Fiber optic cable

Abstract

To provide an optical fiber cable that includes both small-diameter and ultra-small-diameter optical fibers and has good bending characteristics. [Solution] A thin optical fiber in a first state, comprising a glass optical fiber portion including a core portion and a cladding portion, and a covering portion surrounding the outer circumference of the glass optical fiber portion, wherein the outer diameter of the covering portion is 176 μm or more and 220 μm or less; and an ultra-thin optical fiber in a second state, comprising a glass optical fiber portion including a core portion and a cladding portion, and a covering portion surrounding the outer circumference of the glass optical fiber portion, wherein the outer diameter of the covering portion is 150 μm or more and 175 μm or less, wherein the microbend loss of a certain optical fiber when it is in the first state is greater than the microbend loss when the optical fiber is in the second state.

Description

Technical Field

[0005] , , ,

[0001] The present invention relates to an optical fiber cable.

Background Art

[0002] Reducing the outer diameter of an optical fiber provided with a coating is effective in increasing the number of optical fibers accommodated per unit cross-sectional area of an optical fiber cable and increasing the transmission capacity of optical communication. Therefore, many studies have been made on reducing the diameter of optical fibers.

[0003] For example, Patent Documents 1 and 2 disclose techniques for reducing the outer diameter of an optical fiber to 200 μm or less. Further, Patent Documents 3 and 4 disclose techniques for making the outer diameter of an optical fiber smaller than 180 μm to 210 μm by making the cladding diameter of the optical fiber smaller than a typical 125 μm. Furthermore, Patent Document 5 discloses the structure of an optical fiber cable in which an optical fiber having a cladding diameter smaller than a typical 125 μm is accommodated.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

[0006] The present invention has been made in view of the above, and its object is to provide an optical fiber cable that includes both small-diameter optical fibers and ultra-small-diameter optical fibers and has good bending characteristics. [Means for solving the problem]

[0007] To solve the above-mentioned problems and achieve the objective, one aspect of the present invention is an optical fiber cable comprising: a glass optical fiber portion including a core portion and a cladding portion; a covering portion surrounding the outer circumference of the glass optical fiber portion, wherein the outer diameter of the covering portion is 176 μm or more and 220 μm or less, and is in a first state; and an ultra-fine optical fiber portion including a glass optical fiber portion including a core portion and a cladding portion; a covering portion surrounding the outer circumference of the glass optical fiber portion, wherein the outer diameter of the covering portion is 150 μm or more and 175 μm or less, and is in a second state, wherein the microbend loss of an optical fiber when it is in the first state is greater than the microbend loss when it is in the second state.

[0008] The optical fiber cable comprises a first cable section including the thin optical fiber and a second cable section including the ultra-thin optical fiber and connected in tandem with the first cable section, wherein the first state is achieved when the first cable section is laid in a first laying environment, and the second state is achieved when the second cable section is laid in a second laying environment.

[0009] The first state may be achieved by arranging the thin optical fiber in the optical fiber cable at a first position, and the second state may be achieved by arranging the ultra-thin optical fiber in the optical fiber cable at a second position.

[0010] The outer diameter of the glass optical fiber portion of the aforementioned ultra-fine optical fiber may be 60 μm or more and 130 μm or less.

[0011] The outer diameter of the glass optical fiber portion of the ultra-fine optical fiber may be 70 μm or more and 110 μm or less.

[0012] The aforementioned thin optical fiber and ultra-thin optical fiber may conform to the standards defined in ITU-T G.657 A1 or A2 with respect to mode field diameter, cutoff wavelength, and macrobend loss. .

[0013] The optical fiber cable may comprise two first cable sections and one second cable section connected in a tandem configuration.

[0014] The number of ultra-fine optical fibers included in the second cable section may be within the range of (2 ± 0.1) times the number of thin optical fibers included in each of the first cable sections. [Effects of the Invention]

[0015] According to the present invention, it is possible to realize an optical fiber cable that includes both small-diameter optical fibers and ultra-small-diameter optical fibers and has good bending characteristics. [Brief explanation of the drawing]

[0016] [Figure 1] Figure 1 is a schematic diagram of the optical fiber cable according to Embodiment 1. [Figure 2] Figure 2 is a schematic cross-sectional view of a small-diameter optical fiber in a plane perpendicular to the longitudinal direction. [Figure 3] Figure 3 is a schematic cross-sectional view of an ultra-fine optical fiber in a plane perpendicular to its longitudinal direction. [Figure 4] Figure 4 shows an example of the relationship between fiber diameter and microbend loss. [Figure 5] Figure 5 shows an example of the relationship between fiber diameter and normalized cross-sectional area. [Figure 6] FIG. 6 is a schematic configuration diagram of an optical fiber cable according to Embodiment 2. [Figure 7] FIG. 7 is a schematic cross-sectional view in a plane perpendicular to the longitudinal direction of the optical fiber cable according to Embodiment 3. **MODE FOR CARRYING OUT THE INVENTION**

[0017] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments described below. Also, in each drawing, the same or corresponding components are appropriately given the same reference numerals, and duplicate descriptions are omitted as appropriate. In this specification, the cutoff wavelength or the effective cutoff wavelength refers to the cable cutoff wavelength defined in ITU-T G.650.1 of the International Telecommunication Union (ITU). Also, for terms not specifically defined in this specification, the definitions and measurement methods in G.650.1 and G.650.2 shall apply.

[0018] (Embodiment 1) FIG. 1 is a schematic configuration diagram of an optical fiber cable according to Embodiment 1. The optical fiber cable 100 includes a first cable portion 110, a second cable portion 120, and a connection portion 130.

[0019] The first cable portion 110 includes a small-diameter optical fiber 11 and a structure. The structure is a structure that constitutes the optical fiber cable and includes, for example, a tension member and a sheath.

[0020] FIG. 2 is a schematic cross-sectional view in a plane perpendicular to the longitudinal direction of the small-diameter optical fiber. The small-diameter optical fiber 11 includes a glass optical fiber portion 11a made of silica-based glass and a coating portion 11b made of resin.

[0021] The glass optical fiber portion 11a includes a core portion 11aa and a cladding portion 11ab. The core portion 11aa is the region where the transmitted optical signal is mainly confined. The core portion 11aa contains dopants used in optical fibers, such as alkali elements, germanium (Ge), fluorine (Fe), and chlorine (Cl). Alternatively, the core portion 11aa may be made of pure silica glass. Pure silica glass is an extremely high-purity silica glass that substantially does not contain dopants that change the refractive index and has a refractive index of approximately 1.444 at a wavelength of 1550 nm.

[0022] The cladding portion 11ab surrounds the outer circumference of the core portion 11aa. The cladding portion 11ab has a refractive index lower than the maximum refractive index of the core portion 11aa. The cladding portion 11ab may contain dopants used in optical fibers, such as fluorine (Fe) or chlorine (Cl), or it may be made of pure silica glass.

[0023] The refractive index profile of the glass optical fiber portion 11a is, for example, a step type, a W type, or a trench type, but is not particularly limited.

[0024] The covering portion 11b surrounds the outer periphery of the glass optical fiber portion 11a. The covering portion 11b comprises a primary layer 11ba surrounding the outer periphery of the cladding portion 11ab, and a secondary layer 11bb surrounding the outer periphery of the primary layer 11ba.

[0025] The resins constituting the primary layer 11ba and the secondary layer 11bb are, for example, UV-curable resins. UV-curable resins are composed of various resin materials and additives, such as oligomers, diluent monomers, photopolymerization initiators, silane coupling agents, sensitizers, and lubricants. Conventionally known materials such as polyether-based urethane acrylates, epoxy acrylates, polyester acrylates, and silicone acrylates can be used as oligomers. Conventionally known materials such as monofunctional monomers and polyfunctional monomers can be used as diluent monomers. Furthermore, the additives are not limited to those mentioned above, and a wide range of conventionally known additives used for UV-curable resins can be used.

[0026] The outer diameter of the glass optical fiber portion 11a is also called the cladding diameter of the small-diameter optical fiber 11. The cladding diameter of the small-diameter optical fiber 11 is about the same as that of a typical optical fiber, for example, 125 μm.

[0027] The outer diameter of the coating portion 11b, which is the outer diameter of the thin optical fiber 11, i.e., the fiber diameter, is, for example, 176 μm to 220 μm, which is smaller than the 250 μm of a typical optical fiber.

[0028] Furthermore, in the thin optical fiber 11, it is preferable that the fiber diameter is 35 μm or more larger than the cladding diameter, as this allows for suitable mechanical strength and reliability in the thin optical fiber 11, and also ensures workability in the wire drawing process during the manufacturing of the thin optical fiber 11. Moreover, it is even more preferable if the fiber diameter is 50 μm or more larger than the cladding diameter, from the viewpoint of mechanical strength, reliability, and workability.

[0029] Returning to Figure 1, the second cable section 120 includes an ultra-fine optical fiber 12 and a structure. The structure is a structure that makes up the optical fiber cable, and includes, for example, a tension member and a sheath.

[0030] Figure 3 is a schematic cross-sectional view of an ultra-fine optical fiber in a plane perpendicular to the longitudinal direction. The ultra-fine optical fiber 12, like the thin optical fiber 11, comprises a glass optical fiber portion 12a made of silica glass and a coating portion 12b made of resin. The glass optical fiber portion 12a includes a core portion 12aa and a cladding portion 12ab. The cladding portion 12ab surrounds the outer circumference of the core portion 12aa. The coating portion 12b surrounds the outer circumference of the glass optical fiber portion 12a. The coating portion 12b comprises a primary layer 12ba and a secondary layer 12bb.

[0031] The material of each component of the ultra-fine optical fiber 12 may be the same as the material of the corresponding component in the thin optical fiber 11. Furthermore, the refractive index profile of the glass optical fiber portion 12a is not particularly limited, but may be, for example, a step type, a W type, or a trench type.

[0032] However, the outer diameter of the coating portion 12b, which is the outer diameter of the ultra-fine optical fiber 12, also called the fiber diameter, is, for example, 150 μm or more and 175 μm or less, which is even smaller than the fiber diameter of the thin optical fiber 11.

[0033] Furthermore, the outer diameter of the glass optical fiber portion 12a, i.e., the cladding diameter, is, for example, 60 μm to 130 μm, and preferably 70 μm to 110 μm. If the cladding diameter is 70 μm or more, the microbend loss of the glass optical fiber portion 12a can be made relatively small (for example, 10 times or less of the microbend loss of a standard SMF described later), and handling performance is also improved. If the cladding diameter is 110 μm or less, it is preferable from the viewpoint of reliability and high density. In the case of the ultra-fine optical fiber 12, the fiber diameter is preferably 35 μm or more larger than the cladding diameter, and more preferably 50 μm or more larger.

[0034] The thin optical fiber 11 and the ultra-thin optical fiber 12 preferably conform to ITU-T G.657 A1 or A2 in terms of mode field diameter, cutoff wavelength, and macrobend loss. Here, ITU-T G.657 A1 and A2 specify that the mode field diameter at wavelength 1310 is 8.6 μm-9.2 μm and the cutoff wavelength is 1260 nm or less. Furthermore, ITU-T G.657 A1 specifies that the microbend loss per 10 turns at a radius of 15 mm is 0.25 dB or less at a wavelength of 1550 nm and 1.0 dB or less at a wavelength of 1625 nm, and that the microbend loss per turn at a radius of 10 mm is 0.75 dB or less at a wavelength of 1550 nm and 1.5 dB or less at a wavelength of 1625 nm. Furthermore, ITU-T G.657 A2 specifies that the microbend loss per 10 turns at a radius of 15 mm should be 0.03 dB or less at a wavelength of 1550 nm and 0.1 dB or less at a wavelength of 1625 nm, and that the microbend loss per turn at a radius of 10 mm should be 0.1 dB or less at a wavelength of 1550 nm and 0.2 dB or less at a wavelength of 1625 nm, and that the microbend loss per turn at a radius of 7.5 mm should be 0.5 dB or less at a wavelength of 1550 nm and 1.0 dB or less at a wavelength of 1625 nm.

[0035] Returning to Figure 1, the connection section 130 connects the first cable section 110 and the second cable section 120 in a vertical arrangement. At the connection section 130, the thin optical fiber 11 and the ultra-thin optical fiber 12 are optically connected. This optical connection may be achieved by fusion splicing, or by a spatial optical system or mechanical splicing.

[0036] In this optical fiber cable 100, the first cable section 110 is laid in the first laying environment E1, thereby enabling the thin optical fiber 11 to be in the first state. In addition, the second cable section 120 is laid in the second laying environment E2, thereby enabling the ultra-thin optical fiber 12 to be in the second state.

[0037] Examples of the first installation environment E1 include deep-sea areas where the optical fiber cable 100 is likely to be bent, areas that wind through forests, residential areas, office districts, farmland, or inside data centers. Examples of the second installation environment E2 include shallow areas of the sea where the optical fiber cable 100 is less likely to be bent, long stretches of natural terrain, and along railway lines.

[0038] The first and second states will be explained. For example, consider a single-mode optical fiber (hereinafter referred to as standard SMF) that is standardly used in optical communications as defined in ITU-T G.652. In this case, when the standard SMF is placed in the first state, its microbend loss is greater than when the standard SMF is placed in the second state.

[0039] In this case, the first state is when the average microbend loss over the length of the optical fiber in that state is relatively large, for example, when the increase in transmission loss due to microbend is 0.3 dB / km@1550 nm or more as specified in ITU-T G.652.C. The second state is when the average microbend loss over the length of the optical fiber in that state is smaller than the microbend loss in the first state, for example, when the increase in transmission loss due to microbend is less than 0.3 dB / km@1550 nm as specified in ITU-T G.652.C.

[0040] The increase in transmission loss due to microbends (=microbend loss) can be measured, for example, by the fixed-diameter drum method specified in JIS C6823:2010.

[0041] Furthermore, microbend loss can also be measured by the following measurement method, called the sandpaper method, which is similar to the fixed-diameter drum method described above. In the sandpaper method, for example, the transmission loss in state A, where a predetermined length (400m or more) of optical fiber is wound in a single layer without overlapping at a tension of 100gf on a fixed drum wound with #1000 grit sandpaper, is defined as the difference between the transmission loss in state B, where the optical fiber is wound on the same fixed drum as state A, but without sandpaper, at the same tension and length as state A, and this difference is defined as the microbend loss. Here, the transmission loss of the optical fiber in state B does not include microbend loss and is considered to be the transmission loss inherent to the optical fiber itself. Also, in this measurement method, the transmission loss is measured at a wavelength of 1550nm, for example, so the microbend loss is also the value at a wavelength of 1550nm. Hereafter, unless otherwise specified, the microbend loss is the value at a wavelength of 1550nm.

[0042] In the optical fiber cable 100 configured as described above, the thin optical fiber 11 is placed in the first state where the microbend loss of the optical fiber tends to be large, and the ultra-thin optical fiber 12 is placed in the second state. As a result, the optical fiber cable 100 exhibits the effect of improving bend characteristics such as microbend characteristics in an optical fiber cable that includes both thin optical fibers and ultra-thin optical fibers.

[0043] Furthermore, if the thin optical fiber 11 and the ultra-thin optical fiber 12 comply with ITU-T G.657 A1 or A2 in terms of mode field diameter, cutoff wavelength, and macrobend loss, the macrobend characteristics will also be good.

[0044] The present inventors will now provide a detailed explanation based on their experimental results. The inventors conducted experiments to measure the microbend loss of optical fibers with various fiber diameters smaller than the typical fiber diameter of 250 μm. The optical fibers measured were those whose refractive index profile, cladding diameter, and coating thickness were optimized to satisfy ITU-T G.657 A1 optical characteristics.

[0045] Figure 4 shows an example of the relationship between fiber diameter and microbend loss. The microbend loss was measured using the sandpaper method described above. As can be seen from Figure 4, even if the optical fiber is optimized, the microbend loss becomes very large when the fiber diameter is less than 150 μm, so it is preferable that the fiber diameter be 150 μm or larger.

[0046] Furthermore, when the fiber diameter was between 150 μm and 175 μm, the microbend loss tended to be greater than when the fiber diameter was between 176 μm and 220 μm.

[0047] Therefore, in the optical fiber cable 100, the first cable section 110, which includes a small-diameter optical fiber 11 with a fiber diameter of 176 μm or more and 220 μm or less, is placed in a first laying environment E1 (an example of an environment in which the first state is realized), which is a more severe environment for optical fibers in terms of microbend loss, and the second cable section 120, which includes an ultra-small-diameter optical fiber 12 with a fiber diameter of 150 μm or more and 175 μm or less, is placed in a second laying environment E2, which is a more lenient environment for optical fibers in terms of microbend loss. This makes it possible to realize an optical fiber cable 100 with good bend characteristics.

[0048] On the other hand, ultra-thin optical fibers 12 have a significant advantage over thin optical fibers 11 in that they make it easier to increase the number of optical fibers that can be accommodated per unit cross-sectional area of ​​an optical fiber cable. In this specification, the advantages of ultra-thin optical fibers 12 will be explained using an indicator called the normalized cross-sectional area. The normalized cross-sectional area is the cross-sectional area of ​​an optical fiber normalized to the cross-sectional area of ​​an optical fiber with a fiber diameter of 250 μm.

[0049] Figure 5 shows an example of the relationship between fiber diameter and normalized cross-sectional area. As shown in Figure 5, for example, the normalized cross-sectional area of ​​a thin optical fiber 11 with a fiber diameter of 200 μm is 64%, while the normalized cross-sectional area of ​​an ultra-thin optical fiber 12 with a fiber diameter of 160 μm is 41%. Therefore, with an ultra-thin optical fiber 12, it is easier to increase the number of optical fibers that can be accommodated per unit cross-sectional area. Alternatively, with an ultra-thin optical fiber 12, it is easier to accommodate the same number of optical fibers in a thinner optical fiber cable.

[0050] To lay the first cable section 110, which includes the thin optical fiber 11, in the first laying environment E1, and the second cable section 120, which includes the ultra-thin optical fiber 12, in the second laying environment E2, for example, the following can be done. That is, a laying design is drawn on a map, and the optical fiber cable 100 is configured and laid so that the first cable section 110 is laid in the first laying environment E1 and the second cable section 120 is laid in the second laying environment E2. Alternatively, at the laying site, it is determined whether the laying environment is the first laying environment E1 or the second laying environment E2, and the cable corresponding to that laying environment is selected from the first cable section 110 and the second cable section 120, and the laying location is moved while sequentially connecting them.

[0051] (Embodiment 2) Figure 6 is a schematic diagram of the optical fiber cable according to Embodiment 2. The optical fiber cable 200 comprises two first cable sections 210, one second cable section 220, and a connecting section 230.

[0052] The first cable section 210 includes a small-diameter optical fiber 11 and a structure. The first cable section 210 is a high-density cable containing a large number of small-diameter optical fibers 11, for example, a high-density cable with 6912 cores.

[0053] The second cable section 220 includes ultra-fine optical fibers 12 and a structure. The second cable section 220 is an ultra-high-density cable containing a large number of ultra-fine optical fibers 12, for example, a high-density cable with 13,824 cores. This number of cores is twice the number of cores of the first cable section 210.

[0054] The connection section 230 connects two first cable sections 210 and one second cable section 220 in a tandem configuration. At the connection section 230, the small diameter optical fiber 11 and the ultra-small diameter optical fiber 12 are optically connected. This optical connection may be achieved by fusion splicing, or by a spatial optical system or mechanical splicing. As described above, the number of ultra-small diameter optical fibers 12 included in the second cable section 220 is twice the number of small diameter optical fibers 11 included in each of the first cable sections 210, so each ultra-small diameter optical fiber 12 in the second cable section 220 is connected to one of the small diameter optical fibers 11 in either of the two first cable sections 210.

[0055] In the optical fiber cable 200 configured as described above, the thin optical fiber 11 of the first cable section 210 is placed in a first state similar to the first laying environment E1, and the ultra-thin optical fiber 12 of the second cable section 220 is placed in a second state similar to the second laying environment E2. As a result, an optical fiber cable 200 with good bending characteristics is realized, similar to the case of optical fiber cable 100.

[0056] Furthermore, the density of the small-diameter optical fibers 11 in the first cable section 210 may be relatively low. While increasing the density of optical fibers in an optical fiber cable tends to increase microbend loss, by relatively low the density of the small-diameter optical fibers 11, the microbend loss can be kept relatively small even if the first cable section 210 is subjected to more stringent conditions for the optical fibers in terms of microbend loss.

[0057] Furthermore, in this embodiment, the number of ultra-fine optical fibers 12 included in the second cable section 220 is twice the number of thin optical fibers 11 included in each of the first cable sections 210, but it may also be in the range of (2 ± 0.1). In this case, some of the thin optical fibers 11 or ultra-fine optical fibers 12 will be unconnected, but since most of the thin optical fibers 11 or ultra-fine optical fibers 12 can be connected and used, there may be no practical problem.

[0058] (Embodiment 3) Figure 7 is a schematic cross-sectional view of an optical fiber cable according to Embodiment 3 in a plane perpendicular to the longitudinal direction. The optical fiber cable 300 comprises a tension member 310 and a slot 320 in which the tension member 310 is located near the center. The slot 320 is provided with a plurality of slits 321, and each slit 321 accommodates a plurality of optical fiber tapes 330. A marker 322 for identifying the circumferential direction of the slot 320 is provided on the outer circumferential surface of the slot 320. The slot 320 is wrapped with a retaining winding material 340, and a tear cord 350 is provided on the retaining winding material 340. Furthermore, a sheath 360 is provided on the outer circumferential surface of the retaining winding material 340.

[0059] The optical fiber tape 330 contains multiple (for example, 4-core) optical fibers. These optical fiber tapes include thin optical fibers 11 and ultra-thin optical fibers 12.

[0060] In the optical fiber cable 300, optical fibers placed close to the slot 320 or close to the retaining winding material 340 tend to experience greater microbend loss. In the optical fiber cable 300, the small-diameter optical fiber 11 is positioned relatively close to the slot 320 or relatively close to the retaining winding material 340, thereby enabling the small-diameter optical fiber 11 to be in the first state. Furthermore, the ultra-small-diameter optical fiber 12 is positioned further from the slot 320 or further from the retaining winding material 340 than the small-diameter optical fiber 11, thereby enabling the ultra-small-diameter optical fiber 12 to be in the second state.

[0061] Even with the optical fiber cable 300 configured as described above, the effect of improved microbend characteristics is achieved.

[0062] Furthermore, when connecting multiple such optical fiber cables 300 in a series, it is preferable to connect the thin-diameter optical fiber 11 and the ultra-thin optical fiber 12 alternately, as this averages out the transmission characteristics in the longitudinal direction.

[0063] (Examples, Comparative Examples) To realize the examples and comparative examples, thin and ultra-thin optical fibers, both 500m in length, were prepared. Both of these optical fibers had a trench-type refractive index profile. Specifically, the core of these optical fibers comprises a center core with a core diameter 2a and a specific refractive index difference Δ1 relative to the cladding, an intermediate core layer surrounding the center core with an outer diameter 2b and a specific refractive index difference Δ2 relative to the cladding, and a trench surrounding the intermediate core layer with an outer diameter 2c and a specific refractive index difference Δ3 relative to the cladding. The structural parameters of the thin and ultra-thin optical fibers are shown in Table 1. Note that the primary diameter is the outer diameter of the primary layer. The secondary diameter is the outer diameter of the secondary layer, i.e., the fiber diameter.

[0064] [Table 1]

[0065] Table 2 shows the optical properties of the thin and ultra-thin optical fibers. "λcc" refers to the cable cutoff wavelength, and "MFD" refers to the mode field diameter. Microbend loss was measured using the sandpaper method. Both the thin and ultra-thin optical fibers had approximately the same mode field diameter and cutoff wavelength, and met the standards defined by ITU-T G.657. Furthermore, the microbend loss was equivalent to ITU-T G.657 A2. [Table 2]

[0066] As examples and comparative examples, the total transmission loss (total loss) at a wavelength of 1550 nm was measured when two of these porous core fibers were connected. However, to achieve the first state, the optical fiber was wound around a commercially available bobbin with a diameter of 405 mm under a tension of 60 gf. To achieve the second state, the optical fiber was wound around a commercially available bobbin with a diameter of 405 mm under a tension of 15 gf. Then, one of these two optical core fibers was placed in the first state and the other in the second state. The results are shown in Table 3.

[0067] In Table 3, "15gf loss" refers to the transmission loss of an optical fiber wound with a tension of 15gf, and "60gf loss" refers to the transmission loss of an optical fiber wound with a tension of 60gf. Therefore, as shown in Table 3, in the comparative example, the transmission loss of the small-diameter optical fiber was 0.097dB, the transmission loss of the ultra-small-diameter optical fiber was 1.016dB, and the total loss including connection loss was 1.213dB. In contrast, in the example, the transmission loss of the ultra-small-diameter optical fiber was 0.256dB, the transmission loss of the small-diameter optical fiber was 0.404dB, and the total loss including connection loss was 0.760dB. Therefore, it was confirmed that the total loss in the example could be reduced to approximately 60% compared to the comparative example. [Table 3]

[0068] It should be noted that the present invention is not limited to the embodiments described above. Configurations that appropriately combine the above-described components are also included in the present invention. Furthermore, further effects and modifications can be easily derived by those skilled in the art. Therefore, broader aspects of the present invention are not limited to the embodiments described above, and various modifications are possible. [Explanation of symbols]

[0069] 2a: Core diameter 2b,2c:Outer diameter 11: Thin optical fiber 11a, 12a: Glass optical fiber section 11aa, 12aa: Core section 11ab, 12ab: Cladding section 11b, 12b: Covering part 11ba, 12ba: Primary layer 11bb, 12bb: Secondary layer 12: Ultra-thin optical fiber 15gf,60gf:Tension 100, 200, 300: Fiber optic cable 110,210: First cable section 120,220: Second cable section 130,230: Connection part 310: Tension Member 320: Slot 321: Slit 322: Marker 330: Fiber optic tape 340: Retaining wrapping material 350: String 360: Sheath 1310: Wavelength A, B: State E1: 1st installation environment E2:Second installation environment Δ1, Δ2, Δ3: Difference in relative refractive index

Claims

1. It is a fiber optic cable, A thin optical fiber is placed in a first state and comprises a glass optical fiber portion including a core portion and a cladding portion, and a covering portion surrounding the outer circumference of the glass optical fiber portion, wherein the outer diameter of the covering portion is 176 μm or more and 220 μm or less. An ultra-fine optical fiber in a second state comprises a glass optical fiber portion including a core portion and a cladding portion, and a covering portion surrounding the outer circumference of the glass optical fiber portion, wherein the outer diameter of the covering portion is 150 μm or more and 175 μm or less, Includes, The microbend loss of a certain optical fiber when it is in the first state is greater than the microbend loss when it is in the second state. Fiber optic cable.

2. The optical fiber cable comprises a first cable section including the thin optical fiber and a second cable section including the ultra-thin optical fiber and connected in tandem with the first cable section. The first state is when the first cable section is laid in the first laying environment. The second state is when the second cable section is laid in the second laying environment. This is achieved by The optical fiber cable according to claim 1.

3. The first state is that in the optical fiber cable, the small-diameter optical fiber is arranged in a first position. The second state is that the ultra-thin optical fiber is positioned at the second position in the optical fiber cable. This is achieved by The optical fiber cable according to claim 1.

4. The outer diameter of the glass optical fiber portion of the aforementioned ultra-fine optical fiber is 60 μm or more and 130 μm or less. The optical fiber cable according to claim 1.

5. The outer diameter of the glass optical fiber portion of the aforementioned ultra-fine optical fiber is 70 μm or more and 110 μm or less. The optical fiber cable according to claim 1.

6. The aforementioned thin optical fiber and ultra-thin optical fiber shall conform to the standards defined in ITU-T G. 657 A1 or A2 with respect to mode field diameter, cutoff wavelength, and macrobend loss. The optical fiber cable according to claim 1.

7. The optical fiber cable comprises two first cable sections and one second cable section connected in tandem. The optical fiber cable according to claim 2.

8. The number of ultra-fine optical fibers included in the second cable section is within the range of (2 ± 0.1) times the number of thin optical fibers included in each of the first cable sections. The optical fiber cable according to claim 7.

Images