Optical fiber ribbon and method for manufacturing same

Abstract

An optical fiber ribbon (10) includes: a plurality of single-core coated optical fibers (20) arranged in parallel; and a ribbon layer (41) that covers the plurality of single-core coated optical fibers (20) and that partially connects adjacent single-core coated optical fibers (20) among the plurality of single-core coated optical fibers (20). The ribbon layer (41) contains a resin having a breaking elongation not less than 24%.

Description

Optical fiber ribbon core and method for manufacturing the same

[0001] The present invention relates to optical fiber ribbon cores and a method for manufacturing the same.

[0002] In recent years, data traffic has increased dramatically due to the spread of IoT (Internet of Things), the full-scale commercialization of 5G, and autonomous driving of automobiles, leading to a growing demand for the development and construction of high-speed, high-capacity fiber optic communication networks to support it. To economically realize the development and construction of high-speed, high-capacity fiber optic communication networks, it is important to accommodate many single-core coated optical fibers (optical fibers) within existing ducts. When laying wiring to accommodate many single-core coated optical fibers within existing ducts in this way, fiber optic ribbon (rollable ribbon), in which single-core coated optical fibers are intermittently connected, is often used to improve work efficiency. In such fiber optic ribbons, resin connecting parts that connect adjacent optical fibers and separating parts that keep them apart are arranged alternately between them. Fiber optic ribbons are sometimes used as fiber optic cables, where multiple fiber optic ribbons are bundled together.

[0003] Patent Document 1 discloses an intermittently bonded optical fiber tape (optical fiber tape core) and an optical cable (optical fiber cable) including the same. The intermittently bonded optical fiber tape described in Patent Document 1 includes a plurality of subtapes. In each subtape, a plurality of single-core coated optical fibers arranged in parallel are bonded together by intermittently arranged first adhesive portions. Furthermore, the plurality of subtapes are bonded together by intermittently arranged second adhesive portions. From the viewpoint of improving workability, the strength of the second adhesive portion is made lower than the breaking strength of the first adhesive portion. In this way, after separating the intermittently bonded optical fiber tape in subtape units, it becomes easy for the worker to separate the single-core coated optical fibers in a specific subtape.

[0004] In Patent Document 1, in order to prevent bending loss from occurring when separating single-core coated optical fibers, the breaking strength of the second adhesive portion is reduced. To reduce the breaking strength of the second adhesive portion, it is described that general material properties such as the Young's modulus of the second adhesive portion may be adjusted, or the second adhesive portion may be formed into a shape that is easy to break.

[0005] Japanese Patent No. 6188097

[0006] When manufacturing or using an optical fiber cable using an optical fiber ribbon core wire in which a plurality of single-core coated optical fibers are intermittently connected, if the breaking strength of the resin that intermittently connects the optical fibers is low, the optical fibers will separate inside the cable. If a plurality of optical fibers are separated in this way, the working efficiency of the operator will decrease when fusing the optical fiber ribbon core wire, for example. Therefore, it is preferable that the breaking strength of the resin that intermittently connects the optical fibers is somewhat high. On the other hand, even though general material properties such as Young's modulus are described in the resin catalog of the resin manufacturer, the breaking strength of the resin that intermittently connects the optical fibers in the optical fiber ribbon core wire is not described. For this reason, it has been difficult to select a resin with an appropriate breaking strength for the resin that intermittently connects the optical fibers in the optical fiber ribbon core wire.

[0007] An object of the present invention is to provide an optical fiber ribbon core wire and a method for manufacturing the same, which can easily select a resin with an appropriate breaking strength for the resin that intermittently connects single-core coated optical fibers.

[0008] In order to solve the above problems, according to one aspect of the present invention, there are provided: a plurality of single-core coated optical fibers arranged in parallel; and a tape layer that covers the plurality of single-core coated optical fibers and partially connects adjacent single-core coated optical fibers among the plurality of single-core coated optical fibers, wherein the tape layer contains a resin having an elongation at break of 24% or more, and an optical fiber ribbon core wire is provided.

[0009] According to another aspect of the present invention, a method for manufacturing an optical fiber ribbon core in which a plurality of single-core coated optical fibers are partially connected is provided, comprising the steps of: selecting a resin with a break elongation of 24% or more after curing, and coating the plurality of single-core coated optical fibers with the uncured resin; partially removing the uncured resin between adjacent single-core coated optical fibers among the plurality of single-core coated optical fibers coated with the uncured resin; and curing the uncured resin remaining on the plurality of single-core coated optical fibers.

[0010] According to the present invention, it is possible to provide an optical fiber ribbon core and a method for manufacturing the same, which allows for easy selection of a resin with appropriate fracture strength for intermittently connecting single-core coated optical fibers.

[0011] Figures 1A to 1C are schematic diagrams showing optical fiber ribbon cores. Figure 2 is a diagram showing the schematic configuration of an optical fiber ribbon core manufacturing apparatus. Figures 3A and 3B are schematic diagrams showing the configuration of the removal section. Figures 4A and 4B are schematic diagrams showing the configuration of the rotating blade. Figure 5 is a flowchart of the optical fiber ribbon core manufacturing method. Figures 6A to 6C are schematic diagrams for explaining the twisting and drawing test. Figure 7A is a graph showing the relationship between the Young's modulus of the resin and the fracture strength of the optical fiber ribbon core, and Figure 7B is a graph showing the relationship between the elongation at break of the resin and the fracture strength of the optical fiber ribbon core.

[0012] The following describes a preferred embodiment of the present invention: an optical fiber ribbon core and a method for manufacturing the same. In this specification, with respect to the notation "~" indicating a numerical range, the lower limit and upper limit are included within that numerical range.

[0013] First, we will explain optical fiber ribbon wires, and then we will explain the manufacturing apparatus and manufacturing method for optical fiber ribbon wires. In the following explanation, the direction in which the optical fibers are arranged in parallel will be referred to as the first direction (D1), the length direction of the optical fibers will be referred to as the second direction (D2), and the direction perpendicular to the first and second directions will be referred to as the third direction (D3). The first direction D1 corresponds to the width direction of the optical fiber ribbon wire, the second direction D2 corresponds to the length direction of the optical fiber ribbon wire, and the third direction D3 corresponds to the thickness direction of the optical fiber ribbon wire.

[0014] [Configuration of Optical Fiber Ribbon] Figure 1A is a schematic plan view of the optical fiber ribbon 10, Figure 1B is a cross-sectional view of line A-A in Figure 1A, and Figure 1C is a cross-sectional view of line B-B in Figure 1A.

[0015] As shown in Figures 1A to C, the optical fiber ribbon cable 10 has multiple single-core coated optical fibers (hereinafter also simply referred to as "optical fibers") 20, multiple connecting portions 30, and multiple separating portions 40. In Figure 1A, the connecting portions 30 are shown in black to make them easier to distinguish from the separating portions 40.

[0016] Multiple optical fibers 20 are arranged in parallel in a first direction D1. The number of optical fibers 20 is not particularly limited as long as there are two or more. The number of optical fibers 20 included in one optical fiber ribbon cable 10 is appropriately selected depending on the application of the optical fiber ribbon cable 10. For example, the number of optical fibers 20 included in one optical fiber ribbon cable 10 is in the range of 2 to 12. In this embodiment, 12 optical fibers 20 are arranged in parallel in one optical fiber ribbon cable 10.

[0017] As shown in Figures 1B and 1C, the single-core coated optical fiber 20 has optical fiber strands 21, a primary coating layer 22, and a secondary coating layer 23. The optical fiber strands 21, primary coating layer 22, and secondary coating layer 23 can be the same as those of known optical fibers, the first coating layer, and the second coating layer. A colored layer may be further formed on the secondary coating layer 23 of the optical fiber 20. It is preferable that the colors of the colored layers of multiple optical fibers 20 within a single optical fiber ribbon cable 10 are different from each other. This makes it possible to distinguish between multiple optical fibers 20 within a single optical fiber ribbon cable 10.

[0018] In this embodiment, multiple optical fibers 20 are covered by a tape layer 41, and adjacent optical fibers 20 are partially connected by the tape layer 41. In this embodiment, the portion of the tape layer 41 that connects adjacent optical fibers 20 is the connecting portion 30, and the space that separates adjacent optical fibers 20 (the area without the tape layer 41) is the separating portion 40. Note that the tape layer 41 does not have to completely cover the periphery of the optical fibers 20. For example, the optical fibers 20 may be partially exposed around the separating portion 40.

[0019] The connecting portion 30 is positioned between adjacent optical fibers 20, partially connecting them. The separating portion 40 is positioned between adjacent optical fibers 20, partially separating them. The arrangement of the connecting portion 30 and the separating portion 40 is not particularly limited. In the optical fiber ribbon cable 10 of this embodiment, the connecting portion 30 and the separating portion 40 are arranged alternately in the longitudinal direction (second direction D2) of the optical fiber ribbon cable 10. That is, the connecting portion 30 is arranged intermittently in the longitudinal direction (second direction D2) of the optical fiber ribbon cable 10. Furthermore, in the optical fiber ribbon cable 10, it is preferable that two or more separating portions 40 are positioned between adjacent connecting portions 30 in the width direction (first direction D1) of the optical fiber ribbon cable 10. In the optical fiber ribbon cable 10 of this embodiment, two separating portions 40 are positioned between adjacent connecting portions 30 in the width direction (first direction D1) of the optical fiber ribbon cable 10. This reduces the number of connecting portions 30, thereby shortening the overall width of the optical fiber ribbon core 10. Furthermore, it is preferable that the multiple spacing portions 40 are arranged such that the extent of existence of two adjacent spacing portions 40 in the length direction (second direction D2) of the optical fiber ribbon core 10 partially overlaps in the width direction (first direction D1) of the optical fiber ribbon core 10.

[0020] As shown in Figure 1A, the length L1 of the connecting portion 30 when the optical fiber ribbon core 10 is viewed from above is not particularly limited. The length L1 is, for example, within the range of 5 mm to 15 mm. Also, as shown in Figure 1B, the thickness T of the connecting portion 30 is not particularly limited. The thickness T is, for example, within the range of 209 μm to 290 μm. When the length L1 and thickness T of the connecting portion 30 are within this range, the strength of the connecting portion 30 is increased, and the connecting portion 30 is less likely to tear even when the optical fiber ribbon core 10 is wound or twisted in the width direction. On the other hand, as shown in Figure 1A, the length L2 of the separating portion 40 when the optical fiber ribbon core 10 is viewed from above is not particularly limited. The length L2 is, for example, within the range of 45 mm to 55 mm. When the length L2 of the separating portion 40 is within this range, it becomes easier to wind or twist the optical fiber ribbon core 10 in the width direction when housing the optical fiber ribbon core 10 in the cable. In this embodiment, length L1, thickness T, and length L2 are the average values ​​obtained when measured at any five locations within the optical fiber ribbon core 10.

[0021] The tape layer 41 is composed of a resin or a resin composition. That is, the tape layer 41 contains resin, and the connecting portion 30 also contains resin. The type of resin is not particularly limited, but for example, it may be a photocurable resin or a thermosetting resin. In this embodiment, the resin contained in the tape layer 41 is a cured product of a photocurable resin. Examples of photocurable resins include urethane resins and epoxy resins.

[0022] The elongation at break of the resin contained in the tape layer 41 is 24% or more. The elongation at break of the resin is measured in accordance with JIS K 7127:1999. As mentioned above, when manufacturing or using an optical fiber cable using the optical fiber ribbon core 10, if the fracture strength of the resin intermittently connecting the optical fibers 20 is low, the optical fibers 20 will separate within the cable. If multiple optical fibers 20 separate in this way, the work efficiency of the worker will decrease when fusing the optical fiber ribbon core 10. Therefore, it is preferable that the fracture strength of the resin intermittently connecting the optical fibers 20 be relatively high. On the other hand, although general material properties such as Young's modulus are listed in the resin catalogs of resin manufacturers, the fracture strength of the resin intermittently connecting the optical fibers 20 in the optical fiber ribbon core 10 is not listed. For this reason, it has been difficult to select a resin with appropriate fracture strength for intermittently connecting the optical fibers 20 in the optical fiber ribbon core 10. Therefore, the inventors attempted to select a resin using Young's modulus, but could not find a correlation between the Young's modulus of the resin and the fracture strength of the resin (see Examples and Figure 7A). The inventors investigated various parameters of the resin and found a strong correlation between the elongation at break of the resin and the fracture strength of the resin (see Examples and Figure 7B). The inventors then found that in order to ensure the fracture strength required for the optical fiber ribbon core 10, it is sufficient to use a resin with an elongation at break of 24% or more. The elongation at break of the resin may be 30% or more, or 40% or more. There is no particular upper limit to the elongation at break of the resin. If the elongation at break of the resin is too large, the optical fiber ribbon core 10 may become difficult to tear. For example, the elongation at break of the resin may be 100% or less, 60% or less, or 56% or less.

[0023] The Young's modulus of the resin contained in the tape layer 41 is not particularly limited. For example, the Young's modulus of the resin is in the range of 100 to 2000 MPa, preferably in the range of 130 to 1200 MPa, and more preferably in the range of 138 to 1150 MPa.

[0024] The shape of the cross-section of the optical fiber 20 covered by the tape layer 41 in the portion not connected by the connecting portion 30 (tape layer 41) (the portion located between the two separated portions 40 in the width direction (first direction D1) of the optical fiber tape core 10) is not particularly limited and may be, for example, substantially rectangular or substantially circular. In this embodiment, as shown in Figure 1C, the shape of the cross-section of the optical fiber 20 covered by the tape layer 41 is substantially rectangular. Here, "shape of the cross-section of the optical fiber 20 covered by the tape layer 41" means the shape of the cross-section of the portion including the tape layer 41, not just the cross-section of the optical fiber 20 alone. Therefore, if the entire circumference of the optical fiber 20 is covered by the tape layer 41, the shape formed by the outer edge of the tape layer 41 corresponds to "shape of the cross-section of the optical fiber 20 covered by the tape layer 41". Furthermore, in this embodiment, the cross-sectional shape of the optical fiber 20 covering the tape layer 41 in that portion is substantially symmetrical in the thickness direction (third direction D3) of the optical fiber tape core 10, and also substantially symmetrical in the width direction (first direction D1) of the optical fiber tape core 10. That is, in the cross-section, the shape of the optical fiber 20 covering the tape layer 41 is substantially symmetrical with respect to a straight line passing through the center of the optical fiber 20 along the width direction (first direction D1) of the optical fiber tape core 10, and also substantially symmetrical with respect to a straight line passing through the center of the optical fiber 20 along the thickness direction (third direction D3) of the optical fiber tape core 10. Here, "substantially symmetrical" means that there is no intentionally formed difference in shape between one side and the other with respect to the aforementioned straight line. For example, even if the thickness of the tape layer 41 differs slightly between one side and the other with respect to the aforementioned straight line, it can be said that they are substantially symmetrical. On the other hand, if convex or concave portions are intentionally formed at asymmetrical positions between one side and the other with respect to the aforementioned straight line, it can be said that they are not substantially symmetrical.

[0025] In the description so far, we have described an optical fiber ribbon cable 10 in which connecting portions 30 and separating portions 40 are provided between all adjacent optical fibers 20. However, the optical fiber ribbon cable according to the present invention is not limited to this. For example, the optical fiber ribbon cable according to the present invention may be an optical fiber ribbon cable 10 in which connecting portions 30 and separating portions 40 are provided between subtapes in which a plurality of (e.g., two) optical fibers 20 arranged in parallel are collectively covered with resin. In this case, connecting portions 30 and separating portions 40 are formed between the subtapes, but only connecting portions are continuously formed between the optical fibers 20 within the subtapes, and no separating portions are formed. In this case, it is sufficient that the elongation at break of the resin constituting the connecting portion 30 that connects the subtapes is 24% or more.

[0026] [Configuration of the Optical Fiber Ribbon Manufacturing Apparatus] Next, the optical fiber ribbon manufacturing apparatus 100 will be described. Figure 2 is a perspective view of the optical fiber ribbon manufacturing apparatus 100.

[0027] As shown in Figure 2, the optical fiber ribbon core manufacturing apparatus 100 has a coating section 110, a removal section 120, and a hardening section 140. The optical fiber ribbon core manufacturing apparatus 100 manufactures an optical fiber ribbon core 10 in which adjacent optical fibers 20 are partially connected, by feeding a plurality of optical fibers 20 arranged in parallel in a first direction D1 in a second direction D2 which is the longitudinal direction of the plurality of optical fibers 20.

[0028] The coating portion 110 forms an uncured tape layer 41 by coating a plurality of optical fibers 20 arranged in parallel at a predetermined pitch with an uncured photocurable resin (hereinafter also simply referred to as "uncured resin"). Here, the plurality of optical fibers 20 are coated with a resin that has a break elongation of 24% or more after curing. The configuration of the coating portion 110 is not particularly limited as long as it can perform the above functions. In this embodiment, the coating portion 110 has a die (not shown). The die has an insertion hole through which a plurality of optical fibers 20 arranged in parallel in a first direction D1 pass, and the shape of the opening of the insertion hole is the shape of the cross-section perpendicular to the length direction of the tape layer 41. By feeding the plurality of optical fibers 20 arranged in parallel at a predetermined pitch and coating them with the uncured resin using the die, a tape layer 41 can be formed on a plurality of optical fibers 20 in a continuous manner at once.

[0029] The removal section 120 partially removes the uncured resin between adjacent optical fibers 20 from among a plurality of optical fibers 20 coated with uncured resin, thereby forming a separated section 40 where adjacent optical fibers 20 are partially separated and a connected section 30 where adjacent optical fibers 20 are partially connected.

[0030] The configuration of the removal unit 120 is not particularly limited as long as it can perform the above functions. Figures 3A and 3B are diagrams illustrating an example of the removal unit 120 shown in Figure 2. Figure 3A is a plan view of the positioning unit 122, and Figure 3B is a cross-sectional view taken along line A-A shown in Figure 3A. Figure 3B also shows a part of the suction unit 123 located on top of the positioning unit 122. As shown in Figures 3A and 3B, the removal unit 120 is positioned between adjacent optical fibers 20 and includes a plurality of rotating blades 121 for intermittently pushing out the uncured resin between adjacent optical fibers 20, a positioning unit 122 for positioning the optical fibers 20 covered with uncured resin relative to the plurality of rotating blades 121, and a suction unit 123 for sucking up the uncured resin pushed out by the plurality of rotating blades 121.

[0031] The positioning unit 122 includes a positioning unit body 124, a through hole 125 for passing multiple optical fibers 20 covered with uncured resin, multiple slits 126 communicating with the through hole 125 and for multiple rotating blades 121 to rotate inside, and multiple exit openings 126a for the slits 126 from which the resin extruded by the multiple rotating blades 121 comes out. The through hole 125, the multiple slits 126, and the exit openings 126a are provided in the positioning unit body 124.

[0032] Multiple rotating blades 121 partially extrude the uncured resin between adjacent optical fibers 20. Each of the multiple rotating blades 121 is positioned inside each of the multiple slits 126. The ends of the rotating blades 121 on the side of the exit opening 126a of the slit 126 are positioned closer to the exit opening 126a of the slit 126 than the upper end of the incoming optical fiber 20. The rotation of the multiple rotating blades 121 is controlled by a motor (not shown) and rotates in accordance with the transport of the optical fiber 20, with their rotation axes 127 coinciding. The shapes of the multiple rotating blades 121 may all be the same, or they may be different. In this embodiment, all of the multiple rotating blades 121 have the same shape.

[0033] Figures 4A and 4B are schematic diagrams showing the configuration of the rotating blade 121. Figure 4A shows only one rotating blade 121, and Figure 4B shows three rotating blades 121. As shown in Figure 4A, in this embodiment, the rotating blade 121 has a notch 128 and a blade portion 129. The circumferential length of the notch 128 corresponds to the length of the connecting portion 30, and the circumferential length of the blade portion 129 corresponds to the length of the separating portion 40. The number of rotating blades 121 is the same as the number of slits 126. As shown in Figure 4B, the multiple rotating blades 121 are arranged such that the position of the notch 128 differs between adjacent rotating blades 121. When the rotating blades 121 rotate in accordance with the transport of the optical fiber 20, the multiple rotating blades 121 rotate while the positions of the notches 128 of each of the multiple rotating blades 121 remain different, and the connecting portion 30 and the separating portion 40 are formed alternately. The positions of the notches 128 in each of the multiple rotating blades 121 are appropriately set according to the positions of the connecting portion 30 and the separating portion 40 in the optical fiber ribbon core 10. Specifically, when the notches 128 are located between adjacent optical fibers 20, the uncured photocurable resin is not pushed out, and a connecting portion 30 is formed. On the other hand, when the blades 129 are located between adjacent optical fibers 20, the uncured resin is pushed out from between the adjacent optical fibers 20, so that the uncured resin is no longer present between the adjacent optical fibers 20 and a separating portion 40 is formed.

[0034] Although not specifically shown in the figures, it is preferable that the rotating blade 121 is positioned such that the distance between the rotating blade 121 and the optical fiber 20 is in the range of 0 to 10 μm, and more preferably in the range of 0 to 5 μm. By shortening the distance between the rotating blade 121 and the optical fiber 20 in this way, the tape layer 41 formed on the side surface of the optical fiber 20 can be made thinner (see Figure 1B).

[0035] As described above, the positioning unit 122 has a positioning unit body 124, a through hole 125, a plurality of slits 126, and an exit opening 126a.

[0036] In this embodiment, the positioning unit body 124 is formed in a substantially rectangular parallelepiped shape. The positioning unit body 124 has through holes 125 for passing multiple optical fibers 20 through, multiple slits 126 for each of the multiple rotating blades 121 to rotate inside, and multiple outlet openings 126a of the slits 126 from which the resin extruded by the multiple rotating blades 121 comes out.

[0037] The through-hole 125 allows multiple optical fibers 20, which are coated with uncured resin, to pass through. In this embodiment, the through-hole 125 opens on the back surface 124a (right side in Figure 3B) and the front surface 124b (left side in Figure 3B) of the positioning unit body 124. The cross-sectional shape of the through-hole 125 in the direction along the third direction D3 and the first direction D1 is complementary to the cross-section of the optical fiber 20 coated with uncured resin.

[0038] Multiple slits 126 are configured so that multiple rotating blades 121 can rotate inside them. The multiple slits 126 are arranged along a second direction D2 and in parallel along a first direction D1. The exit opening 126a of the slit 126 opens onto the surface of the positioning unit body 124 on the suction unit 123 side (the top surface in this embodiment). The downstream end of the slit 126 opens onto the front surface 124b of the positioning unit body 124. The multiple slits 126 may all be the same shape, or they may all be different shapes. In this embodiment, all the multiple slits 126 are the same shape. The number of slits 126 is equal to or greater than the number of spaces between adjacent optical fibers 20. In this embodiment, the number of spaces between adjacent optical fibers 20 is 11, so there are 11 slits 126.

[0039] Since the rotating blade 121 is positioned in the slit 126, the uncured resin is pushed out from the exit opening 126a of the slit. Also, as described above, since the rotating blade 121 follows the transport of the optical fiber 20, stress is generated in the direction of the optical fiber 20's feed in the uncured resin pushed out from the slit 126 by the rotating blade 121. At this time, since the downstream end of the slit 126 opens to the front surface 124b of the positioning unit body 124, the uncured resin does not get stuck and is prevented from coming into contact with the optical fiber 20 again.

[0040] The suction unit 123 sucks up the uncured resin extruded from the outlet opening 126a of the slit 126. The suction unit 123 has an intake unit 131, a negative pressure device (not shown), and a connecting unit 132 for connecting the intake unit 131 and the negative pressure device.

[0041] The intake section 131 is formed in a hollow box shape and has a suction opening 131a that is positioned to cover the multiple outlet openings 126a of the multiple slits 126 from which the resin extruded by the multiple rotating blades 121 comes out. Preferably, the downstream end of the suction opening 131a is positioned further downstream than the downstream ends of the multiple outlet openings 126a. This allows for proper suction of the uncured resin accumulated downstream of the multiple outlet openings 126a, and prevents the uncured resin accumulated downstream of the multiple outlet openings 126a from coming into contact with the optical fiber 20 again. Also, the upstream end of the suction opening 131a is positioned further upstream than the upstream ends of the multiple outlet openings 126a. In this embodiment, the upstream end of the suction opening 131a is positioned at the same location as the upstream ends of the multiple outlet openings 126a.

[0042] Furthermore, the length of the suction opening 131a in the direction of arrangement of the multiple optical fibers 20 (first direction D1) is preferably within the range of 100 to 120% of the length of the multiple outlet openings 126a in the direction of arrangement of the multiple optical fibers 20. Here, "length L3 of the multiple outlet openings 126a in the direction of arrangement of the multiple optical fibers 20" means the length between the outer end of the slit 126 located at one end in the first direction D1 (in the example shown in Figure 3A, the outer end of the lower slit 126) and the outer end of the slit 126 located at the other end in the first direction D1 (in the example shown in Figure 3A, the outer end of the upper slit 126). This reduces the volume of the space surrounded by the upper surface of the intake section 131 and the positioning section body 124, allowing the space to be efficiently subjected to negative pressure by the suction device. Therefore, the uncured resin can be efficiently and appropriately suctioned.

[0043] The connection part 132 connects to the intake part 131 and a negative pressure device (not shown). In this embodiment, the connection part 132 is connected to the surface of the intake part 131 opposite to the suction opening 131a. By operating the negative pressure device, the space surrounded by the intake part 131 and the upper surface of the positioning part body 124 can be made into a negative pressure state, and the uncured resin that has been pushed into the space is sucked up without sucking up the uncured resin remaining around the multiple optical fibers 20. The conditions for sucking up the uncured resin that has been pushed into the space without sucking up the uncured resin remaining around the multiple optical fibers 20 are appropriately adjusted by the volume of the space and the suction pressure from the negative pressure device. It is preferable that the negative pressure device is constantly running during the manufacturing of the optical fiber ribbon core 10.

[0044] The curing unit 140 cures the uncured resin remaining in the plurality of optical fibers 20. The configuration of the curing unit 140 is not particularly limited as long as it can exhibit the above functions. In the present embodiment, the curing unit 140 includes a first light irradiation unit 141 and a second light irradiation unit 142. The first light irradiation unit 141 is disposed on the upstream side and irradiates the tape layer 41 with light to semi-cure the uncured tape layer 41. The second light irradiation unit 142 further irradiates light to completely cure the semi-cured tape layer 41. In the present embodiment, the integrated irradiation amounts of the first light irradiation unit 141 on the upstream side and the second light irradiation unit 142 on the downstream side are adjusted such that the integrated irradiation amount of the first light irradiation unit 141 is small and the integrated irradiation amount of the second light irradiation unit 142 is large.

[0045] [Method for manufacturing an optical fiber ribbon core wire] Next, a method for manufacturing an optical fiber ribbon core wire will be described. FIG. 5 is a flowchart of a method for manufacturing an optical fiber ribbon core wire.

[0046] As shown in FIG. 5, the method for manufacturing an optical fiber ribbon core wire includes a step (S110) of coating a plurality of optical fibers with an uncured resin, a step (S120) of partially removing the uncured resin, and a step (S130) of curing the resin.

[0047] In the step (S110) of coating a plurality of optical fibers with an uncured resin, the plurality of optical fibers 20 arranged in parallel at a predetermined pitch are coated with an uncured resin. Here, a resin having a breaking elongation of 2% or more after curing is selected and used. For example, the coating unit 110 of the manufacturing apparatus shown in FIG. 2 may be used to form an uncured tape layer 41. Specifically, while feeding the plurality of optical fibers 20, an uncured resin is applied to the plurality of optical fibers 20 in a tape shape by a die to form the tape layer 41.

[0048] In the step of partially removing the resin in the uncured state (S120), among the plurality of optical fibers 20 coated with the resin in the uncured state, the resin in the uncured state between adjacent optical fibers is partially removed. For example, the removing portion 120 of the manufacturing apparatus shown in FIGS. 2, 3A, and 3B may be used to form the connecting portion 30 and the separating portion 40. Specifically, a plurality of rotary blades 121 are rotated with respect to the tape layer 41, a part of the tape layer 41 is removed, and the connecting portion 30 and the separating portion 40 are formed. When the rotary blade 121 rotates following the conveyance of the optical fiber 20, the separating portion 40 and the connecting portion 30 are alternately formed. At this time, the resin in the uncured state removed by the rotary blade 121 is pushed toward the outlet opening 126a of the slit 126. The resin in the uncured state pushed out from the outlet opening 126a of the slit 126 is sucked by the suction portion 123.

[0049] In the step of curing the resin (S130), the resin in the uncured state remaining on the plurality of optical fibers 20 is cured. For example, using the curing portion 140 of the manufacturing apparatus shown in FIG. 2, the uncured tape layer 41 is semi-cured by irradiating light with the first light irradiation portion 141 on the tape layer 41, and further irradiated with light with the second light irradiation portion 142 to completely cure the semi-cured tape layer 41. The elongation at break of the cured resin is 24% or more.

[0050] By the above procedure, an optical fiber tape core wire 10 having an appropriate breaking strength of the connecting portion 30 (tape layer 41) can be manufactured.

[0051] (Effect) As described above, according to the present invention, since the connecting portion 30 (tape layer 41) is formed using a resin having an elongation at break of 24% or more, an optical fiber tape core wire 10 having an appropriate breaking strength of the connecting portion 30 (tape layer 4) can be obtained. Further, according to the present invention, it becomes possible to easily select or develop a resin suitable for use in forming the tape layer 41 using the elongation at break as an index.

[0052] Using the manufacturing apparatus 100 shown in FIG. 2, an optical fiber tape core wire including 12 single-core coated optical fibers was manufactured. In the coating portion 110, different types of photocurable resins (resins A to I) were applied to the 12 single-core coated optical fibers arranged in parallel.

[0053] For each sample, the fracture strength was measured by the twisting and squeezing test shown in Figures 6A and 6C. First, as shown in Figure 6A, a 600g weight was suspended from the other end of a sample (optical fiber ribbon core) with one end fixed (applying a tension of 600gf), and the sample was twisted a predetermined number of times. The length of the sample between the clamp and the weight was 600mm. The tension applied to the sample and the twisted state of the sample were maintained thereafter. Next, as shown in Figure 6B, two connected pulleys (16mm in diameter) were placed on top of the sample and moved back and forth once between the top and bottom of the sample. In other words, the twisted sample was squeezed by the two pulleys. Finally, as shown in Figure 6C, the state of the sample was checked with the pulleys removed. This series of procedures was repeated while varying the number of twists, and the maximum number of twists at which no fracture occurred in the sample (especially at the connecting part) was defined as the fracture strength of that sample (unit: twists). Based on the inventors' previous experience, when the breaking strength (maximum number of twists) was less than 2, the optical fibers sometimes separated during the manufacturing of the optical fiber cable. However, when the breaking strength (maximum number of twists) was 2 or more, the optical fibers did not separate during the manufacturing of the optical fiber cable. Therefore, a breaking strength (maximum number of twists) of 2.0 or more was evaluated as passing (○), and less than 2.0 was evaluated as failing (×).

[0054] Table 1 shows the type of resin, Young's modulus of the resin, elongation at break of the resin, fracture strength of the sample (maximum number of twists), relative value of the fracture strength of the sample, and evaluation results of the fracture strength of the sample for each sample. The relative value of the fracture strength of the sample is based on the acceptance standard of 2.0 twists.

[0055]

[0056] Figure 7A is a graph showing the relationship between the Young's modulus of the resin and the fracture strength (relative value) of the sample, and Figure 7B is a graph showing the relationship between the elongation at break of the resin and the fracture strength (relative value) of the sample. As shown in Figure 7A, no significant correlation was found between the Young's modulus of the resin and the fracture strength of the sample, indicating that it is difficult to select a resin based on Young's modulus. On the other hand, as shown in Figure 7B, there is a strong correlation between the elongation at break of the resin and the fracture strength of the sample, indicating that it is possible to select or develop a resin based on elongation at break. Furthermore, as shown in Table 1, it was found that optical fiber ribbon cores with the required fracture strength can be manufactured by using a resin with an elongation at break of 24% or more.

[0057] The optical fiber ribbon core according to the present invention is useful, for example, in the development and construction of high-speed, high-capacity optical fiber communication networks.

[0058] 10 Optical fiber ribbon core 20 Optical fiber (single-core coated optical fiber) 21 Optical fiber strand 22 Primary coating layer 23 Secondary coating layer 30 Connecting part 40 Separating part 41 Tape layer 100 Manufacturing apparatus 110 Coating part 120 Removal part 121 Rotating blade 122 Positioning part 123 Suction part 124 Positioning part body 124a Back view 124b Front view 125 Through hole 126 Slit 126a Exit opening 127 Rotating shaft 128 Notch part 129 Blade part 131 Intake part 131a Suction opening 132 Connection part 140 Hardening part 141 First light irradiation part 142 Second light irradiation part

Claims

1. An optical fiber ribbon core comprising: a plurality of single-core coated optical fibers arranged in parallel; and a tape layer covering the plurality of single-core coated optical fibers and partially connecting adjacent single-core coated optical fibers, wherein the tape layer contains a resin with an elongation at break of 24% or more.

2. The optical fiber ribbon cable according to claim 1, characterized in that the shape of the cross-section of the single-core coated optical fiber covered by the tape layer in the portion not connected by the tape layer is substantially symmetrical in the thickness direction of the optical fiber ribbon cable and substantially symmetrical in the width direction of the optical fiber ribbon cable.

3. A method for manufacturing an optical fiber ribbon core in which a plurality of single-core coated optical fibers are partially connected, comprising: a step of selecting a resin with a break elongation of 24% or more after curing, and coating the plurality of single-core coated optical fibers with the uncured resin; a step of partially removing the uncured resin between adjacent single-core coated optical fibers among the plurality of single-core coated optical fibers coated with the uncured resin; and a step of curing the uncured resin remaining on the plurality of single-core coated optical fibers.

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