Optical fiber ribbon

Abstract

An optical fiber ribbon (1A) is provided with a plurality of coated optical fibers (11) arranged in parallel in a direction orthogonal to the longitudinal direction thereof, and a collective covering layer (20) that covers the respective outer peripheries of the plurality of coated optical fibers (11). The collective covering layer (20) includes a coupling part (21) that couples adjacent coated optical fibers (11) in at least some of the plurality of coated optical fibers (11). The outer diameters of the plurality of coated optical fibers (11) are each 215 μm or less. The kinetic friction force of the collective covering layer (20) is 0.3 N or less.

Description

[Technical Field]

[0001] The present disclosure relates to an optical fiber ribbon. This application claims priority to Japanese Application No. 2020-175368, filed on October 19, 2020, and incorporates by reference all of the contents of said Japanese application. [Background technology]

[0002] In recent years, there has been an increasing demand for higher density optical fiber cables. Known examples of higher density include reducing the outer diameter of the optical fiber core wire mounted in the optical fiber cable and using multiple optical fiber core wires with different outer diameters. Also known is an optical fiber ribbon in which multiple optical fiber ribbons are arranged in parallel and integrally coated to improve workability and identification during splicing (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2014-238480 Summary of the Invention

[0004] The optical fiber ribbon of the present disclosure comprises: a plurality of optical fiber cores arranged in parallel in a direction perpendicular to the longitudinal direction; a collective coating layer that coats the outer periphery of each of the plurality of optical fiber cores, The collective coating layer includes a connecting portion that connects adjacent optical fibers in at least a portion of the plurality of optical fibers, The outer diameter of each of the plurality of optical fiber cores is 215 μm or less, The dynamic friction force of the blanket coating layer is 0.3 N or less. [Brief explanation of the drawings]

[0005] [Figure 1]FIG. 1 is a cross-sectional view of an optical fiber ribbon according to a first embodiment of the present disclosure. [Figure 2] FIG. 2 is a cross-sectional view of the optical fiber ribbon shown in FIG. [Figure 3] FIG. 3 is a schematic diagram showing the relationship between the pitch of the optical fiber ribbon according to the first embodiment and the V-groove of the fusion splicer in the fusion step. [Figure 4] FIG. 4 is a cross-sectional view of an optical fiber ribbon according to the first modification. [Figure 5] FIG. 5 is a view showing a part of the longitudinal direction of an optical fiber ribbon according to the second modification. [Figure 6] FIG. 6 is a cross-sectional view of the optical fiber ribbon shown in FIG. [Figure 7] FIG. 7 is a cross-sectional view of an optical fiber ribbon according to the third modification. [Figure 8] FIG. 8 is a cross-sectional view of the optical fiber of the optical fiber ribbon shown in FIG. [Figure 9] FIG. 9 is a cross-sectional view of the optical fiber ribbon used in the evaluation experiment. [Figure 10] FIG. 10 is a schematic diagram of the measurement experiment of the dynamic friction force used in the evaluation experiment. [Figure 11] FIG. 11 is a cross-sectional view of the optical fiber ribbon used in the evaluation experiment. DETAILED DESCRIPTION OF THE INVENTION

[0006] (Problem to be solved by this disclosure) When optical fiber ribbons are densely packed in an optical fiber cable, the optical fibers tend to come into contact with each other, which can cause friction between the optical fibers. If this friction occurs unevenly along the cable's length, the cable can easily become meandering. Furthermore, the cable's transmission characteristics tend to deteriorate at low temperatures. In particular, when the outer diameters of the optical fiber ribbons differ from one another, the cable is more likely to become meandering, and its transmission characteristics are more likely to deteriorate.

[0007] The present disclosure provides an optical fiber ribbon that allows optical fiber core wires to be densely packed in an optical fiber cable and is less likely to cause cable meandering.

[0008] (Description of one embodiment of the present disclosure) First, embodiments of the present disclosure will be listed and described. (1) An optical fiber ribbon according to one aspect of the present disclosure includes: a plurality of optical fiber cores arranged in parallel in a direction perpendicular to the longitudinal direction; a collective coating layer that coats the outer periphery of each of the plurality of optical fiber cores, The collective coating layer includes a connecting portion that connects adjacent optical fibers in at least a portion of the plurality of optical fibers, The outer diameter of each of the plurality of optical fiber cores is 215 μm or less, The dynamic friction force of the blanket coating layer is 0.3 N or less.

[0009] According to the present disclosure, the dynamic friction force of the bundled coating layer of the optical fiber ribbon is 0.3 N or less, thereby reducing the friction between adjacent optical fiber ribbons. Therefore, even when optical fiber ribbons are densely packed in a cable, cable meandering can be suppressed. Furthermore, the transmission characteristics of the cable can be ensured even at low temperatures. Since the outer diameter of each optical fiber in the optical fiber ribbon of the present disclosure is 215 μm or less, it can be packaged in a cable at high density.

[0010] (2) The surface hardness of the blanket coating layer may be 1.2 GPa or more and 3 GPa or less. According to the present disclosure, the surface hardness of the blanket coating layer is 1.2 GPa or more and 3 GPa or less, thereby reducing the meandering that occurs between adjacent optical fiber ribbons. Therefore, even when optical fiber ribbons are densely packed in a cable, cable meandering can be suppressed. Furthermore, the transmission characteristics of the cable can be ensured even at low temperatures.

[0011] (3) The distance between the centers of adjacent optical fibers may be 220 μm or more and 280 μm or less. According to the present disclosure, since the distance between the centers of adjacent optical fibers is 220 μm or more and 280 μm or less, a general-purpose splicing device can be used. Even if each optical fiber is thinned, there is no need to prepare a splicing device specifically for thin-diameter optical fibers, so a versatile optical fiber ribbon can be provided.

[0012] (4) The collective coating layer may include, in at least some of the plurality of coated optical fibers, non-connected portions where adjacent coated optical fibers are not connected to each other. The connecting portions may be formed intermittently in the longitudinal direction. According to the present disclosure, since the non-connecting portions are provided intermittently in the longitudinal direction, the optical fiber ribbon is easily deformed in a cross section perpendicular to the longitudinal direction. Therefore, the optical fiber ribbon can be packed at a high density in the optical fiber cable.

[0013] (5) In a cross-sectional view of the optical fiber core, the collectively coated layer may have a thick portion and at least two thin portions in which the thickness of the collectively coated layer is thinner than the thickness of the collectively coated layer in the thick portion. The difference between the thickness of the blanket coating layer in the thick portion and the thickness of the blanket coating layer in the thin portion may be 5 μm or more and 19 μm or less.

[0014] In the optical fiber ribbon of the present disclosure, the collectively coated layer has a thick portion and at least two thin portions, and the thickness of the collectively coated layer is non-uniform. In particular, the difference between the thickness of the collectively coated layer in the thick portion and the thickness of the collectively coated layer in the thin portion is relatively large, at 5 μm or more and 19 μm or less, so that the contact area between the optical fiber ribbons can be reduced. As a result, friction between adjacent optical fiber ribbons is less likely to occur, and cable meandering can be further suppressed even when the optical fiber ribbons are densely packed in a cable.

[0015] (6) The plurality of optical fibers may include a first optical fiber having a first outer diameter and a second optical fiber having a second outer diameter. According to the present disclosure, the multiple optical fiber ribbon core wires have a first optical fiber core wire having a first outer diameter and a second optical fiber core wire having a second outer diameter, thereby making it possible to pack the optical fiber core wires at a high density in the optical fiber cable while suppressing cable meandering. (Effects of the present disclosure)

[0016] According to the present disclosure, it is possible to provide an optical fiber ribbon that allows optical fiber core wires to be densely packed in an optical fiber cable and is less likely to cause cable meandering.

[0017] (Details of the first embodiment of the present disclosure) A specific example of an optical fiber ribbon according to the first embodiment of the present disclosure will be described with reference to the drawings. It should be noted that the present disclosure is not limited to these examples, but is defined by the scope of the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0018] Fig. 1 is a cross-sectional view perpendicular to the longitudinal direction of an optical fiber ribbon 1A according to one embodiment of the present disclosure. As shown in Fig. 1, the optical fiber ribbon 1A includes a plurality of optical fibers 11 and a collective coating layer 20 that coats the plurality of optical fibers 11. In this example, 12 optical fibers 11A to 11L are arranged in parallel in a direction perpendicular to the longitudinal direction of the optical fiber ribbon 1A. The plurality of optical fibers 11 are arranged with a fixed interval between each other. The outer periphery of each of the plurality of optical fibers 11 is covered with a collective coating layer 20, and the entirety is connected by the collective coating layer 20.

[0019] The outer diameter D of each of the multiple optical fiber cores 11 is 215 μm or less. In this example, the outer diameter D of each optical fiber core is 200 μm. Each optical fiber core 11 includes, for example, a glass fiber 12 having a core and a cladding, a primary resin layer 13 covering the outer periphery of the glass fiber 12, and a secondary resin layer 14 covering the outer periphery of the primary resin layer 13. The glass fiber 12 may contain pure silica glass, germanium-doped silica glass, or fluorine-doped silica glass. The primary resin layer 13 may contain a soft material with a relatively low Young's modulus as a buffer layer. The secondary resin layer 14 may contain a hard material with a relatively high Young's modulus as a protective layer.

[0020] The Young's modulus of the primary resin layer 13 is preferably 0.04 MPa or more and 0.8 MPa or less at 23°C, more preferably 0.05 MPa or more and 0.7 MPa or less, and even more preferably 0.05 MPa or more and 0.6 MPa or less. Because the Young's modulus of the primary resin layer 13 is 0.04 MPa or more and 0.8 MPa or less, voids (gaps) are less likely to occur in the optical fiber. The Young's modulus of the secondary resin layer 14 is preferably 900 MPa or more at 23°C, more preferably 1000 MPa or more, and even more preferably 1200 MPa or more. The Young's modulus of the secondary resin layer 14 may be 3000 MPa or less, 2500 MPa or less, 2000 MPa or less, or 1800 MPa or less at 23°C. Because the Young's modulus of the secondary resin layer 14 is 900 MPa or more, lateral pressure resistance is easily improved. When the Young's modulus of the secondary resin layer 14 is 3000 MPa or less, the layer has an appropriate breaking elongation, making coating removal easy.

[0021] The bundled coating layer 20 includes connecting portions 21 that connect adjacent optical fibers in at least some of the multiple optical fibers 11. In this example, the connecting portions 21 are arranged between all adjacent optical fibers. The connecting portions 21 are arranged so that the distance P between the centers of adjacent optical fibers is 220 μm or more and 280 μm or less.

[0022] The blanket coating layer 20 may contain, for example, an ultraviolet curable resin. The blanket coating layer 20 has a dynamic friction force of 0.3 N or less. The blanket coating layer 20 also has a surface hardness of 1.2 GPa or more and 3 GPa or less. From the viewpoint of the pressure measurement resistance and flexibility of the optical fiber ribbon, the Young's modulus of the blanket coating layer 20 is preferably 50 MPa or more and 900 MPa or less at 23°C, and more preferably 100 MPa or more and 800 MPa or less.

[0023] Fig. 2 is a cross-sectional view of one optical fiber 11B among the multiple optical fiber coated wires 11 included in the optical fiber ribbon 1A shown in Fig. 1. The configurations of the other optical fiber coated wires 11A, 11C to 11L are the same as the configuration of the optical fiber coated wire 11B shown in Fig. 2, so repeated explanations will be omitted.

[0024] 2, in a cross-sectional view of the optical fiber 11B, the blanket coating layer 20 covers the entire outer periphery of the optical fiber 11B, so that there is no portion of the optical fiber 11B exposed from the blanket coating layer 20. In other words, the thickness of the blanket coating layer 20 is uniform around the outer periphery of the optical fiber 11B. The thickness of the blanket coating layer 20 is, for example, 20 μm or less. In this example, the thickness of the blanket coating layer between the optical fiber 11B and the optical fiber 11A or 11C refers to the thickness excluding the connecting portion 21.

[0025] Next, fusion splicing of the optical fiber ribbon 1A will be described. Generally, when splicing an optical fiber ribbon to another optical fiber ribbon, a multi-fiber fusion splicer (not shown) can be used to fusion-splice multiple optical fibers at once. FIG. 3 is a schematic diagram showing the relationship between the pitch (the distance P between the centers of adjacent optical fibers) of the optical fiber ribbon 1A and the V-groove base 30 of the fusion splicer. As shown in FIG. 3, the fusion splicer includes a V-groove base 30 having multiple V-grooves 31 in which multiple optical fibers 11 are arranged. In this example, the 12 optical fibers 11A-11L are arranged in 12 V-grooves 31A-31L, one by one. The pitch P0 of the V-grooves 31A-31L is 250 μm, in accordance with the international standard for the outer diameter of optical fibers.

[0026] During fusion splicing, the optical fibers 11A-11L from which the collective coating layer 20 has been removed are placed above the V-groove base 30. The optical fibers 11A-11L are placed such that, for example, the center positions of the V-grooves 31A-31L in the parallel arrangement direction coincide with the center positions of the optical fibers 11A-11L in the parallel arrangement direction. In this state, a clamp lid (not shown) of the multi-fiber fusion splicer is closed, and the clamp lid presses down the optical fibers 11A-11L from above.

[0027] If the optical fiber ribbon has no joints and the distance between the centers of adjacent optical fibers is zero, the distance between the centers is smaller than the pitch P0 of the V-grooves 31A-31L. In this case, the optical fibers are arranged so that they converge toward the center of the V-groove base 30, and are not arranged so as to face the V-grooves 31A-31L. Therefore, it is not guaranteed that each of the optical fibers will be accommodated in the V-groove 31A-31L; for example, there may be cases where no optical fiber is accommodated in the V-groove 31A, 31L. This can occur even when the distance P between the centers of adjacent optical fibers is less than 220 μm.

[0028] On the other hand, in the optical fiber ribbon 1A of this example, the connecting portions 21 are arranged so that the distance P between the centers of adjacent optical fibers is 220 μm or more and 280 μm or less, and therefore the optical fibers 11A to 11L are arranged to face the V-grooves 31A to 31L, respectively. Therefore, when the optical fibers 11A to 11L are pushed down substantially vertically, they are accommodated one by one in the V-grooves 31A to 31L.

[0029] Although Figure 3 shows that the optical fiber cores 11A to 11L with the bulk coating layer 20 removed are accommodated in the V-grooves 31A to 31L, for example, the primary resin layer 13 and secondary resin layer 14 may also be removed in addition to the bulk coating layer 20, and only the glass fiber 12 may be accommodated in the V-grooves 31A to 31L.

[0030] As described above, in the optical fiber ribbon 1A according to this example, the dynamic friction force of the bundled coating layer 20 is 0.3 N or less, so that the friction between adjacent optical fiber ribbons can be reduced. Even when a plurality of optical fiber ribbons 1A are densely packed in an optical fiber cable, the friction between adjacent optical fiber ribbons 1A is reduced, so that cable meandering can be suppressed and cable installation work can be improved.

[0031] In the optical fiber ribbon 1A of this example, the outer periphery of each of the multiple optical fibers is coated with a collective coating layer 20. If the outer periphery of any optical fiber 11 is not completely covered with the collective coating layer 20 and there is an exposed portion from the collective coating layer 20, the exposed portion may act as a starting point for peeling off the collective coating layer 20 from the optical fiber 11, resulting in the optical fiber 11 being separated into individual fibers from the optical fiber ribbon. However, in this example, the outer periphery of each of the multiple optical fibers is covered with the collective coating layer 20, so there is no separation of the individual fibers.

[0032] Since the outer diameter of each optical fiber 11 of the optical fiber ribbon 1A of this example is 215 μm or less, the cross-sectional area of ​​the optical fiber 11 is small, allowing it to be densely packed into an optical fiber cable.

[0033] In the optical fiber ribbon 1A of this example, the surface hardness of the collective coating layer 20 is 1.2 GPa or more and 3 GPa or less, so that friction between adjacent optical fibers can be reduced. Therefore, even when the optical fiber ribbon is densely packed in a cable, cable meandering can be suppressed, improving cable installation work. Furthermore, the transmission characteristics of the cable can be ensured even at low temperatures.

[0034] In this example, the distance between the centers of adjacent optical fibers is 220 μm or more and 280 μm or less, so that the optical fiber ribbon 1A can be used with a general multi-fiber fusion splicer or connection device. Even if the diameter of each optical fiber 11 is reduced, there is no need to prepare a multi-fiber fusion splicer specifically for small diameters, such as those with narrow-pitch V-grooves. This makes the optical fiber ribbon 1A highly versatile and reduces manufacturing costs.

[0035] (Variation 1) In the optical fiber ribbon 1A according to the first embodiment, the optical fibers 11 all have the same outer diameter, but the optical fibers 11 do not have to have the same outer diameter. Fig. 4 is a cross-sectional view perpendicular to the longitudinal direction of the optical fiber ribbon 1B according to Modification 1. In the description of Fig. 4, elements that are substantially the same as or correspond to the configuration illustrated in Fig. 1 are given the same reference numerals, and repeated description will be omitted.

[0036] As shown in Figure 4, the optical fiber ribbon 1B includes a plurality of optical fiber cores 11, each of which has a first optical fiber core having an outer diameter D1 (an example of a first outer diameter) and a second optical fiber core having an outer diameter D2 (an example of a second outer diameter). In this example, the outer diameters D1 of the first optical fiber cores 11A', 11C', 11E', 11G', 11I', and 11K' are different from the outer diameters D2 of the second optical fiber cores 11B, 11D, 11F, 11H, 11J, and 11L, and the first optical fiber cores with the outer diameter D1 and the second optical fiber cores with the outer diameter D2 are alternately arranged. The outer diameters D1 of the first optical fiber cores and D2 of the second optical fiber cores are both 215 µm or less. In this example, the outer diameter D1 is 200 µm, and the outer diameter D2 is 180 µm. Each of the first optical fiber cores 11A', 11C', 11E', 11G', 11I', and 11K' includes a glass fiber 12, a primary resin layer 13, and a secondary resin layer 14. Even if the outer diameters D1 and D2 are different from each other, the connecting portions 21 of the collective coating layer 20 are arranged so that the distance P between the centers of adjacent optical fiber cores is 220 μm or more and 280 μm or less.

[0037] When the optical fiber ribbon 1B according to the first modification is mounted in an optical fiber cable, the second optical fiber 11B, 11D, 11F, 11H, 11J, and 11L having a small outer diameter D2 are arranged in the gaps between the first optical fiber 11A', 11C', 11E', 11G', 11I', and 11K' having a large outer diameter D1. Therefore, compared to when the optical fiber 11 have the same outer diameter, when the optical fiber 11 have different outer diameters D1 and D2, the mounting density of the optical fiber 11 in the optical fiber cable is higher.

[0038] In this way, the optical fiber ribbon core wire 1B of this variant example 1 comprises a plurality of optical fiber core wires 11 each having a first optical fiber core wire having an outer diameter D1 and a second optical fiber core wire having an outer diameter D2, and therefore the optical fiber core wires 11 can be packed more densely in the optical fiber cable.

[0039] (Variation 2) Although the connecting portions 21 of the optical fiber ribbon 1A according to the first embodiment connect all adjacent optical fibers, the arrangement of the connecting portions is not limited to this. Fig. 5 is a view showing a portion of the longitudinal direction of an optical fiber ribbon 1C according to a second modification. Fig. 6 is a cross-sectional view of the optical fiber ribbon 1C. In the description of Fig. 6, elements that are substantially the same as or correspond to the configuration illustrated in Fig. 1 are given the same reference numerals, and repeated description will be omitted.

[0040] As shown in Figures 5 and 6, the bundled coating layer 20C of the optical fiber ribbon 1C includes, in at least some of the optical fibers 11, non-coupling portions 24 where adjacent optical fiber ribbons are not coupled. In other words, Figures 5 and 6 show the optical fiber ribbon 1C having the non-coupling portions 24. In this second modification, the non-coupling portions 24 are formed between the optical fibers 11A and 11B, between 11C and 11D, between 11D and 11E, between 11F and 11G, between 11G and 11H, between 11I and 11J, and between 11J and 11K. The positions of the non-coupling portions 24 shown in Figure 6 are merely an example and are not limiting. The non-coupling portions 24 are formed intermittently in the longitudinal direction of the optical fiber ribbon 1C. Even if the non-connected portions 24 are formed, the optical fibers 11A to 11L are arranged so that the distance P between the centers of adjacent optical fibers is 220 μm or more and 280 μm or less.

[0041] As described above, in the optical fiber ribbon 1C according to the present modification 2, the non-connected portions 24 are formed intermittently in the longitudinal direction of the optical fiber ribbon 1C, which increases the deformability of the optical fiber ribbon 1C in a cross section perpendicular to the longitudinal direction. Because the optical fiber ribbon 1C is easily deformable, multiple optical fiber ribbons 1C can be densely packed in an optical fiber cable.

[0042] Although the outer diameters of the optical fiber core wires 11 of the optical fiber ribbon core wire 1C in this variant example 2 are all the same, the optical fiber core wires 11 of the optical fiber ribbon core wire 1C may have different outer diameters D1 and D2 as shown in variant example 1.

[0043] (Variation 3) In the optical fiber ribbon 1A according to the first embodiment, the thickness of the collective coating layer 20 is uniform around the outer periphery of each optical fiber 11, but the thickness of the collective coating layer 20 does not have to be uniform. Fig. 7 is a cross-sectional view perpendicular to the longitudinal direction of an optical fiber ribbon 1D according to a third modification. Fig. 8 is a cross-sectional view of one optical fiber 11B among the multiple optical fibers 11 included in the optical fiber ribbon 1D shown in Fig. 7. In the explanations of Figs. 7 and 8, elements that are substantially the same as or correspond to the configurations illustrated in Figs. 1 and 2 are designated by the same reference numerals, and repeated explanations will be omitted.

[0044] As shown in FIGS. 7 and 8 , in a cross-sectional view of the optical fiber 11B, the blanket coating layer 20D includes a thick portion 22 and at least two thin portions 23. In other words, in this third modification, the thickness of the blanket coating layer 20D is nonuniform around the outer periphery of the optical fiber 11B. Here, the thickness of the blanket coating layer 20D around the outer periphery of the optical fiber 11B is measured at a total of five locations, excluding the connecting portion 21. Of the five locations, the area around the thickest portion of the blanket coating layer 20D is designated as the thick portion 22, and the area around the area where the blanket coating layer 20D is thinner than the thick portion 22 by 5 μm or more is designated as the thin portion 23. The positions of the thick portion 22 and the thin portion 23 around the outer periphery of the optical fiber 11B shown in FIG. 8 are merely examples and are not limiting. Furthermore, because the blanket coating layer 20D completely covers the outer periphery of the optical fiber 11B, there are no locations where the optical fiber 11B is exposed from the blanket coating layer 20D.

[0045] The thickness d2 of the lumped coating layer 20D in the thin portion 23 is thinner than the thickness d1 of the lumped coating layer 20D in the thick portion 22. Specifically, the difference between the thickness d1 of the lumped coating layer 20D in the thick portion 22 and the thickness d2 of the lumped coating layer 20D in the thin portion 23 is 5 μm or more and 19 μm or less. The thickness d1 of the lumped coating layer 20D in the thick portion 22 is, for example, 20 μm or less. The thickness d2 of the lumped coating layer 20D in the thin portion 23 is, for example, 1 μm or more and 15 μm or less. The thickness of the lumped coating layer between the optical fiber 11B and the optical fiber 11A or 11C refers to the thickness from the midpoint of the connecting portion 21 to the optical fiber 11B.

[0046] As described above, in the optical fiber ribbon 1D according to the third modification, the blanket coating layer 20D includes the thick portion 22 and at least two thin portions 23, and the thickness of the blanket coating layer 20D is non-uniform. In particular, the difference between the thickness d1 of the blanket coating layer 20D at the thick portion 22 and the thickness d2 of the blanket coating layer 20D at the thin portion 23 is relatively large, at 5 μm or more and 19 μm or less. Therefore, even when multiple optical fiber ribbons 1D are densely packed in an optical fiber cable, the contact area between the optical fibers of adjacent optical fiber ribbons 1D and the contact area between the optical fiber ribbons can be reduced. Therefore, friction between adjacent optical fiber ribbons is less likely to occur, cable meandering can be suppressed, and cable installation work can be improved.

[0047] Furthermore, when the optical fiber ribbon 1D is mounted in an optical fiber cable, the thick-walled portion 22 of each optical fiber may be disposed in a position facing the thin-walled portion 23 of another optical fiber. Therefore, compared to when the collective coating layer 20D has a uniform thickness, the provision of the thick-walled portion 22 and the thin-walled portion 23 allows for a higher mounting density of the optical fibers 11 in the optical fiber cable.

[0048] (Evaluation experiment 1) The dynamic friction force and surface hardness of the optical fiber ribbon according to the present disclosure were evaluated. Fig. 9 is a cross-sectional view perpendicular to the longitudinal direction of the optical fiber ribbon 1X used in evaluation experiment 1. In the description of Fig. 9, elements that are substantially the same as or correspond to the configuration illustrated in Fig. 4 are given the same reference numerals, and repeated description will be omitted.

[0049] As shown in FIG. 9, the optical fiber ribbon 1X used in this evaluation experiment 1 has four optical fibers 11A', 11B, 11C', and 11D. Each optical fiber includes a glass fiber 12, a primary resin layer 13, and a secondary resin layer 14. The optical fibers 11A' and 11C' have an outer diameter D1 of 200 μm. The optical fibers 11B and 11C have an outer diameter D2 of 180 μm. In other words, optical fibers having an outer diameter D1 of 200 μm and optical fibers having an outer diameter D2 of 180 μm are alternately arranged along a direction perpendicular to the longitudinal direction of the optical fiber ribbon 1X. The distance between the centers of adjacent optical fibers 11 is 255 μm.

[0050] In the manufacturing process of the optical fiber ribbon 1X, an ultraviolet curable resin is applied to the outer periphery of four parallelly arranged optical fibers 11A' to 11D. The ultraviolet curable resin is then cured by irradiation with ultraviolet light to form a collective coating layer 20. At this time, the outer periphery of each of the optical fibers 11A' to 11D is covered with the collective coating layer 20. The dynamic friction force and surface hardness of the collective coating layer 20 vary depending on the components of the applied ultraviolet curable resin. The ultraviolet curable resin is cured to form connection portions 21 between all adjacent optical fibers. In the optical fiber ribbon 1X, the collective coating layer 20 has a thickness of 5 to 20 μm.

[0051] In evaluation experiment 1, samples No. 1 to No. 5 of the optical fiber ribbon 1X were created with various dynamic friction forces or surface hardness by adjusting the components of the applied ultraviolet curable resin. Samples No. 6 to No. 7 were also created as comparative examples. In this evaluation experiment 1, the dynamic friction force, surface hardness, and low-temperature characteristics of the optical fiber ribbon 1X were evaluated.

[0052] 10 is a schematic diagram of the experiment for measuring the dynamic friction force used in evaluation experiment 1. As shown in FIG. 10, first, an optical fiber ribbon 1X1 to be measured is wound around a mandrel 41 having an outer diameter of 10 mm. Another optical fiber ribbon 1X2 to be measured is placed from above the mandrel 41 via a roller 42 so as to be in contact with the optical fiber ribbon 1X1 wound around the mandrel 41. A tensioning machine 43 is placed at one end (above in FIG. 10) of the optical fiber ribbon 1X2, and a weight 44 is placed at the other end (below in FIG. 10) of the optical fiber ribbon 1X2. The optical fiber ribbon 1X2 extending from the roller 42 to the mandrel 41 is bent 90 degrees with respect to the optical fiber ribbon 1X2 extending from the tensioning machine 43 to the roller 42. The optical fiber ribbon 1X2 extending from the mandrel 41 to the weight 44 is bent at 90 degrees relative to the optical fiber ribbon 1X2 extending from the roller 42 to the mandrel 41. A detector provided inside the tensioning machine 43 measures the tension of the optical fiber ribbon 1X2, which is taken as the kinetic friction force. The measurement temperature is 23°C. The kinetic friction coefficient μ can be determined by the method described in Japanese Patent Application Laid-Open No. 6-265737. In this evaluation experiment 1, the weight of the weight 44 is 10 g. In this state, the tensioning machine 43 pulls the optical fiber ribbon 1X2 in a fixed direction (upward in FIG. 10) at a speed of 500 mm / min, and a detector provided inside the tensioning machine 43 measures the tension as a dynamic friction force of the optical fiber ribbon 1X2.

[0053] In addition, for the measurement of optical fiber ribbon 1X, BRUKER HYSITRON TI The composite modulus of elasticity in the depth direction was determined using a 950 Tribolndenter according to a test method based on ISO 14577. In this evaluation experiment 1, the composite modulus of elasticity refers to surface hardness. The indentation depth was 100 nm, and measurements were made using a Berkovich indenter. Furthermore, in this evaluation experiment 1, the low-temperature characteristics of the optical fiber ribbon 1X were evaluated. Here, the low-temperature characteristics were evaluated by measuring the attenuation per unit distance when light with a wavelength of 1.55 μm was incident on the optical fiber core 11A' inside the cable at temperatures of 23°C and -30°C, and then calculating the difference between the measured values ​​under the two temperature environments. The evaluation results are shown in Table 1.

[0054] [Table 1]

[0055] As shown in Table 1, the low-temperature properties of samples No. 1 to No. 5 were all 0.3 dB / km or less, confirming low cable loss. Meanwhile, the low-temperature properties of samples No. 6 and No. 7 both exceeded 0.3 dB / km. In particular, despite the surface hardness of both sample No. 1 and sample No. 6 being 1.2 MPa, sample No. 1 exhibited superior low-temperature properties compared to sample No. 6. From the above, it was confirmed that an optical fiber ribbon 1X with low cable loss characteristics can be achieved when the dynamic friction force is 0.3 N or less. Furthermore, since the low-temperature properties of samples No. 1 to No. 5 were all relatively good, it was confirmed that an optical fiber ribbon 1X with low cable loss characteristics can be achieved when the surface hardness is 1.2 GPa or more and 3 GPa or less.

[0056] (Evaluation experiment 2) The low-temperature characteristics and the presence or absence of separation of single fibers of the optical fiber ribbon according to the present disclosure were evaluated. Fig. 11 is a cross-sectional view perpendicular to the longitudinal direction of the optical fiber ribbon 1Y used in evaluation experiment 2. In the description of Fig. 11, elements that are substantially the same as or correspond to the configuration illustrated in Fig. 9 are given the same reference numerals, and repeated description will be omitted.

[0057] As shown in FIG. 11 , the optical fiber ribbon 1Y used in Evaluation Experiment 2 has a non-coupling portion 24. In the manufacturing process of the optical fiber ribbon 1Y, an ultraviolet curing resin is applied to the outer peripheries of four parallel-arranged optical fibers 11A′ to 11D. The ultraviolet curing resin is then cured by irradiation with ultraviolet light to form a collective coating layer 20D. At this time, the outer periphery of each of the optical fibers 11A′ to 11D is covered with the collective coating layer 20D. The thickness of the applied ultraviolet curing resin is adjusted by a die shape or the like to form thick portions 22 and thin portions 23. After the ultraviolet curing resin is cured to form coupling portions 21 between all adjacent optical fibers, a cutting blade such as a cutter is intermittently inserted between adjacent optical fibers 11A′ and 11B and between adjacent optical fibers 11C′ and 11D in the longitudinal direction of the optical fiber ribbon 1Y to form non-coupling portions 24. A connecting portion 21 remains between the optical fibers 11B and 11C' where the cutting blade is not inserted.

[0058] In evaluation experiment 2, samples No. 1 to No. 3 of the optical fiber ribbon 1Y were prepared, each having a different thickness of the blanket coating layer 20D, by adjusting the thickness of the applied ultraviolet curable resin. Sample No. 4 was also prepared as a comparative example. In this evaluation experiment 2, an optical fiber 11A' was selected as an arbitrary optical fiber for each sample, and the thickness of the blanket coating layer 20D was measured at eight arbitrary measurement positions I to VIII on the optical fiber 11A'. Furthermore, the optical fiber ribbon 1Y was mounted in an optical fiber cable, and the cable loss characteristics were evaluated as the low-temperature characteristics of the optical fiber ribbon 1Y. The evaluation method for the cable loss characteristics was the same as that used in Evaluation Experiment 1. The optical fiber ribbon 1Y was also removed from the optical fiber cable, and the presence or absence of separation of the optical fibers was checked. The evaluation results are shown in Table 2.

[0059] [Table 2]

[0060] As shown in Table 2, no fiber separation was observed in the optical fiber ribbon 1Y for Samples No. 1 to No. 3. On the other hand, fiber separation was observed in the optical fiber ribbon 1Y for Sample No. 4, which is a comparative example. Sample No. 4 has two locations where the thickness of the lumped coating layer 20D is zero, at measurement positions II and IV. These measurement positions II and IV are portions where the optical fiber 11A', not covered by the lumped coating layer 20D, is exposed from the lumped coating layer 20D. It was confirmed that the exposed portions were the starting points for peeling the lumped coating layer 20D from the optical fiber 11A', resulting in separation of the optical fiber 11A' from the optical fiber ribbon 1Y. From the above, it was confirmed that fiber separation does not occur when the outer periphery of each of the multiple optical fibers 11 is covered with the lumped coating layer 20D.

[0061] In sample No. 2, measurement positions I, III, V to VIII correspond to the thick portion 22. The thickness of the lumped coating layer 20D at the fixed position was 20 μm. In sample No. 4, measurement positions II and IV correspond to the thin-walled portion 23, and the thickness of each lumped coating layer 20D was 1 μm. The cable loss of sample No. 2 was confirmed to be 0.27 dB / km. In sample No. 3, measurement positions I, III, V, VII, and VIII correspond to the thick-walled portion 22, and the thickness of the lumped coating layer 20D at each measurement position was 20 μm. In sample No. 3, measurement positions II, IV, and VI correspond to the thin-walled portion 23, and the thickness of each lumped coating layer 20D was 1 μm. The cable loss of sample No. 3 was confirmed to be 0.25 dB / km. From the above, it was confirmed that when the difference between the thickness of the blanket coating layer 20D in the thick portion 22 and the thickness of the blanket coating layer 20D in the thin portion 23 is 19 μm or less, an optical fiber ribbon 1Y with low cable loss can be realized.

[0062] As shown in Table 2, it was confirmed that the cable loss of Sample No. 1 was 0.3 dB / km. In Sample No. 1, measurement positions I, III, V to VIII corresponded to the thick part 22. In this case, measurement positions II and IV correspond to the thin portion 23. In sample No. 1, the thickness of the blanket coating layer 20D in the thick portion 22 is 20 μm, and the thickness of the blanket coating layer 20D in the thin portion 23 is 15 μm. From the above, it was confirmed that an optical fiber ribbon 1Y with low cable loss can be realized when the difference between the thickness of the blanket coating layer 20D in the thick portion 22 and the thickness of the blanket coating layer 20D in the thin portion 23 is 5 μm or more.

[0063] Furthermore, as shown in Samples No. 1 to 3 in Table 2, it was confirmed that the lower the thickness of the collective coating layer 20D in the thin-walled portions 23 and the greater the number of thin-walled portions 23, the more improved the low-temperature characteristics. This is thought to be because the formation of the thin-walled portions 23 reduces the number of contact points between the optical fiber ribbons.

[0064] Although the present disclosure has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present disclosure. Furthermore, the number, position, shape, etc. of the components described above are not limited to the above embodiments, and can be changed to the number, position, shape, etc. that are suitable for implementing the present disclosure. [Explanation of symbols]

[0065] 1A, 1B, 1C, 1X, 1X1, 1X2, 1Y: Optical fiber ribbon 11, 11A to 11L: Optical fiber core 12: Glass fiber 13: Primary resin layer 14: Secondary resin layer 20, 20C, 20D: Bulk coating layer 21:Connection part 22: Thick wall part 23: Thin section 24: Unconnected part 30: V-groove base 31, 31A~31L: V groove 41: Mandrel 42: Laura 43: Tension machine 44: Weight D, D1, D2: Outer diameter of optical fiber core P: Distance between the centers of adjacent optical fibers P0: V-groove pitch d1: Thickness of the blanket coating layer in the thick-walled part d2: Thickness of the blanket coating layer in the thin-walled part

Claims

1. a plurality of optical fiber cores arranged in parallel in a direction perpendicular to the longitudinal direction; a collective coating layer that coats the outer periphery of each of the plurality of optical fiber cores, The collective coating layer includes a connecting portion that connects adjacent optical fibers in at least a portion of the plurality of optical fibers, The outer diameter of each of the plurality of optical fibers is 215 μm or less, The kinetic friction force of the collective coating layer is 0.3 N or less, The optical fiber ribbon has a surface hardness of the collective coating layer, the surface hardness being 1.2 GPa or more and 3 GPa or less as a composite elastic modulus in the depth direction obtained when the indentation depth is 100 nm using a test method based on ISO 14577.

2. 2. The optical fiber ribbon according to claim 1, wherein the distance between the centers of adjacent optical fibers is 220 [mu]m or more and 280 [mu]m or less.

3. The collective coating layer includes a non-connected portion in which adjacent optical fibers are not connected to each other in at least a part of the plurality of optical fibers, 3. The optical fiber ribbon according to claim 1, wherein the connecting portions are formed intermittently in the longitudinal direction.

4. In a cross-sectional view of the optical fiber core, the collective coating layer includes a thick portion and at least two thin portions, the thickness of which is thinner than the thickness of the collective coating layer in the thick portion; 4. The optical fiber ribbon according to claim 1, wherein a difference between a thickness of the lumped coating layer in the thick portion and a thickness of the lumped coating layer in the thin portion is 5 μm or more and 19 μm or less.

5. 5. The optical fiber ribbon according to claim 1, wherein the plurality of optical fiber core wires include a first optical fiber core wire having a first outer diameter and a second optical fiber core wire having a second outer diameter.

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