Optical fiber cable

Abstract

The fiber optic cable (1) of the present invention is characterized in that a plurality of F with geometric micro-bending loss characteristics are housed in the internal space (3S) of the sheath (3). μBL_G and optical microbending loss characteristics F μBL_Δβ The fiber (10), when the cable characteristics Dc of the fiber cable (1) are defined using the porosity a of the internal space (3S) and the number of cores b of the fiber (10) housed in the internal space (3S), has the microbending loss characteristic factor F expressed by the following formula. μBL_GΔβ The value is 1.2 × 10 －9 The following F μBL_GΔβ =F μBL_G ×F μBL_Δβ ×Dc.

Description

Technical Field

[0001] This invention relates to optical fiber cables. Background Technology

[0002] In recent years, due to the maturity of Fiber To The Home (FTTH) services, the widespread adoption of mobile devices, the increased use of cloud services, and the rise in video communication, the volume of communication infrastructure built with fiber optic cables is increasing. Therefore, there is a demand for more economical and efficient construction of communication infrastructure than ever before. Against this backdrop, there is a need to increase the number of fiber cores and the installation density in fiber optic cables. Furthermore, typically, in fiber optic cables, multiple fibers are housed within a sheath that is a tubular resin component.

[0003] As a means to increase the number of fiber cores and the installation density housed within the sheath, reducing the fiber diameter is considered. However, in this case, the fiber is susceptible to lateral pressure, and the optical loss caused by so-called microbending due to the slight bending of the fiber axis, i.e., microbending loss, may increase. Patent Document 1 describes a technique that reduces the cladding thickness of the fiber by adjusting the elastic modulus and glass transition temperature, thereby suppressing microbending loss even when the fiber diameter is reduced.

[0004] Patent Document 1: Japanese Patent Publication No. 2012-508395

[0005] However, if the fiber optic cable is placed in a low-temperature environment, the sheath shrinks due to the low temperature, and the optical fiber is bent by the pressure of the shrinking sheath. As a result, there is a tendency for micro-bending loss to occur in the optical fiber, thus increasing the transmission loss of the fiber optic cable. In particular, when using the optical fiber described in Patent Document 1 to construct the fiber optic cable, since each optical fiber is thinner than a typical optical fiber, it can be considered that it is more prone to bending due to pressure from the sheath, and the transmission loss is more likely to increase. Summary of the Invention

[0006] Therefore, the purpose of this invention is to provide an optical fiber cable that can suppress the increase in transmission loss in low-temperature environments.

[0007] To achieve the above objectives, the present invention provides an optical fiber cable comprising a plurality of optical fibers and a sheath housing the plurality of optical fibers within an internal space. The plurality of optical fibers include: a glass portion comprising a core and a cladding surrounding the core; a primary cladding covering the cladding; and a secondary cladding covering the primary cladding. The optical fiber cable is characterized in that the optical fibers possess a geometric microbending loss characteristic F. μBL_G (Pa -1 ·m -10.5 ), and optical microbending loss characteristics F μBL_Δβ(1 / (rad / m) 8 ), where the bending rigidity of the aforementioned glass portion is set to H f (Pa·m 4 The deformation resistance of the above-mentioned sub-coating layer is set as D0 (Pa), and the bending stiffness of the above-mentioned sub-coating layer is set as H0 (Pa·m). 4 Let E be the Young's modulus of the glass portion mentioned above. g (GPa), let E be the Young's modulus of the main coating layer. p (MPa), set the Young's modulus of the above-mentioned sub-coating layer as E. s (MPa), Let the outer diameter of the glass part be d. f (μm), Let the radius of the outer periphery of the main coating layer be R. p (μm), Let the radius of the outer periphery of the above-mentioned sub-coating layer be R. s (μm), let the thickness of the above main coating layer be t. p (μm), and the thickness of the above-mentioned sub-coating layer is set as t. s In the case of (μm), the above geometric micro-bending loss characteristic F μBL_G (Pa -1 ·m -10.5 )use

[0008]

[0009]

[0010] To indicate,

[0011] If the difference between the propagation constant in the waveguide mode and the propagation constant in the radiation mode propagating in the aforementioned optical fiber is defined as the propagation constant difference Δβ (rad / m), then the aforementioned optical microbending loss characteristic F μBL_Δβ (1 / (rad / m) 8 )use

[0012]

[0013] To indicate,

[0014] When using the porosity 'a' of the aforementioned internal space and the number of optical fibers 'b' housed within the aforementioned internal space, and defining the cable characteristics 'Dc' of the aforementioned optical fiber cable using the following formula,

[0015] Dc = (0.5 - a) 2 / b

[0016] The microbending loss characteristic factor F is expressed by the following formula. μBL_GΔβ The value is 1.2 × 10 －9 The following F μBL_GΔβ =FμBL_G ×F μBL_Δβ ×Dc.

[0017] Examples include non-patent literature 1 (J. Baldauf, et al., “Relationship of Mechanical Characteristics of Dual Coated Single Mode Optical Fibers and Microbending Loss,” IEICE Trans. Commun., vol. E76-B, No. 4, 1993.), non-patent literature 2 (K. Petermann, et al., “Upper and Lower Limits for the Microbending Loss in Arbitrary Single-Mode Fibers,” J. Lightwave Technology, vol. LT-4, no. 1, pp. 2-7, 1986.), non-patent literature 3 (Ogoshi, “Optical Fibers,” Ohmsha, pp. 235-239, 1989.), and non-patent literature 4 (P. Sillard, et al., “Micro-Bend Losses of Trench-Assisted Single-Mode Fibers”). As documented in Fibers, ECOC 2010, We. 8. F. 3, 2010, the microbending loss of optical fibers tends to be influenced by both the geometry and optical properties of the fiber.

[0018] Here, the geometry of the optical fiber refers to parameters related to the construction of the optical fiber. In this invention, it refers to the bending stiffness H of the glass portion of the optical fiber. f The deformation resistance of the secondary coating layer (D0), the flexural stiffness of the secondary coating layer (H0), and the Young's modulus of the glass portion (E) g Young's modulus E of the main coating layer p Young's modulus E of the secondary coating layer s The outer diameter d of the glass section f (diameter of the glass part), radius R of the glass part g The radius R of the main coating layer p The radius R of the secondary coating layer s The thickness t of the main coating layer p and the thickness t of the secondary coating layer s .

[0019] Furthermore, according to the aforementioned non-patent documents 2-4, microbending loss is a phenomenon caused by mode coupling between the waveguide mode and the radiation mode propagating in the optical fiber. This mode coupling can be attributed to the aforementioned minute bending, and furthermore, it can be said to be determined by the difference between the propagation constants of the waveguide mode and the radiation mode of the light propagating in the optical fiber, i.e., the propagation constant difference (Δβ). The aforementioned optical properties of the optical fiber are parameters related to the properties of the light propagating in the optical fiber; in this invention, this refers to the aforementioned propagation constant difference Δβ (rad / m).

[0020] Furthermore, if fiber optic cables are placed in low-temperature environments, as mentioned above, there is a tendency for fiber bending to cause micro-bending loss, thus increasing transmission loss. Therefore, considering this increase in transmission loss, it is sometimes required that the increase in transmission loss at -40°C, based on room temperature, be less than 0.15 dB / km. Moreover, this increase in transmission loss is sometimes referred to as the increase in temperature characteristic test loss.

[0021] The inventors of this invention have conducted in-depth research on the aforementioned transmission losses in optical fiber cables. As a result, the inventors of this invention discovered the micro-bending loss characteristic factor F, expressed by the above formula. μBL_GΔβ The value of is roughly proportional to the increase in loss during temperature characteristic testing, with a positive slope.

[0022] Furthermore, the inventors of this invention conducted further research and discovered that the value of the aforementioned microbending loss characteristic factor is 1.2 × 10⁻⁶. －9 At that time, the increase in loss during the temperature characteristic test became slightly less than 0.15 dB / km. As mentioned above, the value of the microbending loss characteristic factor and the value of the increase in loss during the temperature characteristic test are approximately proportional with a positive slope. Therefore, by setting the value of the microbending loss characteristic factor of the optical fiber cable to 1.2 × 10⁻⁶, －9 The following method can suppress the increase in transmission loss, so that the increase in transmission loss is less than 0.15 dB / km in a low-temperature environment of -40°C. Thus, this fiber optic cable can suppress the increase in transmission loss in low-temperature environments.

[0023] Furthermore, the aforementioned micro-bending loss characteristic factor F is preferred. μBL_GΔβ The value is 9.9 × 10 －10 the following.

[0024] By adjusting the microbending loss characteristic factor F μBL_GΔβ The value is 9.9 × 10 －10 The following values ​​are used to ensure that the increase in temperature characteristic test loss, which is the increase in transmission loss, is less than 0.12 dB / km.

[0025] Furthermore, the micro-bending loss characteristic factor F is further optimized.μBL_GΔβ The value is 7.9 × 10 －10 the following.

[0026] By adjusting the microbending loss characteristic factor F μBL_GΔβ The value is 7.9 × 10 －10 The following values ​​are used to ensure that the increase in temperature characteristic test loss, which is the increase in transmission loss, is less than 0.10 dB / km.

[0027] As described above, according to the present invention, an optical fiber cable capable of suppressing increased transmission loss in low-temperature environments is provided. Attached Figure Description

[0028] Figure 1 This is a schematic diagram showing the structure of a cross-section perpendicular to the length direction of an optical fiber cable according to an embodiment of the present invention.

[0029] Figure 2 It means Figure 1 A schematic perspective view of an example of the fiber optic ribbon core included in the fiber optic cable shown.

[0030] Figure 3 It means Figure 2 The diagram shows a schematic representation of the cross-section of the optical fiber, which is perpendicular to the length direction and includes the fiber ribbon core.

[0031] Figure 4 This is a graph showing the relationship between the value of the microbending loss characteristic factor in optical fiber cables and the increase in loss during temperature characteristic tests. Detailed Implementation

[0032] The following is related to the appendix. Figure 1 The following examples illustrate methods for implementing the optical fiber cable involved in this invention. The embodiments illustrated below are for ease of understanding of the invention and are not intended to limit the invention. The invention can be modified and improved based on the following embodiments without departing from its spirit. Furthermore, in this specification, the dimensions of various components are sometimes exaggerated for ease of understanding.

[0033] Figure 1 This is a schematic diagram showing the construction of a cross-section perpendicular to the length direction of the optical fiber cable 1 according to the embodiment. (See diagram below.) Figure 1 As shown, the optical fiber cable 1 has a sheath 3, multiple core wires 4, and a tensile body 6 as its main structures.

[0034] The sheath 3 is a tubular component, for example, formed of a thermoplastic resin such as polyethylene. Multiple cored wires 4 are housed within the internal space 3S surrounded by the sheath 3. Thus, the optical fiber cable 1 of this embodiment is configured as a so-called ultra-high density cable (UHDC) with multiple cored wires 4 densely housed within the internal space 3S of the sheath 3. In this embodiment, the multiple cored wires 4 have the same structure.

[0035] In this embodiment, an anti-tension body 6 is embedded in the thick-walled portion of the sheath 3. Figure 1 In the cross-sectional view, the tension resisting elements 6 are positioned opposite each other at the center of the fiber optic cable 1. These tension resisting elements 6 prevent excessive elongation of the core wire 4 when tension is applied along its length. Furthermore, the position and number of tension resisting elements 6 are not limited to this example; alternatively, tension resisting elements 6 may not be provided.

[0036] Figure 2 This is a schematic three-dimensional diagram showing an example of a core wire 4. (See diagram below.) Figure 2 As shown, the cored wire 4 in this embodiment is a so-called intermittently bonded cored wire. In the cored wire 4 of this embodiment, a plurality of optical fibers 10 are arranged along a direction perpendicular to the length direction, and the arranged optical fibers 10 are bonded to each other. Figure 2 In the example, the optical fiber 10 constituting the cored wire 4 has 12 cores. However, the number of cores in the optical fiber 10 constituting the cored wire 4 is not limited to 12; it can have more or fewer cores. Furthermore, the cored wire 4 is not limited to an intermittently bonded type.

[0037] The cored wire 4 includes adhesive portions 4A and single-core portions 4B. Adhesive portions 4A are formed, for example, from UV-curable resin or thermosetting resin, and are bonded to adjacent optical fibers 10, connecting these optical fibers 10 to each other. Adhesive portions 4A are intermittently arranged at certain intervals along the length direction. Single-core portions 4B are located between adhesive portions 4A and are the portions where the optical fibers 10 are not bonded to each other. With this structure, the cored wire 4 can be easily deformed, for example, twisted or bundled into a generally cylindrical shape. Figure 1 The image shows a general outline of the state in which the four core wires are bundled into a roughly cylindrical shape.

[0038] However, if the volume of the internal space 3S of the sheath 3 is set as A, and the total volume of the various components housed in the internal space 3S is set as B, then the porosity a of the internal space 3S can be determined as follows.

[0039] a=(A-B) / A

[0040] The smaller the porosity 'a', the denser the fiber 10 is configured. In this embodiment, such as... Figure 1 As shown, the components housed in the internal space 3S are multiple core wires 4. Therefore, the value of B described above corresponds to the sum of the volumes of the multiple core wires 4 within the internal space 3S. Furthermore, in this embodiment, as described above, the multiple core wires 4 have the same structure and therefore have approximately the same volume. Therefore, if this volume is set as V, and the number of core wires 4 housed in the internal space 3S is set as c, then the value of B described above can be expressed as c × V.

[0041] Furthermore, the value of the aforementioned porosity α is not particularly limited. However, if the porosity α is too small, the density of the optical fibers becomes too high, and the lateral pressure exerted on adjacent optical fibers 10 increases, sometimes leading to an increase in microbending loss. Therefore, considering increasing the number of optical fibers 10 within the optical fiber cable 1 and suppressing the aforementioned lateral pressure, the porosity α can, for example, be between 0.31 and 0.42.

[0042] Figure 3 This diagram shows the structure of a cross-section perpendicular to the length direction of the optical fiber 10 constituting the core wire 4. The optical fiber 10 in this embodiment is a single-mode optical fiber. Figure 3 As shown, the optical fiber 10 has a core 11, a cladding 12 that surrounds the core 11 without gaps, a main cladding 14 covering the cladding 12, and a secondary cladding 15 covering the main cladding 14 as its main structure. In the optical fiber 10, the cladding 12 has a lower refractive index than the core 11.

[0043] The core 11 can be formed from pure quartz without any added dopants, or it can be formed from quartz with added dopants such as germanium (Ge) to increase the refractive index.

[0044] As described above, the cladding 12 has a lower refractive index than the core 11. For example, if the core 11 is formed of pure quartz, the cladding 12 can also be formed of quartz with dopants such as fluorine (F) or boron (B) added to lower the refractive index. If the core 11 is formed of quartz with dopants such as germanium (Ge) added to raise the refractive index, the cladding 12 can also be formed of pure quartz without dopants. Alternatively, the cladding 12 can also be formed of quartz with added chlorine (Cl2). Furthermore, the cladding 12 can be a single layer, or it can consist of multiple layers with different refractive indices, or it can be a porous type.

[0045] Thus, both the core 11 and the cladding 12 are formed of quartz (glass). Therefore, when the core 11 and the cladding 12 are collectively referred to as the glass portion 13, the glass portion 13 includes the core 11 and the cladding 12, and this glass portion 13 is covered by the main cladding layer 14. Furthermore, the glass portion 13 is also referred to as the bare optical fiber. The outer diameter (d) of the glass portion 13 in this embodiment is... fIt is a diameter smaller than the outer diameter of the glass section of a typical optical fiber, which is approximately 125 μm. For example, it can be between 80 μm and 90 μm.

[0046] The main coating layer 14 is formed, for example, from a UV-curable resin or a thermosetting resin, with a thickness of t. p (μm) is formed on the outer side of the glass portion 13. In this embodiment, the Young's modulus E of the main coating layer 14 is... g Young's modulus E of the secondary coating layer 15 s Low. This results in the main cladding layer 14, which is in direct contact with the glass portion, having a low Young's modulus. Consequently, the main cladding layer 14 functions as a cushioning material, reducing the external forces acting on the glass portion 13. Furthermore, if the radius of the outer periphery of the main cladding layer 14 is set to R... p (μm), then the outer diameter of the main coating layer 14 is 2R p In addition, if the radius of the glass part (d) is... f Let R be (×1 / 2). g (μm), then the aforementioned thickness t of the main coating layer 14 p It is represented by the following formula.

[0047] t p =R p -R g

[0048] In this embodiment, the secondary cladding layer 15 is the outermost layer forming the optical fiber 10. For example, it is formed of a different type of UV-curable resin or thermosetting resin than the resin forming the main cladding layer 14, with a thickness t. s (μm) is formed on the outer side of the main coating layer 14. For example, if the main coating layer 14 is formed of a UV-curable resin, the secondary coating layer 15 may be formed of a UV-curable resin different from the UV-curable resin forming the main coating layer 14; if the main coating layer 14 is formed of a thermosetting resin, the secondary coating layer 15 may be formed of a thermosetting resin different from the main coating layer 14. In this embodiment, the Young's modulus E of the secondary coating layer 15 is... s Young's modulus E of the main coating layer 14 g High. This ensures that the outermost subcladding layer 15 forming the optical fiber 10 has a high Young's modulus, thereby appropriately protecting the glass portion 13 from external forces. Furthermore, if the radius of the outer periphery of the subcladding layer 15 is set to R... s Then the outer diameter of the secondary cladding layer 15, i.e. the outer diameter of the optical fiber 10, is 2R s In addition, the thickness t of the sub-coating layer 15 is as described above. s It is represented by the following formula.

[0049] t s =R s -Rp

[0050] Furthermore, the outer diameter of the optical fiber used in optical fiber cables is typically around 240 μm to 250 μm. However, in this embodiment, the outer diameter of the secondary cladding layer 15 may, for example, be between 150 μm and 161 μm.

[0051] In addition, if the thickness t of the main covering layer 14 is increased... p The thickness t of the secondary coating layer 15 s Let the sum be the cladding thickness t. The cladding thickness of the optical fiber used in the optical fiber cable is usually around 60 μm. However, in this embodiment, the cladding thickness t of the optical fiber 10 can be, for example, between 35.0 μm and 37.5 μm.

[0052] As described above, the thin-diameter optical fibers 10 are bundled together to form 12 cores, forming a cored wire 4, which is densely housed within the internal space 3S of the sheath 3 of the optical fiber cable 1. This results in an optical fiber cable 1 comprising, for example, 288, 1728, or 2000 or more optical fibers. Furthermore, since the optical fibers 10 in this embodiment are thinned as described above, the size of the cored wire 4 can be smaller than that of a typical cored wire. Therefore, the number of optical fibers housed within the internal space 3S of the sheath 3 can be effectively increased. Alternatively, by housing the small cored wire 4 within the internal space 3S, the size of the optical fiber cable 1 can be reduced.

[0053] When fiber optic cables are placed in low-temperature environments, such as -40°C, the sheath shrinks due to the low temperature, causing the optical fiber to bend under the pressure of the shrinking sheath. As a result, there is a tendency for micro-bending loss to occur in the optical fiber, leading to an increase in the transmission loss of the fiber optic cable. In particular, since thinner optical fibers are thinner than ordinary optical fibers, they are considered to be more easily bent by the pressure from the sheath. Therefore, it can be considered that the increase in transmission loss is greater for thinner optical fibers placed in low-temperature environments compared to ordinary optical fibers. Furthermore, the resin forming the sheath generally tends to shrink more at lower temperatures. Therefore, it can be considered that the lower the temperature of the environment in which the fiber optic cable is used, the greater the pressure exerted on the optical fiber from the sheath, resulting in a greater increase in the transmission loss of the fiber optic cable.

[0054] However, the optical fiber cable 1 in this embodiment is configured with the micro-bending loss characteristic factor F described later. μBL_GΔβ The value is 1.2 × 10 －9 Therefore, even when the fiber optic cable 1 is placed in a low-temperature environment such as -40°C, the increase in transmission loss can be suppressed. The reasons for this will be explained in detail below.

[0055] As described in the aforementioned non-patent documents 1-4, the microbending loss of optical fibers tends to be influenced by both the geometry and optical properties of the optical fiber.

[0056] The geometry of an optical fiber refers to parameters related to its construction. In this embodiment, it refers to the bending stiffness H of the glass portion of the optical fiber. f The deformation resistance of the secondary coating layer (D0), the flexural stiffness of the secondary coating layer (H0), and the Young's modulus of the glass portion (E) g Young's modulus E of the main coating layer p Young's modulus E of the secondary coating layer s The outer diameter d of the glass section f (diameter of the glass part), radius R of the glass part g The radius R of the main coating layer p The radius R of the secondary coating layer s The thickness t of the main coating layer p and the thickness t of the secondary coating layer s .

[0057] Furthermore, according to the aforementioned non-patent documents 2-4, microbending loss is a phenomenon caused by mode coupling between the waveguide mode and the radiation mode propagating in the optical fiber. This waveguide mode is, for example, designated as the LP01 mode. Such mode coupling can be attributed to a so-called microbending, caused by a slight bend in the fiber's axis, and can also be considered to be determined by the difference between the propagation constant in the waveguide mode and the propagation constant in the radiation mode, i.e., the propagation constant difference (Δβ). The aforementioned optical characteristics of the optical fiber are parameters related to the characteristics of light propagating in the optical fiber; in this invention, this refers to the aforementioned propagation constant difference Δβ (rad / m).

[0058] Furthermore, as mentioned above, when fiber optic cables are placed in low-temperature environments, there is a tendency for micro-bending loss to occur in the fiber, leading to increased transmission loss. Therefore, in fiber optic cables, considering this increase in transmission loss, it is sometimes required that the increase in transmission loss at -40°C, based on room temperature, be less than 0.15 dB / km. This increase in transmission loss can be determined, for example, through cable temperature characteristic tests specified in GR-20, Issue 4, July 2013, "Generic Requirements for Optical Fiber and Optical Fiber Cable," and is sometimes referred to as the temperature characteristic test loss increase.

[0059] The inventors of this invention have conducted in-depth research on the aforementioned transmission losses of optical fiber cables. As a result, the inventors of this invention, based on the geometric micro-bending loss characteristics F of optical fiber 10... μBL_G Optical microbending loss characteristics F of fiber 10 μBL_ΔβAnd the cable characteristics Dc of optical fiber cable 1 revealed the microbending loss characteristic factor F. μBL_GΔβ The value of is roughly proportional to the increase in loss during temperature characteristic testing, with a positive slope.

[0060] The geometric microbending loss characteristics F of the aforementioned optical fiber 10 μBL_G Using the aforementioned geometry-related parameters, it can be expressed by the following equation (1).

[0061]

[0062] The optical microbending loss characteristic F of the aforementioned optical fiber 10 μBL_Δβ Using the aforementioned parameters related to optical properties, it can be expressed by the following equation (2).

[0063]

[0064] The cable characteristics Dc of the aforementioned optical fiber cable 1 are defined by the following formula (3) using the aforementioned porosity a and the number of cores b of the optical fiber 10 housed in the internal space 3S of the sheath 3.

[0065] Dc = (0.5 - a) 2 / b···(3)

[0066] The above micro-bending loss characteristic factor F μBL_GΔβ It can be expressed by the following formula (4)

[0067] F μBL_GΔβ =F μBL_G XF μBL_Δβ XDc···(4)

[0068] Furthermore, according to non-patent literature 5 (K. Kobayashi, et al., “Study of Microbending loss in thin coated fibers and fiber ribbons,” IWCS, pp. 386-392, 1993.), the typical value of the constant μ in the above equation (1) is “3”. Therefore, the above equation (1) becomes the following equation (5).

[0069]

[0070] Furthermore, according to the aforementioned non-patent literature 2 and non-patent literature 6 (CD Hussey, et al., “Characterization and design of single-mode optical fibres,” Optical and Quantum Electronics, vol. 14, no. 4, pp. 347–358, 1982.), the typical value of the constant p in the above equation (2) is “4”. Therefore, the above equation (2) becomes the following equation (6).

[0071]

[0072] Furthermore, the inventors of this invention conducted further research and discovered that the value of the aforementioned microbending loss characteristic factor is 1.2 × 10⁻⁶. －9 At that time, the increase in loss during the temperature characteristic test became slightly less than 0.15 dB / km. As mentioned above, the value of the microbending loss characteristic factor and the value of the increase in loss during the temperature characteristic test are approximately proportional with a positive slope. Therefore, by setting the value of the microbending loss characteristic factor of the optical fiber to 1.2 × 10⁻⁶, －9 The following method can suppress the increase in transmission loss so that the increase in transmission loss is less than 0.15 dB / km in a low temperature environment of -40°C.

[0073] Next, the value of the microbending loss characteristic factor is 1.2 × 10⁻⁶. －9 The point that the increase in temperature characteristic test loss becomes slightly less than 0.15 dB / km will be explained in detail.

[0074] The inventors of this invention aimed to verify the micro-bending loss characteristic factor F. μBL_GΔβ The following experiment was conducted to investigate the relationship between the value of and the increase in temperature characteristic test loss. Furthermore, the method of implementing the present invention is not limited to this experiment.

[0075] The inventors of this invention have prepared optical fiber cables, samples 1 to 21. Samples 1 to 21 all involve... Figure 2 The cable shown is a so-called fine-diameter high-density cable, comprising a 12-core optical fiber 10 and a cored wire 4 housed within the aforementioned internal space 3S. The specifications of the parameters for each of samples 1 to 21 are shown in Tables 1 to 5 below. In Tables 1 to 5, except for porosity, core count, and microbending loss characteristic factor F... μBL_GΔβThe parameters other than the increase in loss during temperature characteristic testing are parameters representing the various specifications of the multiple optical fibers constituting samples 1 to 21. For example, the optical fiber cable of sample 1 shown in Table 1 has 288 optical fibers of the same specification and 24 (288 / 12) cored wires 4. Similarly, the optical fiber cable of sample 12 shown in Table 3 has 1728 optical fibers of the same specification and 144 (1728 / 12) cored wires 4. Furthermore, the sheaths 3 of samples 1 to 21 each have the same structure.

[0076] Table 1

[0077] Sample No. 1 2 3 4 5 Outer diameter of the glass section (μm) 80.0 80.0 80.0 80.0 80.0 Outer diameter of the main coating layer (μm) 115.0 115.0 115.0 115.0 115.0 Outer diameter (μm) of the secondary coating layer 153.0 153.0 153.0 153.0 153.0 Young's modulus (GPa) of the glass portion 74.0 74.0 74.0 74.0 74.0 Young's modulus (MPa) of the main coating layer 0.15 0.15 0.17 0.14 0.15 Young's modulus (MPa) of the secondary coating layer 1751 1724 1242 1143 1751 Thickness of the primary coating layer (μm) 17.5 17.5 17.5 17.5 17.5 Thickness (μm) of the secondary coating layer 19.0 19.0 19.0 19.0 19.0 Coating thickness (μm) 36.5 36.5 36.5 36.5 36.5 <![CDATA[Flexural rigidity of the glass part (Pa·m 4 )]]> <![CDATA[1.49×10 -7 ]]> <![CDATA[1.49×10 -7 ]]> <![CDATA[1.49×10 -7 ]]> <![CDATA[1.49×10 -7 ]]> <![CDATA[1.49×10 -7 ]]> <![CDATA[Flexural rigidity of the secondary coating (Pa·m 4 )]]> <![CDATA[3.21×10 -8 ]]> <![CDATA[3.16×10 -8 ]]> <![CDATA[2.28×10 -8 ]]> <![CDATA[2.09×10 -8 ]]> <![CDATA[3.21×10 -8 ]]> κs(Pa) <![CDATA[7.0×10 5 ]]> <![CDATA[6.9×10 5 ]]> <![CDATA[7.8×10 5 ]]> <![CDATA[6.5×10 5 ]]> <![CDATA[7.0×10 5 <!-- 7 -->]]> Deformation resistance of the secondary coating (Pa) <![CDATA[3.5×10 6 ]]> <![CDATA[3.5×10 6 ]]> <![CDATA[2.6×10 6 ]]> <![CDATA[2.3×10 6 ]]> <![CDATA[3.5×10 6 ]]> μ(au) 3 3 3 3 3 <![CDATA[F μBL_G (Pa -1 ·m -10.5 )]]> <![CDATA[3.8×10 27 ]]> <![CDATA[3.7×10 27 ]]> <![CDATA[6.6×10 27 ]]> <![CDATA[5.0×10 27 ]]> <![CDATA[3.8×10 27 ]]> Mode field diameter (μm) 8.6 7.7 8.3 8.6 8.6 Cable cutoff wavelength (μm) 1.2 1.2 1.2 1.2 1.2 MAC value 7.08 6.51 7.05 7.00 7.08 Macrobend loss (dB / turn) 0.17 0.08 0.06 0.03 0.17 Difference in propagation constant (rad / m) <![CDATA[1.16×10 4 ]]> <![CDATA[1.25×10 4 ]]> <![CDATA[1.53×10 4 ]]> <![CDATA[1.32×10 4 ]]> <![CDATA[1.16×10 4 ]]> <![CDATA[F μBL_Δβ (1 / (rad / m) 8 )]]> <![CDATA[3.02×10 -33 ]]> <![CDATA[1.63×10 -33 ]]> <![CDATA[3.28×10 -34 ]]> <![CDATA[1.08×10 -33 ]]> <![CDATA[3.02×10 -33 ]]> porosity 0.31 0.31 0.31 0.31 0.42 Chip count 288 288 288 288 288 <![CDATA[F μBL_GΔβ ]]> <![CDATA[1.5×10 -9 ]]> <![CDATA[8.0×10 -10 ]]> <![CDATA[2.9×10 -10 ]]> <![CDATA[7.1×10 -10 ]]> <![CDATA[2.9×10 -10 ]]> Increase in temperature characteristic test loss (dB / km) 0.18 0.06 0.11 0.09 0.06

[0078] Table 2

[0079] Sample No. 6 7 8 9 10 Outer diameter of the glass section (μm) 80.0 80.0 80.0 80.0 80.0 Outer diameter of the main coating layer (μm) 115.0 115.0 115.0 115.0 115.0 Outer diameter (μm) of the secondary coating layer 153.0 153.0 153.0 153.0 153.0 Young's modulus (GPa) of the glass portion 74.0 74.0 74.0 74.0 74.0 Young's modulus (MPa) of the main coating layer 0.15 0.15 0.15 0.17 0.14 Young's modulus (MPa) of the secondary coating layer 1761 1724 1711 1242 1143 Thickness of the primary coating layer (μm) 17.5 17.5 17.5 17.5 17.5 Thickness (μm) of the secondary coating layer 19.0 19.0 19.0 19.0 19.0 Coating thickness (μm) 36.5 36.5 36.5 36.5 36.5 <![CDATA[Flexural rigidity of the glass part (Pa·m 4 )]]> <![CDATA[1.49×10 -7 ]]> <![CDATA[1.49×10 -7 ]]> <![CDATA[1.49×10 -7 ]]> <![CDATA[1.49×10 -7 ]]> <![CDATA[1.49×10 -7 ]]> <![CDATA[Flexural rigidity of the secondary coating (Pa·m 4 )]]> <![CDATA[3.22×10 -8 ]]> <![CDATA[3.16×10 -8 ]]> <![CDATA[3.13×10 -8 ]]> <![CDATA[2.28×10 -8 ]]> <![CDATA[2.09×10 -8 ]]> κs(Pa) <![CDATA[6.8×10 5 ]]> <![CDATA[6.9×10 5 ]]> <![CDATA[7.1×10 5 ]]> <![CDATA[7.8×10 5 ]]> <![CDATA[6.5×10 5 ]]> Deformation resistance of the secondary coating (Pa) <![CDATA[3.5×10 6 ]]> <![CDATA[3.5×10 6 ]]> <![CDATA[3.4×10 6 ]]> <![CDATA[2.6×10 6 ]]> <![CDATA[2.3×10 6 ]]> μ(au) 3 3 3 3 3 <![CDATA[F uBL_G (Pa -1 ·m -10.5 )]]> <![CDATA[3.5×10 27 ]]> <![CDATA[3.7×10 27 ]]> <![CDATA[3.9×10 27 ]]> <![CDATA[6.6×10 27 ]]> <![CDATA[5.0×10 27 ]]> Mode field diameter (μm) 8.7 7.7 8.4 8.3 8.6 Cable cutoff wavelength (μm) 1.2 1.2 1.2 1.2 1.2 MAC value 7.03 6.51 7.07 7.05 7.00 Macrobend loss (dB / turn) 0.03 0.08 0.09 0.06 0.03 Difference in propagation constant (rad / m) <![CDATA[1.32×10 4 ]]> <![CDATA[1.25×10 4 ]]> <![CDATA[1.53×10 4 ]]> <![CDATA[1.53×10 4 ]]> <![CDATA[1.32×10 4 ]]> <![CDATA[F uBL_Δβ (1 / (rad / m) 8 )]]> <![CDATA[1.10×10 -33 ]]> <![CDATA[1.63×10 -33 ]]> <![CDATA[3.37×10 -34 ]]> <![CDATA[3.28×10 -34 ]]> <![CDATA[1.08×10 -33 ]]> porosity 0.42 0.42 0.42 0.42 0.42 Chip count 288 288 288 288 288 <![CDATA[F μBL_GΔβ ]]> <![CDATA[9.6×10 -11 ]]> <![CDATA[1.5×10 -10 ]]> <![CDATA[3.3×10 -11 ]]> <![CDATA[5.4×10 -11 ]]> <![CDATA[1.4×10 -10 ]]> Increase in temperature characteristic test loss (dB / km) 0.02 0.04 0.04 0.04 0.05

[0080] Table 3

[0081] Sample No. 11 12 13 14 15 Outer diameter of the glass section (μm) 90.0 80.4 81.1 81.0 81.0 Outer diameter of the main coating layer (μm) 122.0 115.5 115.9 109.6 119.1 Outer diameter (μm) of the sub-coating layer 161.0 152.5 153.2 152.5 152.1 Young's modulus (GPa) of the glass portion 74.0 74.0 74.0 74.0 74.0 Young's modulus (MPa) of the main coating layer 0.22 0.13 0.13 0.13 0.14 Young's modulus (MPa) of the secondary coating layer 1254 1249 1261 1231 1272 Thickness of the primary coating layer (μm) 16.0 17.6 17.4 14.3 19.1 Thickness (μm) of the secondary coating layer 19.5 18.5 18.7 21.5 16.5 Coating thickness (μm) 35.5 36.1 36.1 35.8 35.6 <![CDATA[Flexural rigidity of the glass part (Pa·m 4 )]]> <![CDATA[2.38×10 -7 ]]> <![CDATA[1.52×10 -7 ]]> <![CDATA[1.57×10 -7 ]]> <![CDATA[1.56×10 -7 ]]> <![CDATA[1.56×10 -7 ]]> <![CDATA[Flexural rigidity of the secondary coating layer (Pa·m 4 )]]> <![CDATA[2.77×10 -8 ]]> <![CDATA[2.22×10 -8 ]]> <![CDATA[2.29×10 -8 ]]> <![CDATA[2.40×10 -8 ]]> <![CDATA[2.09×10 -8 ]]> <![CDATA[κ s (Well)]]> <![CDATA[1.2×10 6 ]]> <![CDATA[6.2×10 5 ]]> <![CDATA[6.2×10 5 ]]> <![CDATA[7.5×10 5 ]]> <![CDATA[6.0×10 5 ]]> Deformation resistance of the secondary coating (Pa) <![CDATA[2.4×10 6 ]]> <![CDATA[2.4×10 6 ]]> <![CDATA[2.4×10 6 ]]> <![CDATA[3.6×10 6 ]]> <![CDATA[1.8×10 6 ]]> μ(au) 3 3 3 3 3 <![CDATA[F μBL_G (Bye -1 ·m -10.5 )]]> <![CDATA[5.7×10 27 ]]> <![CDATA[4.1×10 27 ]]> <![CDATA[3.7×10 27 ]]> <![CDATA[4.7×10 27 ]]> <![CDATA[4.2×10 27 ]]> Mode field diameter (μm) 8.4 8.6 7.6 8.3 8.3 Cable cutoff wavelength (μm) 1.2 1.2 1.3 1.2 1.2 MAC value 6.86 7.08 6.01 6.98 6.98 Macrobend loss (dB / turn) 0.08 0.05 0.01 0.13 0.13 Difference in propagation constant (rad / m) <![CDATA[1.35×10 4 ]]> <![CDATA[1.32×10 4 ]]> <![CDATA[1.45×10 4 ]]> <![CDATA[1.10×10 4 ]]> <![CDATA[1.13×10 4 ]]> <![CDATA[F μBL_Δβ (1 / (rad / m) 8 )]]> <![CDATA[8.99×10 -34 ]]> <![CDATA[1.09×10 -33 ]]> <![CDATA[5.17×10 -34 ]]> <![CDATA[4.74×10 -33 ]]> <![CDATA[3.72×10 -33 ]]> porosity 0.42 0.42 0.42 0.42 0.42 Chip count 288 1728 1728 1728 1728 <![CDATA[F μBL_GΔβ ]]> <![CDATA[1.3×10 -10 ]]> <![CDATA[1.6×10 -11 ]]> <![CDATA[6.8×10 -12 ]]> <![CDATA[7.8×10 -11 ]]> <![CDATA[5.4×10 -11 ]]> Increase in temperature characteristic test loss (dB / km) 0.04 0.02 0.01 0.03 0.00

[0082] Table 4

[0083] Sample No. 16 17 18 19 Outer diameter of the glass section (μm) 80.2 81.0 80.8 80.0 Outer diameter of the main coating layer (μm) 114.1 113.3 114.2 114.6 Outer diameter (μm) of the secondary coating layer 150.8 151.0 153.6 151.4 Young's modulus (GPa) of the glass portion 74.0 74.0 74.0 74.0 Young's modulus (MPa) of the main coating layer 0.15 0.15 0.14 0.22 Young's modulus (MPa) of the secondary coating layer 1252 1305 1332 1357 Thickness of the primary coating layer (μm) 17.0 16.2 16.7 17.3 Thickness of the secondary coating layer (gm) 18.4 18.9 19.7 18.4 Coating thickness (gm) 35.3 35.0 36.4 35.7 <![CDATA[Flexural rigidity of the glass part (Pa·m 4 )]]> <![CDATA[1.50×10 -7 ]]> <![CDATA[1.56×10 -7 ]]> <![CDATA[1.55×10 -7 ]]> <![CDATA[1.49×10 -7 ]]> <![CDATA[Flexural rigidity of the secondary coating (Pa·m 4 )]]> <![CDATA[2.14×10 -8 ]]> <![CDATA[2.27×10 -8 ]]> <![CDATA[2.53×10 -8 ]]> <![CDATA[2.35×10 -8 ]]> <![CDATA[κ s (Well)]]> <![CDATA[7.2×10 5 ]]> <![CDATA[7.3×10 5 ]]> <![CDATA[6.5×10 5 ]]> <![CDATA[1.0×10 6 ]]> Deformation resistance of the secondary coating (Pa) <![CDATA[2.4×10 6 ]]> <![CDATA[2.7×10 6 ]]> <![CDATA[2.9×10 6 ]]> <![CDATA[2.7×10 6 ]]> μ(au) 3 3 3 3 <![CDATA[F μBL_G (Bye -1 ·m -10.5 )]]> <![CDATA[5.7×10 27 ]]> <![CDATA[5.1×10 27 ]]> <![CDATA[3.8×10 27 ]]> <![CDATA[1.1×10 28 ]]> Mode field diameter (μm) 8.3 8.3 8.5 8.5 Cable cutoff wavelength (μm) 1.2 1.2 1.2 1.2 MAC value 6.98 6.98 7.23 7.07 Macrobend loss (dB / turn) 0.13 0.13 0.10 0.13 Difference in propagation constant (rad / m) <![CDATA[1.13×10 4 ]]> <![CDATA[1.13×10 4 ]]> <![CDATA[1.12×10 4 ]]> <![CDATA[1.15×10 4 ]]> <![CDATA[F μBL_Δβ (1 / (rad / m) 8 )]]> <![CDATA[3.65×10 -33 ]]> <![CDATA[3.65×10 -33 ]]> <![CDATA[4.15×10 -33 ]]> <![CDATA[3.20×10 -33 ]]> porosity 0.42 0.42 0.42 0.42 Chip count 1728 1728 1728 1728 <![CDATA[F μBL_GΔβ ]]> <![CDATA[7.4×10 -11 ]]> <![CDATA[6.5×10 -11 ]]> <![CDATA[5.5×10 -11 ]]> <![CDATA[1.2×10 -10 ]]> Increase in temperature characteristic test loss (dB / km) 0.04 0.04 0.01 0.01

[0084] Table 5

[0085] Sample No. 20 21 Outer diameter of the glass section (μm) 81.1 80.5 Outer diameter of the main coating layer (μm) 114.6 114.7 Outer diameter (μm) of the secondary coating layer 152.8 151.0 Young's modulus (GPa) of the glass portion 74.0 74.0 Young's modulus (MPa) of the main coating layer 0.18 0.19 Young's modulus (MPa) of the secondary coating layer 1279 1246 Thickness of the main coating layer (μm) 16.8 17.1 Thickness (μm) of the secondary coating layer 19.1 18.2 Coating thickness (μm) 35.9 35.3 <![CDATA[Flexural rigidity of the glass part (Pa·m 4 )]]> <![CDATA[1.57×10 -7 ]]> <![CDATA[1.53×10 -7 ]]> <![CDATA[Flexural rigidity of the secondary coating (Pa·m4 ) > <![CDATA[2.34×10- 8 ]]> <![CDATA[2.12×10- 8 ]]> κs(Pa) <![CDATA[8.9×10 5 ]]> <![CDATA[8.8×10 5 ]]> Deformation resistance of the secondary coating layer (Pa) <![CDATA[2.7×10 6 ]]> <![CDATA[2.4×10 6 ]]> μ(au) 3 3 <![CDATA[F μBL G(Pa- 1 ·m- 105 )]]> <![CDATA[7.3×10 27 ]]> <![CDATA[8.5×10 27 ]]> Mode field diameter (μm) 8.5 8.2 Cable cutoff wavelength (μm) 1.2 1.2 MAC value 7.07 6.99 Macrobending loss (dB / tum) 0.13 0.08 Difference in propagation constant (rad / m) <![CDATA[1.15×10 4 ]]> <![CDATA[1.11×10 4 ]]> <![CDATA[F μBL_Δβ (1 / (rad / m) 8 )]]> <![CDATA[3.20×10 -33 ]]> <![CDATA[4.48×10 -33 ]]> porosity 0.42 0.42 Chip count 1728 1728 <![CDATA[F μBL_GΔβ ]]> <![CDATA[8.2×10 -11 ]]> <![CDATA[1.3×10 -10 ]]> Increase in temperature characteristic test loss (dB / km) 0.01 0.02

[0086] The parameters representing various specifications of optical fibers, including mode field diameter (MFD), cutoff wavelength, MAC value, macrobending loss, and propagation constant difference, are as follows.

[0087] The mode field diameter is the mode field diameter of the LP01 mode light that propagates in an optical fiber at a wavelength of 1310 nm. The mode field diameter is defined in ITU-T Recommendation G.650.1 by Petermann II (Equation (7) below). Here, E(r) represents the electric field intensity at a point at a distance r from the central axis of the optical fiber.

[0088]

[0089] The cutoff wavelength represents the minimum wavelength at which higher-order modes are sufficiently attenuated. This higher-order mode, for example, refers to the LP11 mode. Specifically, it is the minimum wavelength at which the loss of higher-order modes becomes 19.3 dB. Cutoff wavelengths include fiber cutoff wavelengths and cable cutoff wavelengths, which can be determined, for example, by the method described in ITU-T Recommendation G.650. Cable cutoff wavelengths are listed in Tables 1-5. Furthermore, the MAC value is the ratio of the mode field diameter of light with a wavelength of 1310 nm to the cable cutoff wavelength. If the mode field diameter is set to 2ω and the cable cutoff wavelength is set to λ... cc It is then defined as 2w / λcc Additionally, macrobending loss is the bending loss caused by light with a wavelength of 1625 nm propagating in the bent portion of the fiber when it is bent with a radius of 10 mm. The " / turn" in the unit of macrobending loss refers to "each bend of the fiber". Furthermore, the propagation constant difference is the difference between the propagation constant of light with a wavelength of 1550 nm in the waveguide mode and the propagation constant of light with a wavelength of 1550 nm in the radiation mode; in this experiment, it is the difference between the propagation constant of light with a wavelength of 1550 nm in the LP01 mode and the propagation constant in the LP11 mode. The propagation constant is calculated based on the refractive index distribution of the prototype fiber using the two-dimensional finite element method described in Non-Patent Document 7 (K. Saitoh and M. Koshiba, "Full-Vectorial Imaginary-DistanceBeam Propagation Method Based on a Finite Element scheme: Application to Photonic Crystal Fibers," IEEE J. Quant. Elect. vol. 38, pp. 927-933, 2002.).

[0090] The microbending loss characteristic factor F of optical fiber cables in samples 1 to 21 μBL_GΔβ The value is obtained by substituting the values ​​of the parameters recorded in Tables 1 to 5 into equations (3), (4), (5) and (6).

[0091] As described above, the increase in loss during temperature characteristic tests for each of the fiber optic cables in samples 1 to 21 was determined using the cable temperature characteristic test specified in GR-20, Issue 4, July 2013, "Generic Requirements for Optical Fiber and Optical Fiber Cable". Specifically, after winding a 1km long cable onto a spool and placing the spool into a constant-temperature bath at room temperature, one end of the cable and the other end were each exposed 3m above the bath and connected to an OTDR (Optical Time Domain Reflectometer). A spool with a diameter where the overlap of the wound cable was 7 layers or less was selected. Furthermore, it is known that this spool diameter has almost no effect on the measured values ​​in the aforementioned cable temperature characteristic test. Therefore, a spool with a different diameter can also be used. Next, the transmission loss of light with a wavelength of 1625nm propagating in the cable was measured while the constant-temperature bath was at room temperature. Then, the temperature of the constant temperature bath was lowered for more than 1.5 hours. After confirming that the temperature reached -40°C, the temperature was maintained at -40°C for 12 hours. After that, the transmission loss of light with a wavelength of 1625nm propagating in the above-mentioned cable was measured. The difference between this transmission loss value and the transmission loss value measured at the above-mentioned room temperature was calculated, and this difference was taken as the increase in loss in the temperature characteristic test.

[0092] The inventors of this invention used the micro-bending loss characteristic factor F μBL_GΔβ The values ​​are plotted on the x-axis and the increase in temperature characteristic test loss is plotted on the y-axis, showing the micro-bending loss characteristic factors F for samples 1 to 21 respectively. μBL_GΔβ The values ​​of the temperature characteristic test and the increase in loss were obtained. The result was that... Figure 4 The scatter plot is shown. Based on this scatter plot, the function is obtained using the least squares method, resulting in a first-order function with a positive slope, expressed by the following equation (8). Furthermore, Figure 4 The correlation coefficient of the data was over 87%.

[0093] Y = 10 8 X+0.021···(8)

[0094] In addition, Figure 4 In this equation, the first-order function is represented by the straight line L. Thus, the micro-bending loss characteristic factor F can be determined. μBL_GΔβ The value of the microbending loss characteristic factor F is highly correlated with the value of the increase in loss during temperature characteristic testing. Specifically, the value of the microbending loss characteristic factor F is... μBL_GΔβ The value of is roughly proportional to the increase in loss during temperature characteristic testing, with a positive slope.

[0095] As mentioned above, in optical fiber cables, there is a trend to ensure that the increase in transmission loss at -40°C, based on room temperature, is less than 0.15 dB / km. Therefore, based on equation (8), the microbending loss characteristic factor F is calculated. μBL_GΔβ The value is 1.2 × 10. －9 Under these conditions, the increase in temperature characteristic test loss becomes slightly less than 0.15 dB / km.

[0096] Therefore, according to the micro-bending loss characteristic factor F μBL_GΔβ The value is 1.2 × 10 －9 The optical fiber cable 1 described in the above embodiments can suppress the increase in transmission loss so that the increase in transmission loss is less than 0.15 dB / km in a low temperature environment of -40°C.

[0097] In addition, such as Figure 4 As shown, it can be seen that if the micro-bending loss characteristic factor F μBL_GΔβ The value is 9.9 × 10 －10 Below, the increase in temperature characteristic test loss, which is the increase in transmission loss, can be kept below 0.12 dB / km. Furthermore, it is known that if the microbending loss characteristic factor F... μBL_GΔβ The value is 7.9 × 10 －10 Below this, the increase in temperature characteristic test loss, which is the increase in transmission loss, can be kept below 0.10 dB / km.

[0098] The present invention has been described above using the above embodiments as examples, but the present invention is not limited thereto.

[0099] For example, in the above embodiment, an example was described where the secondary cladding layer is the outermost layer of the optical fiber. However, even when a colored layer is provided as a third cladding layer on the outer periphery of the secondary cladding layer, as long as the Young's modulus of the colored layer is not significantly different from that of the secondary cladding layer, it can be considered as a second cladding layer, i.e., a secondary cladding layer, including both the secondary layer and the colored layer, and applied to the present invention.

[0100] Furthermore, in the above embodiment, an example of constructing an optical fiber cable by housing a cored fiber within the internal space 3S of the sheath 3 was described. However, it is also possible to construct an optical fiber cable by housing multiple single-core optical fibers within the internal space 3S. In an optical fiber cable constructed from single-core optical fibers, if the sheath 3 shrinks in a low-temperature environment, each optical fiber is compressed by the sheath 3. However, unlike the case of the cored fiber, these single-core optical fibers are not fixed to other optical fibers, and therefore, even when compressed by the sheath 3, they can move freely within the internal space 3S without being constrained by other optical fibers, compared to the case of the cored fiber. Thus, the single-core optical fiber has a greater degree of freedom of movement within the internal space 3S. Therefore, the pressure exerted on each optical fiber from the sheath 3 is reduced, thereby reducing the microbending loss of the optical fiber. Therefore, it can be considered that the increase in transmission loss is smaller compared to the case of the cored fiber. On the other hand, in the case of an optical fiber cable constructed from cored fibers, the movement of each optical fiber constituting the cored fiber is constrained by the other optical fibers constituting the cored fiber. In this respect, it is the same regardless of the number of cores in the optical fiber constituting the cored fiber. That is, it can be considered that in a cored cable, the degree of freedom of movement of each optical fiber is independent of the number of cores in the cored cable and is approximately equal. Therefore, it can be considered that in the case of an optical fiber cable composed of cored cables, even if the number of cores in the cored cable is more than 12, the compression of each optical fiber from the sheath 3 is approximately equal to that in the case of 12 cores, and the microbending loss is also approximately equal. Therefore, even in the case of an optical fiber cable composed of cored cables with a number of cores other than 12, the microbending loss characteristic factor F μBL_GΔβ The relationship between the value of and the increase in temperature characteristic test loss can also be roughly expressed by equation (8). Therefore, by making the micro-bending loss characteristic factor F μBL_GΔβ The value is 1.2 × 10 －9 The following can be achieved by reducing the increase in transmission loss to less than 0.15 dB / km at a low temperature of -40°C, regardless of the number of cores in the fiber constituting the cored fiber.

[0101] According to the present invention, an optical fiber cable capable of suppressing increased transmission loss in low-temperature environments is provided, which can be used, for example, in communication infrastructure and other fields.

Claims

1. An optical fiber cable comprising a plurality of optical fibers and a sheath housing the plurality of optical fibers within an internal space, wherein the plurality of optical fibers include: The glass portion includes a core and a cladding surrounding the core; The main overlay covers the cladding layer; and a secondary coating layer, covering the primary coating layer, characterized in that, The optical fiber has geometric microbending loss characteristics F μBL_G (Pa) -1 ·m -10.5 ), and optical microbending loss characteristics F μBL_Δβ (1 / (rad / m)) 8 ), When the bending stiffness of the glass portion is set to H f (Pa·m) 4 The deformation resistance of the sub-coating layer is set as D0 (Pa), and the bending stiffness of the sub-coating layer is set as H0 (Pa·m). 4 The Young's modulus of the glass portion is set as E. g (GPa), the Young's modulus of the main coating layer is set to E. p (MPa), set the Young's modulus of the sub-coating layer as E. s (MPa), Let the outer diameter of the glass part be d f (μm), Let the radius of the outer periphery of the main coating layer be R. p (μm), Let the radius of the outer periphery of the sub-coating layer be R. s (μm), let the thickness of the main coating layer be t. p (μm), and the thickness of the sub-coating layer is set as t. s In the case of (μm), the geometric microbending loss characteristic F μBL_G (Pa) -1 ·m -10.5 )use To indicate, When the difference between the propagation constant in the waveguide mode and the propagation constant in the radiation mode propagating in the optical fiber is defined as the propagation constant difference Δβ (rad / m), the optical microbending loss characteristic F μBL_Δβ (1 / (rad / m)) 8 )use To indicate, When the porosity 'a' of the internal space and the number of optical fibers 'b' housed within the internal space are used to define the cable characteristics 'Dc' of the optical fiber cable using the following formula, The microbending loss characteristic factor F is expressed by the following formula. μBL_GΔβ The value is 1.2 × 10 －9 the following ， The porosity α of the internal space is above 0.31 and below 0.

42.

2. The optical fiber cable according to claim 1, characterized in that, The microbending loss characteristic factor F μBL_GΔβ The value is 9.9 × 10 －10 the following.

3. The optical fiber cable according to claim 2, characterized in that, The microbending loss characteristic factor F μBL_GΔβ The value is 7.9 × 10 －10 the following.

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