Optical fiber ribbon core wire

Abstract

An optical fiber ribbon according to the present invention is provided with: a plurality of optical fibers arrayed along an array direction that is perpendicular to the lengthwise direction; and a plurality of joint sections. The plurality of joint sections are each formed between a pair of the optical fibers that are adjacent to each other with respect to the array direction. The plurality of joint sections are disposed non-contiguously with respect to the lengthwise direction and the array direction. The optical fiber ribbon has a first high-density region and a low-density region that are adjacent to each other with respect to the lengthwise direction. In the first high-density region, among the plurality of joint sections, at least two joint sections having mutually different positions with respect to the lengthwise direction and the array direction are disposed. The number density of the joint sections in the low-density region is lower than the number density of the joint sections in the first high-density region. The maximum value of the amount of increase in transmission loss that occurs with light having a wavelength of 1550 nm and propagated through the optical fibers in a kink test is not greater than 1 dB.

Description

Technical Field

[0001] The present invention relates to an optical fiber ribbon core wire. This application claims priority based on US 63 / 251,692 filed in the United States on October 4, 2021, the content of which is incorporated herein by reference.

Background Art

[0002] Conventionally, an optical fiber ribbon core wire including a plurality of optical fibers and a plurality of connecting portions has been known (see, for example, Patent Document 1). The plurality of optical fibers are arranged in an arrangement direction perpendicular to the longitudinal direction. The plurality of connecting portions connect two adjacent optical fibers in the arrangement direction. Patent Document 1 discloses an optical fiber ribbon core wire having a connection region where the connecting portions are arranged and a non-connection region where the connecting portions are not arranged.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, when the optical fiber ribbon core wire as described above is formed into a cable, a compressive stress along the longitudinal direction may be applied to the optical fiber ribbon core wire. Here, in the non-connection region of the optical fiber ribbon core wire, since the optical fiber is not fixed by the connecting portion, the optical fiber may be curved by the compressive stress, and a sharp bend (so-called kink) may occur. The occurrence of such a kink can cause an increase in the transmission loss of light propagating through the optical fiber.

[0005] The present invention has been made in consideration of such circumstances, and an object thereof is to provide an optical fiber ribbon core wire capable of suppressing an increase in transmission loss due to kinks.

Means for Solving the Problem

[0006] In order to solve the above problems, an optical fiber ribbon core wire according to one aspect of the present invention includes a plurality of optical fibers arranged in an arrangement direction perpendicular to the longitudinal direction, and a plurality of connecting portions formed between two adjacent optical fibers in the arrangement direction and connecting the two optical fibers. The plurality of connecting portions are intermittently arranged in the longitudinal direction and the arrangement direction. The optical fiber ribbon core wire has a first high-density region and a low-density region adjacent to each other in the longitudinal direction. In the first high-density region, at least two connecting portions having different positions in the longitudinal direction and the arrangement direction among the plurality of connecting portions are arranged. The number density of the connecting portions in the low-density region is lower than the number density of the connecting portions in the first high-density region. When the edge of the low-density region on the side opposite to the first high-density region is brought closer to the first high-density region along the longitudinal direction in a state where the first high-density region is fixed and a tension of 100 gf is applied to the entire optical fiber ribbon core wire, the maximum value of the increase amount of the transmission loss generated in the light with a wavelength of 1550 nm propagating through the optical fiber is 1 dB or less.

Advantages of the Invention

[0007] According to the above aspect of the present invention, it is possible to provide an optical fiber ribbon core wire capable of suppressing an increase in transmission loss due to kinking.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3A

Figure 3B

Figure 3C

Figure 4A

Figure 4B

Figure 4C

Figure 5

Figure 6

Figure 7

Figure 8

Embodiments for Carrying Out the Invention

[0009] (First Embodiment) Hereinafter, the optical fiber ribbon core wire according to the first embodiment will be described with reference to the drawings. As shown in FIG. 1, the optical fiber ribbon core wire 1A includes a plurality of optical fibers 20. The plurality of optical fibers 20 are arranged in a direction perpendicular to the longitudinal direction of each optical fiber 20. The optical fiber ribbon core wire 1A further includes a plurality of connecting portions 10 that connect two adjacent optical fibers 20 among the plurality of optical fibers 20. In the example of FIG. 1, the optical fiber ribbon core wire 1A includes 12 optical fibers 20. In this specification, each optical fiber 20 may be referred to as the first fiber 201 to the twelfth fiber 212 in order. However, the number of optical fibers 20 can be appropriately changed.

[0010] (Definition of Directions) Here, in the present embodiment, an XYZ orthogonal coordinate system is set to explain the positional relationship of each component. The X-axis direction is the longitudinal direction of the optical fiber ribbon core wire 1A. The Y-axis direction is the direction in which a plurality of optical fibers 20 are arranged. The Z-axis direction is the direction orthogonal to both the X-axis direction and the Y-axis direction. In this specification, the X-axis direction may be referred to as the longitudinal direction X, the Y-axis direction may be referred to as the arrangement direction Y, and the Z-axis direction may be referred to as the plane orthogonal direction Z. One direction along the longitudinal direction X is referred to as the +X direction or the right direction. The direction opposite to the +X direction is referred to as the -X direction or the left direction. Along the arrangement direction Y, the direction from the 12th fiber 212 to the 1st fiber 201 is referred to as the +Y direction or the upper direction. The direction opposite to the +Y direction is referred to as the -Y direction or the lower direction.

[0011] As shown in FIG. 2, each optical fiber 20 has a waveguide 21 and a coating portion 22. The waveguide 21 is formed of, for example, glass. The waveguide 21 (glass portion) has a core 21a and a cladding 21b. The cladding 21b covers the core 21a. The coating portion 22 is formed of a resin or the like and covers the glass portion 21. As a specific material of the coating portion 22, for example, a UV curable resin can be used. The coating portion 22 according to the present embodiment has a primary layer 22a and a secondary layer 22b. The primary layer 22a covers the glass portion 21 (cladding 21b). The secondary layer 22b covers the primary layer 22a.

[0012] As shown in FIG. 1, each optical fiber 20 extends along the longitudinal direction X. A plurality of optical fibers 20 are arranged in the arrangement direction Y. The pitch P1 at which the plurality of optical fibers 20 are arranged in the arrangement direction Y is larger than the diameter (fiber diameter) R of each optical fiber 20. In other words, a gap G is provided between two adjacent optical fibers 20 in the arrangement direction Y.

[0013] The plurality of optical fibers 20 includes a pair of outermost fibers located outermost in the array direction Y and a plurality of intermediate fibers. The plurality of intermediate fibers are located between the pair of outermost fibers in the array direction Y. In the example of FIG. 1, the first fiber 201 and the twelfth fiber 212 correspond to the outermost fibers, and the second fiber 202 to the eleventh fiber 211 correspond to the intermediate fibers.

[0014] Each of the plurality of connecting portions 10 is formed in the gap G. The plurality of connecting portions 10 are intermittently arranged in the longitudinal direction X and the array direction Y. In this specification, the term "intermittently arranged" includes both cases where the intervals between the plurality of connecting portions 10 are constant and cases where they are not constant. Each connecting portion 10 connects two optical fibers 20 adjacent to the gap G in which the connecting portion 10 is arranged. More specifically, each connecting portion 10 connects the coating portions 22 of two optical fibers 20 adjacent to the gap G in which the connecting portion 10 is arranged. That is, in the optical fiber ribbon core wire 1A according to the present embodiment, two optical fibers 20 adjacent in the array direction Y are intermittently connected to each other in the longitudinal direction X by the plurality of connecting portions 10. The optical fiber ribbon core wire 1A is also referred to as an intermittent fixed ribbon core wire 1A. As the connecting portion 10, any material capable of connecting the coating portions 22 of adjacent optical fibers 20 can be adopted. For example, a UV curable resin may be used as the connecting portion 10. In the present embodiment, the dimensions in the longitudinal direction X and the array direction Y are substantially equal to each other among the plurality of connecting portions 10.

[0015] The plurality of connecting portions 10 also includes a plurality of outermost connecting portions 10a in contact with either one of the pair of outermost fibers 201, 212 and a plurality of intermediate connecting portions 10b connecting the intermediate fibers 202 to 211. In the example of FIG. 1, each outermost connecting portion 10a connects the first fiber 201 and the second fiber 202, or the eleventh fiber 211 and the twelfth fiber 212. Each intermediate connecting portion 10b connects the second fiber 202 to the eleventh fiber 211.

[0016] The optical fiber ribbon core wire 1A according to this embodiment has a plurality of high-density regions D and a plurality of low-density regions S. The plurality of high-density regions D and the plurality of low-density regions S are alternately arranged in the longitudinal direction X and are in contact with each other. In this embodiment, the plurality of high-density regions D include a first high-density region D1 and a second high-density region D2. The first high-density region D1 and the second high-density region D2 are arranged at different positions from each other. Further, the first high-density region D1 and the second high-density region D2 are in contact with the same low-density region S. In other words, the first high-density region D1 and the second high-density region D2 are arranged so as to sandwich one low-density region S in the longitudinal direction X.

[0017] In this embodiment, each high-density region D is formed in a substantially rectangular shape. Similarly, each low-density region S is formed in a substantially rectangular shape. In this specification, each of the boundary lines between the high-density region D and the low-density region S may be particularly referred to as a boundary B. In this embodiment, each boundary B is a line segment parallel to the arrangement direction Y. At least one connecting portion 10 (boundary connecting portion 10c) is in contact with each boundary B.

[0018] In this specification, among the plurality of connecting portions 10 included in each high-density region D, the connecting portion 10 located at the rightmost position may be referred to as the right-end connecting portion 10R. Similarly, among the plurality of connecting portions 10 included in each high-density region D, the connecting portion 10 located at the leftmost position may be referred to as the left-end connecting portion 10L. In the example of FIG. 1, each high-density region D has six right-end connecting portions 10R and six left-end connecting portions 10L.

[0019] In this specification, for each high-density region D, the dimension LD in the longitudinal direction X is defined as follows. That is, the dimension LD is the distance in the longitudinal direction X between the right end of the right-end connecting portion 10R included in the high-density region D and the left end of the left-end connecting portion 10L included in the high-density region D. In the example of FIG. 1, among the plurality of high-density regions D, the dimension in the longitudinal direction X is substantially constant with the dimension LD.

[0020] In this specification, for each low-density region S, the dimension LS in the longitudinal direction X is defined as follows. That is, the dimension LS is the distance in the longitudinal direction X between the right end of the right-end connecting portion 10R included in the high-density region D adjacent to the left side of the low-density region S and the left end of the left-end connecting portion 10L included in the high-density region D adjacent to the right side of the low-density region S. In the example of FIG. 1, among the plurality of low-density regions S, the dimension in the longitudinal direction X is substantially constant with the dimension LS. Note that the dimension LD may not be constant among the plurality of high-density regions D, and the dimension LS may not be constant among the plurality of low-density regions S either.

[0021] Hereinafter, the configuration of each high-density region D and the configuration of each low-density region S will be described.

[0022] In each high-density region D, at least two connecting portions 10 having different positions in the longitudinal direction X and the arrangement direction Y among the plurality of connecting portions 10 are arranged. In the example of FIG. 1, 28 connecting portions 10 are arranged in each high-density region D. In the example of FIG. 1, the arrangement pattern of the 28 connecting portions 10 included in each high-density region D is substantially the same among the plurality of high-density regions D. Note that the number of connecting portions 10 included in each high-density region D can be appropriately changed, and as long as it is two or more, the number of connecting portions 10 is not limited.

[0023] Hereinafter, in this specification, the connecting portion 10 located at the boundary B between the high-density region D and the low-density region S is referred to as the boundary connecting portion 10c, and the connecting portion 10 away from the boundary B is referred to as the non-boundary connecting portion 10d. In the present embodiment, each high-density region D has a plurality of boundary connecting portions 10c and non-boundary connecting portions 10d. For example, the first high-density region D1 has a plurality of first boundary connecting portions 10c1, and the second high-density region D2 has a plurality of second boundary connecting portions 10c2. Here, the plurality of first boundary connecting portions 10c1 and the plurality of second boundary connecting portions 10c2 are in contact with the same low-density region S.

[0024] The previously defined right-end connection part 10R and left-end connection part 10L are included in a plurality of boundary connection parts 10c. In other words, all the right-end connection parts 10R and left-end connection parts 10L are boundary connection parts 10c. In particular, in the example of FIG. 1, all the boundary connection parts 10c correspond to either the right-end connection part 10R or the left-end connection part 10L. In other words, the boundary connection parts 10c are not shifted from each other in the longitudinal direction X. However, the high-density region D may have a boundary connection part 10c that does not correspond to either the right-end connection part 10R or the left-end connection part 10L. In other words, the boundary connection parts 10c may be shifted from each other in the longitudinal direction X (see also FIG. 5).

[0025] The plurality of boundary connection parts 10c overlap each other in the array direction Y. More specifically, in each high-density region D, all of the plurality of boundary connection parts 10c that are in contact with the same low-density region S overlap each other in the array direction Y. For example, as shown in FIG. 1, all of the plurality of first boundary connection parts 10c1 overlap each other in the array direction Y. In other words, each high-density region D has a rectangular region in which the plurality of boundary connection parts 10c overlap each other in the array direction Y. In this specification, this region is referred to as the "boundary region BA". As shown in FIG. 1, all of the plurality of first boundary connection parts 10c1 are included in the same boundary region BA. The side of the boundary region BA that faces the side opposite to the center of the high-density region D in the longitudinal direction X is located on the boundary B. In other words, the boundary B extends along the side of the boundary region BA that faces the side opposite to the center of the high-density region D in the longitudinal direction X.

[0026] In the example of FIG. 1, each high-density region D has first to fifth columns C1 to C5. The first to fifth columns C1 to C5 are arranged in this order in the direction from left to right. Also, the pitch P2 at which the columns C1 to C5 are arranged is substantially constant. Each of the columns C1 to C5 is parallel to the array direction Y. Each of the first column C1 and the fifth column C5 includes six boundary connection parts 10c. For example, the fifth column C5 of the first high-density region D1 includes six first boundary connection parts 10c1. The first column C1 of the second high-density region D2 includes six second boundary connection parts 10c2. Each of the second column C2 and the fourth column C4 includes five non-boundary connection parts 10d. The third column C3 includes six non-boundary connection parts 10d.

[0027] Here, the number of the first boundary connection parts 10c1 is equal to or greater than the number of the non-boundary connection parts 10d overlapping in the array direction Y. In other words, the number of the non-boundary connection parts 10d overlapping in the array direction Y is equal to or less than the number of the first boundary connection parts 10c1. In the example of FIG. 1, the number of the first boundary connection parts 10c1 is six, the number of the non-boundary connection parts 10d included in each of the columns C2 and C4 of each high-density region D is five, and the number of the non-boundary connection parts 10d included in the third column C3 is six. Therefore, the number of the non-boundary connection parts 10d included in each of the columns C2 to C4 of each high-density region D is six or less. In other words, among the columns C1 to C5, the first column C1 and the fifth column C5 have the largest number of the connection parts 10 included in the column.

[0028] Also, in each high-density region D, all of the plurality of optical fibers 20 are in contact with any one of the plurality of boundary connection portions 10c. In other words, all of the plurality of optical fibers 20 are in contact with any one of the plurality of connection portions 10 included in the first column C1 or the fifth column C5. For example, in the first high-density region D1, all of the plurality of optical fibers 20 are in contact with any one of the plurality of first boundary connection portions 10c1. In the second high-density region D2, all of the plurality of optical fibers 20 are in contact with any one of the plurality of second boundary connection portions 10c2. Further, in each high-density region D, the gap G in which the connection portions 10 included in the first column C1, the third column C3, and the fifth column C5 are located and the gap G in which the connection portions 10 included in the second column C2 and the fourth column C4 are located are shifted in the arrangement direction Y. Thereby, in each high-density region D, all of the plurality of optical fibers 20 are connected to each other by the connection portions 10.

[0029] Also, the arrangement pattern of the plurality of boundary connection portions 10c in contact with the left side of the low-density region S and the arrangement pattern of the plurality of boundary connection portions 10c in contact with the right side of the low-density region S are the same as each other. In other words, the plurality of boundary connection portions 10c in contact with a certain low-density region S are arranged to be symmetric with respect to the left and right with respect to the low-density region S. For example, the arrangement pattern of the plurality of second boundary connection portions 10c2 is the same as the arrangement pattern of the plurality of first boundary connection portions 10c1. Note that the phrase "the arrangement pattern of the plurality of first boundary connection portions 10c1" means the position of each first boundary connection portion 10c1 in the arrangement direction Y. The phrase "the arrangement pattern of the plurality of second boundary connection portions 10c2" means the position of each second boundary connection portion 10c2 in the arrangement direction Y.

[0030] Also, in each high-density region D, at least one of the plurality of boundary connecting portions 10c connects the outermost fibers 201 and 212 and the intermediate fibers 202 and 211. In other words, the plurality of boundary connecting portions 10c includes at least one outermost connecting portion 10a. In the example of FIG. 1, each high-density region D includes a boundary connecting portion 10c that connects the first fiber 201 and the second fiber 202, and a boundary connecting portion 10c that connects the eleventh fiber 211 and the twelfth fiber 212. Further in other words, each high-density region D includes a boundary connecting portion 10c that contacts the first fiber 201 and a boundary connecting portion 10c that contacts the twelfth fiber 212. Note that the number of boundary connecting portions 10c that connect the outermost fibers 201 and 212 and the intermediate fibers 202 and 211 may be 1 or less.

[0031] The number density of the connecting portions 10 in each low-density region S is lower than the number density of the connecting portions 10 in each high-density region D. Note that the "number density of the connecting portions 10 in the low-density region S" is a value obtained by dividing the number of connecting portions 10 included in the low-density region S by the area of the low-density region S. The "number density of the connecting portions 10 in the high-density region D" is a value obtained by dividing the number of connecting portions 10 included in the high-density region D by the area of the high-density region D. In the example of FIG. 1, each low-density region S does not include a connecting portion 10. That is, the number density of the connecting portions 10 in the low-density region S is zero. However, the low-density region S may include a connecting portion 10.

[0032] Incidentally, generally, when an optical fiber ribbon core wire is cabled or the like, a compressive stress along the longitudinal direction may be applied to the optical fiber ribbon core wire. Here, when the optical fiber ribbon core wire has a low-density region with a small number of connection parts, the optical fiber may bend in the low-density region due to the above compressive stress, and a sharp bend (so-called kink) may occur. The occurrence of such a kink can lead to an increase in the transmission loss of the light propagating through the optical fiber. In addition, a force may be applied to the optical fiber ribbon core wire to twist it around a rotation axis parallel to the longitudinal direction. When the optical fiber ribbon core wire is twisted, minute bends (so-called microbends) may occur in the optical fiber in the low-density region, and an increase in transmission loss may occur.

[0033] To address these issues, the optical fiber ribbon core wire 1A according to this embodiment is configured such that the maximum value of the increase in the amount of transmission loss generated in the light with a wavelength of 1550 nm propagating through the optical fiber 20 in a kink test (details will be described later) is 1 dB or less. In addition, the optical fiber ribbon core wire 1A according to this embodiment is configured such that the increase in the amount of transmission loss generated in the light with a wavelength of 1550 nm propagating through the optical fiber 20 in a twist test (details will be described later) is 1 dB or less. Hereinafter, using specific test examples, a specific configuration will be described in which the maximum value of the increase in the amount of transmission loss in the kink test is 1 dB or less and the increase in the amount of transmission loss in the twist test is 1 dB or less. However, the optical fiber ribbon core wire 1A does not necessarily have to be configured such that the increase in the amount of transmission loss in the twist test is 1 dB or less.

[0034] (Test Example 1: Kink Test) A plurality of optical fiber ribbon cores were prepared in which the Young's modulus of the primary layer 22a and the dimension LS in the longitudinal direction X of the low-density region S were different from each other. Then, a kink test was performed on each optical fiber ribbon core. The Young's modulus of the secondary layer 22b and the dimension LD in the longitudinal direction X of the high-density region D were considered to be the same among the plurality of prepared optical fiber ribbon cores. Specifically, the Young's modulus of the secondary layer 22b was considered to be the same at a certain value of 900 MPa or more, and the dimension LD of the high-density region D was considered to be the same at 4.5 cm.

[0035] Here, the "kink test" is a test for examining the increase in the transmission loss generated in the light with a wavelength of 1550 nm propagating through the optical fiber 20 when, with the first high-density region D1 fixed and a tension of 100 gf applied to the entire optical fiber ribbon core, the edge (boundary B) of the low-density region S on the side opposite to the first high-density region D1 is brought closer to the first high-density region D1 along the longitudinal direction X.

[0036] Specifically, in this test example, the kink test was performed in the following procedure. First, each of the plurality of optical fibers 20 constituting the optical fiber ribbon core was linearly extended in the longitudinal direction X, and the plurality of optical fibers 20 were arranged in the arrangement direction Y. That is, the optical fiber ribbon core was flattened so that the optical fiber ribbon core did not curl or twist. In this state, the first high-density region D1 was fixed to a first fixture (not shown), and the second high-density region D2 was fixed to a second fixture (not shown). As a result, a situation was realized in which the boundary B between the first high-density region D1 and the low-density region S could not move relative to the first fixture, and the boundary B between the second high-density region D2 and the low-density region S could not move relative to the second fixture. Then, a load (tension) of 100 gf was applied in the longitudinal direction X to the entire optical fiber ribbon core (including the low-density region S located between the two fixtures). This state was set as the initial state.

[0037] Next, the second fixture was brought closer to the first fixture by a predetermined distance along the longitudinal direction X. Then, a power meter connected to both ends of the optical fiber tape core wire was used to measure the increase in the transmission loss generated in the light with a wavelength of 1550 nm propagating through the optical fiber 20. In other words, the state in which the second fixture was brought closer to the first fixture by a predetermined distance was compared with the initial state in which the second fixture was not brought closer to the first fixture, and the increase in the transmission loss generated in the light with a wavelength of 1550 nm was measured.

[0038] Figure 3A is a graph summarizing the results of the kink test for an optical fiber tape core wire using an optical fiber a with a Young's modulus of the primary layer 22a of 0.5 MPa or more. Note that the "kink length" means the distance by which the second fixture is brought closer to the first fixture (the moving distance from the initial state). Figure 3B is a graph summarizing the results of the kink test for an optical fiber tape core wire using an optical fiber b with a Young's modulus of the primary layer 22a of less than 0.5 MPa. Tables 1 and 2 are tables summarizing the respective plotted points shown in Figures 3A and 3B. Figure 3C is a graph summarizing the maximum values of the increase in the transmission loss in each optical fiber tape core wire. Note that Figure 3C is a semi-logarithmic graph.

[0039]

Table 1

[0040]

Table 2

[0041] As shown in Figure 3C, in both the optical fiber tape core wire using optical fiber a and the optical fiber tape core wire using optical fiber b, the larger the dimension LS in the longitudinal direction X of the low-density region S, the smaller the maximum value of the increase in the transmission loss. This is presumably because the larger the dimension LS of the low-density region S, the easier it is for the optical fiber 20 to deform so as to relieve its own bending, and the less likely it is for a sharp bend (kink) to occur.

[0042] Therefore, by setting the dimension LS of the low-density region S to be relatively large to some extent, an optical fiber ribbon core wire can be realized that suppresses the increase in transmission loss due to kinks. More specifically, by setting the dimension LS in the longitudinal direction X of the low-density region S to be 5.0 cm or more, regardless of the Young's modulus of the primary layer 22a, the maximum value of the increase in the amount of transmission loss in the kink test can be made 1 dB or less. Further, by setting the dimension LS in the longitudinal direction X of the low-density region S to be 6.0 cm or more, regardless of the Young's modulus of the primary layer 22a, the maximum value of the increase in the amount of transmission loss in the kink test can be made 0.1 dB or less.

[0043] (Test Example 2: Twisting Test) A plurality of optical fiber ribbon core wires were prepared under the same conditions as in Test Example 1. Then, a twisting test was performed on each optical fiber ribbon core wire.

[0044] Here, the "twisting test" is a test for examining the increase in the amount of transmission loss that occurs in the light with a wavelength of 1550 nm propagating through the optical fiber 20 when the first high-density region D1 is fixed and the edge (boundary B) on the side opposite to the first high-density region D1 of the low-density region S is rotated around a rotation axis parallel to the longitudinal direction X while a tension of 100 gf is applied to the entire optical fiber ribbon core wire.

[0045] Specifically, in this test example, the twisting test was performed according to the following procedure. First, each of the plurality of optical fibers 20 that constitute the optical fiber ribbon core wire extends linearly in the longitudinal direction X, and these plurality of optical fibers 20 are arranged in the arrangement direction Y. That is, the optical fiber ribbon core wire was flattened so that the optical fiber ribbon core wire would not curl or twist. In this state, the first high-density region D1 was fixed to a first fixture (not shown), and the second high-density region D2 was fixed to a second fixture (not shown). As a result, a situation was realized in which the boundary B between the first high-density region D1 and the low-density region S could not move relative to the first fixture, and the boundary B between the second high-density region D2 and the low-density region S could not move relative to the second fixture. Then, a load (tension) of 100 gf was applied in the longitudinal direction X to the entire optical fiber ribbon core wire (including the low-density region S located between the two fixtures). This state was set as the initial state.

[0046] Next, the second fixture was rotated by a predetermined angle around a rotation axis parallel to the longitudinal direction X with respect to the first fixture. Then, the increase in the transmission loss generated in the light with a wavelength of 1550 nm propagating through the optical fiber 20 was measured by power meters connected to both ends of the optical fiber ribbon core wire. In other words, the state in which the second fixture was rotated by a predetermined angle with respect to the first fixture was compared with the initial state in which the second fixture was not rotated with respect to the first fixture, and the increase in the transmission loss generated in the light with a wavelength of 1550 nm was measured.

[0047] Figure 4A is a graph summarizing the results of the twisting test for an optical fiber ribbon core wire using an optical fiber a whose Young's modulus of the primary layer 22a is 0.5 MPa or more. Note that the "number of twists" is a parameter corresponding to the rotation angle of the second fixture. That is, the number of twists when the second fixture is rotated by 180° is 0.5 turns, and the number of twists when the second fixture is rotated by 360° is 1 turn. Figure 4B is a graph summarizing the results of the twisting test for an optical fiber ribbon core wire using an optical fiber b whose Young's modulus of the primary layer 22a is less than 0.5 MPa. Tables 1 and 2 are tables summarizing each plotted point shown in Figures 4A and 4B. Figure 4C is a graph summarizing the increase in the transmission loss when the number of twists is 4 for each optical fiber ribbon core wire.

[0048]

Table 3

[0049]

Table 4

[0050] As shown in FIG. 4C, in both the optical fiber ribbon core wire using the optical fiber a and the optical fiber ribbon core wire using the optical fiber b, it is confirmed that the larger the dimension LS in the longitudinal direction X of the low density region S, the smaller the increase amount of the transmission loss. This is presumably because the larger the dimension LS, the smaller the twist angle per unit length of the optical fiber 20, and it becomes difficult for the optical fiber 20 to generate minute bending (microbend). In this test example, the transmission loss has only been measured up to the case of LS = 10 cm, but it is expected that the same tendency will be observed in the region where LS > 10 cm.

[0051] Therefore, by setting the dimension LS of the low density region S to be larger to some extent, an optical fiber ribbon core wire in which the increase in transmission loss due to twisting is suppressed can be realized. In particular, by setting the dimension LS in the longitudinal direction X of the low density region S to be 5.0 cm or more, regardless of the Young's modulus of the primary layer 22a, the maximum value of the increase amount of the transmission loss in the kink test can be made 1 dB or less, and the increase amount of the transmission loss in the twisting test can also be made 1 dB or less.

[0052] Next, other functions of the optical fiber ribbon core wire 1A will be described.

[0053] The optical fiber ribbon core wire 1A according to this embodiment has a plurality of high-density regions D where many connecting portions 10 are arranged, and a plurality of low-density regions S where few connecting portions 10 to be arranged (in particular, in the example of FIG. 1, no connecting portion 10 is arranged). Here, in each high-density region D, a plurality of optical fibers 20 are connected to each other and integrated. The connecting portion 10 also has a role of fixing the pitch P1 at which two adjacent optical fibers 20 are arranged. Therefore, in each high-density region D, the pitch P1 of the optical fibers 20 can be stabilized.

[0054] By the way, generally, when fusion-connecting an optical fiber ribbon core wire to another optical fiber ribbon core wire, a fusion splicer is used. The fusion splicer includes a holder for aligning the optical fiber ribbon core wire. A plurality of grooves extending along the longitudinal direction X are formed in the holder. Inside the fusion splicer, a plurality of optical fibers 20 included in the optical fiber ribbon core wire are inserted one by one into the above-mentioned plurality of grooves for alignment. Here, since the pitch P1 is fixed by the connecting portion 10, when performing a fusion operation on a certain optical fiber ribbon core wire, conventionally, a fusion splicer having grooves arranged at the pitch P1 of the optical fibers in the optical fiber ribbon core wire has been used.

[0055] However, in recent years, research and development for reducing the diameter of the optical fiber 20 has been actively carried out, and accordingly, the pitch P1 of the optical fiber 20 has also been reduced. Therefore, when trying to fusion-connect two optical fiber ribbon core wires with different manufacturing times, since the pitch P1 in both optical fiber ribbon core wires is different from each other, there has been a problem that it becomes difficult to fusion-connect both optical fiber ribbon core wires using a fusion splicer.

[0056] In contrast, the optical fiber ribbon core wire 1A according to this embodiment has a plurality of low-density regions S. In each low-density region S, there is no or few connecting portions 10 that fix the pitch P1 in which the optical fibers 20 are arranged. Therefore, a user who uses the optical fiber ribbon core wire 1A can widen the pitch P1 by pulling the optical fiber ribbon core wire 1A in the arrangement direction Y in the low-density region S. Also, a gap G is provided between two adjacent optical fibers 20 in the arrangement direction Y. Therefore, the user can narrow the pitch P1 by pushing and contracting the optical fiber ribbon core wire 1A in the arrangement direction Y in the low-density region S. Accordingly, by the user changing the pitch P1 in the low-density region S and setting the low-density region S with the changed pitch P1 in a fusion splicer, it becomes possible to use a fusion splicer having a pitch P1 different from that of the optical fiber ribbon core wire 1A. Also, it becomes possible to perform fusion splicing of the optical fiber ribbon core wire 1A to an optical fiber ribbon core wire having a pitch P1 different from that of the optical fiber ribbon core wire 1A.

[0057] As described above, the optical fiber ribbon core wire 1A according to this embodiment includes a plurality of optical fibers 20 arranged in an arrangement direction Y perpendicular to the longitudinal direction X, and a plurality of connecting portions 10 formed between two adjacent optical fibers 20 in the arrangement direction Y and connecting the two optical fibers 20. The plurality of connecting portions 10 are intermittently arranged in the longitudinal direction X and the arrangement direction Y. The optical fiber ribbon core wire 1A has a first high-density region D1 and a low-density region S adjacent to each other in the longitudinal direction X. In the first high-density region D1, at least two connecting portions 10 having different positions in the longitudinal direction X and the arrangement direction Y among the plurality of connecting portions 10 are arranged. The number density of the connecting portions 10 in the low-density region S is lower than the number density of the connecting portions 10 in the first high-density region D1. In the kink test, the maximum value of the increase amount of the transmission loss generated in the light with a wavelength of 1550 nm propagating through the optical fiber 20 is 1 dB or less. With this configuration, it is possible to realize an optical fiber ribbon core wire in which an increase in transmission loss due to kinking is suppressed.

[0058] In addition, in the twisting test of twisting the low-density region S four times, the maximum value of the increase in the transmission loss occurring in the light with a wavelength of 1550 nm propagating through the optical fiber 20 is 1 dB or less. With this configuration, an optical fiber ribbon core wire that suppresses the increase in transmission loss due to twisting can be realized.

[0059] In addition, when the dimension in the longitudinal direction X of the low-density region S is LS, LS ≧ 5.0 cm is satisfied. With this configuration, it is possible to more reliably suppress the increase in transmission loss due to kinking.

[0060] In addition, the pitch P1 at which a plurality of optical fibers 20 are arranged in the arrangement direction Y is larger than the diameter R of each of the plurality of optical fibers 20. With this configuration, when fusing and connecting the optical fiber ribbon core wire 1A, it becomes possible to use a fusion splicer having a pitch P1 different from that of the optical fiber ribbon core wire 1A. Further, it becomes possible to perform fusion splicing of the optical fiber ribbon core wire 1A to an optical fiber ribbon core wire having a pitch P1 different from that of the optical fiber ribbon core wire 1A.

[0061] Generally, the outermost fibers 201 and 212 are more likely to be displaced or bent with respect to the groove of the fusion splicer when setting the optical fiber ribbon core wire 1A in the fusion splicer, as compared with the intermediate fibers 202 to 211. On the other hand, in the optical fiber ribbon core wire 1A according to the present embodiment, the plurality of optical fibers 20 include a pair of outermost fibers 201 and 212 located on the outermost side in the arrangement direction Y, and intermediate fibers 202 to 211 located between the pair of outermost fibers 201 and 212 in the arrangement direction Y. The plurality of connecting portions 10 include a first boundary connecting portion 10c1 located at the boundary B between the first high-density region D1 and the low-density region S. The first boundary connecting portion 10c1 connects the outermost fibers 201 and 212 and the intermediate fibers 202 and 211. According to this configuration, at the boundary B between the high-density region D and the low-density region S, the outermost fibers 201 and 212 can be made difficult to move. Therefore, when setting the optical fiber ribbon core wire 1A in the groove of the fusion splicer, it is possible to suppress the displacement and bending of the outermost fibers 201 and 212 with respect to the groove.

[0062] Further, the plurality of connecting portions 10 include a plurality of first boundary connecting portions 10c1 that are located at the boundary B between the first high-density region D1 and the low-density region S and overlap each other in the arrangement direction Y, and all of the plurality of optical fibers 20 are in contact with any one of the plurality of first boundary connecting portions 10c1. Thereby, at the boundary B between the high-density region D and the low-density region S, all of the optical fibers 20 can be made difficult to move. Therefore, the operation of setting the optical fiber ribbon core wire 1A in the fusion splicer can be made easier.

[0063] Also, the number of the first boundary connecting portions 10c1 is equal to or greater than the number of the non-boundary connecting portions 10d that overlap in the arrangement direction Y. Thereby, at the boundary B between the high-density region D and the low-density region S, the rigidity of the optical fiber ribbon core wire 1A can be increased. Therefore, the operation of setting the optical fiber ribbon core wire 1A in the fusion splicer can be made easier.

[0064] Furthermore, it further has a second high-density region D2 which is arranged at a position different from the first high-density region D1 in the longitudinal direction X and is arranged to be in contact with the low-density region S in the longitudinal direction X. At least two connecting parts 10, which are different from each other in positions in the longitudinal direction X and the arrangement direction Y among the plurality of connecting parts 10, are arranged in the second high-density region D2. The number density of the connecting parts 10 in the second high-density region D2 is higher than the number density of the connecting parts 10 in the low-density region S. Among the plurality of connecting parts 10, there are a plurality of first boundary connecting parts 10c1 which are located at the boundary B between the first high-density region D1 and the low-density region S and overlap with each other in the arrangement direction Y, and a plurality of second boundary connecting parts 10c2 which are located at the boundary B between the second high-density region D2 and the low-density region S and overlap with each other in the arrangement direction Y. The arrangement pattern of the plurality of second boundary connecting parts 10c2 is the same as the arrangement pattern of the plurality of first boundary connecting parts 10c1. Thereby, when setting the optical fiber ribbon core wire 1A in the fusion splicer, the movement of the optical fiber 20 at the left end of the low-density region S and the movement of the optical fiber 20 at the right end of the low-density region S are likely to be interlocked. In other words, the movement of the optical fiber 20 at the left end of the fusion splicer and the movement of the optical fiber 20 at the right end of the fusion splicer are likely to be interlocked. Therefore, the operation of setting the optical fiber ribbon core wire 1A in the fusion splicer can be made easier.

[0065] Moreover, regarding the difference in the number of the connecting parts 10 between the high-density region D and the low-density region S, it also has an effect on the distinguishability between the high-density region D and the low-density region S. Since the number of the connecting parts 10 is large in the high-density region D, the high-density region D can be easily distinguished due to the scattering of external light. On the other hand, in the low-density region S, by pulling the optical fiber ribbon core wire 1A in the arrangement direction Y, the pitch P1 can be widened, and the low-density region S can be easily distinguished. Also, by coloring the resin of the connecting parts 10 or attaching markings, the distinguishability between the high-density region D and the low-density region S can be made more effective.

[0066] Incidentally, when an external force (tearing force) directed outward, for example, in the array direction Y, is applied to the optical fiber ribbon core wire 1A, the connecting portion 10, that is, the boundary connecting portion 10c and the non-boundary connecting portion 10d, may crack. Here, the above-described external force is dispersed to each of the plurality of boundary connecting portions 10c and the plurality of non-boundary connecting portions 10d. At this time, since the boundary connecting portion 10c is adjacent to the low-density region S where the number of connecting portions 10 is small, it is considered that the external force is likely to concentrate compared to the non-boundary connecting portion 10d. In other words, the boundary connecting portion 10c is considered to be more likely to crack than the non-boundary connecting portion 10d.

[0067] The inventors of the present application considered that the longer the dimension LS of the low-density region S is, the more likely the external force is to concentrate on the boundary connecting portion 10c. More specifically, it was considered that the magnitude of the external force concentrated on the boundary connecting portion 10c is proportional to the dimension LS. That is, it is considered that the longer the dimension LS is, the more likely the boundary connecting portion 10c is to crack. For example, when the strength of the boundary connecting portion 10c is 3.0 gf, it is considered necessary to set the dimension LS of the low-density region S to be equal to or less than a certain upper limit value so that the magnitude of the external force concentrated on the boundary connecting portion 10c does not exceed 3.0 gf. Note that the "strength of the connecting portion 10" is the maximum value of the external force that the connecting portion 10 can hold without cracking when an external force is applied to the connecting portion 10.

[0068] The inventors of the present application conducted the following test in order to investigate the upper limit value of the dimension LS at which each connecting portion 10 does not crack. That is, when a predetermined external force was applied to the optical fiber ribbon core wire 1A having the dimension LS of the low-density region S of about 30 mm, it was tested whether the connecting portion 10 (boundary connecting portion 10c) cracked. More specifically, a squeezing test was performed on the optical fiber ribbon core wire 1A having 200 optical fibers 20 at a tension of 130 kgf, a mandrel diameter of 250 mm, and a bending angle of 90°, and it was observed whether the connecting portion 10 was cracked.

[0069] As a result of the test, it was confirmed that when the strength of each connecting portion 10c was less than 1.5 gf for the optical fiber ribbon core wire 1A with the dimension LS of about 30 mm, cracks occurred in the boundary connecting portion 10c. On the other hand, when the strength of each connecting portion 10 was 1.5 gf or more, it was confirmed that cracks did not occur in the non-boundary connecting portion 10d and the boundary connecting portion 10c. From these facts, it is considered that the magnitude of the external force concentrated on the boundary connecting portion 10c in the test was about 1.5 gf. From the results of the test and the above-mentioned consideration that the magnitude of the external force concentrated on the boundary connecting portion 10c is proportional to the dimension LS, the following formula (1) is considered to hold. F [gf] = 1.5 [gf] × LS [mm] / 30 [mm] …(1) However, F is the magnitude of the external force concentrated on the boundary connecting portion 10c under the condition that the dimension of the low-density region S is LS mm.

[0070] In view of the fact that the boundary connecting portion 10c is more likely to crack than the non-boundary connecting portion 10d and the fact that there is variation in the strength of the connecting portion 10, the inventors of the present application considered that it is desirable that the following formula (2) holds in order for no crack to occur in the connecting portion 10. F [gf] ≦ A [gf] - 3S [gf] …(2) However, A is the average value of the strength (tearing strength) of the connecting portion 10, and S is the standard deviation of the strength of the connecting portion 10.

[0071] By combining the above formulas (1) and (2) and eliminating F, the following formula (3) is derived. LS [mm] ≦ 30 [mm] × (A - 3S) [gf] / 1.5 [gf] …(3) That is, by determining the upper limit value of the dimension LS of the low-density region S by formula (3), an optical fiber ribbon core wire 1A in which cracks are less likely to occur in the connecting portion 10 (boundary connecting portion 10c) can be obtained. However, the technical scope of the present invention is not limited to this, and the dimension LS may not satisfy formula (3).

[0072] Alternatively, an upper limit value may be defined for the dimension LS as follows. That is, the dimension LS may be 100 mm or less. The dimension in the longitudinal direction X of the fusion machine is generally about 200 mm. Therefore, considering the case where two optical fiber tape cores 1A are fusion-connected in each other's low-density regions S, it is preferable that the total of the dimensions LS of both low-density regions S is 200 mm or less. This is because when the total of the two dimensions LS exceeds 200 mm, at least one of the low-density regions S protrudes outside the fusion machine, and the operation of setting the optical fiber tape core 1A in the fusion machine becomes complicated. On the other hand, by setting the value of the dimension LS to 100 mm or less, the total of the two dimensions LS can be made 200 mm or less. Thereby, the operation of setting the two optical fiber tape cores 1A in the fusion machine can be made easier.

[0073] Further, according to Japanese Patent Application Laid-Open No. 2013-182157, the strength of the connecting portion 10 is preferably in the range of 1.5 to 21.0 gf. When this is applied to the present embodiment, in view of the variation in the strength of the connecting portion 10, it is desirable that the following formula (4) holds. 1.5[gf]<A - 3S[gf]<A + 3S[gf]<21.0[gf]…(4)

[0074] (Second Embodiment) Next, a second embodiment of the present invention will be described. The basic configuration is the same as that of the first embodiment. Therefore, the same components are denoted by the same reference numerals and their description is omitted, and only the differences will be described. The optical fiber tape core 1B according to the present embodiment shown in FIG. 5 is different from the optical fiber tape core 1A according to the first embodiment in the dimensions and positional relationships of the respective connecting portions 10.

[0075] As shown in FIG. 5, in the present embodiment, in each high-density region D, the dimension (first dimension) d1 of each outermost connecting portion 10a in the longitudinal direction X is larger than the dimension (second dimension) d2 of each intermediate connecting portion 10b in the longitudinal direction X. Also, in each high-density region D, the arrangement interval I1 (first arrangement interval) of the outermost connecting portions 10a in the longitudinal direction X is smaller than the arrangement interval I2 (second arrangement interval) of the intermediate connecting portions 10b in the longitudinal direction X.

[0076] In this case, for example, compared with the case where the dimension d1 and the dimension d2 are equal, the outermost fibers 201 and 212 can be more firmly connected to the intermediate fibers 202 and 211. Similarly, for example, compared with the case where the arrangement interval I1 and the arrangement interval I2 are equal, the outermost fibers 201 and 212 can be more firmly connected to the intermediate fibers 202 and 211. Therefore, when setting the optical fiber ribbon core wire 1B in the groove of the fusion splicer, the possibility of displacement or bending of the outermost fibers 201 and 212 with respect to the groove can be further reduced.

[0077] As described above, in the optical fiber ribbon core wire 1B according to the present embodiment, the dimension d1 of the outermost connecting portion 10a in the longitudinal direction X is larger than the dimension d2 of the intermediate connecting portion 10b in the longitudinal direction X. With this configuration, when setting the optical fiber ribbon core wire 1B in the groove of the fusion splicer, the possibility of displacement or bending of the outermost fibers 201 and 212 with respect to the groove can be further reduced.

[0078] Also, the arrangement interval I1 of the outermost connecting portions 10a in the longitudinal direction X is smaller than the arrangement interval I2 of the intermediate connecting portions 10b in the longitudinal direction X. With this configuration, when setting the optical fiber ribbon core wire 1B in the groove of the fusion splicer, the possibility of displacement or bending of the outermost fibers 201 and 212 with respect to the groove can be more reliably reduced.

[0079] (Third Embodiment) Next, a third embodiment of the present invention will be described. The basic configuration is the same as that of the first embodiment. Therefore, the same components are denoted by the same reference numerals and their description is omitted, and only the differences will be described. The optical fiber ribbon core wire 1C according to the present embodiment shown in FIG. 6 differs from the optical fiber ribbon core wire 1A according to the first embodiment in the dimensions and positional relationships of the respective connecting portions 10.

[0080] As shown in FIG. 6, in the present embodiment, in each high-density region D, the dimension (third dimension) d3 of each boundary connecting portion 10c in the longitudinal direction X is larger than the dimension (fourth dimension) d4 of each non-boundary connecting portion 10d in the longitudinal direction X. For example, in the first high-density region D1, the dimension d3 of the first boundary connecting portion 10c1 in the longitudinal direction X is larger than the dimension d4 of the non-boundary connecting portion 10d in the longitudinal direction X.

[0081] In this case, for example, compared with the case where the dimensions d3 and d4 are equal, the rigidity of the optical fiber ribbon core wire 1C can be increased at the boundary B between the high-density region D and the low-density region S. Therefore, the operation of setting the optical fiber ribbon core wire 1C in the fusion splicer can be made easier.

[0082] As described above, in the optical fiber ribbon core wire 1C according to the present embodiment, the dimension d3 of the first boundary connecting portion 10c1 in the longitudinal direction X is larger than the dimension d4 of the non-boundary connecting portion 10d in the longitudinal direction X. With this configuration, the operation of setting the optical fiber ribbon core wire 1C in the fusion splicer can be made easier.

[0083] In this specification, for example, "substantially equal" includes cases where they can be regarded as equal if manufacturing errors are removed. The same applies to other expressions using "substantially". That is, expressions using "substantially" include cases where the meaning indicated by the words following "substantially" can be considered to hold if manufacturing errors are removed.

[0084] Further, the technical scope of the present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the present invention.

[0085] For example, in the above embodiment, the number of non-boundary connection parts 10d included in each of the columns C2 to C4 of each high-density region D was 6 or less, which was the number of the first boundary connection parts 10c1. However, the configuration of the non-boundary connection parts 10d is not limited to this. The number of non-boundary connection parts 10d included in each of the columns C2 to C4 of each high-density region D may be less than the number of the first boundary connection parts 10c1. To show a specific example, like the optical fiber ribbon core wire 1D shown in FIG. 7, the number of non-boundary connection parts 10d included in the third column C3 may be less than the number of the first boundary connection parts 10c1.

[0086] Also, like the optical fiber ribbon core wire 1E shown in FIG. 8, the boundary connection parts 10c may be shifted from each other in the longitudinal direction X. In other words, the high-density region D may have a boundary connection part 10c that does not correspond to either the right-end connection part 10R or the left-end connection part 10L. In the example of FIG. 8, each high-density region D has three right-end connection parts 10R and three left-end connection parts 10L. Also in the example of FIG. 8, similar to the above embodiment, each high-density region D has a boundary region BA where a plurality of boundary connection parts 10c overlap each other in the arrangement direction Y. And the boundary B extends along the side of the boundary region BA. At this time, similar to the above embodiment, a lower limit value and an upper limit value may be set for the dimension LS. With this configuration, the same operational effects as those of the above embodiment can be obtained.

[0087] For example, in the above embodiment, the optical fiber ribbon core wires 1A to 1C had a plurality of high-density regions D and a plurality of low-density regions S. However, the configuration of the optical fiber ribbon core wires 1A to 1C is not limited to this. For example, the optical fiber ribbon core wires 1A to 1C may have only one high-density region D and only one low-density region S.

[0088] Also, the arrangement patterns of the plurality of connection parts 10 included in each high-density region D may not be the same among the high-density regions D. Similarly, the arrangement patterns of the connection parts 10 included in each low-density region S may not be the same among the low-density regions S.

[0089] Further, the shapes of the regions D and S do not have to be substantially rectangular. In other words, each boundary B does not have to be parallel to the arrangement direction Y. However, generally, since the shape of the fusing machine (holder) is rectangular, a configuration in which the boundary B is parallel to the arrangement direction Y is preferable.

[0090] Also, the plurality of connecting portions 10 included in each high-density region D do not have to form columns C1 to C5. In other words, in each high-density region D, the plurality of connecting portions 10 may be randomly arranged. Similarly, in each low-density region S, the plurality of connecting portions 10 may be randomly arranged.

[0091] Also, a gap G does not have to be provided between two adjacent optical fibers 20 in the arrangement direction Y. In other words, two adjacent optical fibers 20 may be in contact with each other. Even in such a configuration, two adjacent optical fibers 20 can be intermittently connected by the connecting portion 10.

[0092] In addition, within the scope not departing from the gist of the present invention, it is possible to appropriately replace the components in the above-described embodiments with well-known components, and the above-described embodiments and modified examples may be appropriately combined.

Explanation of Reference Numerals

[0093] 1A, 1B, 1C, 1D, 1E... optical fiber ribbon core wire 10... connecting portion 10a... outermost connecting portion 10b... intermediate connecting portion 10c1... first boundary connecting portion 10c2... second boundary connecting portion 10d... non-boundary connecting portion 20... optical fiber 201... first fiber (outermost fiber) 202 to 211... second fiber to 11th fiber (intermediate fiber) 212... 12th fiber (outermost fiber) G... gap D1... first high-density region D2... second high-density region S... low-density region B... boundary P1... pitch R... fiber diameter (diameter) d1 to d4... dimensions I1, I2... arrangement interval X... longitudinal direction Y... arrangement direction

Claims

1. An optical fiber ribbon core wire, comprising: a plurality of optical fibers arranged in an arrangement direction perpendicular to the longitudinal direction; a plurality of connecting portions formed between two adjacent optical fibers in the arrangement direction and connecting the two optical fibers; the plurality of connecting portions are intermittently arranged in the longitudinal direction and the arrangement direction; the optical fiber ribbon core wire has a first high-density region and a low-density region adjacent to each other in the longitudinal direction; at least two connecting portions, whose positions in the longitudinal direction and the arrangement direction are different from each other, among the plurality of connecting portions are arranged in the first high-density region; the number density of the connecting portions in the low-density region is lower than the number density of the connecting portions in the first high-density region; each of the optical fibers has a core formed of glass, a cladding formed of glass and covering the core, a primary layer formed of resin and covering the cladding, and a secondary layer formed of resin and covering the primary layer; when the dimension in the longitudinal direction of the low-density region is LS, LS≧5.0 cm is satisfied; when the edge on the side opposite to the first high-density region of the low-density region is brought closer to the first high-density region along the longitudinal direction in a state where the first high-density region is fixed and a tension of 100 gf is applied to the entire optical fiber ribbon core wire, the maximum value of the increase in transmission loss generated in the light with a wavelength of 1550 nm propagating through the optical fiber is 1 dB or less; an optical fiber ribbon core wire in which the low-density region does not include the connecting portions.

2. The optical fiber ribbon core wire according to claim 1, wherein when the edge on the side opposite to the first high-density region of the low-density region is rotated 4 times around a rotation axis parallel to the longitudinal direction in a state where the first high-density region is fixed and a tension of 100 gf is applied to the entire optical fiber ribbon core wire, the increase in transmission loss generated in the light with a wavelength of 1550 nm propagating through the optical fiber is 1 dB or less.

3. The optical fiber ribbon core wire according to claim 1 or 2, wherein the pitch at which the plurality of optical fibers are arranged in the arrangement direction is larger than the diameter of each of the plurality of optical fibers.

4. The plurality of optical fibers include a pair of outermost fibers located on the outermost side in the arrangement direction and a plurality of intermediate fibers located between the pair of outermost fibers in the arrangement direction. Among the plurality of connecting parts, there are included an outermost connecting part that contacts either one of the pair of outermost fibers, and an intermediate connecting part that connects the two intermediate fibers. The dimension of the outermost connecting part in the longitudinal direction is larger than the dimension of the intermediate connecting part in the longitudinal direction. The optical fiber ribbon core wire according to claim 1 or 2.

5. Among the plurality of optical fibers, there are included a pair of outermost fibers that are located outermost in the arrangement direction, and a plurality of intermediate fibers that are located between the pair of outermost fibers in the arrangement direction. Among the plurality of connecting parts, there are included an outermost connecting part that contacts either one of the pair of outermost fibers, and an intermediate connecting part that connects the two intermediate fibers. The arrangement interval of the outermost connecting part in the longitudinal direction is smaller than the arrangement interval of the intermediate connecting part in the longitudinal direction. The optical fiber ribbon core wire according to claim 1 or 2.

6. Among the plurality of connecting parts, there are included a first boundary connecting part that is located at the boundary between the first high-density region and the low-density region, and a non-boundary connecting part that is away from the boundary. The dimension of the first boundary connecting part in the longitudinal direction is larger than the dimension of the non-boundary connecting part in the longitudinal direction. The optical fiber ribbon core wire according to claim 1 or 2.

7. Among the plurality of optical fibers, there are included a pair of outermost fibers that are located outermost in the arrangement direction, and intermediate fibers that are located between the pair of outermost fibers in the arrangement direction. Among the plurality of connecting parts, there is included a first boundary connecting part that is located at the boundary between the first high-density region and the low-density region. The first boundary connecting part connects the outermost fiber and the intermediate fiber. The optical fiber ribbon core wire according to claim 1 or 2.

8. Among the plurality of connecting parts, there are included a plurality of first boundary connecting parts that are located at the boundary between the first high-density region and the low-density region and overlap each other in the arrangement direction. All of the plurality of optical fibers are in contact with any one of the plurality of first boundary connecting parts. The optical fiber ribbon core wire according to claim 1 or 2.

9. Among the plurality of connecting parts, there are included a plurality of first boundary connecting parts that are located at the boundary between the first high-density region and the low-density region and overlap each other in the arrangement direction, and one or more non-boundary connecting parts that are away from the boundary. The number of the first boundary connection parts is equal to or greater than the number of the non-boundary connection parts overlapping in the array direction, the optical fiber ribbon core wire according to claim 1 or 2.

10. It further has a second high-density region which is arranged at a position different from the first high-density region in the longitudinal direction and is arranged so as to be in contact with the low-density region in the longitudinal direction. In the second high-density region, at least two connection parts, whose positions in the longitudinal direction and the array direction among the plurality of connection parts are different from each other, are arranged. The number density of the connection parts in the second high-density region is higher than the number density of the connection parts in the low-density region. Among the plurality of connection parts, there are included a plurality of first boundary connection parts which are located at the boundary between the first high-density region and the low-density region and overlap each other in the array direction, and a plurality of second boundary connection parts which are located at the boundary between the second high-density region and the low-density region and overlap each other in the array direction. The arrangement pattern of the plurality of second boundary connection parts is the same as the arrangement pattern of the plurality of first boundary connection parts, the optical fiber ribbon core wire according to claim 1 or 2.

11. When the dimension in the longitudinal direction of the low-density region is LS, the average value of the tearing strength of the connection parts is A, and the standard deviation of the tearing strength of the connection parts is S, LS [mm] ≦ 30 [mm] × (A - 3S) [gf] / 1.5 [gf] holds, the optical fiber ribbon core wire according to claim 1 or 2.

12. When the average value of the tearing strength of the connection parts is A and the standard deviation of the tearing strength of the connection parts is S, 1.5 [gf] < A - 3S [gf] < A + 3S [gf] < 21.0 [gf] holds, the optical fiber ribbon core wire according to claim 1 or 2.

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