Optical fiber cables and cables with connectors

Abstract

An optical fiber cable (1A) comprises: a central tension member (5A); a plurality of coated optical fibers disposed around the central tension member (5A); a tension member set (50) disposed outside the plurality of coated optical fibers; and an outer sheath (4) disposed outside the plurality of coated optical fibers. In the outer sheath (4), at least four tension member sets (50) are contained separately from each other.

Description

[Technical Field]

[0001] The present disclosure relates to fiber optic cables and connectorized cables. This application claims priority to Japanese Application No. 2021-002862, filed on January 12, 2021, and incorporates by reference all of the contents of said Japanese application. [Background technology]

[0002] Conventionally, as a microduct cable that is laid in a thin pipe by air pressure feeding or pulling, a loose-tube cable is known in which optical fiber units each consisting of a bundle of optical fiber cores are covered with a resin tube and then covered with a cable jacket. Also known is a slotless cable that omits the resin tube and packs optical fiber cores at high density inside the cable jacket (for example, Patent Documents 1, 2, and 3). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japan Special Publication No. 2015-517679 [Patent Document 2] Japanese Patent Publication No. 2010-008923 [Patent Document 3] Japanese Patent Application Publication No. 2014-071441 Summary of the Invention

[0004] The optical fiber cable of the present disclosure comprises: a central tension member; a plurality of optical fiber cores arranged around the central tension member; a set of strength members arranged outside the plurality of optical fiber cores; an outer jacket disposed on the outside of the plurality of optical fiber cores, At least four sets of the tension members are enclosed in the outer jacket and spaced apart from one another. And, The allowable tension is between 1163N and 2363N. .

[0005] The connectorized cable of the present disclosure comprises: the optical fiber cable; a multi-fiber connector attached to the plurality of optical fiber cores at one end of the optical fiber cable. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is a cross-sectional view of an optical fiber cable according to a first embodiment. [Figure 2] FIG. 2 is a partial development view showing the optical fiber ribbon housed in the optical fiber cable in the longitudinal direction. [Figure 3] FIG. 3 is a cross-sectional view of an optical fiber cable according to a modified example of the first embodiment. [Figure 4] FIG. 4 is a schematic perspective view of a connectorized cable to which an optical fiber cable has been terminated. DETAILED DESCRIPTION OF THE INVENTION

[0007] (Problem to be solved by this disclosure) Loose-tube cables have a tension member in the center. This eliminates anisotropy in the bending direction, making wiring easy by air pressure feeding. However, the resin tube that covers the optical fiber unit is generally thick. This makes it difficult to reduce the outer diameter of loose-tube cables or to pack optical fiber cores at high density.

[0008] On the other hand, slotless cables do not have a resin tube, so they can pack optical fiber cores at high density. However, because slotless cables have multiple tension members embedded in the jacket, the cable's rigidity becomes uneven depending on the position where the tension members are embedded. This results in anisotropy in the bending direction, which can lead to buckling during air pumping.

[0009] Furthermore, when a cable is laid in a duct by air-blown, it is generally preferable that the cable be small in diameter and lightweight, and that the cable jacket be thin in thickness, in order to extend the feeding distance. On the other hand, when a cable is laid in a duct by pulling, the cable may be stretched by the pulling force. When an air-blown cable is laid in a duct by pulling, the air-blown cable may be stretched, which may have an adverse effect on the transmission loss of the optical fiber core.

[0010] The present disclosure provides fiber optic cables and connectorized cables that are easy to route by air pumping and towing.

[0011] (Description of Embodiments of the Present Disclosure) First, embodiments of the present disclosure will be listed and described. (1) An optical fiber cable according to one embodiment of the present disclosure includes: a central tension member; a plurality of optical fiber cores arranged around the central tension member; a set of strength members arranged outside the plurality of optical fiber cores; an outer jacket disposed on the outside of the plurality of optical fiber cores, At least four sets of the tension members are enclosed in the outer jacket and spaced apart from one another. And, The allowable tension is between 1163N and 2363N. .

[0012] According to the optical fiber cable of the present disclosure, at least four strength member sets are contained in the jacket at a distance from each other, which improves the non-uniformity of the cable's rigidity due to the positions of the strength member sets contained therein and makes the cable less likely to buckle when air is pumped. Furthermore, because the optical fiber cable of the present disclosure includes not only the strength member sets contained in the jacket but also a central strength member, the cable is less likely to stretch when pulled. This makes wiring by air pumping and pulling easier.

[0013] (2) At least one of the central strength member and the set of strength members may include aramid fiber reinforced plastic. According to the present disclosure, the central strength member or strength member set includes aramid fiber reinforced plastic, resulting in an optical fiber cable having lightweight and highly flexible strength members that facilitates routing by air pumping and towing.

[0014] (3) The central tension member may include aramid fiber reinforced plastic and have a diameter of 3 mm or less. According to the present disclosure, the central strength member contains aramid fiber-reinforced plastic, resulting in an optical fiber cable equipped with a lightweight and highly flexible strength member. Furthermore, if the central strength member is too thick, the optical fibers in the cable tend to be packed so tightly together that they exert lateral pressure on each other. This can result in high cable transmission loss. However, because the diameter of the central strength member of the present disclosure is 3 mm or less, cable transmission loss can be suppressed while cable elongation during pulling can be suppressed.

[0015] (4) The outer covering may contain 1.5% by mass or more of a lubricant. The outer sheath of the present disclosure contains 1.5% by mass or more of a lubricant, which facilitates wiring by air pressure feeding.

[0016] (5) The outer covering may contain a flame-retardant inorganic material having an oxygen index of 50 or more. The jacket of the present disclosure contains a flame-retardant inorganic material with an oxygen index of 50 or more, which further improves the flame retardancy of the optical fiber cable.

[0017] (6) The outer covering includes an outer layer and an inner layer. The inner layer may include a flame-retardant inorganic material. The outer layer may include a lubricant. According to the present disclosure, the flame retardancy of the optical fiber cable can be improved by including a flame-retardant inorganic material in the inner layer of the jacket, and a lubricant in the outer layer of the jacket, which facilitates wiring by air pressure feeding.

[0018] (7) The plurality of optical fiber core wires , longThe optical fiber ribbon may be in the form of an intermittently connected optical fiber ribbon, in which the optical fiber ribbons are arranged in parallel in a direction perpendicular to the longitudinal direction, and in which, among some or all of the optical fiber ribbons, connected sections in which adjacent optical fiber ribbons are connected and non-connected sections in which adjacent optical fiber ribbons are not connected are provided intermittently in the longitudinal direction. The optical fiber cable of the present disclosure can also use intermittently connected optical fiber ribbons, and therefore has excellent cable accommodation capacity and is easy to separate into individual fibers.

[0019] (8) Each of the plurality of optical fibers may be a multi-core fiber. Since the multiple optical fiber cores of the present disclosure are multi-core fibers, the transmission capacity of the optical fiber cable can be increased.

[0020] (9) A connector-attached cable according to one aspect of the present disclosure includes: the optical fiber cable; and a multi-fiber connector attached to the plurality of optical fiber cores at one end of the optical fiber cable. This configuration makes cable connection easy.

[0021] (Effects of the Invention) According to the present disclosure, it is possible to provide an optical fiber cable and a cable with connectors that can be easily routed by air pressure feeding and towing.

[0022] (Details of the embodiments of the present disclosure) A specific example of an optical fiber cable according to one embodiment of the present disclosure will be described with reference to the drawings. It should be noted that the present disclosure is not limited to these examples, but is defined by the scope of the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0023] (First embodiment) An optical fiber cable 1A according to a first embodiment will be described with reference to FIGS. Fig. 1 is a cross-sectional view perpendicular to the longitudinal direction of an optical fiber cable 1A. As shown in Fig. 1, the optical fiber cable 1A includes a central strength member 5A, a plurality of optical fibers in the form of a plurality of optical fiber ribbons 2, a water-absorbing tape 3, an outer jacket 4, a plurality of strength members 5B (strength member sets 50), at least one tear cord 6 (fibrous inclusions), and a plurality of protrusions 7. The outer diameter of the optical fiber cable 1A is, for example, 10 mm.

[0024] The central strength member 5A is disposed along the longitudinal direction of the optical fiber cable 1A. The cross section of the central strength member 5A in the direction perpendicular to the longitudinal direction is formed to be circular. The diameter of the central strength member 5A is 3 mm or less, for example, 2.5 mm. The central strength member 5A includes aramid fiber reinforced plastic. The central strength member 5A may also be formed from fiber reinforced plastic (FRP) such as glass fiber reinforced plastic or carbon fiber reinforced plastic, or a liquid crystal polymer. It is preferable that the central strength member 5A is non-inductive.

[0025] The optical fiber ribbons 2 are arranged around the central strength member 5A and are formed as optical fiber ribbons 2. Each optical fiber ribbon 2 includes optical fiber ribbons.

[0026] FIG. 2 is a partial development view of an example of an optical fiber ribbon 2 housed in an optical fiber cable 1A, shown in the longitudinal direction. As shown in FIG. 2, the optical fiber ribbon 2 is an intermittently connected optical fiber ribbon in which a plurality of optical fibers 11A to 11L are arranged in parallel in a direction perpendicular to the longitudinal direction of the optical fibers. In this state, some or all of the optical fibers 11A to 11L are intermittently provided with connection portions 12 connecting adjacent optical fibers and non-connection portions 13 not connecting adjacent optical fibers. The outer diameter of each of the optical fibers 11A to 11L is, for example, 200 μm, but may also be 250 μm or 180 μm. Each of the optical fibers 11A to 11L in this example may be a multi-core fiber. Alternatively, only some of the optical fiber ribbons 2 may be intermittently connected optical fiber ribbons, or only some of the optical fibers 11A to 11L may be multi-core fibers.

[0027] In the optical fiber ribbon 2 of this example, twelve optical fibers 11A to 11L are arranged in parallel. The locations where the connecting portions 12 and non-connecting portions 13 are provided intermittently may be between some of the optical fiber cores (intermittent every two cores) as shown in Fig. 2, or may be between all of the optical fiber cores (intermittent every other core). Fig. 2 shows an example where the connecting portions 12 and non-connecting portions 13 are provided intermittently every two cores, and no non-connecting portions 13 are provided between the optical fiber cores 11A and 11B, 11C and 11D, 11E and 11F, 11G and 11H, 11I and 11J, or 11K and 11L.

[0028] The connecting portions 12 in the optical fiber ribbon 2 are formed by applying a connecting resin 14, such as an ultraviolet-curable resin or a thermosetting resin, between the optical fibers. By applying the connecting resin 14 between predetermined intervals between the optical fibers, the connecting portions 12 and the non-connecting portions 13 are intermittently provided, and the optical fibers 11A-11L are integrated in a parallel state. The connecting resin 14 may be applied to only one side of the parallel surface formed by the parallel optical fibers 11A-11L, or may be applied to both sides. The optical fiber ribbon 2 may also be fabricated by applying a ribbon resin to one or both sides of the parallel optical fibers 11A-11L to connect all of the parallel optical fibers 11A-11L, and then cutting a portion with a rotary blade or the like to form the non-connecting portions 13.

[0029] As shown in Fig. 1, the water-absorbing tape 3 is wound around the entirety of the plurality of optical fiber ribbons 2, for example, vertically or spirally, so as to cover the periphery of the plurality of optical fiber ribbons 2. The water-absorbing tape 3 is a tape that has been treated to absorb water by adhering water-absorbing powder to a base fabric made of, for example, polyester. The thickness of the water-absorbing tape 3 is, for example, 0.3 mm. In this example, the optical fiber cable 1A is provided with the water-absorbing tape 3, but the optical fiber cable 1A does not necessarily have to be provided with the water-absorbing tape 3.

[0030] The jacket 4 is disposed on the outside of the multiple optical fiber ribbons 2 and is configured to enclose the tension members 5B (tension member set 50). In this example, the jacket 4 is configured to cover the periphery of the water-absorbing tape 3. The thickness of the jacket 4 is, for example, 1.0 mm. The jacket 4 is mainly formed of, for example, a vinyl resin such as polyvinyl chloride (PVC) or a polyolefin resin such as polyethylene (PE). The jacket 4 further contains a flame-retardant inorganic material and a lubricant. Examples of the flame-retardant inorganic material include polyvinyl chloride or flame-retardant polyethylene. The jacket 4 also contains 1.5 mass % or more of a lubricant. Examples of the lubricant include a silicon-based lubricant such as silicon or siloxane. Note that adding more than 2.5 wt % of lubricant can cause the optical fiber cable to collapse and make it difficult to handle. Therefore, the lubricant content is preferably 1.5 wt % or more and 2.5 wt % or less.

[0031] More specifically, the jacket 4 contains a flame-retardant inorganic material with an oxygen index of 50 or higher. The oxygen index, as defined in JIS K7201-2 (2007), is an index of the flame retardancy of plastic materials. The oxygen index here is an index, expressed as a percentage, of the minimum oxygen concentration required for a plastic to sustain a lit state. The oxygen index of typical air is 20, and the flame retardancy of plastic materials is determined based on an oxygen index of 20. For example, materials with an oxygen index of 22 or lower are flammable, materials with an oxygen index of 23 to 27 are flammable but self-extinguishing, and materials with an oxygen index of 27 or higher are flame-retardant. Since the jacket 4 in this example has an oxygen index of 50 or higher, it can be said to be flame-retardant. The upper limit of the oxygen index is 100.

[0032] Each strength member 5B is arranged along the longitudinal direction of the optical fiber cable 1A and is provided so as to be enclosed in the jacket 4. The diameter of each strength member 5B is, for example, 0.5 mm. Each strength member 5B includes aramid fiber reinforced plastic. Each strength member 5B may be formed of fiber reinforced plastic (FRP) such as glass fiber reinforced plastic or carbon fiber reinforced plastic, or liquid crystal polymer. Each strength member 5B is preferably non-inductive. Note that fiber reinforced plastic (FRP) is generally a flammable material. From the perspective of improving the flame retardancy of the entire optical fiber cable 1A, each strength member 5B is preferably arranged inside the jacket 4 at a position closer to the center of the optical fiber cable 1A rather than near the surface of the jacket 4.

[0033] The cross section of each strength member 5B in a direction perpendicular to the longitudinal direction is formed into a circular shape. As shown in FIG. 1 , in the present disclosure, multiple strength members 5B are provided in groups of four. The four strength members 5B in a group are, for example, provided in close proximity to each other or with at least partial contact. In this example, the four strength members 5B are arranged in a row. In the following description, a group of four strength members 5B will be collectively referred to as a strength member set 50. In the present disclosure, the optical fiber cable 1A includes at least four strength member sets 50.

[0034] In this example, four strength member sets 50 are spaced apart from one another and enclosed within the jacket 4. In the optical fiber cable 1A, the four strength member sets 50 are arranged at equal intervals from one another. Specifically, the four strength member sets 50 are provided in pairs at positions facing each other across the center of the optical fiber cable 1A in a cross section of the optical fiber cable 1A in a direction perpendicular to the longitudinal direction.

[0035] The tear cord 6 is provided to tear the jacket 4 and is arranged inside the jacket 4 along the longitudinal direction of the optical fiber cable 1A. In this example, two tear cords 6 are provided. The two tear cords 6 are arranged facing each other at approximately the midpoint between adjacent strength member sets 50. Furthermore, the four strength member sets 50 are arranged symmetrically with respect to a line L connecting the tear cord 6 and the center of the optical fiber cable 1A in a cross-sectional view of the cable. By pulling out the tear cord 6, an operator can tear the jacket 4 in the longitudinal direction and remove the optical fiber ribbon 2. The tear cord 6 is fibrous and is formed, for example, from a tensile-resistant plastic material (e.g., polyester).

[0036] A plurality of protrusions 7 (two in this example) are provided. The two protrusions 7 are provided along the longitudinal direction of the optical fiber cable 1A. The protrusions 7 may be provided continuously or intermittently along the longitudinal direction. Furthermore, in a radial cross section of the optical fiber cable 1A, the two protrusions 7 are provided circumferentially on the outer periphery of the jacket 4 so as to face each other across the center of the optical fiber cable 1A. In this example, the protrusions 7 are provided on a straight line L connecting the tear cord 6 and the center of the optical fiber cable 1A. The protrusions 7 are formed on the outer periphery of the jacket 4 so as to protrude in the radial direction of the optical fiber cable 1A. The surface 7a of the protrusion 7 in the protruding direction is curved. The protrusions 7 are formed integrally with the jacket 4 by extrusion molding. The presence of the protrusions 7 makes it easy to determine the position of the tear cord 6. Furthermore, friction between the jacket 4 and the duct is reduced, thereby extending the pumping distance.

[0037] As described above, in this embodiment, at least four strength member sets 50 are contained in the jacket 4 at a distance from one another, thereby improving the non-uniformity in stiffness of the optical fiber cable 1A due to the positions of the strength member sets 50 contained therein. Therefore, the optical fiber cable 1A is less likely to buckle when air-pumped. Furthermore, the optical fiber cable 1A of this embodiment includes not only the strength member sets 50 contained in the jacket 4 but also the central strength member 5A, so the optical fiber cable 1A is less likely to stretch when pulled. This makes it easier to wire the optical fiber cable 1A by air-pumping and pulling.

[0038] Since the central reinforcing member 5A or reinforcing member set 50 in this embodiment contains aramid fiber reinforced plastic, the optical fiber cable 1A is equipped with reinforcing members that are lightweight and highly flexible, making it easy to wire by air pressure feeding and towing.

[0039] Because the central strength member 5A of this embodiment contains aramid fiber-reinforced plastic, the optical fiber cable 1A is equipped with a strength member that is lightweight and highly flexible. Furthermore, if the central strength member 5A were too thick for the diameter of the optical fiber cable 1A, the optical fiber ribbons 2 within the cable would likely be packed so tightly together that they would exert lateral pressure on each other. This could result in increased cable transmission loss. However, because the diameter of the central strength member 5A of this embodiment is 3 mm or less, cable transmission loss can be suppressed while also suppressing cable elongation during pulling.

[0040] The jacket of this embodiment contains 1.5% by mass or more of lubricant, which makes it easy to wire the optical fiber cable 1A by air pressure feeding.

[0041] Since the jacket 4 of this embodiment contains a flame-retardant inorganic material with an oxygen index of 50 or more, the flame retardancy of the optical fiber cable 1A is further improved.

[0042] The optical fiber cable 1A of this embodiment can also use an intermittently connected optical fiber ribbon, and therefore has excellent cable accommodation capacity and is easy to separate into individual fibers.

[0043] In the multiple optical fiber ribbons 2 of this embodiment, each of the optical fiber ribbons 11A to 11L can be a multi-core fiber, which increases the transmission capacity of the optical fiber cable. Each optical fiber ribbon 2 may have two cores or eight cores. For example, if the optical fiber cable 1A contains 36 optical fiber ribbons 2, each of which has two cores, and the cable outer diameter of the optical fiber cable 1A is 10 mm, the number of cores per cable cross-sectional area will be 11 cores / mm. 2 The above high density mounting can be achieved.

[0044] The optical fiber cable 1A of this embodiment includes tear cords 6 arranged along the multiple optical fiber ribbons 2, allowing an operator to tear the jacket 4 with the tear cords 6 and easily remove the individual optical fiber ribbons 2. Furthermore, the four strength member sets 50 of the optical fiber cable 1A are arranged symmetrically with respect to the line L connecting the tear cords 6 and the center of the optical fiber cable 1A, which further improves the non-uniformity of the cable rigidity and improves the wiring work during air pressure feeding.

[0045] According to the optical fiber cable 1A of this embodiment, a plurality of protrusions 7 that protrude in the radial direction of the optical fiber cable 1A are provided on the outer periphery of the jacket 4. Therefore, when the optical fiber cable 1A is compressed air fed through a duct, the protrusions 7 come into contact with the inner wall of the duct, thereby reducing the contact area between the jacket 4 and the duct. This reduces friction between the jacket 4 and the duct, allowing the pumping distance to be extended.

[0046] 1, one strength member set 50 includes four strength members 5B, but the number of strength members 5B is not limited thereto. One strength member set 50 may include one, two, or five or more strength members 5B.

[0047] 2 shows a 12-core intermittently connected optical fiber ribbon, but the number of optical fibers is not limited to this. Furthermore, the optical fibers may be formed by twisting together a plurality of single-core optical fibers instead of a ribbon.

[0048] (Modification of the first embodiment) An optical fiber cable 1B according to a modified example of the first embodiment will be described with reference to Fig. 3. Note that the same components as those in the optical fiber cable 1A according to the first embodiment will be given the same reference numerals and descriptions thereof will be omitted.

[0049] Fig. 3 is a cross-sectional view perpendicular to the longitudinal direction of optical fiber cable 1B. As shown in Fig. 3, optical fiber cable 1B has the same configuration as optical fiber cable 1A according to the first embodiment, but in addition, optical fiber cable 1B has an outer jacket 4 including an inner layer 41 and an outer layer 42. The outer cable diameter of optical fiber cable 1B is, for example, 12 mm.

[0050] The inner layer 41 of the jacket 4 is disposed outside the plurality of optical fiber ribbon cores and is configured to enclose the plurality of strength member sets 50. The plurality of strength member sets 50 and the tear cord 6 are encased in the inner layer 41 of the jacket 4. The inner layer 41 of the jacket 4 contains, as a flame-retardant inorganic material, for example, magnesium hydroxide or aluminum hydroxide. The thickness of the inner layer 41 is, for example, 1 mm.

[0051] The outer layer 42 of the outer covering 4 is disposed on the outside of the inner layer 41. The protrusions 7 are provided on the outer periphery of the outer layer 42. The outer layer 42 of the outer covering 4 contains a silicone-based lubricant such as silicone or siloxane as a lubricant. The thickness of the outer layer 42 is, for example, 0.5 mm.

[0052] As described above, in this modification, the inner layer 41 contains a flame-retardant inorganic material, thereby realizing an optical fiber cable 1B with excellent flame retardancy. Furthermore, the outer layer 42 contains a lubricant, which allows the optical fiber cable 1B to be smoothly fed through a duct when compressed air is used for feeding. This makes wiring easier.

[0053] Although the embodiments and modifications of the present disclosure have been described above, the present disclosure is not limited to the above embodiments or modifications, and other modifications may be adopted as necessary for some of the configuration. For example, as shown in FIG. 4, the optical fiber cable 1A or the optical fiber cable 1B may be terminated. The connectorized cable 1X shown in FIG. 4 includes a multi-fiber connector 90 attached to multiple optical fiber ribbons 2 at one end of the optical fiber cable 1A or the optical fiber cable 1B. As shown in FIG. 4, optical fiber cores 11 are exposed at the end of the multi-fiber connector 90. The number of optical fiber cores 11 shown in FIG. 4 is an example and is at least 12 or more, but is not particularly limited. The connectorized optical fiber 1X may have, for example, 432 optical fiber cores. By providing the multi-fiber connector 90 at one end of the optical fiber cable 1A or the optical fiber cable 1B in advance, the optical fiber cable 1A or the optical fiber cable 1B can be easily optically connected.

[0054] (Evaluation experiment) The allowable tension, pumping distance, cable transmission loss, and packaging density of the optical fiber cable 1A according to the first embodiment were evaluated. In this evaluation experiment, the central tension member 5A and the multiple tension members 5B (tension member set 50) had a tensile modulus of elasticity of 6300 kg / mm 2 The allowable tension was measured by applying tension to the optical fiber cable 1A and measuring the tension when the cable length was elongated by 0.3%.

[0055] The pumping distance was evaluated using the microduct pumping test specified by the IEC (International Electrotechnical Commission). A general-purpose microduct was used for the pumping test. The inner diameter of the duct was 20 mm. The total pumping distance within the duct was set to 1,000 m or more, with the duct folded back every 100 m. The radius of curvature of the duct was 40 times the outer diameter of the duct. The pressure within the duct was 1.3 MPa to 1.5 MPa.

[0056] The cable loss characteristics were evaluated by determining whether the transmission loss was less than 0.3 dB / km when light with a wavelength of 1.55 μm was incident on the fiber cable 1A.

[0057] The packaging density was evaluated as a percentage when 36 optical fiber ribbons 2 were housed in the optical fiber cable 1A. The optical fiber cable 1A had an outer cable diameter of 11 mm, and the diameter (core diameter) of the space housing the multiple optical fiber ribbons 2 and the central tensile strength member 5A was 9 mm. The optical fiber ribbon 2 had 12 optical fibers with a diameter of 250 μm arranged in parallel, and the ribbon width of the optical fiber ribbon 2 was 3.1 mm and the ribbon thickness was 0.3 mm. The area of ​​each optical fiber ribbon 2, including tolerances, was 0.786 mm 2 The mounting density was calculated as follows. The evaluation results are shown in Table 1.

[0058] [Table 1]

[0059] In Table 1, Samples No. 1 and No. 2 are comparative examples. The cable structure of Sample No. 1 is a slotless cable, and the strength members contained in the jacket are arranged one above and one below the center of the cable in the radial cross section of the cable. The diameter of the strength members of Sample No. 1 is 0.7 mm. The strength members of Sample No. 1 are made of glass fiber reinforced plastic. Sample No. 2 is an optical fiber cable in which 16 strength members 5B are contained in the jacket but which does not have a central strength member 5A. Specifically, one strength member set 50 has four strength members 5B arranged in a row, and the four strength member sets 50 are arranged one above, one below, one to the left, and one to the right, facing each other across the center of the cable in the radial cross section of the cable. The diameter of the strength members 5B of Sample No. 2 is 0.5 mm.

[0060] Samples No. 3 to No. 6 are optical fiber cables 1A according to the first embodiment. However, the diameter of the central strength member 5A differs in each sample. The diameter of the central strength member 5A of sample No. 3 is 2.0 mm. The diameter of the central strength member 5A of sample No. 4 is 2.5 mm. The diameter of the central strength member 5A of sample No. 5 is 3.0 mm. The diameter of the central strength member 5A of sample No. 6 is 3.5 mm.

[0061] As shown in Table 1, the allowable tension of sample No. 1 was 109 N, and the allowable tension of sample No. 2 was 582 N. On the other hand, it was confirmed that the allowable tension of samples No. 3 to No. 6 was all 1000 N or more. Generally, a tension of 1000 N or more is required for wiring by pulling. It was also confirmed that the allowable tension of sample No. 3, which is equipped with the central tension member 5A, is approximately twice the allowable tension of sample No. 2, which is not equipped with the central tension member 5A. From the above, it was confirmed that by providing the central tension member 5A, an optical fiber cable 1A that can be wired by pulling can be obtained.

[0062] The pumping distance of each of Samples No. 2 to No. 6 was 1000 m or more, but the pumping distance of Sample No. 1 did not reach 1000 m. From the above, it was confirmed that the pumping distance of optical fiber cable 1A is guaranteed by including 16 tensile members 5B in jacket 4.

[0063] As shown in Table 1, the cable transmission loss of Sample No. 6 was 0.3 dB / km or more, and the packaging density was 53%. This is because the diameter of the central strength member 5A of Sample No. 6 was 3.5 mm, which was relatively large compared to the diameter of the optical fiber cable 1A. In other words, in Sample No. 6, the multiple optical fiber ribbons 2 in the cable tend to be packed so tightly that they exert lateral pressure on each other, confirming that the packaging density was high and the cable transmission loss was high. On the other hand, the cable transmission loss of Samples No. 3 to No. 5 was all confirmed to be less than 0.3 dB / km. From the above, it was confirmed that when the diameter of the central strength member 5A is 3.0 mm or less, it is possible to realize an optical fiber cable 1A with low cable transmission loss while densely packing the optical fiber ribbons 2 in the cable.

[0064] Furthermore, the flame retardancy of the optical fiber cable 1A was evaluated. The flame retardancy evaluation method used was a test based on the standards set forth in the European CPR (Construction Products Regulation). Flame retardancy is rated on a seven-level scale: Aca, B1ca, B2ca, Cca, Dca, Eca, and Fca, with Aca representing the highest flame retardancy and Fca representing the lowest. As a result of the evaluation experiment, samples No. 3 to No. 6 were all rated Cca, confirming their high flame retardancy.

[0065] Although the present disclosure has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present disclosure. Furthermore, the number, position, shape, etc. of the components described above are not limited to the above embodiments, and can be changed to the number, position, shape, etc. that are suitable for implementing the present disclosure. [Explanation of symbols]

[0066] 1A, 1B: Optical fiber cable 1X: Cable with connector 2: Optical fiber ribbon 3: Water-absorbing tape 4:Outer cover 5A: Central tensile strength body 5B: Tensile strength body 6: Tear string (fibrous inclusion) 7: Protrusion 7a: Surface 11A~11L: Optical fiber core 12:Connection part 13: Unconnected part 14: Connected resin 41: Inner layer 42: Outer layer 50: Tensile strength member set 90: Multi-fiber connector

Claims

1. a central tension member; a plurality of optical fiber cores arranged around the central tension member; a set of strength members arranged outside the plurality of optical fiber cores; an outer jacket disposed on the outside of the plurality of optical fiber cores, At least four of the strength member sets are enclosed in the outer jacket and spaced apart from one another, An optical fiber cable having an allowable tension of 1163N or more and 2363N or less.

2. 10. The fiber optic cable of claim 1, wherein at least one of the central strength member and the set of strength members comprises aramid fiber reinforced plastic.

3. 3. The optical fiber cable according to claim 1, wherein the central strength member comprises aramid fiber reinforced plastic and has a diameter of 3 mm or less.

4. The optical fiber cable according to claim 1 , wherein the jacket contains 1.5 mass % or more of a lubricant.

5. 5. The optical fiber cable according to claim 1, wherein the jacket contains a flame-retardant inorganic material having an oxygen index of 50 or more.

6. the jacket includes an outer layer and an inner layer; the inner layer comprises a flame-retardant inorganic material; The optical fiber cable according to claim 1 , wherein the outer layer includes a lubricant.

7. 7. An optical fiber cable as described in any one of claims 1 to 6, in which the plurality of optical fiber core wires are arranged in parallel in a direction perpendicular to the longitudinal direction, and in which, among some or all of the plurality of optical fiber core wires, connected sections in which adjacent optical fiber core wires are connected and non-connected sections in which adjacent optical fiber core wires are not connected are intermittently provided in the longitudinal direction, in the form of an intermittently connected optical fiber ribbon core wire.

8. The optical fiber cable according to claim 1 , wherein each of the plurality of optical fiber cores is a multi-core fiber.

9. The optical fiber cable according to any one of claims 1 to 8; a multi-fiber connector attached to the plurality of optical fiber cores at one end of the optical fiber cable.

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