WO2023127421A1

WO2023127421A1 - Optical fiber assembly, optical fiber cable, and method for manufacturing optical fiber assembly

Info

Publication number: WO2023127421A1
Application number: PCT/JP2022/044827
Authority: WO
Inventors: 正敏大野; 拓哉植草; 耕司滝口; 尚人淺村; 大典佐藤; 彰鯰江; 健大里
Original assignee: 株式会社フジクラ
Priority date: 2021-12-27
Filing date: 2022-12-06
Publication date: 2023-07-06
Also published as: TW202331326A

Abstract

This optical fiber assembly comprises a plurality of optical fibers, the position of the center of gravity Gall of all of the optical fibers in a cross-sectional view changing in the longitudinal direction.

Description

Optical fiber assembly, optical fiber cable, and method for manufacturing optical fiber assembly

The present invention relates to an optical fiber assembly, an optical fiber cable, and a method for manufacturing an optical fiber assembly.
This application claims priority based on Japanese Patent Application No. 2021-212168 filed in Japan on December 27, 2021, the content of which is incorporated herein.

Patent Document 1 discloses a technique for suppressing an increase in microbend loss of an optical fiber.

Japanese Patent Application Laid-Open No. 2019-56837

As a result of intensive studies by the inventors of the present application, it has been found that if the cross-sectional shape of each optical fiber ribbon is constant in the longitudinal direction, micro bend loss can be concentrated in a specific optical fiber. If microbend loss occurs in such a concentrated manner in a specific optical fiber, the probability of occurrence of an optical fiber that does not meet the standards for transmission loss when the optical fiber cable is bent increases, and the quality of the optical fiber cable deteriorates. Degradation and yield deterioration can occur.

The present invention has been made in consideration of such circumstances, and an object thereof is to provide an optical fiber assembly and an optical fiber cable capable of suppressing concentration of microbend loss on a specific optical fiber.

In order to solve the above problems, an optical fiber assembly according to one aspect of the present invention includes a plurality of optical fibers, and a position of G _all (center of gravity all), which is the center of gravity of all the optical fibers, in a cross-sectional view. varies in the longitudinal direction.
In addition, the method for manufacturing an optical fiber assembly according to an aspect of the present invention changes the position of G _all (center of gravity all), which is the center of gravity of all the optical fibers in a cross-sectional view, in the longitudinal direction.

According to the above aspect of the present invention, it is possible to provide an optical fiber assembly and an optical fiber cable capable of suppressing concentration of microbend loss on a specific optical fiber.

1 is a cross-sectional view showing an optical fiber assembly and an optical fiber cable according to an embodiment of the invention; FIG. 1 is a perspective view showing an optical fiber unit according to an embodiment of the invention; FIG. 1 is a perspective view showing an intermittently fixed tape core wire according to an embodiment of the present invention; FIG. 5 is a graph showing changes in position in the longitudinal direction of the center of gravity in, the center of gravity out, and the center of gravity all according to Example 1. FIG. FIG. 5 is a graph obtained by extracting plots in the SZ twist reversal portion from the data shown in FIG. 4 . FIG. FIG. 5 is a graph obtained by extracting plots in one section from one reversal of SZ twist to the adjacent reversal from the data shown in FIG. 4 ; FIG. 9 is a graph showing changes in position of the center of gravity all in the longitudinal direction according to Example 2. FIG.

An optical fiber assembly 1 and an optical fiber cable 100 according to embodiments of the present invention will be described below with reference to the drawings.
As shown in FIG. 1, an optical fiber cable 100 according to this embodiment includes an optical fiber assembly 1 including a plurality of optical fibers 11. As shown in FIG. In the example shown in FIG. 1, the optical fiber cable 100 comprises an optical fiber assembly 1 including a plurality of optical fiber units U. As shown in FIG. As shown in FIG. 2, each optical fiber unit U has a plurality of intermittently fixed fiber ribbons 10 . In other words, the plurality of intermittently fixed fiber ribbons 10 constitute the plurality of optical fiber units U. As shown in FIG. Also, each intermittent fixing tape core wire 10 includes a plurality of optical fibers 11 . In other words, the plurality of optical fibers 11 constitute the plurality of intermittently fixed tape core wires 10 . The outer diameter of each optical fiber 11 is, for example, 250 μm. However, the outer diameter of the optical fiber 11 may be 200 μm, or may be another value.
Note that the optical fiber aggregate 1 is not limited to a structure having a plurality of optical fiber units U formed of a plurality of intermittently fixed tape core wires 10 . For example, the optical fiber assembly 1 may be formed by bundling a plurality of optical fibers 11 that are not intermittently fixed without forming the intermittently fixed tape cable core 10 .

(direction definition)
Here, in this embodiment, the longitudinal direction of the optical fiber assembly 1 (optical fiber cable 100) is simply referred to as the longitudinal direction Z. As shown in FIG. The longitudinal direction Z is also a direction parallel to the central axis O of the optical fiber assembly 1 (optical fiber cable 100). One orientation along the longitudinal direction Z is referred to as the +Z orientation or forward. The orientation opposite to the +Z orientation is referred to as the -Z orientation or back. A section perpendicular to the longitudinal direction Z is called a transverse section. Viewing a cross section from the longitudinal direction Z is called a cross section view. A direction perpendicular to the central axis O of the optical fiber assembly 1 (optical fiber cable 100) is referred to as a radial direction. Along the radial direction, the direction approaching the central axis O is referred to as the radial inner side, and the direction away from the central axis O is referred to as the radial outer side. The direction of rotation around the central axis O when viewed from the longitudinal direction Z is called the circumferential direction.

As shown in FIG. 1, the optical fiber cable 100 according to this embodiment is a so-called slotless optical cable. That is, the optical fiber cable 100 according to this embodiment does not have a slot rod in which a groove (slot groove) for accommodating the optical fiber 11 (the intermittent fixing tape core wire 10) is formed. However, the optical fiber cable 100 may be a slot type optical cable having a slot rod. In this case, the optical fiber assembly 1 according to this embodiment may be accommodated in the slot groove of the optical fiber cable 100 .

As shown in FIG. 1, the optical fiber cable 100 according to the present embodiment includes the optical fiber assembly 1 described above, a pressure wrap 120 covering the optical fiber assembly 1, and the optical fiber assembly 1 via the pressure wrap 120. and a jacket 110 that covers and houses the . In other words, the optical fiber assembly 1 can be regarded as a portion of the optical fiber cable 100 excluding the jacket 110, the pressure wrap 120, and the like. Also, the optical fiber assembly 1 and the pressure winding 120 may be collectively referred to as a core.

The pressure wrap 120 is a tape-shaped member that bundles the plurality of optical fiber units U. As shown in FIG. The type of the pressing wrap 120 is not particularly limited as long as the optical fiber units U can be bundled. The press wrap 120 may have water absorbency. The pressure winding 120 may be wound vertically or horizontally with respect to the optical fiber assembly 1, for example.
For example, when the pressure wrap 120 is a tape extending in the longitudinal direction Z, the pressure wrap 120 may be formed in a cylindrical shape that wraps the optical fiber unit U. In this case, both ends in the circumferential direction of the pressure winding 120 may overlap each other to form a wrap portion. Also, the pressing wrap 120 may be a tube forming body that wraps the optical fiber unit U instead of the tape. By wrapping the optical fiber unit U with the pressing wrap 120 in the longitudinal direction Z, the optical fiber 11 can be protected.
Note that there may be a portion in the longitudinal direction Z where the optical fiber 11 is not wrapped by the pressure wrap 120 , and the optical fiber cable 100 may not have the pressure wrap 120 .

Polyolefins such as polyethylene (PE), polypropylene (PP), ethylene ethyl acrylate copolymer (EEA), ethylene vinyl acetate copolymer (EVA), ethylene propylene copolymer (EP), etc. PO) resin, polyvinyl chloride (PVC), and the like can be used. Moreover, the jacket 110 may be formed using a mixture (alloy, mixture) of the above resins. Moreover, various additives may be added to the jacket 110 depending on the purpose. Examples of additives include flame retardants, colorants, antidegradants, inorganic fillers, and the like. Also, the jacket 110 may have a two-layer structure or other multi-layer structure. For example, a protective layer covering the outer cover 110 is provided outside the outer cover 110 (first outer cover) in the illustrated example, and a second outer cover covering the protective layer is provided outside the protective layer. may The protective layer may be made of, for example, metal or fiber reinforced plastic (FRP). Alternatively, jacket 110 may have no protective layer and may simply be formed by multiple layers of jacket.

The external shape of the jacket 110 according to the present embodiment is substantially circular in cross-sectional view, except for projections 110a, which will be described later. However, the shape of the jacket 110 can be changed as appropriate. As shown in FIG. 1, a plurality of (four in the illustrated example) tensile strength members 130 and a pair of ripcords 140 are arranged on the jacket 110 according to the present embodiment.

The tensile strength member 130 is a member having a higher spring constant or tensile strength in the longitudinal direction Z than the jacket 110 . As the material of the tensile strength member 130, for example, a metal wire (steel wire or the like), a material in which metal wires are bundled, a glass fiber, a material in which glass fibers are bundled, or the like can be used. Alternatively, fiber reinforced plastic (FRP) or the like may be used as the tensile member 130 . The tensile member 130 has a role of receiving the tension and protecting the optical fibers 11 when the tension along the longitudinal direction Z is applied to the optical fiber assembly 1 (optical fiber cable 100).
A plurality of strength members 130 are disposed on the jacket 110 . A plurality of tensile members 130 according to this embodiment are arranged so as to sandwich the optical fiber assembly 1 in the radial direction. However, the plurality of tensile members 130 may be isotropically arranged on the jacket 110 so as to surround the optical fiber assembly 1 (core). Note that the tensile strength member 130 may not be embedded in the jacket. For example, strength member 130 may be included in the center or core of optical fiber assembly 1 . Alternatively, depending on the application of the optical fiber cable 100, the optical fiber cable 100 may not have the strength member 130. FIG.

A ripcord 140 is a member used to tear the jacket 110 . As a material of the rip cord 140, for example, synthetic fiber (polyester or the like) thread, polypropylene (PP) or nylon cylindrical rod, or the like can be used.
A ripcord 140 is disposed on the jacket 110 . Note that, in a cross-sectional view, the ripcord 140 may be arranged so that the entire circumference is embedded in the outer cover 110, or may be partially exposed from the outer peripheral surface or the inner peripheral surface of the outer cover 110. may be placed. A pair of ripcords 140 according to this embodiment are arranged so as to sandwich the optical fiber assembly 1 in the radial direction. In addition, the position of each tensile strength member 130 and the position of each ripcord 140 are shifted from each other in the circumferential direction. Note that the number of ripcords 140 may be one, or three or more. Also, the ripcord 140 may not be embedded in the jacket 110 . For example, the ripcord 140 may be tandemly attached to the optical fiber assembly 1 . Alternatively, fiber optic cable 100 may not have ripcord 140 .

A pair of protrusions 110a projecting radially outward from the outer peripheral surface of the outer cover 110 are provided on the outer cover 110 according to the present embodiment. The position of the projection 110a in the circumferential direction and the position of the ripcord 140 correspond to each other. The protrusion 110 a serves as a mark that makes it easier for the user to recognize the position of the ripcord 140 from the outside of the optical fiber cable 100 . Note that the outer cover 110 may not have the projections 110a. In this case, the protrusions 110a may be replaced by linear coloring on the jacket 110. FIG. However, the outer cover 110 does not have to have the projections 110a, and the outer cover 110 may not be colored.

As described above, the optical fiber assembly 1 has a plurality of (12 in the example shown in FIG. 1) optical fiber units U. As shown in FIG. 1, an optical fiber assembly 1 including a plurality of optical fiber units U according to this embodiment has a two-layer structure. That is, the multiple optical fiber units U include multiple (nine in the illustrated example) outer layer units Uout and multiple (three in the illustrated example) inner layer units Uin. Each outer layer unit Uout is located on the outer circumference of the optical fiber assembly 1 . The plurality of inner layer units Uin are surrounded from the radially outer side by the plurality of outer layer units Uout. That is, the plurality of inner layer units Uin are positioned at the center of the optical fiber assembly 1 in a cross-sectional view. However, the number of inner layer units Uin and the number of outer layer units Uout can be changed as appropriate. Also, the optical fiber assembly 1 does not have to have a two-layer structure.

As shown in FIG. 2, the optical fiber unit U according to the present embodiment includes the above-described multiple intermittently fixed tape core wires 10 and a bundle material 20 that bundles the multiple intermittently fixed tape core wires 10 . The number of intermittently fixed tape core wires 10 included in one optical fiber unit U may be two or more, and may be six, for example.

The bundle material 20 is a member capable of bundling a plurality of intermittently fixed tape core wires 10 . As the bundle material 20, for example, a thread-like, string-like, tape-like member, or the like can be used. The intermittently fixed fiber ribbon 10 according to the present embodiment is bundled by winding a bundle material 20 thereon. However, the configuration in which the bundle material 20 bundles the intermittently fixed tape core wires 10 is not limited to the illustrated example. For example, the bundle material 20 may be spirally wound around the intermittent fixing ribbon 10 . Alternatively, the optical fiber unit U may not have the bundle material 20 . In this case, for example, the intermittently fixed tape core wires 10 may be bundled by twisting a plurality of the intermittently fixed tape core wires 10 in the optical fiber unit U.

The optical fiber assembly 1 may not have the optical fiber unit U. In other words, the plurality of intermittently fixed ribbon core wires 10 may not constitute the optical fiber unit U. That is, the optical fiber assembly 1 may have a structure in which the pressure wrap 120 and the jacket 110 directly cover the intermittently fixed tape cable core 10 .

Further, when the optical fiber assembly 1 is formed of the optical fibers 11 that are not intermittently fixed, the optical fiber unit is formed by a partial assembly of the optical fibers 11 bundled with the bundle material 20 . U may be formed. The optical fibers 11 may be SZ-twisted or unidirectionally twisted to form a sub-aggregate of the optical fibers 11, and the sub-aggregate of the optical fibers 11 may be used as the optical fiber unit U.
Further, when the optical fiber assembly 1 formed by the optical fibers 11 which are not intermittently fixed has a two-layer structure, the inner layer unit Uin and the outer layer unit Uout are intermittently fixed. It becomes a unit formed by a plurality of optical fibers 11 that are not connected.

In addition, in the example shown in FIG. 1, the inner layer unit Uin is formed in a fan shape, and the outer layer unit Uout is formed in a square shape. The cross-sectional shape of the optical fiber unit U is not limited to the illustrated example, and may be circular, elliptical, or polygonal. Further, even when the optical fiber 11 is bundled with the bundle material 20 , the bundle material 20 is deformed, and the optical fiber 11 appropriately moves to an empty space inside the jacket 110 . Therefore, for example, as shown in FIG. 5, the cross-sectional shape of the optical fiber unit U may be deformed.

As shown in FIG. 3 , each intermittently fixed ribbon core 10 includes a plurality of (12 in the illustrated example) optical fibers 11 and a plurality of fixing portions 12 . Each optical fiber 11 has a core and a cladding. A coating layer such as resin is provided on the outer periphery of the clad. Before the optical fiber assembly 1 is formed, the plurality of optical fibers 11 in the intermittently fixed tape cable core 10 are arranged in a row. Thereby, the intermittently fixed tape core wire 10 has a tape-like shape. Hereinafter, the direction in which the optical fibers 11 are arranged in the intermittently fixed fiber ribbon 10 may be referred to as the tape width direction W for ease of explanation.

Each fixing portion 12 fixes two optical fibers 11 adjacent in the tape width direction W to each other. A gap may be provided between two adjacent optical fibers 11 . In this case, a plurality of fixing portions 12 are intermittently arranged in the longitudinal direction Z in the gap. Alternatively, there may be no gap between two adjacent optical fibers 11 . Also, two optical fibers 11 may be continuously fixed in the longitudinal direction Z to form an optical fiber set, and a plurality of optical fiber sets may be intermittently fixed by a plurality of fixing portions 12 .
As shown in FIG. 3, the plurality of fixing portions 12 are two-dimensionally intermittently arranged in the longitudinal direction Z and the tape width direction W. As shown in FIG. Note that the arrangement of the fixing portion 12 is not limited to the example in FIG. 3, and can be changed as appropriate. Also, the arrangement pattern of the fixed portions 12 may not be a constant pattern in the longitudinal direction Z or the tape width direction W. The arrangement pattern of the fixing portions 12 does not have to be a constant pattern between different intermittently fixed tape core wires 10 . As the material of the fixed part 12, for example, a UV curable resin may be adopted. However, the material of the fixing portion 12 is not particularly limited as long as the adjacent optical fibers can be fixed, and can be changed as appropriate.

In the optical fiber assembly 1, a plurality of optical fibers 11 are twisted together in an SZ shape. In the SZ twist, a cycle includes a normal twisted portion in which the optical fibers 11 are twisted around the central axis O and a reverse twisted portion in which the optical fibers 11 are twisted around the central axis O in a direction opposite to the normal twisted portion. Repeated in the longitudinal direction. Here, when a plurality of optical fibers 11 are twisted together in an SZ shape, the intermittently fixed ribbon core 10 and the optical fiber unit U formed by the plurality of optical fibers 11 are also twisted together in an SZ shape. There will be The twist angle (winding angle) of the inner layer unit Uin and the twist angle (winding angle) of the outer layer unit Uout may be equal or different.

The above embodiments will be described below using specific examples. In addition, the present invention is not limited to the following examples.

(Example 1)
An optical fiber assembly 1 having three inner layer units Uin and nine outer layer units Uout was prepared. Each of the inner layer unit Uin and the outer layer unit Uout is obtained by binding six intermittently fixed tape core wires 10 with a bundle material. Each intermittent fixing tape core wire 10 has 12 optical fibers 11 respectively. That is, the optical fiber assembly 1 in Example 1 has a total of 864 optical fibers 11 . The outer diameter of each optical fiber 11 was set to 250 μm. An optical fiber cable 100 was produced by wrapping this optical fiber assembly 1 with a pressure wrap 120 and covering it with a jacket 110 . The outer diameter of the jacket 110 was 18.2 mm, and the inner diameter of the jacket 110 was 11.5 mm. The thickness of the pressure winding 120 was set to 0.2 mm. The outer diameter of the optical fiber assembly 1 was approximately 11.1 mm.

The above optical fiber cable 100 was cut into 8 pitches in the SZ twist. Here, one pitch in the SZ twist is the dimension of the period of the SZ twist structure repeated in the longitudinal direction Z. The optical fiber cable 100 for eight pitches was cut at predetermined intervals in the longitudinal direction to obtain a total of 28 cross sections. In these cross sections, the center of gravity (center of gravity in) of all the optical fibers 11 contained in the three inner layer units Uin, the center of gravity (center of gravity out) of all the optical fibers 11 contained in the nine outer layer units Uout, and the three The center of gravity (center of gravity all) of all the optical fibers 11 included in the inner layer unit Uin and the nine outer layer units Uout was obtained. The center of gravity in can also be said to be the center of gravity of the structure including only all the optical fibers 11 included in the three inner layer units Uin. Hereinafter, the center of gravity in will also be referred to as “G _in ”. The center of gravity out can also be said to be the center of gravity of the structure including only all the optical fibers 11 included in the nine outer layer units Uout. Hereinafter, the center of gravity out will also be referred to as "G _out ". The center of gravity all can also be said to be the center of gravity of the structure including only all the optical fibers 11 included in the optical fiber assembly 1 . Hereinafter, the center of gravity all is also referred to as "G _all ".

The positions such as the center of gravity in at each position in the longitudinal direction were identified by the following procedure. That is, after cutting the optical fiber assembly 1 at each position in the longitudinal direction, it is hardened with an epoxy resin, and the hardened optical fiber assembly 1 is polished so that the cross section becomes clear. Taken with On the image obtained by the microscope, the position of each optical fiber 11 was plotted on the xy plane to specify the center of gravity in and the like. The optical fiber assembly 1 may be fixed with epoxy resin, and then the optical fiber cable 100 may be cut at each position in the longitudinal direction. In this case, the sheath 110 may be filled with the epoxy resin, for example, by injecting the epoxy resin from one end in the longitudinal direction of the optical fiber cable 100 and sucking the epoxy resin from the other end.

4 to 6 are graphs plotting the center of gravity in, the center of gravity out, and the center of gravity all determined from the images of each cross section. In the longitudinal direction Z, the plotted points are connected by lines in the order of the position where the optical fiber assembly 1 is cut. The horizontal and vertical axes in FIGS. 4 to 6 are the orthogonal coordinate system (XY coordinate system) set on the cross section. The XY coordinate system was common to each cross section. Therefore, each data of FIGS. 4 to 6 represents how the respective positions of the center of gravity in, the center of gravity out, and the center of gravity all change in the longitudinal direction. As described above, it is sufficient to grasp the change in the longitudinal direction of each center of gravity, so the positions of the X-axis and the Y-axis can be set arbitrarily.
FIG. 4 is a graph plotting all of the center of gravity in, the center of gravity out, and the center of gravity all determined from the images of each cross section.

FIG. 5 is a graph that extracts plots located at the SZ twist reversal portion from the data shown in FIG. The reversal portion of the SZ twist is a position where the normal twist portion and the reverse twist portion of the SZ twist are switched. FIG. 6 is a graph obtained by extracting plots in one section from one inversion portion to the adjacent inversion portion from the data shown in FIG. As shown in FIGS. 4-6, the center of gravity all varies in the longitudinal direction. Also, both the center of gravity in and the center of gravity out are out of position with respect to the center of gravity all. This means that the cross-sectional shapes of both the inner layer unit Uin and the outer layer unit Uout are collapsed, and the state of collapse varies in the longitudinal direction.

In this way, by changing the collapsed state of the intermittent fixing tape core wire 10 in the longitudinal direction, it is possible to suppress the application of strong stress to only a specific optical fiber 11 due to the bending of the optical fiber cable 100 . In other words, the optical fiber 11 on which a strong stress may act due to bending of the optical fiber cable 100 is different at each position in the longitudinal direction. This disperses the risk of microbend loss occurring in each optical fiber 11 due to bending of the optical fiber cable 100 .

4 to 6, the amount of movement of the center of gravity in is greater than the amount of movement of the center of gravity out. In other words, the cross-sectional shape of the inner layer unit Uin changes more in the longitudinal direction than the cross-sectional shape of the outer layer unit Uout. When the cross-sectional shape of the inner layer unit Uin is greatly changed in the longitudinal direction in this manner, a gap is likely to occur in the radially inner region (region near the central axis O) of the optical fiber assembly 1 . If a gap occurs in the radially inner region, the outer layer unit Uout tends to enter into the gap.
Here, generally, when the optical fiber cable 100 is bent, elongation strain and microbending loss are more likely to occur in the optical fiber 11 positioned farther from the neutral line of bending. Therefore, the outer layer unit Uout is more susceptible to microbend loss due to bending of the optical fiber cable 100 than the inner layer unit Uin.
As described above, in this embodiment, a gap is created in the radially inner region of the optical fiber assembly 1, and the outer layer unit Uout is inserted into the gap, so that the outer layer unit Uout is positioned close to the neutral line. can be provided. In this way, by making the amount of movement of the center of gravity in larger than the amount of movement of the center of gravity out, it is possible to suppress the concentration of the risk of elongation strain and microbend loss occurring only in a specific optical fiber 11 .

The amount of movement Δ in the longitudinal direction of each center of gravity can be calculated by the following formula (1) based on the formula for determining the distance between two points.
Δ＝√((X(n+1)-X(n))^2+(Y(n+1)-Y(n))^2) …(1)
In Equation (1), n is a natural number and indicates the position of the cross section. For example, in this embodiment, a total of 28 cross-sections are obtained, so each cross-section is assigned n=1 to 27 (when n=27, n+1 corresponds to the 28th cross-section). ). X(n) is the X coordinate at the nth cross-section, and X(n+1) is the X coordinate at the n+1th cross-section. Similarly, Y(n) is the Y coordinate at the nth cross-section and Y(n+1) is the Y coordinate at the n+1th cross-section. In the data of FIG. 4, the average value of the amount of movement of the center of gravity in (expressed as Δin) is 0.504 mm (4.54% of the outer diameter of the optical fiber assembly 1), and the amount of movement of the center of gravity out (Δout and ) is 0.416 mm (3.75% of the outer diameter of the optical fiber assembly 1). That is, the average value of Δin is greater than the average value of Δout. From the shapes of the graphs in FIGS. 4 to 6, it can be seen that Δin is larger than Δout, but the average value of both may be obtained and compared quantitatively as described above.
In this embodiment, a total of 28 cross-sections are cut out from the length of 8 pitches in the SZ twist, and the movement amount Δ is obtained from the n-th cross-section and the (n+1)-th cross-section. Therefore, when the dimension in the longitudinal direction Z of one pitch of SZ twist is P, the movement amount Δ is the movement amount Δ of the center of gravity between two points separated by 8/(28−1)×P in the longitudinal direction Z. You can think of it.
Tables 1 and 2 show the results of examination of the preferable range of the average value of Δin.

In Table 1, the maximum loss increase of the outer layer unit Uout in the bending test was measured under the following conditions based on ICEA S-87-640-2016 (Item No. 7.21 Cable Low and High Temperature Bend Test). The optical fiber cable 100 was wound four times around a mandrel (540 mm in diameter) approximately 30 times the outer diameter of the optical fiber cable 100 . The measurement wavelength was 1550 nm. The temperature was -30°C.
In Table 2, the length of the sample optical fiber cable 100 was set to 1000 mm. The maximum outer diameter and the minimum outer diameter of the optical fiber cable 100 in the sample were measured at 10 points in total at intervals of 100 mm in the longitudinal direction. The "non-circularity of the optical fiber cable" shown in Table 2 is the average value of the non-circularity at the above 10 locations. The non-circularity at each location was calculated by minimum outer diameter÷maximum outer diameter×100.

From the results in Table 1, the average value of Δin is preferably 0.010 mm or more (0.090% or more of the outer diameter of the optical fiber assembly 1). As a result, the maximum loss increase of the outer layer unit Uout in the bending test can be 0.15 dB or less.
From the results of Table 2, the average value of Δin is preferably 2.250 mm or less (20.27% or less of the outer diameter of the optical fiber assembly 1). Thereby, the non-circularity of the optical fiber cable 100 can be made 80% or more.

In summary, the average value of Δin should be within the range of 0.010 mm to 2.250 mm (0.090% to 20.27% of the outer diameter of the optical fiber assembly 1). If the average value of Δin is too small, the effect of suppressing loss increase in the outer layer unit Uout due to bending of the optical fiber cable 100 is reduced. If the average value of Δin is too large, the non-circularity of the optical fiber cable 100 is reduced, and other problems (undulation of the optical fiber cable 100, deterioration of ease of handling, etc.) occur.

(Example 2)
In Example 1, the inner layer unit Uin and the outer layer unit Uout are configured by binding a plurality of intermittently fixed ribbon cords 10 with a bundle material. On the other hand, in Example 2, 24 intermittently fixed tape core wires 10 each having 12 optical fibers 11 were SZ-twisted without being bound with a bundle material to create an optical fiber assembly 1 . An optical fiber cable 100 was produced by wrapping this optical fiber assembly 1 with a pressure wrap 120 and covering it with a jacket 110 . That is, the optical fiber cable 100 of the second embodiment has 288 optical fibers 11 in total. Also, in the second embodiment, the optical fiber 11 is not divided into an inner layer and an outer layer. The outer diameter of the jacket 110 was 11.8 mm, and the inner diameter of the jacket 110 was 7.0 mm. The thickness of the pressure winding 120 was set to 0.2 mm. The outer diameter of the optical fiber assembly 1 was approximately 6.6 mm.

FIG. 7 shows the result of obtaining the center of gravity all of the optical fiber cable 100 produced as described above by the same method as in Example 1. The plotting method of the center of gravity all in the graph shown in FIG. 7 is the same as in FIGS. As shown in FIG. 7, also in the second embodiment, the position of the center of gravity all varies in the longitudinal direction. In this way, even if the intermittent fixing tape core wire 10 is not bound with a bundle material, and even if the optical fiber 11 is not divided into inner and outer layers, the position of the center of gravity all can be changed.

As described above, the center of gravity all (G _all ), which is the position of the center of gravity of all the optical fibers 11 in the cross-sectional view, changes in the longitudinal direction, so that the bending of the optical fiber cable 100 causes the specific optical fiber It is possible to suppress the occurrence of microbend loss concentrating on 11 . In other words, the risk of increased transmission loss is distributed to a plurality of optical fibers, and when viewed as a whole optical fiber cable 100, the emergence of optical fibers 11 that do not satisfy the standards for transmission loss can be suppressed. Therefore, it is possible to improve the bending performance and yield of the optical fiber cable 100 .

Also, at least a portion of the plurality of optical fibers 11 may be SZ-twisted. According to this configuration, concentration of strain on a specific optical fiber 11 can be more reliably suppressed, and an increase in the maximum transmission loss of the optical fiber assembly 1 can be more reliably suppressed.

In addition, the plurality of optical fibers 11 form a plurality of intermittently fixed tape core wires 10, and the plurality of intermittently fixed tape core wires 10 are respectively two or more optical fibers 11 out of the plurality of optical fibers 11 and the two A plurality of fixing portions 12 for intermittently fixing the optical fibers 11 of one or more in the longitudinal direction may be included.
Even when the optical fiber 11 constitutes the intermittently fixed tape core wire 10 , the above-described configuration can more reliably suppress the concentration of strain on a specific optical fiber 11 .

Further, the plurality of optical fibers 11 form an inner layer unit Uin and an outer layer unit Uout located radially outside the inner layer unit Uin. G _in , which is the position of the center of gravity of the outer layer unit Uout, may move in the longitudinal direction Z more than G _out , which is the position of the center of gravity of all the optical fibers 11 included in the outer layer unit Uout.
As a result, when the optical fiber cable 100 is bent, it is possible to create a gap in the radially inner region of the optical fiber assembly 1 and allow the outer layer unit Uout to enter the gap. It is possible to suppress the concentration of the risk of elongation strain and microbend loss occurring only on 11 .

Also, the average value of Δin, which is the amount of movement of G _in in the longitudinal direction Z, may be within the range of 0.090% to 20.27% with respect to the outer diameter of the optical fiber assembly 1 .
As a result, an increase in loss in the outer layer unit Uout and a decrease in the non-circularity of the optical fiber cable 100 due to bending of the optical fiber cable 100 can be suppressed.

Further, the optical fiber cable 100 according to this embodiment includes the above-described optical fiber assembly 1 and a jacket 110 that accommodates the optical fiber assembly 1 . According to this configuration, it is possible to suppress an increase in the maximum transmission loss of the optical fiber cable 100 .

Based on the above, this embodiment proposes a method for manufacturing the optical fiber assembly 1 or the optical fiber cable 100 in which the position of the center of gravity all, which is the center of gravity of all the optical fibers 11 in the cross-sectional view, is changed in the longitudinal direction. do.
In order to shift the center of gravity all in the longitudinal direction, the following technique is used in the manufacturing process of the optical fiber assembly 1, for example. The first method is to change the tension applied to the intermittently fixed tape core wires 10 with time in the process of twisting the intermittently fixed tape core wires 10 in an SZ shape. A second technique is to change the rotational speed of battens used when intermittently fixing ribbon cords 10 are twisted in an SZ shape with time. A third method is a method of varying the distance between each through-hole and the center of the batten plate for a plurality of through-holes formed in the batten plate and through which the intermittent fixing tape core wires 10 are inserted. . A fourth technique is to vary the shape and size of each of the plurality of through holes. A fifth technique is to adjust the length of the pause time (the rotation of the battens) when reversing the twisting direction. A sixth method is a method of arranging optical fiber units having different numbers of cores adjacent to each other.
According to these techniques, it is possible to change the collapsed state of each intermittently fixed ribbon cable 10 in the cross section in the longitudinal direction. Therefore, the position of the center of gravity all can also be changed in the longitudinal direction. The above-described first to sixth methods are examples, and other methods may be used as long as the optical fiber assembly 1 satisfying the above relationship can be manufactured. Also, some of the methods described above may be used in combination.

The technical scope of the present invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the present invention.
For example, in the first embodiment, the optical fiber assembly 1 is divided into an inner layer and an outer layer, but it is also conceivable that the optical fiber assembly 1 is divided into three or more layers such as an outer layer, an intermediate layer, and an inner layer. In other words, the description of the first embodiment can be extended to the relative relationships between the outer layer and the middle layer, and between the middle layer and the inner layer.

In addition, it is possible to appropriately replace the components in the above-described embodiments with well-known components within the scope of the present invention, and the above-described embodiments and modifications may be combined as appropriate.

1... Optical fiber assembly 10... Intermittent fixing tape core wire 11... Optical fiber 12... Fixed part Uin... Inner layer unit Uout... Outer layer unit

Claims

with multiple optical fibers,
An optical fiber assembly in which the positions of G all , which are the centers of gravity of all the optical fibers, in a cross-sectional view change in the longitudinal direction.
The optical fiber assembly according to claim 1, wherein at least part of the plurality of optical fibers are SZ-twisted.
The plurality of optical fibers form a plurality of intermittently fixed tape core wires,
wherein each of said plurality of intermittently fixed tape core wires includes two or more optical fibers among said plurality of optical fibers and a plurality of fixing portions for intermittently fixing said two or more optical fibers in a longitudinal direction; Item 3. An optical fiber assembly according to Item 1 or 2.
The plurality of optical fibers form an inner layer unit and an outer layer unit located radially outside the inner layer unit,
G in , which is the position of the center of gravity of all the optical fibers included in the inner layer unit, in a cross-sectional view is longer than G out , which is the position of the center of gravity of all the optical fibers included in the outer layer unit, in the longitudinal direction. 4. The optical fiber assembly according to any one of claims 1 to 3, wherein the optical fiber assembly moves significantly at .
5. The method according to claim 4, wherein the average value of Δin, which is the amount of movement of G in in the longitudinal direction, is within a range of 0.090% to 20.27% with respect to the outer diameter of the optical fiber assembly. Optical fiber assembly.
an optical fiber assembly according to any one of claims 1 to 5;
and a jacket that houses the assembly of optical fibers.
A method for manufacturing an optical fiber assembly, wherein the position of Gall , which is the center of gravity of all optical fibers in a cross-sectional view, is changed in the longitudinal direction.