Optical fiber unit, optical fiber cable, and method for manufacturing optical fiber unit

Abstract

This optical fiber unit (10) comprises: a plurality of optical fiber core wires (11) having an outer diameter of 200 μm or less; an inner layer (12) that is in contact with the plurality of optical fiber core wires and covers the plurality of optical fiber core wires; and an outer layer (13) disposed outside the inner layer, wherein the plurality of optical fiber core wires (11) are integrated by being covered by the inner layer in a bundled state, and in a cross-sectional view of the optical fiber unit (10), the outer shape of the optical fiber unit is circular and the Young's modulus of the inner layer (12) is lower than the Young's modulus of the outer layer (13).

Description

Optical fiber unit, optical fiber cable, and method of manufacturing the optical fiber unit

[0001] The present disclosure relates to an optical fiber unit, an optical fiber cable, and a method for manufacturing an optical fiber unit.

[0002] Patent document 1 discloses an optical fiber unit having an optical fiber ribbon core wire comprising a plurality of optical fiber core wires and a ribbon resin that integrates the plurality of optical fiber core wires in a parallel state, and a coating resin that covers the optical fiber ribbon core wire in an aggregated form.

[0003] International Publication No. 2019 / 088256

[0004] An optical fiber unit according to one aspect of the present disclosure comprises: a plurality of optical fiber cores each having an outer diameter of 200 μm or less; an inner layer in contact with and covering the plurality of optical fiber cores; and an outer layer positioned outside the inner layer, wherein the plurality of optical fiber cores are integrated by being covered by the inner layer in a bundled state; in a cross-sectional view of the optical fiber unit, the outer shape of the optical fiber unit is circular; and the Young's modulus of the inner layer is lower than the Young's modulus of the outer layer.

[0005] Fig. 1 is a cross-sectional view of an optical fiber unit according to this embodiment. Fig. 2 is a schematic configuration diagram of an optical fiber unit manufacturing apparatus according to this embodiment. Fig. 3 is a flow chart illustrating a method for manufacturing an optical fiber unit according to this embodiment. Fig. 4 is a cross-sectional view of an optical fiber cable including six optical fiber units. Fig. 5 is a cross-sectional view of an optical fiber cable including 24 optical fiber units.

[0006] [Problems to be Solved by the Present Disclosure] For example, in an optical fiber cable having an optical fiber ribbon including a plurality of optical fiber core wires each having an outer diameter of 200 μm or less, it may be difficult to remove the coating of the optical fiber ribbon all at once or to fusion splice the optical fiber ribbon. Furthermore, for example, when an optical fiber cable is manufactured using optical fiber core wires with a thin coating layer, the optical fiber core wires may break during the optical fiber cable manufacturing process. Furthermore, when a plurality of optical fiber core wires are unitized, there is also a need to improve the lateral pressure resistance and external damage resistance of the optical fiber unit and the ease of removing the optical fiber core wires.

[0007] The present disclosure aims to provide an optical fiber unit, an optical fiber cable, and a method for manufacturing an optical fiber unit that can suppress breakage of the optical fiber core wire while using a thin-diameter optical fiber core wire, and that has good resistance to lateral pressure and external damage and good core wire removal properties for the optical fiber core wire.

[0008] [Description of Embodiments of the Present Disclosure] First, embodiments of the present disclosure will be described. An optical fiber unit according to one aspect of the present disclosure is: (1) an optical fiber unit comprising: a plurality of optical fiber core wires each having an outer diameter of 200 μm or less; an inner layer in contact with and covering the plurality of optical fiber core wires; and an outer layer disposed outside the inner layer, wherein the plurality of optical fiber core wires are integrated by being covered by the inner layer in a bundled state; the optical fiber unit has a circular outer shape in a cross-sectional view; and the Young's modulus of the inner layer is lower than that of the outer layer. According to this configuration, the optical fiber unit having a circular outer shape in a cross-sectional view comprises a plurality of optical fiber core wires each having an outer diameter of 200 μm or less; an inner layer covering the optical fiber core wires; and an outer layer disposed outside the inner layer. The optical fiber core wires included in the optical fiber unit are thin optical fiber core wires having an outer diameter of 200 μm or less, and therefore the outer diameter of such an optical fiber unit is relatively small. Furthermore, the multiple optical fibers are bundled together and covered by the inner layer, making them less susceptible to breakage. Furthermore, the optical fiber unit has a two-layer structure, an inner layer and an outer layer, and the Young's modulus of the inner layer is lower than that of the outer layer, so the optical fiber unit according to the above configuration has high resistance to lateral pressure and external damage. Furthermore, the Young's modulus of the inner layer covering the optical fibers is lower than that of the outer layer, so the optical fiber unit according to the above configuration has good optical fiber extraction properties. Therefore, the optical fiber unit according to the above configuration can suppress breakage of the optical fiber even when using small-diameter optical fibers, and can improve the optical fiber unit's resistance to lateral pressure and external damage, as well as the optical fiber extraction properties.

[0009] (2) In the optical fiber unit described in (1), a lubricant may be added to the inner layer. According to this configuration, since the lubricant is added to the inner layer, the optical fiber can be more easily extracted.

[0010] (3) In the optical fiber unit according to (1) or (2), the outer diameter of the optical fiber may be less than 180 μm. With this configuration, since such an optical fiber is an extremely small diameter optical fiber, the outer diameter of the optical fiber unit can be reduced.

[0011] (4) In the optical fiber unit according to any one of (1) to (3), the optical fiber included in the coated optical fiber may be a multi-core fiber. With this configuration, the core density of the optical fiber unit can be increased.

[0012] (5) In the optical fiber unit according to any one of (1) to (4), the Young's modulus of the inner layer may be 300 MPa or less. This configuration can improve lateral pressure resistance.

[0013] (6) In the optical fiber unit according to any one of (1) to (5), the outer layer may be a colored layer to which a pigment is added. This configuration can improve the distinguishability of the optical fiber unit.

[0014] An optical fiber cable according to one aspect of the present disclosure includes: (7) a plurality of optical fiber units according to any one of (1) to (6) above; and a cable jacket covering the plurality of optical fiber units. With this configuration, the optical fiber cable has a relatively small outer diameter. Furthermore, with the above configuration, breakage of the optical fiber core wires can be suppressed when the plurality of cable units are cabled by being covered with the cable jacket. Furthermore, in this optical fiber cable, the optical fiber units have good resistance to lateral pressure and external damage, and the optical fiber core wires have good fiber extraction properties.

[0015] (8) The optical fiber cable described in (7) above may further include a strength member disposed at the center of the optical fiber cable, and the plurality of optical fiber units may be disposed in an area formed between the strength member and the cable jacket. With this configuration, since the plurality of optical fiber units are disposed in an area formed between the strength member and the cable jacket, it is possible to provide a configuration including a relatively large number of optical fiber cables while keeping the outer diameter small. With the optical fiber cable according to the above configuration, it is possible to increase the core density of the optical fiber cable while keeping the outer diameter small.

[0016] (9) The optical fiber cable described in (7) above may further include a strength member disposed at the center of the optical fiber cable, and a water-absorbing tape disposed between the strength member and the cable jacket, wherein the optical fiber units are disposed in each of a first region formed between the strength member and the water-absorbing tape and a second region formed between the cable jacket and the water-absorbing tape. With this configuration, since the optical fiber units are disposed in each of the first region and the second region, the core density of the optical fiber cable can be increased while maintaining a relatively small outer diameter.

[0017] (10) In the optical fiber cable according to any one of (7) to (9), the core density obtained by dividing the number of cores contained in the coated optical fiber by the cross-sectional area of ​​the optical fiber cable is 10 cores / mm ２ According to this configuration, by using the optical fiber unit, it is possible to increase the core density of the optical fiber cable while suppressing breakage of the optical fiber core.

[0018] A method for manufacturing an optical fiber unit according to one aspect of the present disclosure includes: (11) a step of gathering a plurality of optical fiber core wires each having an outer diameter of 200 μm or less; a step of passing the plurality of optical fiber core wires through a die; a step of covering the plurality of optical fiber core wires with a first resin material and covering the first resin material with a second resin material while the plurality of optical fiber core wires are bundled in the die; a step of forming an inner layer covering the plurality of optical fiber core wires by irradiating the first resin material with ultraviolet light to harden the first resin material, and forming an outer layer covering the inner layer by irradiating the second resin material with ultraviolet light to harden the second resin material, wherein the plurality of optical fiber core wires and the inner layer are in contact with each other; and in a cross-sectional view of an optical fiber unit comprising the plurality of optical fiber core wires, the inner layer, and the outer layer, the outer shape of the optical fiber unit is circular; and the Young's modulus of the inner layer is lower than the Young's modulus of the outer layer. According to this configuration, an optical fiber unit can be manufactured that includes a plurality of optical fiber cores each having an outer diameter of 200 μm or less, an inner layer covering the optical fiber cores, and an outer layer covering the inner layer, and that has a circular outer shape in cross section. Because the optical fiber cores included in the fiber unit are small-diameter optical fiber cores having an outer diameter of 200 μm or less, the outer diameter of such an optical fiber unit is relatively small. Furthermore, the plurality of optical fiber cores are covered with an inner layer that has a circular outer shape in cross section and is formed by curing a first resin material. In other words, the plurality of optical fiber cores are integrated in a bundled state by being covered with the inner layer that has a circular outer shape in cross section, making them less susceptible to breakage. Furthermore, the fiber unit has a two-layer structure including an inner layer and an outer layer, and the Young's modulus of the inner layer is lower than that of the outer layer, so the optical fiber unit has high resistance to lateral pressure and external damage. Furthermore, in this fiber unit, the Young's modulus of the inner layer covering the coated optical fiber is lower than that of the outer layer, so that the coated optical fiber can be easily extracted.Therefore, with the optical fiber unit having the above configuration, even when using a thin-diameter optical fiber core, breakage of the optical fiber core can be suppressed, and the optical fiber unit can have good resistance to lateral pressure and external damage, as well as good core removal ability of the optical fiber core.

[0019] [Effects of the Present Disclosure] According to the present disclosure, it is possible to provide an optical fiber unit, an optical fiber cable, and a method for manufacturing an optical fiber unit that can suppress breakage of the optical fiber core wire while using a thin-diameter optical fiber core wire, and that has good resistance to lateral pressure and external damage and good core wire removal properties of the optical fiber core wire.

[0020] [Details of the embodiments of the present disclosure] Specific examples of an optical fiber unit, an optical fiber cable, and a method for manufacturing an optical fiber unit according to embodiments of the present disclosure will be described below with reference to the drawings. Note that the present disclosure is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0021] (Optical fiber unit 10) The optical fiber unit 10 according to this embodiment will be described with reference to Fig. 1. Fig. 1 is a cross-sectional view of the optical fiber unit 10 according to this embodiment. As illustrated in Fig. 1, the optical fiber unit 10 includes a plurality of optical fiber cores 11, an inner layer 12 that covers the plurality of optical fiber cores 11, and an outer layer 13 that is disposed outside the inner layer 12.

[0022] The outer diameter of the optical fiber 11 is 200 μm or less, and preferably less than 180 μm. The outer diameter of the optical fiber 11 is, for example, 160 μm. The optical fiber 11 includes an optical fiber 110 including four cores 111 and a cladding 112, and a protective coating 113 that covers the optical fiber 110. Therefore, the optical fiber 110 included in the optical fiber 11 is a multi-core fiber (MCF). The optical fiber 110 is, for example, a glass fiber in which the cores 111 and the cladding 112 are made of silica glass.

[0023] The core 111 has a circular cross section in the radial direction. The refractive index of the core 111 is higher than the refractive index of the cladding 112. The outer diameter of the core 111 is, for example, not less than 5 μm and not more than 10 μm.

[0024] The clad 112 is provided so as to integrally surround the four cores 111. The outer diameter of the clad 112 is larger than the outer diameter of the cores 111. The outer diameter of the clad 112 is, for example, not less than 80 μm and not more than 125 μm.

[0025] The protective coating 113 is formed from, for example, an acrylate resin, etc. The protective coating 113 is provided so as to cover the periphery of the clad 112 .

[0026] In this embodiment, the optical fiber unit 10 includes, as an example, twelve optical fiber cores 11. The twelve optical fiber cores 11 are bundled together and integrated by being covered with an inner layer 12 having a circular outer shape in a cross-sectional view. Therefore, the outer shape of the optical fiber unit 10 in a cross-sectional view is circular. In this specification, "circular" includes not only a perfect circle but also an approximately circular shape. An approximately circular shape is, for example, an ellipse that is visually recognized as close to a perfect circle. The outer diameter of the optical fiber unit 10 is, for example, 0.8 mm. The coating structure of the optical fiber unit 10 is a two-layer structure consisting of an inner layer 12 and an outer layer 13.

[0027] The inner layer 12 covers the twelve optical fibers 11. The inner layer 12 is in contact with the twelve optical fibers 11. The inner layer 12 can be formed from a resin material such as a urethane acrylate resin. A lubricant is added to the inner layer 12. The lubricant is formed from, for example, silicone. The Young's modulus of the inner layer 12 is, for example, 300 MPa or less.

[0028] The outer layer 13 is disposed outside the inner layer 12. The outer layer 13 may be formed from a resin material such as a urethane acrylate resin. The resin material may contain a pigment of any color. Therefore, the outer layer 13 is a colored layer to which a pigment is added. The Young's modulus of the outer layer 13 is, for example, 1000 MPa. Therefore, the Young's modulus of the inner layer 12 is lower than that of the outer layer 13.

[0029] (Apparatus 1 for manufacturing optical fiber unit 10) Next, the apparatus 1 for manufacturing the optical fiber unit 10 according to this embodiment will be described with reference to Fig. 2. Fig. 2 is a schematic diagram of the apparatus 1 for manufacturing the optical fiber unit 10 according to this embodiment.

[0030] 2 , the manufacturing apparatus 1 for the optical fiber unit 10 includes a supply device 100. The supply device 100 includes 12 bobbins 101 corresponding to the number of fibers in the optical fiber unit 10, 12 dancer rollers 102, and a first guide roller 103. An optical fiber 11 is wound around each of the bobbins 101. The optical fiber 11 is unwound from each of the bobbins 101, has its tension adjusted by the dancer rollers 102, and is arranged on a single arrangement surface when passing through the first guide roller 103. The optical fiber 11 is further collected by an immediately above guide roller 104 and sent to the resin application device 200.

[0031] The resin application device 200 includes a point 210 and a die 220. The optical fiber 11 is inserted into the resin application device 200 and pulled with a predetermined tension. As a result, the inserted optical fiber 11 is guided by the point 210 into a desired arrangement and sent to the die 220. Note that in this embodiment, when the 12 optical fibers 11 are guided by the point 210, they are bundled so that the cross-sectional outer shape is nearly circular, unlike a commonly used tape-shaped optical fiber ribbon.

[0032] The die 220 includes a first portion 220A and a second portion 220B. The first portion 220A is positioned closer to the point 210 than the second portion 220B. Therefore, the 12 optical fibers 11 are fed first to the first portion 220A and then to the second portion 220B. The first portion 220A applies a first resin material to the 12 optical fibers 11. The second portion 220B applies a second resin material to the 12 optical fibers 11 so as to cover the first resin material applied to the 12 optical fibers 11. The outlet holes of the first portion 220A and the second portion 220B are circular, and the resin material is applied around the 12 optical fibers 11 so as to form a circular cross-sectional outline. The first resin material and the second resin material are, for example, ultraviolet-curable resins. The ultraviolet-curable resin is, for example, urethane acrylate resin. A lubricant such as silicone is added to the first resin material. The second resin material contains a pigment of any color. The first resin material is supplied, for example, from a first resin tank 230A. The second resin material is supplied, for example, from a second resin tank 230B. The first resin tank 230A and the second resin tank 230B are, for example, pressurized resin tanks. The twelve optical fiber cores 11 covered with the first resin material and the second resin material are sent to an ultraviolet irradiation device 240.

[0033] In the ultraviolet irradiation device 240, ultraviolet rays are irradiated onto the first resin material and the second resin material. As a result, an inner layer 12 (see FIG. 1) covering the 12 optical fibers 11 is formed, and an outer layer 13 (see FIG. 1) covering the inner layer 12 is formed. The 12 optical fibers 11 are integrated by being covered by the inner layer 12 in a bundled state. In this way, an optical fiber unit 10 is formed, which includes the 12 optical fibers 11, the inner layer 12 covering the 12 optical fibers 11, and the outer layer 13 arranged outside the inner layer 12. The formed optical fiber unit 10 is sent to the marking device 250.

[0034] The marking device 250 is, for example, a dispenser, an inkjet printer, etc. A dispenser is a device that ejects liquid such as ink onto an object. The marking device 250 applies, for example, a band-shaped marking to the optical fiber unit 10.

[0035] The marked optical fiber unit 10 is sent to a winding device 310 having a second guide roller 260 and a bobbin. In the winding device 310, the optical fiber unit 10 is wound onto the bobbin after passing through a guide. In this manner, the optical fiber unit 10 is manufactured.

[0036] (Method for Manufacturing Optical Fiber Unit 10) Next, a method for manufacturing the optical fiber unit 10 will be described with reference to Fig. 3. As illustrated in Fig. 3, for example, 12 optical fibers 11 unwound from each bobbin 101 are collected by an upper guide roller 104 (STEP 01). The collected 12 optical fibers 11 are sent to a resin application device 200.

[0037] The 12 optical fiber cores 11 sent to the resin applying device 200 are arranged in a desired arrangement at a point 210 and then passed through a die 220 (STEP 02).

[0038] The twelve optical fibers 11 passed through the die 220 are bundled in the die 220 so that the cross-sectional shape is nearly circular, and are then covered with a first resin material, and the first resin material is then covered with a second resin material (STEP 03). The twelve optical fibers 11 covered with the first resin material and the second resin material are sent to an ultraviolet irradiation device 240.

[0039] The ultraviolet irradiation device 240 irradiates the first resin material and the second resin material with ultraviolet light, thereby forming an inner layer 12 that covers the twelve optical fiber cores 11, and forming an outer layer 13 that covers the inner layer 12 (STEP 04). As a result, the optical fiber unit 10 is formed.

[0040] The optical fiber unit 10 described above simply includes twelve optical fibers 11 each having an outer diameter of 200 μm or less, an inner layer 12 covering the optical fibers 11, and an outer layer 13 disposed outside the inner layer 12. Therefore, the outer diameter of the optical fiber unit 10 is relatively small. Furthermore, unlike optical fiber ribbons, the twelve optical fibers 11 are bundled together and covered by the inner layer 12 so that the cross-sectional shape is nearly circular. Therefore, the cross-sectional shape of the optical fiber unit 10 is circular. In this optical fiber unit 10, the entire circumference of the twelve optical fibers 11 is covered by the inner layer 12, which has a relatively thick coating thickness. Therefore, compared to commonly used tape-shaped optical fiber ribbons, breakage of the twelve optical fibers 11 is less likely to occur. Thus, the optical fiber unit 10 can suppress breakage of the optical fibers 11 even when using small-diameter optical fibers 11. Furthermore, the optical fiber unit 10 has a two-layer structure consisting of the inner layer 12 and the outer layer 13, resulting in high resistance to external damage. Furthermore, since the Young's modulus of the inner layer 12 is lower than that of the outer layer 13, the optical fiber unit 10 also has high resistance to lateral pressure. Furthermore, since the Young's modulus of the inner layer 12 covering the optical fiber is lower than that of the outer layer 13, the optical fiber unit 10 also has good ease of extracting the optical fiber 11. Therefore, with the optical fiber unit 10, breakage of the optical fiber 11 can be suppressed while the outer diameter of the optical fiber unit 10 is reduced, and the optical fiber unit 10 has good resistance to lateral pressure and external damage, and good ease of extracting the optical fiber 11.

[0041] Furthermore, in the optical fiber unit 10 described above, the outer diameter of the optical fiber 11 is 160 μm. That is, the outer diameter of the optical fiber 11 is less than 180 μm. In other words, since the optical fiber 11 provided in the optical fiber unit 10 is an optical fiber with an extremely small diameter, the outer diameter of the optical fiber unit 10 can be made small.

[0042] Furthermore, according to the optical fiber unit 10 described above, since the optical fiber 110 included in the optical fiber core 11 is a multi-core fiber, it is possible to increase the core density of the optical fiber unit 10. The core density of the optical fiber unit 10 refers to the number of cores per unit area of ​​the optical fiber unit 10.

[0043] Furthermore, according to the optical fiber unit 10 as described above, since the outer layer 13 is a colored layer to which a pigment is added, the optical fiber unit 10 can be made more distinguishable.

[0044] (Experiments on fiber take-out ease, lateral pressure resistance, and external damage resistance) The inventors evaluated the fiber take-out ease, lateral pressure resistance, and external damage resistance of the optical fiber units according to Experimental Examples 1 to 8 in Table 1. The evaluation index for fiber take-out ease was whether the optical fiber core wires inside the optical fiber unit could be taken out by hand without using tools such as nippers. The fiber take-out ease was rated good (evaluated as A) when the optical fiber core wires inside the optical fiber unit could be taken out by hand. The fiber take-out ease was rated fairly good (evaluated as B) when some of the optical fiber core wires were taken out using tools such as nippers. The fiber take-out ease was rated poor (evaluated as C) when the optical fiber core wires inside the optical fiber unit could not be taken out even with tools such as nippers. The evaluation index for lateral pressure resistance was the degree of increase in loss when a lateral pressure of 500 N was applied to the optical fiber unit using a 100 mm metal plate. When the loss increase when 500 N was applied was less than 0.1 dB, the lateral pressure resistance was rated as good (rating A). When the loss increase when 500 N was applied was 0.1 dB or more but less than 0.3 dB, the lateral pressure resistance was rated as somewhat good (rating B). When the loss increase when 500 N was applied was 0.3 dB or more, the lateral pressure resistance was rated as poor (rating C). The evaluation index for damage resistance was whether or not breaks occurred in the optical fiber core during the process of manufacturing the optical fiber unit. When no breaks occurred in the optical fiber core during the process of manufacturing the optical fiber unit, the damage resistance was rated as good (rating A). When breaks occurred in the optical fiber core during the process of manufacturing the optical fiber unit, the damage resistance was rated as poor (rating C). The optical fiber units according to Experimental Examples 1 to 4 were single-layer optical fiber units. The optical fiber units 10 according to Experimental Examples 5 to 8 were double-layer optical fiber units.

[0045] As a result of conducting the above-mentioned experiment on fiber take-out performance for the optical fiber unit according to Experimental Example 1, some of the optical fibers were taken out using a tool such as nippers, and therefore the fiber take-out performance was deemed to be somewhat good (evaluated as B). As a result of conducting the above-mentioned experiment on lateral pressure resistance for the optical fiber unit according to Experimental Example 1, the increase in loss when a pressure of 500 N was applied was 0.3 dB or more, and therefore the lateral pressure resistance was deemed to be poor (evaluated as C). As a result of conducting the above-mentioned experiment on external damage resistance for the optical fiber unit according to Experimental Example 1, no breaks occurred in the optical fiber fibers during the process of manufacturing the optical fiber unit, and therefore the external damage resistance was deemed to be good (evaluated as A).

[0046] As a result of conducting the above-mentioned experiment on fiber take-out performance for the optical fiber unit according to Experimental Example 2, the fiber take-out performance was judged to be good (rating A), since the optical fiber core wire inside the optical fiber unit could be taken out by hand. As a result of conducting the above-mentioned experiment on lateral pressure resistance for the optical fiber unit according to Experimental Example 2, the loss increase when a pressure of 500 N was applied was 0.3 dB or more, so the lateral pressure resistance was judged to be poor (rating C). As a result of conducting the above-mentioned experiment on external damage resistance for the optical fiber unit according to Experimental Example 2, no breaks occurred in the optical fiber core wire during the process of manufacturing the optical fiber unit, so the external damage resistance was judged to be good (rating A).

[0047] As a result of conducting the above-mentioned experiment on fiber removal performance for the optical fiber unit according to Experimental Example 3, it was not possible to remove the optical fiber core wire inside the optical fiber unit even with a tool such as nippers, and therefore the fiber removal performance was judged to be poor (evaluated as C). As a result of conducting the above-mentioned experiment on lateral pressure resistance for the optical fiber unit according to Experimental Example 3, the increase in loss when 500 N was applied was less than 0.1 dB, and therefore the lateral pressure resistance was judged to be good (evaluated as A). As a result of conducting the above-mentioned experiment on external damage resistance for the optical fiber unit according to Experimental Example 3, no breaks occurred in the optical fiber core wire during the process of manufacturing the optical fiber unit, and therefore the external damage resistance was judged to be good (evaluated as A).

[0048] As a result of conducting the above-mentioned experiment on fiber take-out performance for the optical fiber unit according to Experimental Example 4, the fiber take-out performance was judged to be good (rating A) since the optical fiber core wire inside the optical fiber unit could be taken out by hand. As a result of conducting the above-mentioned experiment on lateral pressure resistance for the optical fiber unit according to Experimental Example 4, the loss increase when a pressure of 500 N was applied was 0.3 dB or more, so the lateral pressure resistance was judged to be poor (rating C). As a result of conducting the above-mentioned experiment on external damage resistance for the optical fiber unit according to Experimental Example 4, breakage occurred in the optical fiber core wire during the process of manufacturing the optical fiber unit, so the external damage resistance was judged to be poor (rating C).

[0049] As a result of conducting the above-mentioned experiment on fiber take-out performance for the optical fiber unit 10 according to Experimental Example 5, the fiber take-out performance was judged to be good (rating A), since the optical fiber 11 inside the optical fiber unit 10 could be taken out by hand. As a result of conducting the above-mentioned experiment on lateral pressure resistance for the optical fiber unit 10 according to Experimental Example 5, the increase in loss when a pressure of 500 N was applied was less than 0.1 dB, so the lateral pressure resistance was judged to be good (rating A). As a result of conducting the above-mentioned experiment on external damage resistance for the optical fiber unit 10 according to Experimental Example 5, no breaks occurred in the optical fiber 11 during the process of manufacturing the optical fiber unit 10, so the external damage resistance was judged to be good (rating A).

[0050] As a result of conducting the above-mentioned experiment on fiber take-out performance for the optical fiber unit 10 according to Experimental Example 6, the fiber take-out performance was determined to be good (evaluated as A), since the optical fiber 11 inside the optical fiber unit 10 could be taken out by hand. As a result of conducting the above-mentioned experiment on lateral pressure resistance for the optical fiber unit 10 according to Experimental Example 6, the increase in loss when a pressure of 500 N was applied was less than 0.1 dB, so the lateral pressure resistance was determined to be good (evaluated as A). As a result of conducting the above-mentioned experiment on external damage resistance for the optical fiber unit 10 according to Experimental Example 6, no breaks occurred in the optical fiber 11 during the process of manufacturing the optical fiber unit 10, so the external damage resistance was determined to be good (evaluated as A).

[0051] As a result of conducting the above-mentioned experiment on fiber take-out performance for the optical fiber unit according to Experimental Example 7, some of the optical fibers were taken out using a tool such as nippers, and therefore the fiber take-out performance was deemed to be somewhat good (evaluated as B). As a result of conducting the above-mentioned experiment on lateral pressure resistance for the optical fiber unit according to Experimental Example 7, the increase in loss when a pressure of 500 N was applied was less than 0.1 dB, and therefore the lateral pressure resistance was deemed to be good (evaluated as A). As a result of conducting the above-mentioned experiment on external damage resistance for the optical fiber unit according to Experimental Example 7, no breaks occurred in the optical fiber fibers during the process of manufacturing the optical fiber unit, and therefore the external damage resistance was deemed to be good (evaluated as A).

[0052] As a result of conducting the above-mentioned experiment on fiber take-out performance for the optical fiber unit according to Experimental Example 8, some of the optical fibers were taken out using a tool such as nippers, and therefore the fiber take-out performance was deemed to be somewhat good (evaluated as B). As a result of conducting the above-mentioned experiment on lateral pressure resistance for the optical fiber unit according to Experimental Example 8, the increase in loss when a pressure of 500 N was applied was less than 0.1 dB, and therefore the lateral pressure resistance was deemed to be good (evaluated as A). As a result of conducting the above-mentioned experiment on external damage resistance for the optical fiber unit according to Experimental Example 8, no breaks occurred in the optical fiber fibers during the process of manufacturing the optical fiber unit, and therefore the external damage resistance was deemed to be good (evaluated as A).

[0053] In the single-layer optical fiber units according to Experimental Examples 1 to 4, at least one of the fiber take-out property, lateral pressure resistance, and external damage resistance was poor (evaluated as C). A comparison between the optical fiber unit according to Experimental Example 3 and the optical fiber unit according to Experimental Example 4 revealed that in a single-layer optical fiber unit, a high Young's modulus of the layer covering the optical fiber increases the lateral pressure resistance and external damage resistance, but decreases the fiber take-out property. On the other hand, in the double-layer optical fiber units 10 according to Experimental Examples 5 and 6, the fiber take-out property, lateral pressure resistance, and external damage resistance were all good (evaluated as A). Furthermore, in the double-layer optical fiber units 10 according to Experimental Examples 7 and 8, the fiber take-out property was somewhat good (evaluated as B), and the lateral pressure resistance and external damage resistance were good (evaluated as A). This is because in the two-layer optical fiber unit 10, the Young's modulus of the inner layer 12 can be made different from that of the outer layer 13, and so, for example, by increasing the Young's modulus of the outer layer 13 while decreasing the Young's modulus of the inner layer 12, it is possible to improve the lateral pressure resistance and external damage resistance while also improving the ease of fiber removal. Therefore, if good fiber removal, lateral pressure resistance, and external damage resistance are all desired, the two-layer optical fiber unit 10 is more suitable than the single-layer optical fiber unit.

[0054] Furthermore, a comparison between the optical fiber unit 10 according to Experimental Example 5 and the optical fiber unit according to Experimental Example 7 revealed that the fiber extractability can be further improved by adding a lubricant to the inner layer 12. Furthermore, a comparison between the optical fiber units according to Experimental Examples 5 and 6 and the optical fiber unit according to Experimental Example 8 revealed that the fiber extractability can be further improved by setting the Young's modulus of the inner layer 12 to 300 MPa or less.

[0055] According to the optical fiber unit 10 described above, the Young's modulus of the inner layer 12 is 300 MPa or less, and therefore the lateral pressure resistance is high.

[0056] (Optical fiber cable 20 manufactured using optical fiber unit 10) Next, with reference to Fig. 4, an optical fiber cable 20 manufactured using the optical fiber unit 10 will be described. As illustrated in Fig. 4, the optical fiber cable 20 includes six optical fiber units 10, a tensile strength member 21, a water-absorbent fiber 22, a cable jacket 23, and a tear cord 24. Therefore, the optical fiber cable 20 is a 72-core optical fiber cable. The outer diameter of the optical fiber cable 20 is, for example, 3.6 mm. The core density (number of cores per unit area) obtained by dividing the number of cores 111 contained in the coated optical fiber 11 by the cross-sectional area of ​​the optical fiber cable 20 is 10 cores / mm ２ That's all.

[0057] The optical fiber cable 20 is produced, for example, by arranging six optical fiber units 10 in a ring shape around the strength member 21, with the strength member 21 at the center, and extrusion coating the cable jacket 23 so as to cover the six optical fiber units 10. Therefore, the six optical fiber units 10 are arranged outside the strength member 21 and are covered by the cable jacket 23. In other words, the six optical fiber units 10 are arranged in a region R1 formed between the strength member 21 and the cable jacket 23.

[0058] The strength member 21 is made of, for example, fiber reinforced plastic (FRP). Examples of fiber reinforced plastic include glass fiber reinforced plastic (GFRP) and aramid fiber reinforced plastic (AFRP). The strength member 21 has a substantially circular shape in a cross-sectional view of the optical fiber cable 20. The outer diameter of the strength member 21 is, for example, 0.7 mm or more and 0.8 mm or less. The strength member 21 is located approximately in the center of the optical fiber cable 20 in a cross-sectional view of the optical fiber cable 20.

[0059] The water-absorbent fibers 22 are, for example, plastic fibers coated with water-absorbent powder, or fibers that have been given water-absorbency themselves. The water-absorbent fibers 22 are, for example, linear members with an outer diameter of about 0.1 mm in a dry state. The water-absorbent fibers 22 are arranged along the longitudinal direction of the optical fiber cable 20. The water-absorbent fibers 22 are arranged between the tensile strength members 21 and the cable jacket 23.

[0060] The cable jacket 23 is formed from a resin material such as polyethylene resin or flame-retardant polyethylene resin. The cable jacket 23 has a relatively high Young's modulus of, for example, 1500 MPa or more at 23°C. The cable jacket 23 also preferably has low shrinkage, low friction, and flame retardancy. Identification marks such as numbers and letters may be printed on the cable jacket 23 using a laser printer or the like.

[0061] The tear cord 24 is used to tear the cable jacket 23 and is embedded in the cable jacket 23 along the longitudinal direction of the optical fiber cable 20. In this embodiment, two tear cords 24 are provided. The two tear cords 24 are arranged in opposite positions relative to the tensile strength member 21 in a cross-sectional view of the optical fiber cable 20. By pulling out the tear cord 24, the cable jacket 23 is torn in the longitudinal direction of the optical fiber cable 20, and the optical fiber unit 10 can be removed. The tear cord 24 is made of, for example, a tensile-resistant plastic material (e.g., polyester) or the like.

[0062] According to the optical fiber cable 20 as described above, the optical fiber cable 20 is manufactured using the optical fiber units 10 each having a relatively small outer diameter, and therefore the outer diameter of the optical fiber cable 20 is relatively small. Furthermore, according to the optical fiber cable 20 as described above, it is possible to prevent breakage of the optical fiber cores 11 when the six optical fiber units 10 are covered with the cable jacket 23 to form a cable. Furthermore, in the optical fiber cable 20, the optical fiber units 10 included in the optical fiber cable 20 have good resistance to lateral pressure and external damage, and the optical fiber cores 11 are easy to extract.

[0063] Furthermore, with the optical fiber cable 20 described above, six optical fiber units 10 are arranged in the region R1 formed between the tension members 21 and the cable jacket 23. Therefore, the optical fiber cable 20 can be configured to include a relatively large number of optical fiber units 10 while having a small outer diameter. In other words, with the optical fiber cable 20, the core density of the optical fiber cable 20 can be increased while having a small outer diameter.

[0064] Furthermore, according to the optical fiber cable 20 described above, the core density is 10 cores / mm ２ As described above, it is possible to suppress breakage of the optical fiber 11 while increasing the core density of the optical fiber cable 20 .

[0065] (Optical fiber cable 20A manufactured using optical fiber unit 10) Next, with reference to Fig. 5, an optical fiber cable 20A manufactured using the optical fiber unit 10 will be described. However, in the description of the optical fiber cable 20A, the same components as those of the optical fiber cable 20 will be described using the same reference numerals, and descriptions of overlapping parts will be omitted as appropriate. As illustrated in Fig. 5, the optical fiber cable 20A includes 24 optical fiber units 10, a tensile strength member 21A, a cable jacket 23, a tear string 24, and a water-absorbing tape 25. Therefore, the optical fiber cable 20A is a 288-core optical fiber cable. The outer diameter of the optical fiber cable 20A is, for example, 6.0 mm. Note that the core density of the optical fiber cable 20A is also 10 cores / mm ２ That's all.

[0066] The optical fiber cable 20A has a structure in which the optical fiber units 10 are housed in two layers. For example, the one-layer portion is produced by arranging eight optical fiber units 10 in a ring shape around the strength member 21A at the center and wrapping the water-absorbing tape 25 around the eight optical fiber units 10. The two-layer portion is produced by arranging the remaining 16 optical fiber units 10 in a ring shape to cover the water-absorbing tape 25 and extrusion-coating the cable jacket 23 to cover the 16 optical fiber units 10. Therefore, eight optical fiber units 10 are arranged in the first region R11 formed between the strength member 21A and the water-absorbing tape 25, and 16 optical fiber units 10 are arranged in the second region R12 formed between the cable jacket 23 and the water-absorbing tape 25.

[0067] The tension member 21A may have the same configuration as the tension member 21 of the optical fiber cable 20. However, the outer diameter of the tension member 21A is, for example, 1.2 mm or more and 1.3 mm or less. The tension member 21A is located approximately in the center of the optical fiber cable 20A in a cross-sectional view of the optical fiber cable 20A.

[0068] The water-absorbing tape 25 is disposed between the tension member 21A and the cable jacket 23. The water-absorbing tape 25 is wound, for example, vertically or horizontally, around the eight optical fiber units 10 arranged in the first region R11 formed between the tension member 21A and the water-absorbing tape 25. The water-absorbing tape 25 is formed by applying a water-absorbing powder to a base fabric made of polyester or the like, for example, to absorb water.

[0069] The optical fiber cable 20A as described above also provides the same effects as the optical fiber unit 10 and the optical fiber cable 20.

[0070] Furthermore, according to the optical fiber cable 20A described above, the optical fiber units 10 are arranged in each of the first region R11 and the second region R12, so that the core density of the optical fiber cable 20A can be increased while maintaining a relatively small outer diameter.

[0071] 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.

[0072] In the above embodiment, the optical fiber unit 10 includes twelve optical fiber cores 11, but the number of optical fiber cores 11 included in the optical fiber unit 10 may be two or more, and is not limited to twelve.

[0073] In the above embodiment, the optical fiber cable 20 includes six optical fiber units 10, and the optical fiber cable 20A includes 24 optical fiber units 10. However, the number of optical fiber units 10 included in the optical fiber cables 20 and 20A may be two or more, and is not limited to these.

[0074] In the above embodiment, the optical fiber cable 20 includes six optical fiber units 10, a strength member 21, a water-absorbent fiber 22, a cable jacket 23, and a tear string 24, but the present disclosure is not limited to this. The optical fiber cable 20 does not have to include, for example, the water-absorbent fiber 22 and the tear string 24. Furthermore, the optical fiber cable 20A includes 24 optical fiber units 10, a strength member 21A, a cable jacket 23, a tear string 24, and a water-absorbent tape 25, but the present disclosure is not limited to this. The optical fiber cable 20A does not have to include, for example, the tear string 24.

[0075] In the above embodiment, the optical fiber 11 has four cores 111, but the number of cores 111 included in the optical fiber 11 is not limited to four. The optical fiber 11 may also have one core 111. In other words, the optical fiber 110 included in the optical fiber 11 may be a single-core fiber.

[0076] In the above embodiment, a band-shaped marking is made on the optical fiber unit 10 by the marking device 250, but other markings may be made on the optical fiber unit 10. Also, no marking may be made on the optical fiber unit 10. Also, the marking device 250 may not be provided.

[0077] 1: Manufacturing equipment 10: Optical fiber unit 11: Optical fiber core 12: Inner layer 13: Outer layer 20, 20A: Optical fiber cable 21, 21A: Tensile strength member 22: Absorbent fiber 23: Cable jacket 24: Tear string 25: Absorbent tape 100: Supply device 101: Bobbin 102: Dancer roller 103: First guide roller 104: Directly above guide roller 110: Optical fiber 111: Core 112: Cladding 113: Protective coating 200: Resin application device 210: Point 220: Die 220A: First part 220B: Second part 230A: First resin tank 230B: Second resin tank 240: Ultraviolet irradiation device 250: Marking device 260: Second guide roller 310: Winding device R1: Region formed between the tension member and the cable jacket R11: First region R12: Second region

Claims

1. An optical fiber unit comprising: a plurality of optical fiber cores each having an outer diameter of 200 μm or less; an inner layer in contact with and covering the plurality of optical fiber cores; and an outer layer disposed outside the inner layer, wherein the plurality of optical fiber cores are integrated by being covered by the inner layer in a bundled state; in a cross-sectional view of the optical fiber unit, the outer shape of the optical fiber unit is circular; and the Young's modulus of the inner layer is lower than the Young's modulus of the outer layer.

2. The optical fiber unit according to claim 1, wherein said inner layer contains a lubricant.

3. The optical fiber unit according to claim 1 or 2, wherein the outer diameter of the optical fiber core is less than 180 μm.

4. The optical fiber unit according to claim 1 or 2, wherein the optical fiber included in the optical fiber core is a multi-core fiber.

5. The optical fiber unit according to claim 1 or 2, wherein the Young's modulus of said inner layer is 300 MPa or less.

6. The optical fiber unit according to claim 1 or 2, wherein the outer layer is a colored layer to which a pigment is added.

7. An optical fiber cable comprising: a plurality of optical fiber units according to claim 1 or 2; and a cable jacket surrounding the plurality of optical fiber units.

8. The optical fiber cable according to claim 7, further comprising a strength member disposed at the center of the optical fiber cable, and a plurality of the optical fiber units are disposed in an area formed between the strength member and the cable jacket.

9. The optical fiber cable described in claim 7, further comprising a strength member disposed at the center of the optical fiber cable, and a water-absorbing tape disposed between the strength member and the cable jacket, wherein the optical fiber unit is disposed in each of a first region formed between the strength member and the water-absorbing tape and a second region formed between the cable jacket and the water-absorbing tape.

10. The core density, calculated by dividing the number of cores contained in the optical fiber core by the cross-sectional area of ​​the optical fiber cable, is 10 cores / mm ２ The optical fiber cable according to claim 7 .

11. A method for manufacturing an optical fiber unit, comprising: a step of collecting a plurality of optical fiber core wires each having an outer diameter of 200 μm or less; a step of passing the plurality of optical fiber core wires through a die; a step of covering the plurality of optical fiber core wires with a first resin material and covering the first resin material with a second resin material while the plurality of optical fiber core wires are bundled in the die; a step of forming an inner layer covering the plurality of optical fiber core wires by irradiating the first resin material with ultraviolet light to harden the first resin material, and forming an outer layer covering the inner layer by irradiating the second resin material with ultraviolet light to harden the second resin material, wherein the plurality of optical fiber core wires and the inner layer are in contact with each other, and in a cross-sectional view of an optical fiber unit comprising the plurality of optical fiber core wires, the inner layer, and the outer layer, the outer shape of the optical fiber unit is circular, and the Young's modulus of the inner layer is lower than the Young's modulus of the outer layer.

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