Optical fiber cable and transmission method

Abstract

To provide an optical fiber cable that includes both a photonic bandgap fiber and an antiresonant fiber and has good bending characteristics, and a transmission method using the same. [Solution] An optical fiber cable includes a photonic bandgap fiber placed in a first state and an antiresonant fiber placed in a second state, wherein at least one of the macrobending loss of an optical fiber when placed in the first state is greater than the macrobending loss when placed in the second state, and the microbending loss of the optical fiber when placed in the first state is greater than the microbending loss when placed in the second state.

Description

[Technical Field]

[0001] The present invention relates to an optical fiber cable and a transmission method. [Background technology]

[0002] By transmitting light through a core that is primarily filled with air, air-core optical fibers (HCFs) have the potential to significantly reduce transmission loss compared to solid-core optical fibers. Furthermore, they offer various properties that are not possible with conventional solid-core optical fibers, such as low latency, ultra-low nonlinearity, and resistance to harsh environments, and are expected to open up many new applications.

[0003] Known examples of hole-core fibers include photonic bandgap fibers (PBGFs) and antiresonant fibers (ARFs). Non-patent documents 1 and 2 report techniques for cabling hole-core fibers. Non-patent document 3 reports a photonic bandgap fiber with a structure called a PRISM (Perturbed Resonance for Increased Single Modedness) structure. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] B. Zhu et al, “First demonstration of Hollow-Core-Fiber Cable for Low Latency Data Transmission”, OFC 2020, paper Th4B.3, (2020). [Non-patent document 2] MA Iqbal et al, “First Demonstration of 400ZR DWDM Transmission through Field Deployable Hollow-Core-Fiber Cable”, OFC 2021, paper F4C.2, (2021). [Non-patent document 3] Kazunori Takekasa, "Hole-Core Fiber Cable," Furukawa Electric Review, No. 140 (July 2021), pp. 32-39 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the known optical fiber cables, the structure of an optical fiber cable including both a photonic bandgap fiber and an antiresonant fiber has not been thoroughly studied.

[0006] The present invention has been made in view of the above, and an object of the present invention is to provide an optical fiber cable that includes both a photonic bandgap fiber and an antiresonant fiber and has good bending characteristics, and a transmission method using the same. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems and achieve the object, one aspect of the present invention is an optical fiber cable comprising a photonic bandgap fiber placed in a first state and an antiresonant fiber placed in a second state, wherein at least one of the following is true: the macrobending loss of an optical fiber when placed in the first state is greater than the macrobending loss when placed in the second state; and the microbending loss of the optical fiber when placed in the first state is greater than the microbending loss when placed in the second state.

[0008] The optical fiber cable may comprise a first cable section including the photonic bandgap fiber and a second cable section including the antiresonant fiber and connected in tandem with the first cable section, wherein the first state is achieved by laying the first cable section in a first installation environment and the second state is achieved by laying the second cable section in a second installation environment, and wherein the macrobending loss of the optical fiber when the optical fiber is in the first state is greater than the macrobending loss of the optical fiber when the optical fiber is in the second state.

[0009] The optical fiber cable may comprise a first cable section including the photonic bandgap fiber and a second cable section including the antiresonant fiber and connected in tandem with the first cable section, wherein the first state is achieved by laying the first cable section in a first installation environment and the second state is achieved by laying the second cable section in a second installation environment, and wherein the microbending loss of the optical fiber when the optical fiber is in the first state is greater than the microbending loss of the optical fiber when the optical fiber is in the second state.

[0010] The first state may be achieved by placing the photonic bandgap fiber in a first position in the optical fiber cable, and the second state may be achieved by placing the antiresonant fiber in a second position in the optical fiber cable, and the macrobending loss of the optical fiber when the optical fiber is placed in the first state may be greater than the macrobending loss of the optical fiber when the optical fiber is placed in the second state.

[0011] The first state may be achieved by placing the photonic bandgap fiber in a first position in the optical fiber cable, and the second state may be achieved by placing the antiresonant fiber in a second position in the optical fiber cable, and the microbending loss of the optical fiber when the optical fiber is placed in the first state may be greater than the microbending loss of the optical fiber when the optical fiber is placed in the second state.

[0012] The glass cladding diameter of the photonic bandgap fiber and the glass cladding diameter of the antiresonant fiber may be 250 μm or less.

[0013] One aspect of the present invention is a transmission method using the optical fiber cable, in which the photonic bandgap fiber is used as an optical transmission path and optical transmission is performed using a first wavelength band, and the antiresonant fiber is used as an optical transmission path and optical transmission is performed using a second wavelength band broader than the first wavelength band.

[0014] The number of the photonic bandgap fibers serving as the optical transmission line may be greater than the number of the antiresonant fibers serving as the optical transmission line. [Effects of the Invention]

[0015] According to the present invention, an optical fiber cable that includes both a photonic bandgap fiber and an antiresonant fiber and has good bending characteristics can be realized. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a schematic diagram of the optical fiber cable according to the first embodiment. [Figure 2] FIG. 2 is a schematic cross-sectional view of a photonic bandgap fiber taken along a plane perpendicular to the longitudinal direction thereof. [Figure 3] FIG. 3 is a schematic cross-sectional view of an antiresonant fiber taken along a plane perpendicular to the longitudinal direction thereof. [Figure 4] FIG. 4 is a diagram showing an example of the relationship between bending diameter and bending loss. [Figure 5] FIG. 5 is a diagram showing an example of the relationship between wavelength and microbending loss. [Figure 6] FIG. 6 is a schematic diagram of the optical fiber cable according to the second embodiment. [Figure 7]FIG. 7 is a schematic cross-sectional view of an optical fiber cable according to a third embodiment, taken along a plane perpendicular to the longitudinal direction thereof. DETAILED DESCRIPTION OF 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. Furthermore, in each drawing, the same or corresponding components are appropriately designated by the same reference numerals, and duplicate explanations are appropriately omitted. Furthermore, terms not specifically defined in this specification shall follow the definitions and measurement methods in ITU-T G.650.1 and G.650.2 of the International Telecommunications Union (ITU).

[0018] (Embodiment 1) 1 is a schematic 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 .

[0019] The first cable part 110 includes a photonic bandgap fiber 11 and a structure. The structure is a component of the optical fiber cable, and includes, for example, a tension member and a sheath. The first cable part 110 may also include other optical fibers, such as standard SMF, which will be described later.

[0020] FIG. 2 is a schematic cross-sectional view of a photonic bandgap fiber taken along a plane perpendicular to the longitudinal direction. The photonic bandgap fiber 11 has a PRISM structure. Specifically, the photonic bandgap fiber 11 includes a cladding 11a made of glass. The cladding 11a includes a micro-hole region 11aa. The micro-hole region 11aa includes micro-holes arranged in a triangular lattice pattern. The micro-holes form a photonic bandgap in a wavelength band including a predetermined wavelength. The micro-hole region 11aa includes a main core 11b, which is a hole core, and side cores 11c, which are hole cores arranged on either side of the main core 11b. A resin coating is provided on the outer periphery of the cladding 11a. The glass cladding diameter of the photonic bandgap fiber 11 is the outer diameter of the cladding 11a. To ensure reliability, the glass cladding diameter of the photonic bandgap fiber 11 is preferably 250 μm or less.

[0021] The side core 11c is configured to optically couple with a higher-order propagation mode of a predetermined wavelength in the main core 11b. As a result, light propagating in the higher-order propagation mode in the main core 11b transfers to the side core 11c and leaks while propagating. As a result, the main core 11b propagates only the fundamental mode at the predetermined wavelength with low loss, so the photonic bandgap fiber 11 is essentially a single-mode optical fiber. The predetermined wavelength is a wavelength that belongs to the wavelength band used for optical transmission, such as 1550 nm.

[0022] The size of the main core 11b is equivalent to about 19 of the minute holes that form the photonic band gap. Such a main core 11b is sometimes called a 19-cell type.

[0023] Returning to FIG. 1 , the second cable portion 120 includes the antiresonant fiber 12 and a structure. The structure is a component of the optical fiber cable, including, for example, a tension member and a sheath. The second cable portion 120 may also include other optical fibers, such as standard SMF.

[0024] FIG. 3 is a schematic cross-sectional view of an antiresonant fiber in a plane perpendicular to the longitudinal direction. The antiresonant fiber 12 has a structure also known as NANF (Nested Antiresonant Nodeless Fiber). Specifically, the antiresonant fiber 12 includes an outer tube 12a made of glass and inner capillaries 12b and 12c. The outer tube 12a is covered with a resin coating. The glass cladding diameter of the antiresonant fiber 12 is the outer diameter of the outer tube 12a. To ensure reliability, the glass cladding diameter of the antiresonant fiber 12 is preferably 250 μm or less.

[0025] The inner capillaries 12b are arranged to form a regular pentagon in the cross section of the outer tube 12a. Each inner capillary 12c has a nested structure with the inner capillary 12b. An air hole core 12d is formed in the area surrounded by the inner capillaries 12b. In the antiresonant fiber 12, light of a predetermined wavelength is confined in the air hole core 12d and transmitted due to the antiresonant phenomenon generated by the inner capillaries 12b and 12c. The predetermined wavelength is a wavelength that belongs to the wavelength band used for optical transmission, for example, 1550 nm.

[0026] Returning to FIG. 1 , the connection section 130 connects the first cable section 110 and the second cable section 120. At the connection section 130, the photonic bandgap fiber 11 and the antiresonant fiber 12 are optically connected. This optical connection may be realized by a spatial optical system, or by a fusion splice or a mechanical splice. Alternatively, the photonic bandgap fiber 11 and the antiresonant fiber 12 may be connected via a solid-core fiber.

[0027] In the optical fiber cable 100, the first cable portion 110 is laid in a first installation environment E1, which places the photonic bandgap fiber 11 in a first state. The second cable portion 120 is laid in a second installation environment E2, which places the antiresonant fiber 12 in a second state.

[0028] Examples of the first installation environment E1 include deep seabed areas where the optical fiber cable 100 is likely to bend, areas that wind through forests, residential areas, office areas, farmland, or data centers. Examples of the second installation environment E2 include shallow areas of the ocean where the optical fiber cable 100 is less likely to bend, long-distance natural areas, and along railroad tracks.

[0029] The first and second states will now be described. For example, assume that a certain optical fiber is a single-mode optical fiber (hereinafter referred to as standard SMF) that is standardly used in optical communications and is specified in ITU-T G.652. In this case, at least one of the following (1) and (2) holds true: (1) When a standard SMF is placed in the first state, its macrobending loss is larger than when the standard SMF is placed in the second state. (2) When the standard SMF is placed in the first state, its microbending loss is larger than the microbending loss when the standard SMF is placed in the second state.

[0030] In the case of (1), the second state is when the average bending diameter over the length of the optical fiber in that state is relatively large, for example, a bending diameter of 60 mm or more, which is the prescribed example of the bending diameter for standard SMF. The first state is when the average bending diameter over the length of the optical fiber in that state is smaller than the bending diameter in the second state, for example, a bending diameter of 50 mm or less. In this case, when the standard SMF is in the first state, its macrobending loss is greater than the macrobending loss when the standard SMF is in the second state.

[0031] In the case of (2), the first state is when the average microbending loss over the length of the optical fiber in that state is relatively large, for example, when the increase in transmission loss due to microbending is equal to or greater than 0.3 dB / km@1550 nm as specified in ITU-T G.652.C. The second state is when the average microbending loss over the length of the optical fiber in that state is smaller than the microbending loss in the first state, for example, when the increase in transmission loss due to microbending is less than 0.3 dB / km@1550 nm as specified in ITU-T G.652.C. The increase in transmission loss due to microbending (=microbending loss) can be measured, for example, by the fixed drum method.

[0032] In the case of the optical fiber cable 100, (1) and (2) hold true.

[0033] In the optical fiber cable 100 configured as described above, the photonic bandgap fiber 11 is placed in the first state and the antiresonant fiber 12 is placed in the second state, thereby achieving the effect of improving bending characteristics such as macrobending characteristics or microbending characteristics.

[0034] Furthermore, since both the photonic bandgap fiber 11 and the antiresonant fiber 12 are hole-core fibers, the effects of low latency, ultra-low nonlinearity, and resistance to harsh environments are also achieved.

[0035] The reason why the configuration of the optical fiber cable 100 exhibits the effect of improving the bending characteristics will be explained below. Figure 4 is a diagram showing an example of the relationship between the bending diameter and the bending loss per turn at a wavelength of 1550 nm for a typical photonic bandgap fiber and an antiresonant fiber having the configuration shown in Figure 2 or 3.

[0036] Moreover, Fig. 5 shows an example of the relationship between wavelength and microbending loss for a typical photonic bandgap fiber and antiresonant fiber having the configuration shown in Fig. 2 or 3. Here, the microbending loss is a value measured by the fixed drum method.

[0037] 4 and 5, the glass cladding diameter is 135 μm and the coating diameter is 250 μm. PBGF stands for photonic bandgap fiber, and ARF stands for antiresonant fiber.

[0038] As shown in Figures 4 and 5, photonic bandgap fibers tend to have relatively low macrobending and microbending losses compared to antiresonant fibers.

[0039] Therefore, in the optical fiber cable 100, the first cable portion 110 including the photonic bandgap fiber 11 is placed in a first installation environment E1 (an example of an environment in which a first state is realized), which can be said to be an environment that is more severe for optical fibers in terms of bending characteristics, and the second cable portion 120 including the antiresonant fiber 12 is placed in a second installation environment E2, which can be said to be an environment that is more lenient for optical fibers in terms of bending characteristics. This achieves an optical fiber cable 100 with good bending characteristics.

[0040] In Figure 5, the wavelengths where the microbending loss of the PBGF is relatively large correspond to the wavelength band where the transmission loss is large due to the influence of leaky modes. PBGF is known to have such a wavelength band with large transmission loss in the photonic bandgap band. On the other hand, antiresonant fiber is known to have small transmission loss over a wider band than the photonic bandgap.

[0041] Note that, for example, the following procedure can be used to lay the first cable portion 110 including the photonic bandgap fiber 11 in the first installation environment E1 and the second cable portion 120 including the antiresonant fiber 12 in the second installation environment E2: That is, a design drawing of the installation is drawn on a map, and the optical fiber cable 100 is configured and installed so that the first cable portion 110 is installed in the first installation environment E1 and the second cable portion 120 is installed in the second installation environment E2. Alternatively, at the installation site, it is determined whether the installation environment is the first installation environment E1 or the second installation environment E2, and the cable corresponding to that installation environment is selected from the first cable portion 110 and the second cable portion 120, and the cables are connected sequentially while moving to the installation location.

[0042] (Embodiment 2) 6 is a schematic diagram of an optical fiber cable according to embodiment 2. The optical fiber cable 200 includes a first cable portion 210, a second cable portion 220, and a connection portion 230.

[0043] The first cable portion 210 includes a photonic bandgap fiber 11 and a structure. The first cable portion 210 may include other optical fibers. The first cable portion 210 is a high-density cable including a large number of photonic bandgap fibers 11, for example, a high-density cable with 3000 or more fibers. Such high-density cables are relatively susceptible to microbending loss.

[0044] The second cable portion 220 includes the antiresonant fiber 12 and a structure. The second cable portion 220 may include other optical fibers. The second cable portion 220 is a low-density cable that includes a large number of antiresonant fibers 12, but has a lower density than the first cable portion 210. The second cable portion 220 is a low-density cable with, for example, less than 3,000 fibers. Such a low-density cable is relatively less susceptible to microbending loss.

[0045] The connecting portion 230 connects the first cable portion 210 and the second cable portion 220. At the connecting portion 230, the photonic bandgap fiber 11 and the antiresonant fiber 12 are optically connected. This optical connection may be realized by a spatial optical system, or by fusion splicing or mechanical splicing. Alternatively, the photonic bandgap fiber 11 and the antiresonant fiber 12 may be connected via a solid-core fiber.

[0046] In the optical fiber cable 200 configured as described above, the photonic bandgap fiber 11 is in the first state, the antiresonant fiber 12 is in the second state, and the above-mentioned condition (2) is met. That is, when the standard SMF is in the first state, the microbending loss of the standard SMF is greater than the microbending loss when the standard SMF is in the second state. Such an optical fiber cable 200 also exhibits the effect of improving bending characteristics.

[0047] (Embodiment 3) 7 is a schematic cross-sectional view of an optical fiber cable according to a third embodiment, taken along a plane perpendicular to the longitudinal direction. The optical fiber cable 300 includes a tension member 310 and a slot 320 in which the tension member 310 is disposed near the center. The slot 320 is provided with a plurality of slits 321, and each slit 321 houses a plurality of optical fiber ribbons 330. Markers 322 are provided on the outer peripheral surface of the slot 320 to identify the circumferential direction of the slot 320. The slot 320 is wrapped with a holding winding material 340, and a tear cord 350 is provided in the holding winding material 340. A sheath 360 is provided on the outer periphery of the holding winding material 340.

[0048] The optical fiber ribbon 330 includes a plurality of optical fibers (for example, four fibers). The optical fiber ribbon includes a photonic bandgap fiber 11 and an antiresonant fiber 12.

[0049] Here, in the optical fiber cable 300, optical fibers placed near the slot 320 or near the holding winding 340 tend to have large microbending losses. In the optical fiber cable 300, the photonic bandgap fiber 11 is arranged so as to be placed relatively close to the slot 320 or relatively close to the holding winding 340 in the optical fiber cable 300, thereby realizing the photonic bandgap fiber 11 being placed in the first state. In addition, the antiresonant fiber 12 is arranged so as to be placed farther from the slot 320 or farther from the holding winding 340 than the photonic bandgap fiber 11 in the optical fiber cable 300, thereby realizing the antiresonant fiber 12 being placed in the second state.

[0050] The optical fiber cable 300 configured as above satisfies the above-mentioned condition (2). That is, the microbending loss of the standard SMF when it is placed in the first state is greater than the microbending loss when it is placed in the second state. This optical fiber cable 300 also exhibits the effect of improving the microbending characteristics.

[0051] (Experimental Examples 1 to 4) As the air-hole core fibers, we prepared a 19-cell photonic bandgap fiber with a length of 500 m and a PRISM structure as shown in Figure 2, and an antiresonant fiber with a length of 500 m and a NANF structure as shown in Figure 3. The transmission loss of the photonic bandgap fiber at a wavelength of 1550 nm was 2.5 dB / km, and the transmission loss of the antiresonant fiber at a wavelength of 1550 nm was 1.5 dB / km.

[0052] In Experimental Examples 1 to 4, the total transmission loss (total loss) at a wavelength of 1550 nm was measured when two of these hole-core fibers were spliced. The first state was a bent state with an average bending diameter of 50 mm and two turns, and the second state was a bent state with an average bending diameter of 300 mm and two turns. One of the two hole-core fibers was placed in the first state, and the other was placed in the second state. The results are shown in Table 1. As can be seen from Table 1, it was confirmed that the total loss was smallest in Experimental Example 2, in which the photonic bandgap fiber was placed in the first state and the antiresonant fiber was placed in the second state. Specifically, the total loss in Experimental Example 2 was 1 dB or more smaller than that in Experimental Example 1, in which the antiresonant fiber was placed in the first state and the photonic bandgap fiber was placed in the second state. Furthermore, the total loss in Experimental Example 2 was smaller than that in Experimental Examples 3 and 4, in which the two hole-core fibers were the same type.

[0053] [Table 1]

[0054] It is clear that in all of Experimental Examples 1 to 4, the properties of the holey-core fiber, such as low delay, ultra-low nonlinearity, and resistance to harsh environments, are maintained.

[0055] In the above-mentioned second embodiment, when connecting multiple optical fiber cables 200 in a vertical row, it is preferable to connect a photonic bandgap fiber and an antiresonant fiber, since the characteristics in the longitudinal direction become the average characteristics of both.

[0056] Furthermore, as described above, since the transmission band of an antiresonant fiber is relatively wide, transmission may be performed using a single antiresonant fiber in a wide wavelength band (an example of a second wavelength band) such as WDM (Wavelength Division Multiplexing) transmission, and the signal light output from the single antiresonant fiber may be divided into several wavelength bands (an example of a first wavelength band), and the signal light of each wavelength band may be transmitted through each of a plurality of photonic bandgap fibers. Such a transmission method is an example of a transmission method in which optical transmission is performed using a photonic bandgap fiber as an optical transmission line using a first wavelength band, and optical transmission is performed using an antiresonant fiber as an optical transmission line using a second wavelength band wider than the first wavelength band. Furthermore, such a transmission method is an example of a transmission method in which the number of photonic bandgap fibers used as optical transmission lines is greater than the number of antiresonant fibers used as optical transmission lines. Such a transmission method can be realized, for example, in a form similar to a passive optical network (PON).

[0057] Furthermore, if antiresonant fiber has lower transmission loss than photonic bandgap fiber, the longer distances of the optical fiber cable may be constructed with a second cable section including antiresonant fiber to minimize bending, and in installation environments where bending is more likely to occur, the optical fiber cable may be constructed with a first cable section including photonic bandgap fiber.

[0058] Furthermore, the present invention is not limited to the above-described embodiments. Appropriate combinations of the above-described components are also included in the present invention. For example, the present invention also includes a case where the first state is realized by placing a photonic bandgap fiber at a first position in an optical fiber cable and the second state is realized by placing an antiresonant fiber at a second position in the optical fiber cable, and the macrobending loss of an optical fiber when the optical fiber is in the first state is greater than the macrobending loss when the optical fiber is in the second state. Furthermore, further effects and modifications can be easily derived by those skilled in the art. Therefore, the broader aspects of the present invention are not limited to the above-described embodiments, and various modifications are possible. [Explanation of symbols]

[0059] 11: Photonic bandgap fiber 11a: Cladding part 11aa: Micropore region 11b: Main Core 11c: Side core 12: Antiresonant fiber 12a: Outer tube 12b, 12c: inner capillary 12d: Hole core 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: Optical fiber tape 340: Retaining winding material 350: Tear string 360: Sheath E1: 1st installation environment E2:Second installation environment

Claims

1. 1. A fiber optic cable comprising: a photonic bandgap fiber placed in a first state; an antiresonant fiber placed in a second state; Including, a macrobending loss of an optical fiber when the optical fiber is in the first state is greater than a macrobending loss of the optical fiber when the optical fiber is in the second state; and a microbending loss of the optical fiber when the optical fiber is in the first state is greater than a microbending loss of the optical fiber when the optical fiber is in the second state; At least one of the following holds true Fiber optic cable.

2. the optical fiber cable comprises a first cable section including the photonic bandgap fiber, and a second cable section including the antiresonant fiber and cascaded to the first cable section; The first state is a state in which the first cable portion is laid in a first installation environment, The second state is when the second cable section is laid in a second installation environment. This is achieved by The macrobending loss of the optical fiber when the optical fiber is in the first state is greater than the macrobending loss of the optical fiber when the optical fiber is in the second state.

2. The optical fiber cable according to claim 1.

3. the optical fiber cable comprises a first cable section including the photonic bandgap fiber, and a second cable section including the antiresonant fiber and cascaded to the first cable section; The first state is a state in which the first cable portion is laid in a first installation environment, The second state is when the second cable section is laid in a second installation environment. This is achieved by The microbending loss of the optical fiber when the optical fiber is in the first state is greater than the microbending loss of the optical fiber when the optical fiber is in the second state.

2. The optical fiber cable according to claim 1.

4. The first state includes a state in which the photonic bandgap fiber is disposed at a first position in the optical fiber cable; The second state is a state in which the antiresonant fiber is disposed at a second position in the optical fiber cable. This is achieved by The macrobending loss of the optical fiber when the optical fiber is in the first state is greater than the macrobending loss of the optical fiber when the optical fiber is in the second state.

2. The optical fiber cable according to claim 1.

5. The first state includes a state in which the photonic bandgap fiber is disposed at a first position in the optical fiber cable; The second state is a state in which the antiresonant fiber is disposed at a second position in the optical fiber cable. This is achieved by The microbending loss of the optical fiber when the optical fiber is in the first state is greater than the microbending loss of the optical fiber when the optical fiber is in the second state.

2. The optical fiber cable according to claim 1.

6. The glass cladding diameter of the photonic bandgap fiber and the glass cladding diameter of the antiresonant fiber are 250 μm or less.

2. The optical fiber cable according to claim 1.

7. A transmission method using the optical fiber cable according to any one of claims 1 to 6, transmitting light using a first wavelength band using the photonic bandgap fiber as an optical transmission path; The antiresonant fiber is used as an optical transmission path, and optical transmission is performed using a second wavelength band that is wider than the first wavelength band. Transmission method.

8. The number of the photonic bandgap fibers serving as optical transmission paths is greater than the number of the antiresonant fibers serving as optical transmission paths. The transmission method according to claim 7.

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