fiber cores 21 may be arranged in the optical fiber cable 1 in the form of an optical fiber ribbon, and the rest may be in a single-core state.

[0045] In the above-described embodiment, the optical fiber ribbon 2 is formed by 12 optical fiber cores 21. However, the optical fiber ribbon 2 may be formed by, for example, 16 or 24 optical fiber cores 21.

[0046] In the above-described embodiment, the optical fiber cable 1 according to the present disclosure is described by taking a slottedless type optical fiber cable as an example. However, the optical fiber cable according to the present disclosure may be a slotted type optical fiber cable. Also, as the internal structure of the optical fiber cable, any structure such as a structure in which optical fibers are bundled with bundle yarns, a structure in which optical fibers are put into a loose tube, a structure in which optical fibers are wrapped with a film, etc. may be used.

Description of Reference Numerals

[0047] 1: Optical fiber cable 2: Optical fiber ribbon 21: Optical fiber core 22: Connection part 23: Non-connection part 3: Water-absorbing tape 4: Outer sheath 41: Inner layer 42: Outer layer 5: Tension member 6: Tear string

Claims

1. A plurality of optical fiber cores; a jacket provided around the plurality of optical fiber cores; It is equipped with the jacket has an inner layer provided on the outer side of the plurality of optical fiber cores and an outer layer provided on the outer side of the inner layer, The density of the material used for the outer layer is 1.4 g / cm ３ or more, and the density of the material used for the inner layer is 1.4 g / cm ３ is less than An optical fiber cable, wherein the material used for the outer layer has an oxygen index of 36 or more.

2. The average value of the arithmetic mean roughness Ra of the outer layer is 0.8 um or less, and the average value of the maximum height roughness Rz of the outer layer is 6.0 um or less.

2. The optical fiber cable according to claim 1.

3. A plurality of tension members are disposed within the inner layer, The storage modulus at 23°C of the material used for the inner layer is 800 MPa or more. The optical fiber cable according to claim 1 or 2.

4. 4. The optical fiber cable according to claim 3, wherein a thickness of the inner layer is at least 0.1 mm larger than a diameter of the tension member and is not more than half a thickness of the outer jacket.

Images