Optical fiber ribbon and method for manufacturing optical fiber ribbon

Abstract

Disclosed is an optical fiber ribbon comprising a plurality of optical fibers. Each optical fiber of the plurality of optical fibers comprises: a glass fiber including a plurality of cores and a cladding that surrounds the plurality of cores and has a refractive index lower than the refractive index of the plurality of cores; and a resin coating layer that is in contact with the glass fiber and surrounds the glass fiber. If the non-uniformity ratio (%) of the resin coating layer is defined as (d1 / d2)×100, which is the ratio of the minimum thickness d1 in the radial direction of the resin coating layer to the maximum thickness d2 in the radial direction of the resin coating layer in a cross section perpendicular to the central axis of the optical fiber, the non-uniformity ratio of the resin coating layer in each of the plurality of optical fibers is 80% or less.

Description

Optical fiber ribbon core wire, and method for manufacturing optical fiber ribbon core wire

[0001] The present disclosure relates to an optical fiber ribbon core wire and a method for manufacturing an optical fiber ribbon core wire.

[0002] Patent Document 1 discloses an optical fiber ribbon core wire in which a plurality of multi-core fibers are adhered to each other.

[0003] Japanese Patent Application Laid-Open No. 2017-173514

[0004] The optical fiber ribbon core wire according to an embodiment of the present disclosure includes a plurality of optical fibers. Each of the plurality of optical fibers includes a glass fiber including a plurality of cores and a clad that surrounds the plurality of cores and has a refractive index lower than that of the plurality of cores, and a resin coating layer that contacts the glass fiber and surrounds the glass fiber. When (d1 / d2)×100, which is the ratio of the minimum radial thickness d1 of the resin coating layer to the maximum radial thickness d2 of the resin coating layer in a cross section perpendicular to the central axis of the optical fiber, is defined as the unbiased wall thickness ratio [%] of the resin coating layer, the unbiased wall thickness ratio of the resin coating layer is 80% or less in each of the plurality of optical fibers.

[0005] FIG. 1 is a cross-sectional view showing an optical fiber ribbon core wire according to an embodiment. FIG. 2 is a cross-sectional view showing each optical fiber included in the optical fiber ribbon core wire shown in FIG. 1. FIG. 3 is a schematic cross-sectional view showing the minimum thickness d1 and the maximum thickness d2 when calculating the unbiased wall thickness ratio in an optical fiber. FIG. 4 is a schematic diagram for explaining a method for manufacturing the optical fiber ribbon core wire shown in FIG. 1. In the method shown in FIG. 4, it is a schematic diagram showing the movement of the non-uniformly thick optical fiber in the rotational direction around the central axis.

[0006] [Problems this disclosure aims to solve] In the optical fiber ribbon cable described in Patent Document 1, in order to adjust the rotational position of multiple cores of each optical fiber, light is introduced into the cores and rotational alignment is performed based on the amount of leakage light. However, it is difficult to adjust the core position with leakage light while running at high speed, and the core positions in the optical fiber ribbon cable may shift from one optical fiber to another. When the core positions are shifted, the optical connection becomes unstable when connecting an optical fiber ribbon cable containing multiple multicore fibers to other components. Furthermore, although it is possible to rotate each optical fiber individually during fusion splicing, this takes a considerable amount of time when the number of optical fibers and cores is large, so it is desirable to be able to fuse the optical fiber ribbon cable all at once.

[0007] [Effects of this disclosure] This disclosure provides an optical fiber ribbon core that can stabilize optical connections and a method for manufacturing the optical fiber ribbon core.

[0008] [Description of Embodiments of the Disclosure] First, the contents of embodiments of the Disclosure will be listed and described. [1] An optical fiber ribbon core according to one embodiment of the Disclosure comprises a plurality of optical fibers. Each of the plurality of optical fibers comprises a glass fiber including a plurality of cores and a cladding surrounding the plurality of cores having a refractive index lower than that of the plurality of cores, and a resin coating layer in contact with and surrounding the glass fiber. When the ratio of the minimum radial thickness d1 of the resin coating layer to the maximum radial thickness d2 of the resin coating layer in a cross section perpendicular to the central axis of the optical fiber, (d1 / d2) × 100 is taken as the percentage of uniformity of the resin coating layer, the percentage of uniformity of the resin coating layer is 80% or less in each of the plurality of optical fibers.

[0009] In the optical fiber ribbon cable described in [1] above, the uniformity of the resin coating layer is 80% or less for each of the multiple optical fibers. That is, in this optical fiber ribbon cable, the resin coating layer of each optical fiber is intentionally made to have a uniform thickness. In this case, by aligning the position of each core in the rotational direction around the central axis of the optical fiber with the uniform thickness portion, when multiple optical fibers are made into a ribbon, the cores of each optical fiber can be easily and reliably positioned in the same location relative to the uniform thickness portion. As a result, the core arrangement of each optical fiber included in the optical fiber ribbon cable becomes uniform, and the optical connection in the optical fiber ribbon cable can be stabilized.

[0010] [2] In the optical fiber ribbon cable described in [1] above, the uniformity of the resin coating layer may be 60% or more for each of the multiple optical fibers. In this case, the resin coating layer will retain some thickness in the thinner parts, thus preventing an increase in the transmission loss of each optical fiber.

[0011] [3] In the optical fiber ribbon core described in [1] or [2] above, the uniformity of the resin coating layer in each of the multiple optical fibers may be 65% or more and 75% or less. In this case, the core position of each optical fiber can be easily adjusted, further stabilizing the optical connection and further preventing an increase in the transmission loss of each optical fiber.

[0012] [4] In any of the optical fiber ribbon cables described in [1] to [3] above, the multiple optical fibers may be intermittently connected to each other in the direction of extension of the optical fibers. In this case, individual optical fibers can be removed from the ribbon cable when connecting, making it easier to perform various adjustments.

[0013] [5] In any of the optical fiber ribbon cores described in [1] to [4] above, the relationship between a reference line connecting the location where at least one of the minimum thickness d1 and maximum thickness d2 of the resin coating layer is located in the vertical cross-section of the optical fiber and the central axis of the glass fiber, and the arrangement locations of the multiple cores in the rotational direction around the central axis of the glass fiber, may be the same for each of the multiple optical fibers. In this case, since the core positions of each optical fiber are arranged in the same position, the optical fiber ribbon core can be easily connected to other optical components when optically connecting them. Note that "arranged in the same position" here means not only when the arrangement is exactly the same, but also when it is shifted by ±10 degrees in the rotational direction.

[0014] [6] In any of the optical fiber ribbon cores described in [1] to [5] above, the position where the minimum thickness d1 of the resin coating layer is in each of the multiple optical fibers may be the same with respect to the central axis of the glass fiber in a cross-section perpendicular to the optical fiber. In this case, since the core positions of each optical fiber are aligned, the optical fiber ribbon core can be easily connected to other optical components when optically connecting them.

[0015] [7] A method for manufacturing an optical fiber ribbon core according to one embodiment of the present disclosure comprises the steps of drawing each of a plurality of optical fibers and forming the plurality of optical fibers into a tape. Each of the plurality of optical fibers comprises a glass fiber including a plurality of cores and a cladding surrounding the plurality of cores having a refractive index lower than that of the plurality of cores, and a resin coating layer in contact with and surrounding the glass fiber. In the drawing step, when (d1 / d2) × 100, which is the ratio of the minimum radial thickness d1 of the resin coating layer to the maximum radial thickness d2 of the resin coating layer in a cross section perpendicular to the central axis of the optical fiber, is defined as the uniformity rate of the resin coating layer [%], each of the plurality of optical fibers is drawn such that the uniformity rate of the resin coating layer is 80% or less, and the arrangement of the plurality of cores coincides with the position of the resin coating layer that has the minimum thickness d1.

[0016] In the manufacturing method of optical fiber ribbon cores described in [7] above, each optical fiber is drawn so that the uniformity of the resin coating layer is 80% or less. Then, optical fiber ribbon cores are manufactured using such optical fibers with uneven thickness. In this case, because the uneven thickness creates anisotropy in the bending rigidity (ease of bending), when bending each optical fiber via a roller or the like during tape formation, it becomes easier to position the rotational position of each core in the same direction relative to the unevenly thickened portion, and optical fiber ribbon cores with the same core arrangement for each optical fiber can be easily manufactured. Furthermore, in this case, the same approach can be taken even if the number of optical fibers to be tapered increases, so optical fiber ribbon cores with a large number of cores can be easily manufactured.

[0017] [8] In the method for manufacturing optical fiber ribbon cores described in [7] above, the thickness of the resin coating layer may be unevenly distributed in the drawing step by shifting the die on which the resin coating layer is applied. In this case, optical fibers with unevenly distributed resin coating layers can be manufactured in a simple manner. Furthermore, the uneven thickness of multiple optical fibers used in the optical fiber ribbon core can be easily made similar (for example, having the same thickness of resin coating layer).

[0018] [9] In the method for manufacturing optical fiber ribbon cores according to [7] or [8] above, in the tape formation step, the thickness direction of multiple optical fibers may be aligned and the multiple optical fibers may be connected with tape formation resin. In this case, since the core positions of each optical fiber are aligned, an optical fiber ribbon core that is easy to connect to other optical components can be obtained.

[0019] [Details of Embodiments of the Disclosure] Specific examples of optical fiber ribbons and methods for manufacturing optical fiber ribbons according to embodiments of the Disclosure will be described below with reference to the drawings. In the following description, the same reference numerals will be used for the same elements or elements having the same function, and redundant descriptions will be omitted. The present invention is not limited to these examples, but is indicated by the claims, and all modifications within the meaning and scope of the claims are intended to be included.

[0020] Referring to Figure 1, the optical fiber ribbon cable according to this embodiment will be described. Figure 1 is a cross-sectional view showing an optical fiber ribbon cable according to one embodiment. As shown in Figure 1, the optical fiber ribbon cable 1 includes a plurality of optical fibers 10 arranged in parallel in the transverse direction. The plurality of optical fibers 10 are connected to each other and held integrally by a tape resin 5. Such an optical fiber ribbon cable 1 extends in a direction perpendicular to Figure 1 (extension direction).

[0021] Figure 2 is a cross-sectional view showing each optical fiber 10 included in the optical fiber ribbon core 1 shown in Figure 1. As shown in Figures 1 and 2, each optical fiber 10 has a glass fiber 11 and a resin coating layer 15 that is in contact with and surrounds the glass fiber 11. The glass fiber 11 includes a plurality of cores 12 and a cladding 13 that surrounds the plurality of cores 12 and has a refractive index lower than that of the plurality of cores 12. Both the cores 12 and the cladding 13 are formed from glass. In the example shown in Figure 2, the glass fiber 11 contains four cores 12, but the number of cores 12 is not limited to this. The number of cores 12 included in the glass fiber 11 may be two or more, may be twelve, or may be sixteen. The glass fiber 11 is protected from the external environment (e.g., lateral pressure) by the resin coating layer 15.

[0022] The resin coating layer 15 includes a primary resin layer 16 and a secondary resin layer 17. The primary resin layer 16 is formed by curing an ultraviolet-curable resin composition containing a photopolymerizable compound, a photopolymerization initiator, and a silane coupling agent with ultraviolet light. As the photopolymerizable compound, for example, urethane (meth)acrylate or epoxy (meth)acrylate can be used. The primary resin layer 16 has a lower elastic modulus (Young's modulus) than the secondary resin layer 17 and is softer than the secondary resin layer 17. For example, the Young's modulus of the primary resin layer 16 at 23°C is 0.1 MPa or more and 5 MPa or less. This provides the optical fiber 10 with lateral pressure resistance, and suppresses the increase in transmission loss in the optical fiber 10 even when lateral pressure is applied.

[0023] The secondary resin layer 17 is formed by curing a resin composition containing urethane (meth)acrylate, monomer, and photopolymerization initiator with ultraviolet light. The secondary resin layer 17 has a higher elasticity (Young's modulus) than the primary resin layer 16, and is harder than the primary resin layer 16. For example, the Young's modulus of the secondary resin layer 17 at 23°C is 1200 MPa or more and 2800 MPa or less. The secondary resin layer 17 may be a colored resin layer. In this case, the material forming the secondary resin layer 17 may contain a pigment. The thickness of each layer of the primary resin layer 16 and the secondary resin layer 17 is, for example, 5 μm or more and 50 μm or less.

[0024] In the optical fiber 10 according to this embodiment, as shown in Figures 2 and 3, when viewed in a cross-section perpendicular to the central axis G1 of each optical fiber 10, the glass fiber 11 is formed to be eccentric with respect to the resin coating layer 15. In other words, the maximum radial thickness d2 and minimum radial thickness d1 of the resin coating layer 15 are different, and the resin coating layer 15 is unevenly thickened. Furthermore, the arrangement of the multiple cores 12 is formed to substantially coincide with the position of the resin coating layer 15 at the minimum thickness d1. By causing this eccentricity, as will be explained later in the method for manufacturing optical fiber ribbon cores, the arrangement positions of the multiple cores 12 within the optical fiber 10 can be made the same across multiple optical fibers 10 in the rotational direction around the central axis G2 of the glass fiber 11. As a result, in a vertical cross-section of the optical fiber 10, the relationship between the reference line connecting the locations of the minimum and maximum thicknesses d1 and d2 in the resin coating layer 15 and the central axis G2 of the glass fiber 11, and the arrangement positions of the multiple cores 12 in the rotational direction around the central axis G2 of the glass fiber 14 is the same for each of the multiple optical fibers 10. Furthermore, for example, in Figure 1, the orientation is aligned so that the minimum thickness d1 of the resin coating layer 15 is located on the lower side in all cases. As a result, in the optical fiber ribbon 1, the rotational position of the core 12 in all optical fibers 10 is approximately the same.

[0025] The uniformity rate [%] of the resin coating layer 15, which indicates the state of uneven thickness, is calculated based on (minimum thickness d1 / maximum thickness d2) × 100. In this embodiment, the uniformity rate of the resin coating layer 15 of the optical fiber 10 is, for example, 80% or less. By having a uniformity rate of 80% or less, the arrangement positions of the cores 12 in multiple optical fibers 10 can be easily made the same, as will be explained later in the method for manufacturing optical fiber ribbon cores. Furthermore, the smaller the uniformity rate of the resin coating layer 15 of the optical fiber 10 is than 80%, the easier it is to align the arrangement positions of multiple cores, but the uniformity rate of the resin coating layer 15 may be, for example, 60% or more. By having a uniformity rate of 60% or more, it is possible to prevent an increase in the transmission loss of light transmitted through the glass fiber 11 arranged inside the optical fiber 10. That is, by having a uniformity rate of 60% or more and 80% or less, the core can be easily aligned without increasing the transmission loss. The uniformity rate of the resin coating layer 15 may be further 65% or more and 75% or less. In this case, the core 12 in each optical fiber 10 becomes easier to align, and an increase in transmission loss can be prevented. When determining the minimum thickness d1 and maximum thickness d2, as shown in Figure 3, the thickness of the resin coating layer 15 at 45-degree intervals around the central axis G2 of the glass fiber 11 may be determined, and the minimum and maximum thicknesses among them may be used to calculate the minimum and maximum thicknesses. However, they may also be determined by other methods.

[0026] Here, with reference to Figures 4 and 5, the manufacturing method of the optical fiber ribbon core 1 will be described. To manufacture the optical fiber ribbon core 1, first, each of the multiple optical fibers 10 is produced by drawing them from a glass preform in a drawing furnace. Various known methods for drawing multicore fibers can be used in this drawing process. However, when applying and curing the resin coating layer 15 (primary resin layer 16 and secondary resin layer 17) to the glass fiber 11, the die for resin application is offset from the axis in the normal drawing method. Furthermore, using a known method, the arrangement positions of the multiple cores are controlled so that they substantially coincide with the offset position. As a result, the resin coating layer 15 is formed in an offset (eccentric) state relative to the glass fiber 11, and an optical fiber 10 with no thickness variation shown in Figure 2 is produced. Note that there is a predetermined relationship between the thickness variation portion of the resin coating layer 15 (for example, portion d1) and the position of each core 12 in the rotational direction, and this relationship is the same for each optical fiber 10.

[0027] Next, once the preparation of multiple optical fibers 10 (for example, 12 optical fibers 10) is complete, the tape forming device 20 shown in Figure 4 integrates the multiple optical fibers 10 to form a tape core. Specifically, a predetermined number of optical fibers 10 are prepared, wound on each roll 21. For example, when producing the optical fiber tape core 1 shown in Figure 1, 12 rolls 21 of optical fibers 10 are prepared. Then, the optical fibers 10 are pulled out from each roll 21, passed through the roller 22, and folded downwards by the roller 23. Multiple optical fibers 10 and each roll 21 are installed sequentially at predetermined intervals (in Figure 4, some of the rolls 21 are shown, and others are omitted). Each roller 23 is provided with a wall portion 24 that restricts lateral movement when feeding the optical fibers 10, as shown in Figure 5. In the optical fiber 10, the glass fiber 11 is eccentric with respect to the resin coating layer 15. When such optical fibers 10 are transported via each roller 23, as shown in the enlarged portion of Figure 4, the glass fiber 11 gradually moves inward (downward) toward the center of the roller 23. This occurs similarly in the transport of all optical fibers 10. As a result, the optical fibers 10 are aligned such that the glass fibers 11 are biased (eccentric) to one side, as shown in Figure 1. This inward movement of the glass fibers 11 is caused by a force acting on the glass fibers 11 toward the center of the roller when the optical fibers 10 are passed through the roller 23 under tension. This is because the glass portion, the glass fiber 11, is more energetically stable when positioned closer to the roller 23.

[0028] Next, the roller 23 aligns the eccentric portions of the glass fibers 11 in the optical fibers 10 inward. Then, these optical fibers 10 pass through the tape-forming resin coating device 25, and are cured by the curing device 26 to form a tape. That is, as shown in Figure 1, the tape-forming resin 5 connects the optical fibers 10 to each other in a parallel arrangement. At this time, the position of the core 12 in the rotational direction of each optical fiber 10 is aligned in the same way between fibers. Thus, an optical fiber tape core 1 is manufactured with the core positions of the optical fibers 10 aligned as shown in Figure 1.

[0029] As described above, in the optical fiber ribbon cable 1 according to this embodiment, the uniformity of the resin coating layer 15 is 80% or less in each of the multiple optical fibers 10. That is, in this optical fiber ribbon cable 1, the resin coating layer 15 in each optical fiber 10 is intentionally made to have a uniform thickness. By aligning the position of each core 12 in the rotational direction around the central axes G1 and G2 of the optical fiber 10 with the uniform thickness portion (minimum thickness d1, maximum thickness d2), the core 12 in each optical fiber 10 can be easily and reliably positioned when multiple optical fibers 10 are formed into a ribbon. As a result, the core arrangement of each optical fiber 10 included in the optical fiber ribbon cable 1 becomes uniform, and the optical connection in the optical fiber ribbon cable 1 can be stabilized.

[0030] Although embodiments of the present disclosure have been described in detail above, the present disclosure is not limited to the above embodiments and can be applied to various embodiments. For example, in the above embodiments, the tape resin connecting each optical fiber 10 to each other is formed along the longitudinal direction, but is not limited to this. For example, the tape resin 5 may connect the optical fibers 10 to each other so that they are intermittently connected in the direction in which the multiple optical fibers 10 extend. In this case, individual optical fibers 10 can be removed from the tape core when connecting, making it easier to perform various adjustments.

[0031] 1…Optical fiber ribbon core 5…Tape resin 10…Optical fiber 11…Glass fiber 12…Core 13…Cladding 15…Resin coating layer 16…Primary resin layer 17…Secondary resin layer 20…Tape forming device 21…Roll 22,23…Rollers 24…Wall section 25…Coating device 26…Curing device G1…Central axis of optical fiber 10 G2…Central axis of glass fiber 11 d1…Minimum thickness d2…Maximum thickness

Claims

1. An optical fiber ribbon cable comprising a plurality of optical fibers, wherein each of the plurality of optical fibers comprises: a glass fiber including a plurality of cores and a cladding surrounding the plurality of cores having a refractive index lower than that of the plurality of cores; and a resin coating layer in contact with and surrounding the glass fiber, wherein when the ratio of the minimum radial thickness d1 of the resin coating layer to the maximum radial thickness d2 of the resin coating layer in a cross section perpendicular to the central axis of the optical fiber, (d1 / d2) × 100, is defined as the uniformity of the resin coating layer [%], the uniformity of the resin coating layer is 80% or less for each of the plurality of optical fibers.

2. The optical fiber ribbon cable according to claim 1, wherein in each of the plurality of optical fibers, the uniform thickness ratio of the resin coating layer is 60% or more.

3. The optical fiber ribbon core according to claim 1 or claim 2, wherein in each of the plurality of optical fibers, the uniform thickness ratio of the resin coating layer is 65% or more and 75% or less.

4. The optical fiber ribbon cable according to any one of claims 1 to 3, wherein the plurality of optical fibers are intermittently connected to one another in the direction of extension of the optical fibers.

5. The optical fiber ribbon cable according to any one of claims 1 to 4, wherein, in the vertical cross-section of the optical fiber, the relationship between a reference line connecting the location where at least one of the minimum thickness d1 and the maximum thickness d2 in the resin coating layer is located and the central axis of the glass fiber, and the arrangement locations of the plurality of cores in the rotational direction about the central axis of the glass fiber, is the same for each of the plurality of optical fibers.

6. In each of the plurality of optical fibers, the position where the minimum thickness d1 of the resin coating layer is located is the same with respect to the central axis of the glass fiber in the vertical cross-section of the optical fiber, according to any one of claims 1 to 5.

7. A method for manufacturing optical fiber tape cores, comprising the steps of drawing each of a plurality of optical fibers and forming the plurality of optical fibers into a tape, wherein each of the plurality of optical fibers comprises a glass fiber including a plurality of cores and a cladding surrounding the plurality of cores having a refractive index lower than that of the plurality of cores, and a resin coating layer in contact with and surrounding the glass fiber, and in the drawing step, when (d1 / d2) × 100, which is the ratio of the minimum radial thickness d1 of the resin coating layer to the maximum radial thickness d2 of the resin coating layer in a cross section perpendicular to the central axis of the optical fiber, is defined as the uniformity rate [%] of the resin coating layer, each of the plurality of optical fibers is drawn such that the uniformity rate of the resin coating layer is 80% or less for each of the plurality of optical fibers, and the arrangement of the plurality of cores coincides with the position of the resin coating layer that has the minimum thickness d1.

8. The method for manufacturing an optical fiber ribbon core according to claim 7, wherein in the line drawing step, the thickness of the resin coating layer is made uneven by shifting the die used to apply the resin coating layer.

9. The method for manufacturing an optical fiber ribbon core according to claim 7 or claim 8, wherein in the tape-forming step, the thickness direction of the plurality of optical fibers is aligned and the plurality of optical fibers are connected with a tape-forming resin.

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