Optical fiber unit and optical fiber cable

Abstract

The present invention is provided with: a plurality of bundled optical fibers (11) or an optical fiber ribbon (10); and a plastic film (20) having a thickness of less than 0.1 mm and covering the periphery of the optical fibers (11) or the optical fiber ribbon (10). The plastic film (20) is provided with a base material (21) and an adhesive resin layer (22) provided on at least one surface of the base material (21). The melting point of the adhesive resin layer (22) is less than 200°C, and a part of the plastic film (20) is fused by means of the adhesive resin layer (22) so that the plastic film (20) is formed in an annular shape in a cross-sectional view.

Description

Optical fiber unit and optical fiber cable

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

[0002] Patent Document 1 describes a cable in which intermittently adhesive type optical fiber ribbons are arranged in a circular unit tube.

[0003] Japanese Patent Application Publication No. 2019-124936

[0004] An optical fiber unit according to one aspect of the present disclosure comprises: a plurality of optical fibers or optical fiber ribbons; and a plastic film having a thickness of less than 0.1 mm and covering the plurality of optical fibers or the plurality of optical fiber ribbons; the plastic film comprises a base material and an adhesive resin layer provided on at least one side of the base material, the adhesive resin layer having a melting point of less than 200°C; and the plastic film is formed in a ring shape in cross section by fusing a portion of the plastic film with the adhesive resin layer.

[0005] An optical fiber cable according to one aspect of the present disclosure includes: a plurality of the optical fiber units described above; and a cable jacket covering the plurality of optical fiber units.

[0006] Fig. 1 is a perspective view of an optical fiber unit. Fig. 2 is a cross-sectional view of the optical fiber unit. Fig. 3 is a partial enlarged view of III in Fig. 2. Fig. 4 is a schematic diagram of a manufacturing apparatus for manufacturing an optical fiber unit. Fig. 5 shows another example of a plastic film. Fig. 6 shows an example of the shape of an adhesive resin layer in a plastic film. Fig. 7 shows another example of the shape of an adhesive resin layer in a plastic film. Fig. 8 is a cross-sectional view of an optical fiber cable.

[0007] (Problem to be Solved by the Present Disclosure) In an optical fiber unit with a loose tube structure, the tube may be thinned to enable high-density packaging of optical fibers. However, excessive thinning of the tube can easily cause problems such as lack of resin application during extrusion molding of the resin that forms the tube.

[0008] Effect of the Present Disclosure According to the present disclosure, it is possible to provide an optical fiber unit and an optical fiber cable with improved packaging density and manufacturing yield.

[0009] (Description of Embodiments of the Present Disclosure) First, embodiments of the present disclosure will be described. (1) An optical fiber unit according to one aspect of the present disclosure comprises: a plurality of optical fibers or optical fiber ribbons; and a plastic film having a thickness of less than 0.1 mm and covering the plurality of optical fibers or the plurality of optical fiber ribbons. The plastic film comprises a substrate and an adhesive resin layer provided on at least one side of the substrate, the melting point of the adhesive resin layer being less than 200°C. The plastic film is formed into a ring shape in a cross-sectional view by fusing a portion of the plastic film with the adhesive resin layer. According to the above optical fiber unit, the plurality of optical fibers or the plurality of optical fiber ribbons are covered with a thin plastic film having a thickness of less than 0.1 mm, thereby improving the packaging density of the optical fibers. Furthermore, because the plastic film is formed into a ring shape so as to cover the plurality of optical fibers or the plurality of optical fiber ribbons by bonding with the adhesive resin layer, the occurrence of molding defects is suppressed compared to when a tube is formed around the plurality of optical fibers or the plurality of optical fiber ribbons by extrusion molding, and the manufacturing yield of the optical fiber unit is improved. The thickness is an average value, for example, an average value of thicknesses measured at any 10 points.

[0010] (2) In the optical fiber unit according to (1), the adhesive resin layer may be formed of an adhesive polyolefin resin. By using the adhesive polyolefin resin, an adhesive layer having a melting point of less than 200°C can be formed at any position on the plastic film substrate, and sufficient adhesive strength can be ensured at temperatures less than 200°C.

[0011] (3) In the optical fiber unit according to (1) or (2), the plastic film may have overlapping portions where the plastic films overlap each other in a portion of the circumferential direction covering the peripheries of the plurality of optical fibers or the plurality of optical fiber ribbons, and the adhesive resin layer may be formed only in the overlapping portions. According to the above configuration, since the adhesive resin is not formed in any portion other than the overlapping portions, it is possible to prevent the plastic film from adhering to the optical fibers or the optical fiber ribbons in any portion other than the overlapping portions.

[0012] (4) In the optical fiber unit according to any one of (1) to (3), the plastic films may have overlapping portions where the plastic films overlap each other in a portion of the circumferential direction covering the peripheries of the plurality of optical fibers or the plurality of optical fiber ribbons, and the width of the overlapping portion may be 10% to 30% of the width of the plastic film in the short direction. By making the width of the overlapping portion 10% or more of the width of the plastic film in the short direction, the overlapping portion is reliably adhered, making it easier to maintain a state in which the plastic films are sufficiently adhered to each other. By making the width of the overlapping portion 30% or less of the width of the plastic film in the short direction, it is also easier to disassemble the optical fiber unit.

[0013] (5) In the optical fiber unit according to any one of (1) to (4), the plastic films have overlapping portions where the plastic films overlap each other in a portion of the circumferential direction covering the peripheries of the plurality of optical fibers or the plurality of optical fiber ribbons, and the adhesive resin layer may not be provided on the short-side end portions of the plastic films constituting the overlapping portions. Since the end portions of the plastic films have portions not bonded by the adhesive resin layer at the circumferential end portions of the overlapping portions, the optical fiber unit can be easily disassembled by pinching the unbonded portions.

[0014] (6) In the optical fiber unit according to any one of (1) to (5), a slit may be formed in a portion of the plastic film in the longitudinal direction. Since the slit is formed in a portion of the plastic film in the longitudinal direction, the optical fiber or the optical fiber ribbon can be easily removed during installation.

[0015] (7) In the optical fiber unit according to any one of (1) to (6), the optical fiber unit may have water-absorbent fibers arranged along the plurality of optical fibers or the plurality of optical fiber ribbons, and the plastic film may be formed so as to cover the water-absorbent fibers while in contact with the water-absorbent fibers. Since the plastic film is formed so as to cover the water-absorbent fibers while in contact with the water-absorbent fibers, it is possible to prevent water from flowing inside the plastic film and seeping into the optical fiber unit in the longitudinal direction.

[0016] (8) In the optical fiber unit according to any one of (1) to (7), the resin constituting the surfaces of the optical fibers or the optical fiber ribbons may contain a lubricant, which can prevent the optical fibers or the optical fiber ribbons from unintentionally sticking to the plastic film.

[0017] (9) In the optical fiber unit according to any one of (1) to (8) above, the plastic film may be made of a material having a flame retardancy of a limit oxygen index of 40 or more. Since the plastic film is made of a material having a flame retardancy of a limit oxygen index of 40 or more, the flame retardancy of the entire optical fiber unit is also good.

[0018] (10) In the optical fiber unit according to any one of (1) to (9), the optical fiber packaging density within the optical fiber unit is 10 fibers / mm ２ The optical fiber unit may have an optical fiber packaging density of 10 fibers / mm or more. ２The optical fiber unit having the above configuration is effective for realizing the optical fiber unit described above. Note that the packing density is the number of optical fibers contained in the optical fiber unit divided by the cross-sectional area of ​​the optical fiber unit including the plastic film.

[0019] (11) In the optical fiber unit according to any one of (1) to (10), the plastic films may have overlapping portions where the plastic films overlap each other in a portion of the circumferential direction covering the peripheries of the plurality of optical fibers or the plurality of optical fiber ribbons, and the overlapping portions may have alternately provided adhesive portions where the adhesive resin layer is formed and non-adhesive portions where the adhesive resin layer is not formed in the longitudinal direction of the optical fiber unit. By providing the non-adhesive portions intermittently, the disassembly of the optical fiber unit is improved.

[0020] (12) In the optical fiber unit according to any one of (1) to (11), the plastic film may be made of a biodegradable plastic. Since the plastic film is made of a biodegradable plastic, it is possible to reduce the impact on the natural environment when disposing of the optical fiber unit after use.

[0021] (13) In the optical fiber unit according to any one of (1) to (12) above, a water-absorbent polymer may be applied to the outer surface of the plastic film. Since the water-absorbent polymer is applied to the outer surface of the plastic film, the optical fiber unit has good waterproofing properties.

[0022] (14) In the optical fiber unit according to any one of (1) to (13) above, a two-dimensional code that allows access to identification information of the optical fiber unit may be provided on the outer surface of the plastic film. Since the two-dimensional code is provided on the outer surface of the plastic film, it becomes easy to access the identification information of the optical fiber unit.

[0023] (15) In the optical fiber unit according to any one of (1) to (14), the plastic film may have an overlapping portion where the plastic films overlap each other in a circumferential portion covering the peripheries of the plurality of optical fibers or the plurality of optical fiber ribbons, and the overlapping portion may be formed in a spiral shape in the longitudinal direction of the optical fiber unit. Since the overlapping portion is formed in a spiral shape in the longitudinal direction of the optical fiber unit, it is arranged without being concentrated in a circumferential portion of the optical fiber unit. This allows stress to be dispersed rather than concentrated in a single portion when the optical fiber unit is bent, thereby preventing the plurality of optical fibers or the plurality of optical fiber ribbons from unintentionally popping out of the plastic film.

[0024] (16) In the optical fiber unit according to any one of (1) to (15), the plastic film may be colored in two or more colors. Since the plastic film is colored in two or more colors, the optical fiber unit can be more easily distinguished. In addition, coloring is easier than coloring the optical fiber unit by coating it with a colored resin.

[0025] (17) An optical fiber cable according to an aspect of the present disclosure includes: a plurality of optical fiber units according to any one of (1) to (16); and a cable jacket covering the plurality of optical fiber units. The optical fiber cable described above can improve the packaging density of optical fibers and the manufacturability of the optical fiber cable.

[0026] (Details of the embodiments of the present disclosure) Specific examples of the optical fiber unit and the optical fiber cable according to the embodiments of the present disclosure will be described below with reference to the drawings. Note that the present invention 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.

[0027] Fig. 1 is a perspective view of the optical fiber unit 1. Fig. 2 is a cross-sectional view of the optical fiber unit 1. The optical fiber unit 1 includes a bundle of optical fiber ribbons 10 and a plastic film 20 that covers the optical fiber ribbons 10 and the water-absorbing fibers 30.

[0028] The optical fiber ribbon 10 includes a plurality of optical fiber cores 11 (an example of optical fibers). In this embodiment, the optical fiber ribbon 10 is configured by arranging 12 optical fiber cores 11 in parallel. The optical fiber unit 1 includes 12 optical fiber ribbons 10, and the optical fiber unit 1 includes 144 optical fiber cores 11. The optical fiber ribbon 10 may be configured, for example, by intermittently connecting adjacent optical fiber cores 11 along the longitudinal direction of the optical fiber unit 1. The optical fiber core 11 includes a glass fiber having a core and a cladding, and a resin layer covering the glass fiber. The resin layer may include a colored layer. The diameter of the glass fiber is typically approximately 125 μm. The diameter of the optical fiber core 11 is, for example, 245 μm or more and 265 μm or less, and for small diameter optical fibers, it is, for example, 180 μm or more and 220 μm or less.

[0029] The resin that forms the surface of the optical fiber ribbon 10 may contain a lubricant. The lubricant may be, for example, silicone. In the optical fiber unit 1, the optical fiber packing density, which indicates the number of optical fibers in the cross-sectional area of ​​the optical fiber unit 1, is 10 fibers / mm ２ The optical fiber unit 1 may have a configuration including a plurality of single-core optical fibers 11 instead of the optical fiber ribbon 10. In this case, it is preferable that the outermost layer of the optical fiber 11 contains a lubricant.

[0030] The optical fiber unit 1 includes a plurality of optical fiber cores 11 bundled together in the form of an optical fiber ribbon 10 so that the aggregate cross-sectional shape is roughly circular, and the periphery of the bundle is wrapped and covered by a plastic film 20. That is, the plastic film 20 is formed in a ring shape in cross section. The plastic film 20 is a resin film with a thickness of less than 0.1 mm.

[0031] Fig. 3 is a partial enlarged view of III in Fig. 2. As illustrated in Figs. 2 and 3, the plastic film 20 has an overlapping portion 20A where the plastic films 20 overlap each other in a portion of the circumferential direction covering the optical fiber ribbon 10 and the water-absorbing fiber 30. The width of the overlapping portion 20A is desirably 10% or more and less than 30% of the width of the plastic film 20 in the short direction when unfolded. The ratio of the width of the overlapping portion 20A to the width of the plastic film 20 is sometimes referred to as the overlap ratio. In other words, the overlap ratio is expressed as overlapping portion length / (non-overlapping portion length + overlapping portion length × 2).

[0032] As illustrated in Fig. 3, the plastic film 20 includes a substrate 21 and an adhesive resin layer 22. The substrate 21 is formed of, for example, polyethylene terephthalate (PET). The adhesive resin layer 22 is provided on at least one surface of the substrate 21. In the example of Fig. 3, of the plastic films 20 that constitute the overlapping portion 20A, the adhesive resin layer 22 is formed on the inner side of the plastic film 20 that constitutes the outer surface of the optical fiber unit 1. It is desirable that the adhesive resin layer 22 be formed of, for example, an adhesive polyolefin resin. An example of the adhesive polyolefin resin is adhesive polyethylene.

[0033] The melting point of the adhesive resin layer 22 is less than 200°C. The adhesive resin layer 22 is heated to a temperature equal to or higher than the melting point of the adhesive resin layer 22, and then cooled to a temperature lower than the melting point of the adhesive resin layer 22, whereby the plastic films 20 constituting the overlapping portion 20A are fused together by the adhesive resin layer 22. This allows the plastic film 20 to maintain a ring-shaped state in cross-section. At this time, it is desirable that the substrate 21 be configured so as not to undergo thermal deformation at least at temperatures equal to or higher than the melting point of the adhesive resin layer 22.

[0034] The adhesive resin layer 22 may be formed only in the overlapping portion 20A. Also, the adhesive resin layer 22 does not have to be provided on the end portion 20B (the end portion exposed on the outer periphery of the unit) in the short direction of the plastic film 20 constituting the overlapping portion 20A. In this case, the end portion 20B of the overlapping portion 20A can be separated from the overlapping plastic film 20.

[0035] The water-absorbent fibers 30 are configured to absorb water that has entered the optical fiber unit 1 and prevent water from seeping in the longitudinal direction of the unit. As illustrated in Fig. 2, the plastic film 20 is formed to cover the water-absorbent fibers 30 while being in contact with the water-absorbent fibers 30. Note that the optical fiber ribbon 10 and the water-absorbent fibers 30 covered with the plastic film 20 before the adhesive resin layer 22 is fused may be referred to as the optical fiber ribbon unit 1A.

[0036] 1 , a two-dimensional code C that allows access to identification information is provided on the outer surface of the plastic film 20. The identification information may include, for example, information such as the manufacturer, the year of manufacture, the control number, the number of optical fiber cores, the allowable tension, the allowable bending diameter, and the operating temperature.

[0037] The plastic film 20 may be made of a flame-retardant material with a limiting oxygen index of 40 or more. The limiting oxygen index is the minimum oxygen concentration required for continued combustion, as defined by JIS K7201. The plastic film 20 may also be made of a biodegradable plastic. Furthermore, the outer surface of the plastic film 20 may be coated with a water-absorbent polymer.

[0038] 1, the plastic film 20 may be colored in two or more colors in the longitudinal direction of the plastic film 20. In this case, the plastic film 20 may have a colored layer (not shown) between the substrate 21 and the adhesive resin layer 22, or a coloring pigment may be mixed into the substrate or the adhesive resin layer.

[0039] Next, a description will be given of a manufacturing method for manufacturing the optical fiber unit 1. Fig. 4 is a schematic diagram of a manufacturing apparatus for manufacturing the optical fiber unit 1.

[0040] First, the optical fiber ribbons 10 are unwound from a plurality of supply bobbins around which the optical fiber ribbons 10 are wound, and the plurality of optical fiber ribbons 10 are twisted together to form a bundle, and then the water-absorbing fibers 30 are arranged along the bundle to form an optical fiber ribbon unit 1A. The optical fiber ribbon unit 1A is sent to the film forming section 110.

[0041] The optical fiber ribbon unit 1A and a plastic film 20 having an adhesive resin layer 22 formed on a substrate 21 are supplied to the film forming unit 110. The plastic film 20 is fed from a bobbin 130 and sent to the film forming unit 110. The film forming unit 110 is configured to wrap the plastic film 20 so as to cover the optical fiber ribbon unit 1A. At this time, it is desirable that the plastic film 20 be wrapped lengthwise along the longitudinal direction of the optical fiber ribbon unit 1A.

[0042] The optical fiber ribbon unit 1A, with the plastic film 20 wrapped around it, is sent to the heat welding section 120. The optical fiber ribbon unit 1A sent to the heat welding section 120 is heated to a temperature equal to or higher than the melting point of the adhesive resin layer 22. In this state, the adhesive resin layer 22 melts.

[0043] When the optical fiber ribbon unit 1A passes through the heat welding portion 120 and is cooled to a temperature below the melting point of the adhesive resin layer 22, the adhesive resin layer 22 solidifies. As a result, as illustrated in Fig. 3, the base materials 21 of the plastic films 20 constituting the overlapping portion 20A are fused together with the adhesive resin layer 22 sandwiched therebetween, and the plastic film 20 is formed into a ring shape so as to cover the periphery of the optical fiber ribbon unit 1A.

[0044] According to the optical fiber unit 1 of this embodiment, the optical fiber ribbons 10 are covered with the plastic film 20 having a thickness of less than 0.1 mm, which facilitates an improvement in the optical fiber packaging density. Furthermore, the plastic film 20 is formed into a ring shape so as to cover the periphery of the optical fiber ribbons 10 by bonding with the adhesive resin layer 22. This reduces the occurrence of molding defects compared to when a tube is formed around the optical fiber ribbons 10 by extrusion molding, thereby improving the manufacturing yield of the optical fiber unit 1.

[0045] Next, another example of the optical fiber unit will be described with reference to Fig. 5. The plastic film 20 of the optical fiber unit 1B according to this example has a slit formed in part of its longitudinal direction, which makes it easier to remove the optical fiber 11 or the optical fiber ribbon 10 from the optical fiber unit 1 during installation.

[0046] 5, the overlapping portion 20A is formed in a spiral shape in the longitudinal direction of the optical fiber unit 1. Such an optical fiber unit 1 can be manufactured, for example, by rotating the bobbin 130 and a part of the film forming portion 110 in FIG. 4 around the optical fiber ribbon unit 1A.

[0047] The overlapping portion 20A is formed spirally in the longitudinal direction of the optical fiber unit 1, so that the overlapping portion 20A is arranged without concentrating on one part of the circumferential direction of the optical fiber unit 1. As a result, when the optical fiber unit 1 is bent, the overlapping portion 20A is not concentrated on the outside (region where the unit expands) or inside (region where the unit contracts) of the bend, so that the optical fiber ribbon 10 can be prevented from unintentionally popping out of the plastic film 20.

[0048] Next, an example of the configuration of the adhesive resin layer 22 in the plastic film 220 will be described with reference to Fig. 6. The vertical direction in Fig. 6 corresponds to the longitudinal direction of the optical fiber unit 1 and the plastic film 220. In the example of Fig. 6, adhesive portions 221 where the adhesive resin layer 22 is formed and non-adhesive portions 222 where the adhesive resin layer 22 is not formed are alternately provided in the longitudinal direction of the optical fiber unit 1. In the example of Fig. 6, the adhesive portions 221 and the non-adhesive portions 222 are formed so as to diagonally intersect with the longitudinal direction of the optical fiber unit 1 and the plastic film 220.

[0049] Fig. 7 shows another example of the shape of the adhesive resin layer 22 in the plastic film 320. The vertical direction in Fig. 7 corresponds to the longitudinal direction of the optical fiber unit 1 and the plastic film 320. In the example of Fig. 7 as well, adhesive portions 321 where the adhesive resin layer 22 is formed and non-adhesive portions 222 where the adhesive resin layer 22 is not formed are alternately provided in the longitudinal direction of the optical fiber unit 1. In the example of Fig. 7, the adhesive portions 221 and the non-adhesive portions 322 are formed so as to intersect perpendicularly with the longitudinal direction of the optical fiber unit 1 and the plastic film 320.

[0050] 6 and 7 , adhesive portions 221, 321 where the adhesive resin layer 22 is formed and non-adhesive portions 222, 322 where the adhesive resin layer 22 is not formed are alternately provided in the longitudinal direction of the optical fiber unit 1. This makes it possible for the plastic films 220, 320 to be formed so as to cover the optical fiber ribbon 10 by the adhesive portions 221, 321, and since the adhesive portions 221, 321 and the non-adhesive portions 222, 322 are alternately provided in the overlapping portions, the non-adhesive portions 222, 322 are provided intermittently, which improves the ease of extracting the optical fiber core 11 and the ease of disassembling the optical fiber unit 1.

[0051] In order for the plastic film 20 to adequately protect the optical fiber ribbon 10, it is desirable that the width of the non-adhesive portions 222, 322 in the longitudinal direction of the optical fiber unit 1 and the plastic film 20 be 10 mm or more and 50 mm or less.

[0052] (Optical fiber cable with optical fiber units) Fig. 8 is a cross-sectional view of an optical fiber cable 50. The optical fiber cable 50 is a loose tube type cable that includes a plurality of optical fiber units 1, a cable jacket 51 that covers the plurality of optical fiber units 1, a tension member 52, a water-absorbing tape 53, and a tear cord 54.

[0053] The tension member 52 is made of, for example, fiber reinforced plastic (FRP) or aramid fiber. The tension member 52 prevents excessive stress from being applied to the optical fiber core 11 inside the optical fiber cable 50. In the example of Fig. 8, one tension member 52 is disposed at the center of the optical fiber cable 50 in a cross-sectional view, but the positions and number of tension members 52 provided are not limited.

[0054] Six optical fiber units 1 are provided around the tension member 52. The water-absorbing tape 53 is arranged to cover the six optical fiber units 1. By providing the water-absorbing tape 53 on the optical fiber cable 50, the waterproofing of the optical fiber cable 50 is improved.

[0055] The cable jacket 51 is configured to cover the plurality of optical fiber units 1 and the water-absorbing tape 53. The cable jacket 51 is made of a hard material such as high-density polyethylene. The hard material is, for example, a resin material with a Young's modulus of 800 MPa or more and 1200 MPa or less.

[0056] The tear cord 54 is provided on the outside of the water-absorbing tape 53 so as to be embedded in the cable jacket 51. The cable jacket 51 can be torn by pulling the tear cord 54.

[0057] By providing the optical fiber unit 1 of the present disclosure in such an optical fiber cable 50, the optical fiber packaging density of the optical fiber cable 50 can be improved, and the yield of the optical fiber cable 50 can be improved.

[0058] Next, we will explain the results of evaluating the characteristics of the optical fiber unit 1 when changing the manufacturing conditions of the optical fiber unit 1. The characteristics of the optical fiber unit 1 were evaluated by verifying the transmission loss, the ease of extracting optical fiber, and the manufacturability.

[0059] The transmission loss is measured when the optical fiber mounting density is 3.8 fibers / mm ２ The following is an evaluation of the transmission loss characteristics of the optical fiber unit 1 in the case where the following conditions are met: Evaluation A indicates that the transmission loss is 0.25 dB / km or less; Evaluation B indicates that the transmission loss is greater than 0.25 dB / km and less than or equal to 0.3 dB / km; and Evaluation C indicates that the transmission loss is greater than 0.3 dB / km.

[0060] The optical fiber extraction property is an evaluation of whether the optical fiber 11 can be extracted from the optical fiber unit 1 by manually peeling off the overlapping portion 20A. Evaluation A indicates a case where the optical fiber 11 can be extracted from the optical fiber unit 1 by manually peeling off the overlapping portion 20A. Evaluation A+ indicates a case where the optical fiber 11 can be extracted particularly easily among those that satisfy evaluation A. Evaluation C indicates a case where the optical fiber 11 cannot be extracted from the optical fiber unit 1.

[0061] Manufacturability is an evaluation of whether or not the plastic film 20 can be fused when the optical fiber unit 1 is manufactured at a constant linear velocity. Evaluation A indicates that the plastic film 20 is reliably fused in the longitudinal direction of the optical fiber unit 1. Evaluation B indicates that the plastic film 20 is not fused in a portion of the longitudinal direction of the optical fiber unit 1. Evaluation C indicates that the plastic film 20 is not fused in the entire longitudinal direction of the optical fiber unit 1.

[0062] (Verification 1: Thickness of Plastic Film 20) The transmission loss, optical fiber extraction property, and manufacturability were verified by changing the thickness of the plastic film 20. The results of verification 1 are shown in Table 1.

[0063] Table 1

[0064] The optical fiber units of Samples 1, 2, and 3 were all good in terms of transmission loss, optical fiber extraction property, and manufacturability. However, for Sample 4, in which the plastic film had a thickness of 0.1 mm, the optical fiber unit could not be deformed sufficiently, and the evaluation of transmission loss was poor. This result shows that it is desirable for the plastic film thickness to be less than 0.1 mm.

[0065] (Verification 2: Melting Point of Adhesive Resin Layer 22) The transmission loss, optical fiber extraction property, and manufacturability were verified by changing the melting point of the adhesive resin layer 22. Table 1 shows the results of verification 2.

[0066] The optical fiber units of Samples 2 and 6 were all good in terms of transmission loss, optical fiber extraction, and manufacturability. However, Sample 5, which had a plastic film thickness of 0.015 mm, the same as Samples 2 and 6, and an adhesive resin layer melting point of 200°C, did not fuse together, resulting in a poor manufacturability evaluation. Furthermore, Sample 7, which had a plastic film thickness of 0.015 mm, the same as Samples 2, 5, and 6, and an adhesive resin layer melting point of 70°C, fused together, but began melting before the plastic film was wrapped around the optical fiber ribbon unit, resulting in a slightly poor manufacturability evaluation. Based on these results, it is more desirable for the adhesive resin layer to have a melting point of 70°C or higher and lower than 200°C.

[0067] (Verification 3: Wrap ratio) The wrap ratio was changed to verify the transmission loss, optical fiber extraction property, and manufacturability. The results of verification 3 are shown in Table 1.

[0068] The optical fiber units of Samples 2 and 9 were all good in terms of transmission loss, optical fiber extraction, and manufacturability. However, for Sample 8, which had a 50% wrap ratio, it was difficult to manually extract the optical fiber, resulting in a poor evaluation of optical fiber extraction. Furthermore, for Sample 8, peeling of the fused plastic films occurred in part of the longitudinal direction of the optical fiber unit, resulting in a slight deterioration in manufacturability. For Sample 10, which had a 5% wrap ratio, the plastic films were not sufficiently fused together, causing the optical fiber ribbon to protrude from the plastic film, resulting in a poor evaluation of manufacturability. Based on these results, it is desirable for the wrap ratio to be between 10% and 30%.

[0069] (Verification 4: Width of Non-Bonded Portions) In a plastic film in which bonded portions 221 and non-bonded portions 222 are alternately formed as shown in Figure 6, the width of the non-bonded portions 222 in the longitudinal direction of the optical fiber unit 1 was varied to verify the transmission loss, optical fiber extraction property, and manufacturability. The results of Verification 4 are shown in Table 2. Note that the thickness of the plastic film was 0.015 mm for all samples.

[0070] Table 2

[0071] The optical fiber unit of Sample 11 was good in terms of transmission loss, optical fiber extraction property, and manufacturability. Furthermore, the optical fiber units of Samples 12 and 13 had even better optical fiber extraction property, so the evaluation of optical fiber extraction property was improved. However, Sample 14, which had a non-bonded portion width of 100 mm, had optical fiber ribbons protruding from the non-bonded portion, so the evaluation of manufacturability was poor. From these results, it is desirable that the width of the non-bonded portion in the longitudinal direction of the optical fiber unit be 10 mm or more and 50 mm or less.

[0072] 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.

[0073] In the present embodiment, the optical fiber ribbon 10 is configured by the optical fiber core wires 11 provided inside the optical fiber unit 1. However, the optical fiber core wires 11 provided inside the optical fiber unit 1 may be simply bundled and covered with a plastic film and stored.

[0074] REFERENCE SIGNS LIST 1 Optical fiber unit 1A Optical fiber ribbon unit 10 Optical fiber ribbon 11 Optical fiber core 20 Plastic film 20A Overlapped portion 20B End portion 21 Base material 22 Adhesive resin layer 30 Water-absorbent fiber 50 Optical fiber cable 51 Cable jacket 52 Tension member 53 Water-absorbent tape 54 Tear string 110 Film-forming portion 120 Heat-sealed portion 130 Bobbin 221 Adhesive portion 222 Non-adhesive portion C Two-dimensional code

Claims

1. Multiple optical fibers or optical fiber ribbons, A plastic film having a thickness of less than 0.1 mm and covering the periphery of the plurality of optical fibers or the plurality of optical fiber ribbons, The plastic film comprises a base material and an adhesive resin layer provided on at least one side of the base material. The melting point of the adhesive resin layer is less than 200°C. The aforementioned plastic film is formed in an annular shape in cross-section by fusing a portion of the plastic film with the adhesive resin layer. Optical fiber unit.

2. The adhesive resin layer is formed of an adhesive polyolefin resin. The optical fiber unit according to claim 1.

3. The plastic film has overlapping portions where the plastic films overlap each other in a circumferential part that covers the periphery of the plurality of optical fibers or the plurality of optical fiber ribbons. The adhesive resin layer is formed only in the overlapping portion. The optical fiber unit according to claim 1.

4. The plastic film has overlapping portions where the plastic films overlap each other in a circumferential part that covers the periphery of the plurality of optical fibers or the plurality of optical fiber ribbons. The width of the overlapping portion is 10% to 30% of the width of the plastic film in the shorter direction. The optical fiber unit according to claim 1.

5. The plastic film has overlapping portions where the plastic films overlap each other in a circumferential part that covers the periphery of the plurality of optical fibers or the plurality of optical fiber ribbons. The adhesive resin layer is not provided at the short-side end of the plastic film that constitutes the overlapping portion. The optical fiber unit according to claim 1.

6. A cut is formed in a part of the longitudinal direction of the aforementioned plastic film. The optical fiber unit according to claim 1.

7. Having the plurality of optical fibers or the plurality of optical fiber ribbons along them, The plastic film is formed to cover the water-absorbing fibers while in contact with them. The optical fiber unit according to claim 1.

8. The resin constituting the surface of the plurality of optical fibers or the plurality of optical fiber ribbons contains a lubricant. The optical fiber unit according to claim 1.

9. The aforementioned plastic film is made of a material having a flame retardancy of a limiting oxygen index of 40 or higher. The optical fiber unit according to claim 1.

10. The optical fiber mounting density within the optical fiber unit is 10 cores / mm². ２ That's all. The optical fiber unit according to claim 1.

11. The plastic film has overlapping portions where the plastic films overlap each other in a circumferential part that covers the periphery of the plurality of optical fibers or the plurality of optical fiber ribbons. In the overlapping portion, along the longitudinal direction of the optical fiber unit, adhesive portions where the adhesive resin layer is formed and non-adhesive portions where the adhesive resin layer is not formed are alternately provided. The optical fiber unit according to claim 1.

12. The aforementioned plastic film is made of biodegradable plastic. The optical fiber unit according to claim 1.

13. The outer surface of the plastic film is coated with a water-absorbing polymer. The optical fiber unit according to claim 1.

14. The outer surface of the plastic film is provided with a two-dimensional code that allows access to the identification information of the optical fiber unit. The optical fiber unit according to claim 1.

15. The plastic film has overlapping portions where the plastic films overlap each other in a circumferential part that covers the periphery of the plurality of optical fibers or the plurality of optical fiber ribbons. The overlapping portion is formed in a spiral shape in the longitudinal direction of the optical fiber unit. The optical fiber unit according to claim 1.

16. The aforementioned plastic film is colored in two or more colors. The optical fiber unit according to claim 1.

17. A plurality of optical fiber units according to any one of claims 1 to 16, A cable sheath covering a plurality of optical fiber units, Fiber optic cable.