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

Abstract

An optical fiber unit (10) comprising a plurality of optical fiber core wires (110) having an outer diameter of 200 μm or less, and an outer layer (12) that is in contact with a plurality of the optical fiber core wires and covers a plurality of the optical fiber core wires, wherein a plurality of the optical fiber core wires (110), in a bundled state, is integrated by being covered by the outer layer (12), and in a cross-sectional view of the optical fiber unit (10), an outer shape of the optical fiber unit is circular.

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 core wires each having an outer diameter of 200 μm or less; and an outer layer that contacts the plurality of optical fiber core wires and covers the plurality of optical fiber core wires; the plurality of optical fiber core wires are integrated by being covered by the outer layer in a bundled state; and when viewed in cross section of the optical fiber unit, the outer shape of the optical fiber unit is circular.

[0005] Fig. 1 is a cross-sectional view of an optical fiber unit according to this embodiment. Fig. 2 is a schematic diagram of a manufacturing apparatus for an optical fiber unit according to this embodiment. Fig. 3 is a flow chart illustrating a manufacturing method for an optical fiber unit according to this embodiment. Fig. 4 is a diagram illustrating the relationship between breaking elongation and breaking strength of the outer layer of an optical fiber unit. Fig. 5 is a cross-sectional view of an optical fiber cable including six optical fiber units. Fig. 6 is a cross-sectional view of an optical fiber cable including 24 optical fiber units.

[0006] [Problem to be Solved by the Present Disclosure] For example, in an optical fiber cable including 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 perform fusion splicing. 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 manufacturing process of the optical fiber cable.

[0007] An object of the present disclosure is to provide an optical fiber unit, an optical fiber cable, and a method for manufacturing the optical fiber unit that can suppress breakage of the optical fiber while using a small-diameter optical fiber.

[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 includes: (1) a plurality of optical fiber core wires each having an outer diameter of 200 μm or less; and an outer layer in contact with and covering the plurality of optical fiber core wires, wherein the plurality of optical fiber core wires are integrated by being covered by the outer layer in a bundled state; and the optical fiber unit has a circular outer shape in a cross-sectional view of the optical fiber unit. According to this configuration, the optical fiber unit having a circular outer shape in a cross-sectional view includes a plurality of optical fiber core wires each having an outer diameter of 200 μm or less and an outer layer covering the optical fiber core wires. Since the optical fiber core wires included in the optical fiber unit are small-diameter optical fiber core wires having an outer diameter of 200 μm or less, the outer diameter of such an optical fiber unit is relatively small. Furthermore, since the plurality of optical fiber core wires are integrated by being covered by the outer layer having a circular outer diameter in a cross-sectional view in a bundled state, they are less likely to break. Therefore, according to the optical fiber unit having the above configuration, breakage of the optical fiber can be suppressed even when a small-diameter optical fiber is used.

[0009] (2) In the optical fiber unit described in (1), 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.

[0010] (3) In the optical fiber unit according to (1) or (2), 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.

[0011] (4) In the optical fiber unit according to any one of (1) to (3), the outer layer may have a breaking strength of 20 MPa or less, and a breaking elongation of 100% to 400%. This configuration allows the resin material of the outer layer to be broken with a relatively small force, and the breaking elongation upon breaking is appropriately small. Therefore, the optical fiber unit according to the above configuration provides high fiber extraction efficiency.

[0012] (5) In the optical fiber unit according to any one of (1) to (4), the outer layer may contain silicone, and the silicone content of the outer layer may be 2% by mass or more and less than 5% by mass. This configuration allows the optical fiber to have appropriate adhesion and surface tackiness, thereby improving the optical fiber's ease of extraction.

[0013] An optical fiber cable according to one aspect of the present disclosure includes: (6) a plurality of optical fiber units according to any one of (1) to (5) 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 covering them with the cable jacket.

[0014] (7) The optical fiber cable described in (6) 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.

[0015] (8) The optical fiber cable described in (6) 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.

[0016] (9) In the optical fiber cable according to any one of (6) to (8), the core density obtained by dividing the number of cores included 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.

[0017] A method for manufacturing an optical fiber unit according to one aspect of the present disclosure includes: (10) collecting a plurality of optical fiber core wires each having an outer diameter of 200 μm or less; passing the plurality of optical fiber core wires through a die; covering the plurality of optical fiber core wires in a bundled state in the die with a resin material; and irradiating the resin material with ultraviolet light to harden the resin material, thereby forming an outer layer covering the plurality of optical fiber core wires, wherein the plurality of optical fiber core wires and the outer layer are in contact with each other, and the optical fiber unit including the plurality of optical fiber core wires and the outer layer has a circular outer shape in a cross-sectional view. According to this configuration, an optical fiber unit can be manufactured that includes a plurality of optical fiber core wires each having an outer diameter of 200 μm or less and an outer layer covering the optical fiber core wires, and that has a circular outer shape in a cross-sectional view. The optical fiber core wires provided in the optical fiber unit are thin optical fiber core wires with an outer diameter of 200 μm or less, so the outer diameter of such an optical fiber unit is relatively small. Furthermore, the multiple optical fiber core wires are covered with an outer layer that has a circular outer shape in cross section and is formed by curing a resin material. In other words, the multiple optical fiber core wires are integrated by being covered with the outer layer that has a circular outer shape in cross section, and are therefore less likely to break. Therefore, with an optical fiber unit manufactured by the optical fiber unit manufacturing method according to the above configuration, breakage of the optical fiber core wires can be suppressed even when thin optical fiber core wires are used.

[0018] [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 the optical fiber unit that can suppress breakage of the optical fiber while using a small-diameter optical fiber.

[0019] [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.

[0020] (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 and an outer layer 12 that covers the plurality of optical fiber cores 11.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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 .

[0025] 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 outer 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 single-layer structure.

[0026] The outer layer 12 covers the 12 optical fibers 11. The outer layer 12 is in contact with the 12 optical fibers 11. The outer layer 12 can be formed from a resin material such as a urethane acrylate resin. The outer layer 12 may contain silicone. In this case, the silicone content in the outer layer 12 is, for example, 2 mass% or more and less than 5 mass%. The Young's modulus of the outer layer 12 is, for example, 5 MPa or more and 10 MPa or less. The breaking strength of the outer layer 12 is, for example, 20 MPa or less. The breaking elongation of the outer layer 12 is, for example, 100% or more and 400% or less.

[0027] (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.

[0028] 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.

[0029] 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.

[0030] In the die 220, a resin material is applied to the twelve optical fiber cores 11. The hole shape at the exit of the die 220 is circular, and the resin material is applied around the twelve optical fiber cores 11 so that the cross-sectional outline becomes circular. The resin material is, for example, an ultraviolet-curable resin. An example of the ultraviolet-curable resin is a urethane acrylate resin. A lubricant such as silicone may be added to the resin material. The resin material is supplied, for example, from a pressurized resin tank 230. The twelve optical fiber cores 11 covered with the resin material are sent to an ultraviolet irradiation device 240.

[0031] In the ultraviolet irradiation device 240, ultraviolet rays are irradiated onto the resin material covering the 12 optical fibers 11. As a result, the resin material covering the 12 optical fibers 11 is hardened, and the outer layer 12 (see FIG. 1 ) is formed. In other words, when ultraviolet rays are irradiated onto the resin material covering the 12 optical fibers 11, the 12 optical fibers 11 are covered and integrated by the outer layer 12 in a bundled state. In this way, an optical fiber unit 10 is formed, which includes the 12 optical fibers 11 and the outer layer 12 covering the 12 optical fibers 11. The formed optical fiber unit 10 is sent to the marking device 250.

[0032] 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.

[0033] 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.

[0034] (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.

[0035] 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).

[0036] The twelve optical fibers 11 passed through the die 220 are bundled together in the die 220 so that the cross-sectional shape is nearly circular, and then covered with a resin material (STEP 03). The twelve optical fibers 11 covered with the resin material are sent to an ultraviolet irradiation device 240.

[0037] The ultraviolet irradiation device 240 irradiates the resin material covering the twelve optical fibers 11 with ultraviolet light, thereby forming the outer layer 12 (STEP 04). As a result, the optical fiber unit 10 is formed.

[0038] The optical fiber unit 10 described above simply includes twelve optical fibers 11 each having an outer diameter of 200 μm or less and an outer layer 12 covering the optical fibers 11, and therefore has a relatively small outer diameter. Furthermore, unlike an optical fiber ribbon, the twelve optical fibers 11 are bundled together and covered with the outer 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 with the outer layer 12, which has a relatively thick coating thickness. Therefore, compared to a typical tape-shaped optical fiber ribbon, 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.

[0039] 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.

[0040] 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.

[0041] (Experiment on Fiber Extraction Ease) The inventors evaluated the fiber extractability of the optical fiber 11 in the optical fiber unit 10. The evaluation indexes were the number of times a commercially available fiber separation tool (a simple tool with protrusions) was moved back and forth on each optical fiber unit 10 shown in Table 1 until the optical fiber 11 and the outer layer 12 of the optical fiber unit 10 were separated, and the ease of extraction, including whether the optical fiber 11 could be easily peeled off from the separated state. If the number of times was within 10 and the optical fiber 11 could be easily extracted, the fiber extractability was rated good (evaluated as A). Note that the optical fiber 11 included in the optical fiber unit 10 can be easily extracted from the optical fiber unit 10 when the optical fiber 11 is adhered to the outer layer 12 with a certain appropriate adhesive force. In other words, "if the optical fiber 11 can be easily extracted" means that the optical fiber 11 has appropriate fiber adhesion and surface tackiness. When the number of reciprocating movements required until the optical fiber 11 and the outer layer 12 of the optical fiber unit 10 were separated was 10 or less, but the optical fiber 11 could not be easily taken out, the optical fiber take-out property was rated as slightly poor (evaluated as B). When the number of reciprocating movements required until the optical fiber 11 and the outer layer 12 of the optical fiber unit 10 were separated was 11 or more, the optical fiber take-out property was rated as poor (evaluated as C). Note that the outer diameter of the optical fiber 11 in Experimental Examples 1 to 8 was 200 μm, and the outer diameter of the glass fiber was 125 μm.

[0042] In the optical fiber unit 10 according to Experimental Example 1, even when a commercially available single-fiber separation tool was reciprocated 15 times, the optical fiber core 11 and the outer layer 12 of the optical fiber unit 10 were not separated. Therefore, the optical fiber unit 10 according to Experimental Example 1 was judged to have poor fiber extraction properties (evaluation C).

[0043] In the optical fiber unit 10 according to Experimental Example 2, even when a commercially available single-fiber separation tool was moved back and forth 15 times, the optical fiber core 11 and the outer layer 12 of the optical fiber unit 10 were not separated. Therefore, the optical fiber unit 10 according to Experimental Example 2 was determined to have poor fiber extraction properties (evaluation C).

[0044] In the optical fiber unit 10 according to Experimental Example 3, the number of reciprocating movements required until the optical fiber 11 and the outer layer 12 of the optical fiber unit 10 were separated was about 5 to 10, but the outer layer 12 was not torn off, so it was not easy to remove the optical fiber 11. For this reason, the optical fiber unit 10 according to Experimental Example 3 was judged to have a slightly poor core fiber removal property (evaluation B).

[0045] In the optical fiber unit 10 according to Experimental Example 4, the number of reciprocations required until the optical fiber 11 and the outer layer 12 of the optical fiber unit 10 were separated was about 15. Furthermore, in the optical fiber unit 10 according to Experimental Example 4, the optical fiber 11 and the outer layer 12 of the optical fiber unit 10 were tightly adhered to each other and were difficult to peel off, and the surface of the optical fiber 11 was sticky, so the optical fiber 11 could not be easily removed. For this reason, the optical fiber removal property of the optical fiber unit 10 according to Experimental Example 4 was determined to be poor (evaluated as C).

[0046] In the optical fiber unit 10 according to Experimental Example 5, the number of reciprocations required until the optical fiber 11 and the outer layer 12 of the optical fiber unit 10 were separated was about five. However, in the optical fiber unit 10 according to Experimental Example 5, the separation of the optical fiber 11 and the outer layer 12 of the optical fiber unit 10 progressed in the longitudinal direction of the optical fiber unit 10, and separation occurred in areas other than those that required separation, making it difficult to remove the optical fiber 11. For this reason, the optical fiber removal property of the optical fiber unit 10 according to Experimental Example 5 was determined to be somewhat poor (evaluated as B).

[0047] For the optical fiber unit 10 according to Experimental Example 6, the number of reciprocating movements required until the optical fiber 11 and the outer layer 12 of the optical fiber unit 10 were separated was about five, and the optical fiber 11 could be easily removed. Therefore, the optical fiber removal property of the optical fiber unit 10 according to Experimental Example 6 was determined to be good (evaluated as A).

[0048] For the optical fiber unit 10 according to Experimental Example 7, the number of reciprocating movements required until the optical fiber 11 and the outer layer 12 of the optical fiber unit 10 were separated was about five, and the optical fiber 11 could be easily removed. Therefore, the optical fiber removal property of the optical fiber unit 10 according to Experimental Example 7 was determined to be good (evaluated as A).

[0049] For the optical fiber unit 10 according to Experimental Example 8, even when a commercially available single-fiber separation tool was run back and forth 15 times on the optical fiber unit 10 according to Experimental Example 8, the optical fiber core wire 11 and the outer layer 12 of the optical fiber unit 10 were not separated. Therefore, the core wire extraction property of the optical fiber unit 10 according to Experimental Example 8 was determined to be poor (evaluated as C).

[0050] 4 is a diagram illustrating the relationship between the breaking elongation and breaking strength of the outer layer 12 of the optical fiber units 10 according to Experimental Examples 1 to 8. As described above, the optical fiber units 10 according to Experimental Examples 6 and 7 had good fiber take-out properties (evaluation A), whereas the optical fiber units 10 according to Experimental Examples 3 and 5 had slightly poor fiber take-out properties (evaluation B), and the optical fiber units 10 according to Experimental Examples 1, 2, 4, and 8 had poor fiber take-out properties (evaluation C). This shows that the fiber take-out properties of the optical fiber units 10 whose breaking strength and breaking elongation of the outer layer 12 are within the ranges indicated by the shaded areas in FIG. 4 (the ranges in which the breaking strength of the outer layer 12 is 20 MPa or less and the breaking elongation of the outer layer 12 is 100% or more and 400% or less) are good. Furthermore, the results of Experimental Examples 3, 5, 6 and 7 also showed that the optical fiber unit 10 having a silicone content of 2% by mass or more and less than 5% by mass relative to the outer layer 12 has good fiber extraction properties.

[0051] As described above, in the optical fiber unit 10 in which the breaking strength of the outer layer 12 is 20 MPa or less and the breaking elongation of the outer layer 12 is 100% or more and 400% or less, the resin material of the outer layer 12 can be broken with a relatively small force, and the breaking elongation when broken is appropriately small. Therefore, with such an optical fiber unit 10, the optical fiber 11 can be easily extracted.

[0052] Furthermore, according to the optical fiber unit 10 in which the silicone content of the outer layer 12 is 2% by mass or more and less than 5% by mass, appropriate core wire adhesion and surface tackiness can be obtained, and therefore the core wire extraction of the optical fiber core wire 11 is good.

[0053] (Optical fiber cable 20 manufactured using optical fiber unit 10) Next, with reference to Fig. 5, an optical fiber cable 20 manufactured using the optical fiber unit 10 will be described. As illustrated in Fig. 5, 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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 optical fiber cable 20 has a relatively small outer diameter. 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.

[0060] 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.

[0061] 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 .

[0062] (Optical fiber cable 20A manufactured using optical fiber unit 10) Next, with reference to Fig. 6, 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. 6, 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 1: Manufacturing equipment 10: Optical fiber unit 11: Optical fiber core 12: Outer layer 20, 20A: Optical fiber cable 21, 21A: Tensile strength member 22: Absorbent fiber 23: Cable outer 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 230: Resin tank 240: Ultraviolet irradiation device 250: Marking device 260: Second guide roller 310: Winding device R1: Region formed between the tensile strength member and the cable outer 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; and an outer layer in contact with and covering the plurality of optical fiber cores, wherein the plurality of optical fiber cores are integrated by being covered by the outer layer in a bundled state; and when viewed in cross section, the outer shape of the optical fiber unit is circular.

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

3. 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.

4. An optical fiber unit according to claim 1 or 2, wherein the breaking strength of said outer layer is 20 MPa or less, and the breaking elongation of said outer layer is 100% or more and 400% or less.

5. An optical fiber unit as described in claim 1 or claim 2, wherein the outer layer contains silicone, and the content of the silicone in the outer layer is equal to or greater than 2 mass % and less than 5 mass %.

6. 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.

7. The optical fiber cable according to claim 6, further comprising a strength member disposed at the center of said optical fiber cable, and a plurality of said optical fiber units are disposed in an area formed between said strength member and said cable jacket.

8. The optical fiber cable according to claim 6, 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, the optical fiber unit being 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.

9. 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 6 .

10. 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 resin material while the plurality of optical fiber core wires are bundled in the die; and a step of forming an outer layer covering the plurality of optical fiber core wires by irradiating the resin material with ultraviolet light to harden the resin material, wherein the plurality of optical fiber core wires and the outer layer are in contact with each other, and the outer shape of an optical fiber unit comprising the plurality of optical fiber core wires and the outer layer is circular in cross-sectional view.

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