Optical fiber ribbon core wire

Abstract

An optical fiber ribbon core wire (1A) has a plurality of optical fiber core wires (11) arranged side by side in a direction orthogonal to a length direction, and a collective coating layer (20) that coats outer peripheries of the plurality of optical fiber core wires (11) respectively. The collective coating layer (20) includes a linking portion (21) that links adjacent optical fiber core wires (11) at at least a portion of the plurality of optical fiber core wires (11). The plurality of optical fiber core wires (11) each have an outer diameter of 215 μm or less. The collective coating layer (20) has a dynamic friction of 0.3 N or less.

Description

Technical Field

[0001] This invention relates to fiber ribbon cores.

[0002] This application claims priority based on Japanese Application No. 2020-175368, filed on October 19, 2020, and incorporates all the contents set forth in the aforementioned Japanese application. Background Technology

[0003] In recent years, the demand for high-density optical cables has increased. As examples of high-density applications, there are known examples of reducing the outer diameter of the optical fiber cores installed in the optical cable, and examples of using multiple optical fiber cores with different outer diameters. In addition, in order to improve the workability and identification during connection, there is a known optical fiber ribbon core cable (Patent Document 1) in which multiple optical fiber cores are arranged side by side and integrally wrapped.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2014-238480 Summary of the Invention

[0005] The fiber ribbon core of the present invention has:

[0006] Multiple fiber cores are arranged side-by-side in a direction orthogonal to their length direction; and

[0007] A cladding layer is used to cover the outer periphery of each of the plurality of optical fiber cores.

[0008] The cladding layer includes a connecting portion that connects adjacent fiber cores at least a portion of the plurality of fiber cores.

[0009] The outer diameters of the plurality of optical fiber cores are all below 215 μm.

[0010] The dynamic friction of the coating layer is less than 0.3N. Attached Figure Description

[0011] Figure 1 This is a cross-sectional view of the fiber ribbon core according to the first embodiment of the present invention.

[0012] Figure 2 yes Figure 1 The image shows a cross-sectional view of the fiber core of the fiber ribbon.

[0013] Figure 3 This is a schematic diagram illustrating the relationship between the spacing of the fiber ribbon cores and the V-groove of the fusion splicer in the first embodiment of the fusion splicing process.

[0014] Figure 4 This is a cross-sectional view of the fiber ribbon core involved in Variation Example 1.

[0015] Figure 5 This is a diagram showing a portion of the length direction of the fiber ribbon core involved in Variation Example 2.

[0016] Figure 6 yes Figure 5 The cross-sectional view of the fiber ribbon core shown.

[0017] Figure 7 This is a cross-sectional view of the fiber ribbon core involved in Variation Example 3.

[0018] Figure 8 yes Figure 7 The image shows a cross-sectional view of the fiber core of the fiber ribbon.

[0019] Figure 9 This is a cross-sectional view of the ribbon core of the optical fiber used in the evaluation experiment.

[0020] Figure 10 This is a schematic diagram of the kinetic friction measurement experiment used in the evaluation experiment.

[0021] Figure 11 This is a cross-sectional view of the ribbon core of the optical fiber used in the evaluation experiment. Detailed Implementation

[0022] (The problem to be solved by this invention)

[0023] When fiber ribbon cores are densely installed in an optical cable, the fiber cores are prone to contact with each other, sometimes resulting in friction between them. This friction, as described above, occurs unevenly along the length of the cable, which can cause the cable to bend serpentinely. Furthermore, there is a tendency for the cable's transmission characteristics to degrade at low temperatures. In particular, when the outer diameters of multiple fiber cores differ, the cable is more prone to serpentine bending, and its transmission characteristics are more easily degraded.

[0024] The present invention provides an optical fiber ribbon core wire, which can install the optical fiber core wire in the optical cable at a high density and is not prone to causing the cable to bend in a serpentine manner.

[0025] (Description of one aspect of the present invention)

[0026] First, embodiments of the present invention will be described.

[0027] (1) One embodiment of the present invention relates to an optical fiber ribbon core having:

[0028] Multiple fiber cores are arranged side-by-side in a direction orthogonal to their length direction; and

[0029] A cladding layer is used to cover the outer periphery of each of the plurality of optical fiber cores.

[0030] The cladding layer includes a connecting portion that connects adjacent fiber cores at least a portion of the plurality of fiber cores.

[0031] The outer diameters of the plurality of optical fiber cores are all below 215 μm.

[0032] The dynamic friction of the coating layer is less than 0.3N.

[0033] According to the present invention, the dynamic friction force of the cladding layer of the fiber ribbon core is less than 0.3 N, thus reducing the friction generated between adjacent fiber ribbon cores. Therefore, even when fiber ribbon cores are densely installed in the cable, serpentine bending of the cable can be suppressed. This, in turn, ensures the transmission characteristics of the cable at low temperatures.

[0034] The outer diameter of each fiber core in the fiber ribbon core of the present invention is less than 215 μm, thus enabling high-density installation in cables.

[0035] (2) The surface hardness of the coating layer can be above 1.2 GPa and below 3 GPa.

[0036] According to the present invention, the surface hardness of the cladding layer is 1.2 GPa or more and 3 GPa or less, thus reducing serpentine bending that occurs between adjacent fiber ribbon cores. Therefore, even when fiber ribbon cores are densely installed in the cable, serpentine bending of the cable can be suppressed. This, in turn, ensures the transmission characteristics of the cable at low temperatures.

[0037] (3) The distance between the centers of adjacent optical fiber cores can be more than 220 μm and less than 280 μm.

[0038] According to the present invention, the distance between the centers of adjacent optical fiber cores is 220 μm or more and 280 μm or less, thus allowing the use of conventional connection equipment. Even when the diameter of each optical fiber core is reduced, there is no need to prepare connection equipment specifically for smaller diameters, thus providing a versatile optical fiber ribbon core.

[0039] (4) The cladding layer may include a non-connecting portion that does not connect adjacent optical fiber cores in at least a portion of the plurality of optical fiber cores.

[0040] The connecting portions can be formed intermittently along the length direction. According to the invention, since the non-connecting portions are intermittently arranged along the length direction, the fiber ribbon core is easily deformed in a cross-section perpendicular to the length direction. Therefore, it is possible to install fiber ribbons in optical cables with high density.

[0041] (5) When viewed in cross-section, the cladding layer may have a thick-walled portion and at least two thin-walled portions, wherein the thickness of the cladding layer at the thin-walled portion is thinner than the thickness of the cladding layer at the thick-walled portion.

[0042] The difference between the thickness of the coating layer at the thick-walled portion and the thickness of the coating layer at the thin-walled portion can be more than 5 μm and less than 19 μm.

[0043] The cladding layer of the fiber ribbon core of the present invention has a thick-walled portion and at least two thin-walled portions, and the thickness of the cladding layer is non-uniform. In particular, the difference between the thickness of the cladding layer at the thick-walled portion and the thickness of the cladding layer at the thin-walled portion is relatively large, which is 5 μm or more and 19 μm or less, thus reducing the contact area between the fiber ribbon cores. Therefore, adjacent fiber ribbon cores are less likely to rub against each other, and even when the fiber ribbon cores are installed in a high density in a cable, serpentine bending of the cable can be further suppressed.

[0044] (6) The plurality of optical fiber cores may have: a first optical fiber core having a first outer diameter; and a second optical fiber core having a second outer diameter.

[0045] According to the present invention, a plurality of optical fiber cores have: a first optical fiber core having a first outer diameter; and a second optical fiber core having a second outer diameter, thereby enabling the suppression of cable serpentine bending and the high-density installation of optical fiber cores in the optical cable.

[0046] (Effects of the invention)

[0047] According to the present invention, an optical fiber ribbon core wire can be provided, which can install the optical fiber core wire in the optical cable at a high density and is not prone to causing the cable to bend in a serpentine manner.

[0048] (Details of the first embodiment of the present invention)

[0049] A specific example of the optical fiber ribbon core according to the first embodiment of the present invention will be described with reference to the accompanying drawings.

[0050] Furthermore, the invention is not limited to these examples, but is shown in the claims and is intended to include all modifications equivalent to and within the scope of the claims.

[0051] Figure 1 This is a cross-sectional view of the fiber ribbon core 1A according to one aspect of the present invention, perpendicular to its length direction. Figure 1As shown, the fiber ribbon core 1A has multiple fiber cores 11 and a cladding layer 20 covering the multiple fiber cores 11. In this example, 12 fiber cores 11A to 11L are arranged side by side in a direction orthogonal to the length direction of the fiber ribbon core 1A. The multiple fiber cores 11 are arranged with a certain interval between each core. The outer periphery of each of the multiple fiber cores 11 is covered by the cladding layer 20, and the whole is connected by the cladding layer 20.

[0052] 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, for example, has: 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 comprise pure quartz glass, quartz glass with added germanium, or quartz glass with added fluorine. The primary resin layer 13 may comprise a soft material with a relatively low Young's modulus as a buffer layer. The secondary resin layer 14 may comprise a hard material with a relatively high Young's modulus as a protective layer.

[0053] The Young's modulus of the primary resin layer 13 is preferably 0.04 MPa or higher and 0.8 MPa or lower at 23°C, more preferably 0.05 MPa or higher and 0.7 MPa or lower, and even more preferably 0.05 MPa or higher and 0.6 MPa or lower. Since the Young's modulus of the primary resin layer 13 is 0.04 MPa or higher and 0.8 MPa or lower, voids (gaps) are less likely to form in the optical fiber core. The Young's modulus of the secondary resin layer 14 is preferably 900 MPa or higher at 23°C, more preferably 1000 MPa or higher, and even more preferably 1200 MPa or higher. The Young's modulus of the secondary resin layer 14 at 23°C can be 3000 MPa or lower, 2500 MPa or lower, 2000 MPa or lower, or 1800 MPa or lower. Since the Young's modulus of the secondary resin layer 14 is 900 MPa or higher, it is easier to improve the withstand voltage characteristics. If the Young's modulus of the secondary resin layer 14 is below 3000 MPa, it is easy to remove the coating due to its appropriate elongation at break.

[0054] The cladding layer 20 includes a connecting portion 21 that connects adjacent fiber cores 11 at least a portion thereof. In this example, the connecting portion 21 is disposed between all adjacent fiber cores. The connecting portion 21 is configured such that the distance P between the centers of adjacent fiber cores is 220 μm or more and 280 μm or less.

[0055] The cladding layer 20 may, for example, contain a UV-curable resin. The dynamic friction of the cladding layer 20 is 0.3 N or less. Furthermore, the surface hardness of the cladding layer 20 is 1.2 GPa or more and 3 GPa or less. From the viewpoint of the lateral pressure resistance and flexibility of the fiber ribbon core, the Young's modulus of the cladding layer 20 is preferably 50 MPa or more and 900 MPa or less at 23°C, more preferably 100 MPa or more and 800 MPa or less.

[0056] Figure 2 yes Figure 1 The diagram shows a cross-sectional view of one of the multiple fiber cores 11 in the fiber ribbon core 1A shown, namely fiber core 11B. The structures of the other fiber cores 11A, 11C to 11L are similar. Figure 2 The structure of the fiber core 11B shown is the same, so repeated descriptions are omitted.

[0057] like Figure 2 As shown, when viewed in cross-section of the optical fiber core 11B, the cladding layer 20 completely covers the outer periphery of the optical fiber core 11B, therefore there is no portion of the optical fiber core 11B exposed from the cladding layer 20. In other words, the thickness of the cladding layer 20 is uniform around the outer periphery of the optical fiber core 11B. The thickness of the cladding layer 20 is, for example, 20 μm or less. Furthermore, in this example, the thickness of the cladding layer between the optical fiber core 11B and optical fiber cores 11A or 11C refers to the thickness excluding the connection portion 21.

[0058] Next, the splicing of fiber ribbon core 1A will be explained. Generally, when connecting fiber ribbon cores to other fiber ribbon cores, a multi-core fusion splicer (illustration omitted) is used, which allows multiple fiber cores to be spliced ​​together at the same time. Figure 3 This is a schematic diagram showing the relationship between the spacing of the fiber ribbon cores 1A (the distance P between the centers of adjacent fiber cores) and the V-groove base 30 of the fusion splicer. (Example) Figure 3 As shown, the fusion splicer has a V-groove base 30 with multiple V-grooves 31 for arranging multiple fiber cores 11. In this example, 12 fiber cores 11A to 11L are arranged one by one in the 12 V-grooves 31A to 31L. Furthermore, the spacing P0 of the V-grooves 31A to 31L conforms to the international standard for the outer diameter of fiber cores, which is 250 μm.

[0059] During fusion splicing, fiber cores 11A to 11L, with the cladding layer 20 removed, are positioned above the V-groove base 30. For example, the center positions of the fiber cores 11A to 11L in the side-by-side direction of the V-groove 31A to 31L are aligned with the center positions of the fiber cores 11A to 11L in the side-by-side direction. In this state, the clamping cover (not shown) of the multi-core fusion splicer is closed, and the fiber cores 11A to 11L are pressed down from above through the clamping cover.

[0060] Assuming there are no connecting parts in the fiber ribbon cores and the distance between adjacent fiber cores is zero, the center-to-center distance is less than the spacing P0 of the V-grooves 31A to 31L. In this case, multiple fiber cores are configured to converge towards the center of the V-groove base 30, and are not configured to be opposite to the V-grooves 31A to 31L. Therefore, each fiber core may not necessarily be housed within the V-grooves 31A to 31L; for example, a fiber core may not be housed within the V-grooves 31A or 31L. This may also occur when the center-to-center distance P between adjacent fiber cores is less than 220 μm.

[0061] On the other hand, in the fiber ribbon core 1A of this example, the connecting portion 21 is configured such that the distance P between the centers of adjacent fiber cores is 220 μm or more and 280 μm or less. Therefore, each fiber core 11A to 11L is configured to face each V-groove 31A to 31L. Thus, if the fiber cores 11A to 11L are pressed down approximately vertically, one fiber core is accommodated in each of the V-grooves 31A to 31L.

[0062] also, Figure 3 The example shown is of optical fiber cores 11A to 11L housed in V-grooves 31A to 31L with the cladding layer 20 removed. However, for example, the primary resin layer 13 and the secondary resin layer 14 may also be removed from the cladding layer 20, leaving only the glass fiber 12 housed in the V-grooves 31A to 31L.

[0063] As described above, in this example, the dynamic friction of the cladding layer 20 for the fiber ribbon core 1A is less than 0.3N, thus reducing the friction between adjacent fiber ribbon cores. Even when multiple fiber ribbon cores 1A are densely installed in the optical cable, the friction between adjacent fiber ribbon cores 1A can be reduced, thereby suppressing cable serpentine bending and improving cable laying operations.

[0064] In this example of the fiber ribbon core 1A, the co-cladding layer 20 covers the outer periphery of each of the multiple fiber cores. Suppose that in any case, the outer periphery of the fiber core 11 is not completely covered by the co-cladding layer 20, and there is a portion exposed from the co-cladding layer 20. This exposed portion becomes the starting point for the co-cladding layer 20 to be peeled off from the fiber core 11. As a result, sometimes the fiber core 11 separates from the fiber ribbon core individually. However, in this example, the outer periphery of each of the multiple fiber cores is covered by the co-cladding layer 20, therefore, individual core separation does not occur.

[0065] In this example, the outer diameter of each fiber core 11 of the fiber ribbon core 1A is less than 215μm. Therefore, the cross-sectional area of ​​the fiber core 11 is small, which allows for high-density installation in the optical cable.

[0066] In this example, the surface hardness of the cladding layer 20 of the fiber ribbon core 1A is between 1.2 GPa and 3 GPa, thus reducing friction between adjacent fiber cores. Therefore, even when the fiber ribbon cores are installed in a high density in the cable, serpentine bending of the cable can be suppressed, improving cable laying operations. This, in turn, ensures the transmission characteristics of the cable at low temperatures.

[0067] In this example, the distance between the centers of adjacent fiber cores is greater than 220 μm and less than 280 μm, thus allowing the use of conventional multi-core fusion splicers and connection equipment. For example, even if each fiber core 11 is made thinner, there is no need to prepare a dedicated multi-core fusion splicer for forming V-grooves with narrow spacing. Therefore, the fiber ribbon core 1A has high versatility and can reduce manufacturing costs.

[0068] (Variation Example 1)

[0069] In the first embodiment, the outer diameters of the fiber ribbon cores 1A and 11 are exactly the same, but the outer diameters of the fiber cores 11 can also be different. Figure 4 This is a cross-sectional view of the fiber ribbon core 1B involved in Modified Example 1, perpendicular to its length direction. Figure 4 In the explanation, regarding and Figure 1 For examples of structures that are substantially the same or whose corresponding elements are labeled with the same reference number, duplicate descriptions are omitted.

[0070] like Figure 4As shown, the fiber ribbon core 1B comprises multiple fiber cores 11, each having: a first fiber core with an outer diameter D1 (an example of a first outer diameter); and a second fiber core with an outer diameter D2 (an example of a second outer diameter). In this example, the outer diameter D1 of the first fiber cores 11A', 11C', 11E', 11G', 11I', and 11K' differs from the outer diameter D2 of the second fiber cores 11B, 11D, 11F, 11H, 11J, and 11L, and the first fiber cores with outer diameter D1 and the second fiber cores with outer diameter D2 are alternately arranged. Both the outer diameter D1 of the first fiber core and the outer diameter D2 of the second fiber core are 215 μm or less. In this example, the outer diameter D1 is 200 μm, and D2 is 180 μm. Each of the first optical fiber cores 11A', 11C', 11E', 11G', 11I', and 11K' has a glass fiber 12, a primary resin layer 13, and a secondary resin layer 14. Furthermore, even if the outer diameters D1 and D2 are different, the connecting portion 21 of the cladding layer 20 is configured such that the distance P between the centers of adjacent optical fiber cores is 220 μm or more and 280 μm or less.

[0071] In the case where the fiber ribbon core 1B according to this Modification Example 1 is installed in an optical cable, second fiber cores 11B, 11D, 11F, 11H, 11J, and 11L with smaller outer diameters D2 are arranged between the first fiber cores 11A', 11C', 11E', 11G', 11I', and 11K' with larger outer diameters D1. Therefore, compared with the case where they have the same outer diameter, the installation density of the fiber cores 11 relative to the optical cable is higher when the multiple fiber cores 11 have different outer diameters D1 and D2.

[0072] As described above, the fiber ribbon core 1B involved in this modified example 1 has a plurality of fiber cores 11, which include a first fiber core with an outer diameter D1 and a second fiber core with an outer diameter D2, thus enabling the fiber cores 11 to be installed in the optical cable at a higher density.

[0073] (Variation Example 2)

[0074] The connecting portion 21 of the fiber ribbon core 1A according to the first embodiment connects all adjacent fiber cores, but the configuration of the connecting portion is not limited to this. Figure 5 This is a diagram showing a portion of the length direction of the fiber ribbon core 1C involved in Modified Example 2. Figure 6 This is a cross-sectional view of fiber ribbon core 1C. Figure 6 In the explanation, regarding and Figure 1 For examples of structures that are substantially the same or whose corresponding elements are labeled with the same reference number, duplicate descriptions are omitted.

[0075] like Figure 5 and Figure 6 As shown, the cladding layer 20C of the fiber ribbon core 1C includes a non-connecting portion 24, which does not connect adjacent fiber cores in at least a portion of the plurality of fiber cores 11. In other words, Figure 5 and Figure 6 An optical fiber ribbon core 1C with a non-connection portion 24 is shown. In this modified example 2, the non-connection portion 24 is formed between optical fiber cores 11A and 11B, 11C and 11D, 11D and 11E, 11F and 11G, 11G and 11H, 11I and 11J, and 11J and 11K. Figure 6 The arrangement of the non-connecting portion 24 shown is an example and is not limited thereto. The non-connecting portion 24 is intermittently formed along the length of the fiber ribbon core 1C. Even when the non-connecting portion 24 is formed, the fiber cores 11A to 11L are arranged such that the distance P between the centers of adjacent fiber cores is 220 μm or more and 280 μm or less.

[0076] As described above, according to the fiber ribbon core 1C of this modified example 2, the non-connecting portion 24 is intermittently formed in the length direction of the fiber ribbon core 1C, thus improving the deformability of the fiber ribbon core 1C in a cross-section perpendicular to the length direction. The fiber ribbon core 1C is easily deformable, therefore multiple fiber ribbon cores 1C can be installed in an optical cable with high density.

[0077] Furthermore, in this modified example 2, the outer diameters of the fiber cores 11 of the fiber ribbon core 1C are all the same, but the fiber cores 11 of the fiber ribbon core 1C can also have different outer diameters D1 and D2, as shown in modified example 1.

[0078] (Variation Example 3)

[0079] In the first embodiment, the thickness of the cladding layer 20 of the fiber ribbon core 1A is uniform around the outer periphery of each fiber core 11, but the thickness of the cladding layer 20 may also be non-uniform. Figure 7 This is a cross-sectional view of the fiber ribbon core 1D involved in Variation Example 3, perpendicular to the length direction. Figure 8 yes Figure 7 The diagram shows a cross-sectional view of one of the multiple fiber cores 11 of the fiber ribbon core 1D. Figure 7 and Figure 8 In the explanation, regarding and Figure 1 and Figure 2 For examples of structures that are substantially the same or whose corresponding elements are labeled with the same reference number, duplicate descriptions are omitted.

[0080] like Figure 7 and Figure 8As shown, when viewed in cross-section of the optical fiber core 11B, the cladding layer 20D has a thick-walled portion 22 and at least two thin-walled portions 23. In other words, in this modified example 3, the thickness of the cladding layer 20D is uneven around the outer periphery of the optical fiber core 11B. Here, the thickness of the cladding layer 20D around the outer periphery of the optical fiber core 11B is measured at a total of 5 locations, excluding the connecting portion 21. The periphery of the thickest portion of the cladding layer 20D among the 5 locations is designated as the thick-walled portion 22, and the periphery of the portion of the cladding layer 20D that is 5 μm or more thinner than the thick-walled portion 22 is designated as the thin-walled portion 23. Figure 8 The positions of the thick-walled portion 22 and the thin-walled portion 23 on the outer periphery of the optical fiber core 11B shown are an example and are not limited thereto. In addition, the cladding layer 20D completely covers the outer periphery of the optical fiber core 11B, so there is no part of the optical fiber core 11B exposed from the cladding layer 20D.

[0081] The thickness d2 of the cladding layer 20D of the thin-walled portion 23 is thinner than the thickness d1 of the cladding layer 20D of the thick-walled portion 22. Specifically, the difference between the thickness d1 of the cladding layer 20D of the thick-walled portion 22 and the thickness d2 of the cladding layer 20D of the thin-walled portion 23 is 5 μm or more and 19 μm or less. The thickness d1 of the cladding layer 20D of the thick-walled portion 22 is, for example, 20 μm or less. The thickness d2 of the cladding layer 20D of the thin-walled portion 23 is, for example, 1 μm or more and 15 μm or less. The thickness of the cladding layer between the optical fiber core 11B and the optical fiber core 11A or 11C refers to the thickness from the midpoint of the connecting portion 21 to the optical fiber core 11B.

[0082] As described above, in the fiber ribbon core 1D involved in this modified example 3, the cladding layer 20D has a thick-walled portion 22 and at least two thin-walled portions 23, resulting in uneven thickness of the cladding layer 20D. Specifically, the difference between the thickness d1 of the cladding layer 20D in the thick-walled portion 22 and the thickness d2 of the cladding layer 20D in the thin-walled portion 23 is relatively large, exceeding 5 μm and falling below 19 μm. Therefore, even when multiple fiber ribbon cores 1D are densely installed in the optical cable, the contact area between adjacent fiber ribbon cores 1D and between fiber ribbon cores themselves can be reduced. Consequently, friction is less likely to occur between adjacent fiber ribbon cores, suppressing cable serpentine bending and improving cable laying operations.

[0083] Furthermore, when the fiber ribbon core 1D is installed in the optical cable, the thick-walled portion 22 of each fiber core may be positioned opposite the thin-walled portion 23 of other fiber cores. Therefore, compared to the case where the cladding layer 20D has a uniform thickness, the installation density of the fiber core 11 relative to the optical cable is further increased when it has both thick-walled portions 22 and thin-walled portions 23.

[0084] (Evaluation Experiment 1)

[0085] The dynamic friction and surface hardness of the fiber ribbon core of the present invention were evaluated. Figure 9 This is a cross-sectional view of the fiber ribbon core 1X used in Evaluation Experiment 1, perpendicular to its length direction. Figure 9 In the explanation, regarding and Figure 4 For examples of structures that are substantially the same or whose corresponding elements are labeled with the same reference number, duplicate descriptions are omitted.

[0086] like Figure 9 As shown, the fiber ribbon core 1X used in this evaluation experiment 1 has four fiber cores 11A', 11B, 11C', and 11D. Each fiber core has glass fiber 12, a primary resin layer 13, and a secondary resin layer 14. The outer diameter D1 of fiber cores 11A' and 11C' is 200 μm. The outer diameter D2 of fiber cores 11B and 11C is 180 μm. In other words, fiber cores with an outer diameter D1 of 200 μm and fiber cores with an outer diameter D2 of 180 μm are alternately arranged in a direction orthogonal to the length direction of the fiber ribbon core 1X. The distance between the centers of adjacent fiber cores 11 is 255 μm.

[0087] In the manufacturing process of the fiber ribbon core 1X, an ultraviolet-curable resin is coated on the outer periphery of four fiber cores 11A' to 11D arranged side by side. Then, by irradiating with ultraviolet light, the ultraviolet-curable resin is cured to form a cladding layer 20. At this time, the outer periphery of each fiber core 11A' to 11D is covered by the cladding layer 20. Depending on the composition of the coated ultraviolet-curable resin, the dynamic friction and surface hardness of the cladding layer 20 vary. The ultraviolet-curable resin cures, forming a connection 21 between all adjacent fiber cores. In the fiber ribbon core 1X, the thickness of the cladding layer 20 is 5 to 20 μm.

[0088] In Evaluation Experiment 1, the composition of the UV-curable resin to be coated was adjusted to produce samples No. 1 to No. 5 of the fiber ribbon core 1X, exhibiting various dynamic friction forces or surface hardnesses. Additionally, samples No. 6 to No. 7 were produced as comparative examples. In this Evaluation Experiment 1, the dynamic friction force, surface hardness, and low-temperature characteristics of the fiber ribbon core 1X were evaluated.

[0089] Figure 10 This is a schematic diagram of the experiment used to measure kinetic friction in Experiment 1. (Example) Figure 10As shown, firstly, the fiber ribbon core 1X1 of the object to be measured is wound around the outer circumference of a mandrel 41 with an outer diameter of 10 mm. Then, another fiber ribbon core 1X2 of the object to be measured is positioned to connect to the fiber ribbon core 1X1 wound around the mandrel 41 from above via a roller 42. At one end of the fiber ribbon core 1X2 (at... Figure 10 A stretching machine 43 is configured at the top center of the fiber ribbon core 1X2. Figure 10 Hammer 44 is positioned at the bottom center. The fiber ribbon core 1X2 from roller 42 to mandrel 41 is bent by 90 degrees relative to the fiber ribbon core 1X2 from stretching machine 43 to roller 42. The fiber ribbon core 1X2 from mandrel 41 to hammer 44 is bent by 90 degrees relative to the fiber ribbon core 1X2 from roller 42 to mandrel 41. A detector installed inside stretching machine 43 measures the tension of the fiber ribbon core 1X2, which is set as dynamic friction. The measurement temperature is 23°C. Furthermore, the dynamic friction coefficient μ can be determined using the method described in Japanese Patent Application Laid-Open No. 6-265737.

[0090] In this evaluation experiment 1, the weight of hammer 44 is 10g. Under this condition, the stretching machine 43 stretches the fiber ribbon core 1X2 at a speed of 500mm / min in a constant direction (at... Figure 10 (For upward stretching) The detector installed inside the stretching machine 43 measures the tension and serves as the dynamic friction force of the fiber ribbon core 1X2.

[0091] In addition, in the measurement of the fiber ribbon core 1X, the composite elastic modulus in the depth direction was determined using a BRUKER HYSITRON TI950 Tribolndenter based on the test method of ISO 14577. In this evaluation experiment 1, the composite elastic modulus refers to the surface hardness. The indentation depth was set to 100 nm, and the measurement was performed using a Burkevich indenter. Furthermore, the low-temperature characteristics of the fiber ribbon core 1X were evaluated in this evaluation experiment 1. Here, regarding the low-temperature characteristics, the attenuation per unit distance of the fiber core 11A' with a wavelength of 1.55 μm incident on the cable was measured at 23°C and -30°C, and the difference between the measured values ​​at the two temperature environments was used for evaluation. The evaluation results are shown in Table 1.

[0092] [Table 1]

[0093] Table 1

[0094]

[0095] As shown in Table 1, it was confirmed that samples No. 1 to No. 5 all exhibited low-temperature characteristics below 0.3 dB / km, indicating low cable loss. On the other hand, samples No. 6 and No. 7 both exceeded 0.3 dB / km in terms of low-temperature characteristics. In particular, although the surface hardness of samples No. 1 and No. 6 was 1.2 GPa, sample No. 1 showed superior low-temperature characteristics compared to sample No. 6. Based on the above, it was confirmed that a fiber ribbon core 1X with low cable loss characteristics can be achieved when the dynamic friction force is below 0.3 N. Furthermore, the excellent low-temperature characteristics of samples No. 1 to No. 5 demonstrate that a fiber ribbon core 1X with low cable loss characteristics can be achieved when the surface hardness is above 1.2 GPa and below 3 GPa.

[0096] (Evaluation Experiment 2)

[0097] The low-temperature characteristics of the fiber ribbon core of the present invention and the presence or absence of single-core separation were evaluated. Figure 11 This is a cross-sectional view perpendicular to the length direction of the fiber ribbon core 1Y used in Evaluation Experiment 2. Figure 11 In the explanation, regarding and Figure 9 For examples of structures that are substantially the same or whose corresponding elements are labeled with the same reference number, duplicate descriptions are omitted.

[0098] like Figure 11 As shown, the fiber ribbon core 1Y used in this evaluation experiment 2 has a non-connecting portion 24. In the manufacturing process of the fiber ribbon core 1Y, ultraviolet-curing resin is applied to the outer periphery of four fiber cores 11A' to 11D arranged side by side. Then, by irradiating with ultraviolet light, the ultraviolet-curing resin is cured to form a cladding layer 20D. At this time, the outer periphery of each fiber core 11A' to 11D is covered by the cladding layer 20D. The thickness of the applied ultraviolet-curing resin is adjusted by the mold shape, etc., thereby forming a thick-walled portion 22 and a thin-walled portion 23. In addition, after the ultraviolet-curing resin cures and forms a connecting portion 21 between all adjacent fiber cores, a cutting blade such as a cleaver is intermittently inserted in the length direction of the fiber ribbon core 1Y between adjacent fiber cores 11A' and 11B, and between adjacent fiber cores 11C' and 11D, to form a non-connecting portion 24. A connection 21 is retained between the fiber cores 11B and 11C' without the insertion of the cutting blade.

[0099] In Evaluation Experiment 2, the thickness of the UV-curable resin to be coated was adjusted, and samples No. 1 to No. 3 of fiber ribbon cores 1Y with various thicknesses of the cladding layer 20D were fabricated. Additionally, sample No. 4 was fabricated as a comparative example. In this Evaluation Experiment 2, fiber core 11A' was selected as an arbitrary fiber core for each sample, and the thickness of the cladding layer 20D at eight arbitrary measurement positions I to VIII of the fiber core 11A' was measured. Furthermore, the fiber ribbon core 1Y was installed in an optical cable, and the cable loss characteristics were evaluated based on the low-temperature characteristics of the fiber ribbon core 1Y. The evaluation method for cable loss characteristics was the same as that in Evaluation Experiment 1. Furthermore, the fiber ribbon core 1Y was removed from the optical cable, and the presence or absence of single-core separation was investigated. These evaluation results are shown in Table 2.

[0100] [Table 2]

[0101] Table 2

[0102] As shown in Table 2, no single-core separation of the fiber ribbon core 1Y was confirmed in samples No. 1 to No. 3. However, single-core separation of the fiber ribbon core 1Y was confirmed in sample No. 4, which served as a comparative example. Sample No. 4 had two locations at measurement positions II and IV where the thickness of the cladding layer 20D was zero. These measurement positions II and IV were the portions where the fiber core 11A', not covered by the cladding layer 20D, was exposed. It was confirmed that starting from these exposed portions, the cladding layer 20D was peeled off from the fiber core 11A', resulting in the separation of the fiber core 11A' from the fiber ribbon core 1Y. Therefore, it was confirmed that when the outer periphery of each of the multiple fiber cores 11 is covered by the cladding layer 20D, no single-core separation occurred.

[0103] In sample No. 2, measurement positions I, III, and V to VIII correspond to the thick-walled portion 22, and the thickness of the integrated coating layer 20D at each measurement position is 20 μm. In sample No. 4, measurement positions II and IV correspond to the thin-walled portion 23, and the thickness of the integrated coating layer 20D at each measurement position is 1 μm. The cable loss up to sample No. 2 was confirmed to be 0.27 dB / km. Furthermore, in sample No. 3, measurement positions I, III, V, VII, and VIII correspond to the thick-walled portion 22, and the thickness of the integrated coating layer 20D at each measurement position is 20 μm. In sample No. 3, measurement positions II, IV, and VI correspond to the thin-walled portion 23, and the thickness of the integrated coating layer 20D at each measurement position is 1 μm. The cable loss up to sample No. 3 was confirmed to be 0.25 dB / km. Based on the above, it has been confirmed that when the difference between the thickness of the cladding layer 20D of the thick-walled portion 22 and the thickness of the cladding layer 20D of the thin-walled portion 23 is less than 19 μm, it is possible to achieve a fiber ribbon core 1Y with low cable loss.

[0104] As shown in Table 2, the cable loss of sample No. 1 was confirmed to be 0.3 dB / km. In sample No. 1, measurement positions I, III, V to VIII correspond to the thick-walled portion 22, and measurement positions II and IV correspond to the thin-walled portion 23. In sample No. 1, the thickness of the cladding layer 20D of the thick-walled portion 22 is 20 μm, and the thickness of the cladding layer 20D of the thin-walled portion 23 is 15 μm. Based on the above, it was confirmed that when the difference between the thickness of the cladding layer 20D of the thick-walled portion 22 and the thickness of the cladding layer 20D of the thin-walled portion 23 is 5 μm or more, a fiber ribbon core 1Y with low cable loss can be achieved.

[0105] Furthermore, as shown in samples No. 1 to No. 3 in Table 2, it was confirmed that the thickness of the cladding layer 20D extending to the thin-walled portion 23 is thin, and the more thin-walled portions 23 there are, the better the low-temperature characteristics are. This is because the number of contact points between the fiber ribbon cores is reduced by forming the thin-walled portions 23.

[0106] The present invention has been described above in detail with reference to specific embodiments. However, it will be apparent to those skilled in the art that various changes or modifications can be made without departing from the spirit and scope of the present invention. Furthermore, the number, position, shape, etc., of the structural components described above are not limited to the above embodiments and can be modified to suit the implementation of the present invention.

[0107] Explanation of the label

[0108] 1A, 1B, 1C, 1X, 1X1, 1X2, 1Y: Fiber ribbon core

[0109] 11, 11A~11L: Fiber optic core wire

[0110] 12: Fiberglass

[0111] 13: Primary resin layer

[0112] 14: Secondary resin layer

[0113] 20, 20C, 20D: Co-coating layers

[0114] 21: Connecting Part

[0115] 22: Thick-walled section

[0116] 23: Thin-walled section

[0117] 24: Non-connecting parts

[0118] 30: V-groove base

[0119] 31, 31A~31L: V-groove

[0120] 41: Spindle

[0121] 42: Roller

[0122] 43: Stretching machine

[0123] 44: Hammer

[0124] D, D1, D2: Outer diameter of the optical fiber core

[0125] P: Distance between the centers of adjacent fiber optic cores

[0126] P0: V-groove spacing

[0127] d1: Thickness of the cladding layer covering the thick-walled portion

[0128] d2: Thickness of the coating layer covering the thin-walled portion

Claims

1. An optical fiber ribbon core, comprising: Multiple fiber cores are arranged side-by-side in a direction orthogonal to their length direction; and A cladding layer is used to cover the outer periphery of each of the plurality of optical fiber cores. The cladding layer includes a connecting portion that connects adjacent fiber cores at least a portion of the plurality of fiber cores. The outer diameters of the plurality of optical fiber cores are all below 215 μm. The dynamic friction of the coating layer is less than 0.3N. The surface hardness of the co-coating layer is above 1.2 GPa and below 3 GPa. The surface hardness is the composite elastic modulus in the depth direction, which is determined by the test method based on ISO 14577 with an indentation depth of 100 nm.

2. The fiber ribbon core according to claim 1, wherein, The distance between the centers of adjacent optical fiber cores is greater than 220 μm and less than 280 μm.

3. The fiber ribbon core according to claim 1 or 2, wherein, The cladding layer includes non-connecting portions that do not connect adjacent fiber cores in at least a portion of the plurality of fiber cores. The connecting portion is formed intermittently in the length direction.

4. The fiber ribbon core according to claim 1 or 2, wherein, When viewed in cross-section, the cladding layer has a thick-walled portion and at least two thin-walled portions, wherein the thickness of the cladding layer at the thin-walled portions is thinner than the thickness of the cladding layer at the thick-walled portions. The difference between the thickness of the coating layer at the thick-walled portion and the thickness of the coating layer at the thin-walled portion is 5 μm or more and 19 μm or less.

5. The fiber ribbon core according to claim 1 or 2, wherein, The plurality of optical fiber cores have: a first optical fiber core having a first outer diameter; and a second optical fiber core having a second outer diameter.

Images