Multicore fiber

Abstract

To provide a high-performance or multi-functional multicore fiber.SOLUTION: A multicore fiber provided herein comprises multiple hollow cores. Light may be trapped in the hollow cores by the anti-resonant light confinement effect. Multiple tubular bodies may be provided to surround each hollow core to trap light within the hollow cores by the anti-resonant phenomenon. At least one of the multiple tubular bodies may be shared by at least two of the multiple hollow cores.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a multicore fiber. [Background technology]

[0002] As a multi-core fiber having multiple cores, techniques for improving the characteristics by providing holes between the cores are being studied (Non-Patent Documents 1 to 3). These cores are also called solid cores because they are made of a solid medium such as glass.

[0003] On the other hand, hole-core fibers are also being actively studied. A hole-core fiber is an optical fiber that has a hole-shaped core portion (hole core portion) that is not filled with a solid medium. There are two types of hole-core fibers: antiresonant type and photonic bandgap type (Patent Documents 1 and 2, Non-Patent Document 4). Hole-core fibers are being actively studied due to their innovative high functionality. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2017-520804 [Patent Document 2] International Publication No. 2009 / 040902 [Non-patent literature]

[0005] [Non-Patent Document 1] K. Saitoh et al, “Multi-core hole-assisted fibers for high core density space division multiplexing”, OECC 2010, 7C2-1 (2010). [Non-Patent Document 2] B. Yao et al., “Reduction of Crosstalk by Hole-Walled Multi-Core Fiber”, OFC 2012, paper OM2D.5. (2012). [Non-Patent Document 3] K. Mukasa et al, “Uncoupled 6-core Fibers with a Standard 125mm Cladding, ITU-T G.652 Optical Properties, and Low XT”, OFC 2023, paper M3B.2 (2023). [Non-Patent Document 4] Gregory T. Jasion et al., “0.174 dB / km Hollow Core Double Nested Antiresonant Nodeless Fiber (DNANF)”, OFC 2022, paper Th4C.7 (2022). Summary of the Invention [Problem to be solved by the invention]

[0006] As optical transmission technology becomes more sophisticated, unprecedented high functionality or multiple functions are required of multicore fibers. However, known multicore fibers cannot fully satisfy these requirements.

[0007] The present invention has been made in view of the above, and an object of the present invention is to provide a high-performance or multi-function multi-core fiber. [Means for solving the problem]

[0008] In order to solve the above-mentioned problems and achieve the object, one aspect of the present invention is a multi-core fiber including a plurality of core portions, the plurality of core portions being air-hole core portions.

[0009] The air hole core may confine light by an antiresonant type light confinement effect.

[0010] The optical fiber may further include a plurality of tubular bodies surrounding the periphery of the air hole core portion and having the effect of confining light in the air hole core portion by an antiresonant phenomenon.

[0011] At least one of the plurality of tubular bodies may be shared between at least two of the plurality of air hole core portions.

[0012] An outer tubular body may be included that surrounds the plurality of tubular bodies and supports at least one of the plurality of tubular bodies.

[0013] A support may be provided that is supported by the outer tubular body and supports at least one of the plurality of tubular bodies.

[0014] The support may have a tubular structure that houses at least one of the plurality of tubular bodies.

[0015] The air hole core may confine light by a photonic band gap type light confinement effect. Effect of the Invention

[0016] According to the present invention, an effect is achieved in that a high-function or multi-function multi-core fiber can be realized. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 is a schematic cross-sectional view of a multi-core fiber according to a first embodiment, taken along a plane perpendicular to the longitudinal direction thereof. [Diagram 2] FIG. 2 is a schematic cross-sectional view of a multi-core fiber according to a second embodiment, taken along a plane perpendicular to the longitudinal direction thereof. [Diagram 3] FIG. 3 is a schematic cross-sectional view of a multi-core fiber according to a third embodiment in a plane perpendicular to the longitudinal direction. [Figure 4] FIG. 4 is a schematic cross-sectional view of a multi-core fiber according to a fourth embodiment, taken along a plane perpendicular to the longitudinal direction thereof. [Diagram 5] FIG. 5 is a schematic cross-sectional view of a multi-core fiber according to a fifth embodiment, taken along a plane perpendicular to the longitudinal direction thereof. [Figure 6] FIG. 6 is a schematic cross-sectional view of a multi-core fiber according to a sixth embodiment in a plane perpendicular to the longitudinal direction. [Figure 7] FIG. 7 is a schematic cross-sectional view of a multi-core fiber according to a seventh embodiment in a plane perpendicular to the longitudinal direction. [Figure 8] FIG. 8 is a schematic cross-sectional view of a multi-core fiber according to an eighth embodiment in a plane perpendicular to the longitudinal direction. [Figure 9] FIG. 9 is a schematic cross-sectional view of a multi-core fiber according to a ninth embodiment in a plane perpendicular to the longitudinal direction. [Figure 10] FIG. 10 is a schematic cross-sectional view of a multi-core fiber according to a tenth embodiment in a plane perpendicular to the longitudinal direction. [Figure 11] FIG. 11 is a schematic cross-sectional view of a multi-core fiber according to an eleventh embodiment in a plane perpendicular to the longitudinal direction. [Figure 12] FIG. 12 is a schematic cross-sectional view of a multi-core fiber according to a twelfth embodiment in a plane perpendicular to the longitudinal direction. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] In known multi-core fibers, the core portion is made of a solid medium such as glass. In contrast, the present inventors have conceived of a novel configuration in which a plurality of air-hole core portions are used as the multiple core portions, thereby realizing a multi-core fiber with unprecedented high functionality or multi-functions, and have completed the present invention.

[0019] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiment described below. In addition, in each drawing, the same or corresponding components are appropriately assigned the same reference numerals. In addition, in this specification, the cutoff wavelength or effective cutoff wavelength refers to the cable cutoff wavelength (λcc) defined in ITU-T G.650.1 of the International Telecommunications Union (ITU). In addition, other terms not specifically defined in this specification shall follow the definitions and measurement methods in G.650.1 and G.650.2.

[0020] (Embodiment 1) 1 is a schematic cross-sectional view in a plane perpendicular to the longitudinal direction of a multi-core fiber according to embodiment 1. The multi-core fiber 100 includes ten tubular bodies 10, two air hole core portions 20, two supports 30, and an outer tubular body 40. The ten tubular bodies 10, the two air hole core portions 20, and the two supports 30 are examples of a plurality of tubular bodies, a plurality of air hole core portions as core portions, and a plurality of supports, respectively.

[0021] In the following, first the tubular body 10 and the hollow core portion 20 will be described, then the support body 30 will be described, and finally the outer tubular body 40 will be described.

[0022] [Tubular body and hollow core] The ten tubular bodies 10 are circular tubes and arranged to form two hexagonal lattices in cross section. The hexagonal lattices are, for example, regular hexagonal lattices. The tubular bodies 10 are, for example, silica glass tubes having a predetermined thickness.

[0023] The two air hole cores 20 are formed in an area surrounded by six tubular bodies 10. That is, the tubular bodies 10 surround the air hole cores 20. The multiple tubular bodies 10 have the effect of confining light in the air hole cores 20 by the antiresonant phenomenon. As a result, the air hole cores 20 each confine light by the antiresonant type light confinement effect and propagate it. For example, 80% or more of the light field propagating through each air hole core 20 exists in each air hole core 20, and the remaining 20% ​​or less of the light field exists in the tubular body 10, etc. In FIG. 1, field F indicates the light field propagating through each air hole core 20. In field F, the field intensity is indicated by the shading of the dot pattern, and the higher the dot density, the higher the field intensity. The wavelength of the light propagating through each air hole core 20 can be changed by adjusting the wall thickness of the tubular body 10. That is, the wall thickness of the tubular body 10 is set according to the wavelength of the light propagated through the air hole core portion 20. The wavelength of the light propagated through the air hole core portion 20 is, for example, a wavelength included in a communication wavelength band such as the 1.55 μm band, but is not particularly limited. For example, the light propagated through the air hole core portion 20 and its wavelength may be light and its wavelength used for power transmission such as optical power feeding. Furthermore, the wavelengths of the light propagated through the two air hole core portions 20 may be different from each other. When the wavelengths are different from each other in this way, the structural parameters such as the wall thickness and outer diameter of each tubular body 10 may be different from each other so as to be appropriate for the wavelength.

[0024] The tubular bodies 10 are arranged with appropriate gaps between them. If there are no gaps and the tubular bodies 10 are in contact with each other, the light propagating through the air hole cores 20 may leak through the contacting parts of the tubular bodies 10. If the gaps are too large, the light leaks excessively from the gaps.

[0025] The ten tubular bodies 10 include four tubular bodies 11, four tubular bodies 12, and two tubular bodies 13. The four tubular bodies 11 are mechanically connected to the inner wall of the outer tubular body 40 by welding or the like, and are directly supported by the outer tubular body 40. The four tubular bodies 12 are mechanically connected to the support 30 by welding or the like, and are supported by the support 30. The two tubular bodies 13 are mechanically connected to the support 30 by welding or the like, and are shared between the two air hole core portions 20. That is, each of the two tubular bodies 13 contributes to the light confinement of each of the two air hole core portions 20. The tubular body 13 is an example of a tubular body shared between at least two of the multiple air hole core portions.

[0026] [Support] The two supports 30 are rod-like bodies with a circular cross section. The supports 30 are made of a solid medium such as silica glass. The supports 30 are mechanically connected to the outer tubular body 40 by welding or the like, and are supported by the outer tubular body 40. As described above, the supports 30 support the tubular bodies 12 and 13.

[0027] [Outer tubular body] The outer tubular body 40 is a circular tube. The outer tubular body 40 is, for example, a silica glass tube having a predetermined thickness. The outer tubular body 40 accommodates the tubular body 10, the hole core portion 20, and the support 30. That is, the outer tubular body 40 surrounds the tubular body 10. As described above, the outer tubular body 40 directly supports the tubular body 11 of the tubular body 10. It can also be said that the outer tubular body 40 indirectly supports the tubular bodies 12 and 13 with the support 30 interposed therebetween.

[0028] The multi-core fiber 100 configured as above includes a plurality of air-hole core portions 20. This allows the multi-core fiber 100 to achieve high functionality or multiple functions that cannot be achieved by known multi-core fibers.

[0029] For example, a hole core such as the hole core 20 and optical transmission technology using the same can realize innovative high performance by eliminating various limitations caused by solid media such as glass. Such limitations include optical delay, power tolerance limits, absorption and scattering losses due to the medium, and resistance to harsh environments. Therefore, the hole core 20 can be suitably used for optical power feeding and ultra-low latency optical transmission, for example.

[0030] Furthermore, in the multi-core fiber 100, the tubular bodies 12 and 13 of the tubular body 10 are supported by the support body 30. This allows the arrangement and shape of the tubular body 10 to be set with a higher degree of freedom compared to a case in which the tubular bodies 10 are all directly supported by the outer tubular body 40. As a result, the arrangement and shape of the hole core portions 20 can be set with a higher degree of freedom.

[0031] Furthermore, in the multi-core fiber 100, since the tubular body 13 is shared between the two air-hole core portions 20, the number of tubular bodies used and the cross-sectional area of ​​the multi-core fiber 100 can be reduced.

[0032] The outer diameter of the outer tubular body 40, i.e., the fiber diameter of the multi-core fiber 100, is preferably 125 μm from the viewpoint of compatibility with many known optical fibers. The wall thickness of the tubular body 10 is, for example, 0.65 μm from the viewpoint of confining light in the 1.55 μm wavelength band. The outer diameter of the tubular body 10 is, for example, 35 μm. When the confinement loss at a wavelength of 1550 nm of the air-hole core portion 20 of the multi-core fiber 100 having the structure exemplified in this way was calculated, it was a sufficiently small value of 0.3 dB / km. Moreover, the inter-core crosstalk was a sufficiently low value of -30 dB or less per 100 km at a wavelength of 1550 nm.

[0033] The multi-core fiber 100 can be manufactured, for example, as follows. First, a glass rod that becomes the support 30 is prepared. The glass rod can be formed, for example, by using a known VAD (Vapor Axial Deposition) method, MCVD (Modified Chemical Vapor Deposition) method, or OVD (Outside Vapor Deposition) method. Next, a first glass tube that becomes the tubular body 10 and a second glass tube that becomes the outer tubular body 40 are prepared. As the first glass tube and the second glass tube, a commercially available glass tube may be used, or a glass tube manufactured by drilling holes in a glass rod manufactured by the VAD method may be used. Next, a structure as shown in FIG. 1 is formed to form an optical fiber preform. Next, the optical fiber preform is drawn in the same manner as a known multi-core fiber, thereby manufacturing the multi-core fiber 100. Note that the tubular body 10 is required to have a relatively thin wall thickness, so that a first glass tube with a relatively thick wall thickness may be prepared and the desired wall thickness of the tubular body 10 may be realized by adjusting the drawing conditions during drawing.

[0034] (Embodiment 2) 2 is a schematic cross-sectional view in a plane perpendicular to the longitudinal direction of the multi-core fiber according to embodiment 2. The multi-core fiber 100A has a configuration in which ten tubular bodies 10A are added to the multi-core fiber 100 according to embodiment 1. The ten tubular bodies 10A are each housed in a tubular body 10. The wall thickness of the tubular body 10A is also set so as to realize anti-resonant type light confinement according to the wavelength of light propagated in the air-hole core portion 20.

[0035] In the multi-core fiber 100A, the tubular bodies 10 and 10A form an anti-resonant double light confinement structure for the air-hole core portion 20.

[0036] The multi-core fiber 100A configured as above can achieve high performance or multiple functions similar to those of the multi-core fiber 100 according to the embodiment 1 as described above. Furthermore, since the tubular bodies 10, 10A form a double light confinement structure for the air hole core portion 20, for example, the light field leaking from the tubular body 10 is also confined by the tubular body 10A. As a result, the multi-core fiber 100A can reduce the confinement loss of the air hole core portion 20 more than the multi-core fiber 100.

[0037] (Embodiment 3) FIG. 3 is a schematic cross-sectional view of a multi-core fiber according to the third embodiment in a plane perpendicular to the longitudinal direction. The multi-core fiber 100B has a configuration in which four supports 30B are added to the multi-core fiber 100 according to the first embodiment. The support 30B is a rod-like body having a circular cross section, but has a different diameter from the support 30. The support 30B is made of a solid medium such as silica-based glass. The support 30B is mechanically connected to the outer tubular body 40 by welding or the like, and is supported by the outer tubular body 40. The tubular body 11 is supported by the support 30B and the outer tubular body 40. The tubular body 12 is supported by the supports 30 and 30B. The support 30 and the support 30B are examples of supports having different shapes or sizes.

[0038] The multi-core fiber 100B configured as above can achieve the same high performance or multi-function effect as that of the multi-core fiber according to embodiment 1. Furthermore, since the multi-core fiber 100B includes the support 30B in addition to the support 30, the mechanical strength is increased and the ease and freedom of arrangement of the tubular body 10 is improved.

[0039] (Embodiment 4) 4 is a schematic cross-sectional view in a plane perpendicular to the longitudinal direction of the multi-core fiber according to embodiment 4. The multi-core fiber 100C has a configuration in which ten tubular bodies 10A are added to the multi-core fiber 100B according to embodiment 3. It can also be said that the multi-core fiber 100C has a configuration in which four supports 30B are added to the multi-core fiber 100A according to embodiment 2.

[0040] According to the multi-core fiber 100A configured as above, it is possible to realize the advantages of both the multi-core fibers 100A and 100B according to the second and third embodiments as described above.

[0041] (Embodiment 5) 5 is a schematic cross-sectional view in a plane perpendicular to the longitudinal direction of a multi-core fiber according to embodiment 5. The multi-core fiber 100D includes 15 tubular bodies 10D, three air-hole core portions 20D, ten supports 30D, and an outer tubular body 40. The outer tubular body 40 accommodates the tubular bodies 10D, the air-hole core portions 20D, and the support 30D.

[0042] The ten supports 30D are rod-shaped bodies with a circular cross section, and are made of a solid medium such as quartz glass. The ten supports 30D are arranged to form three line segments in the cross section. The three line segments form approximately equal angles around the central axis and extend from the central axis to the outer tubular body 40. Three of the twelve supports 30D are mechanically connected to the inner wall of the outer tubular body 40 by welding or the like. In addition, the supports 30D adjacent to each other on the line segments are mechanically connected to each other by welding or the like. As a result, the supports 30D are directly or indirectly supported by the outer tubular body 40. In addition, the ten supports 30D are arranged to divide the inner space of the outer tubular body 40 into three.

[0043] The fifteen tubular bodies 10D are arranged in each of the three sections, five of them in each section. The five tubular bodies 10D in the same section are arranged to form a pentagonal lattice in cross section. The pentagonal lattice is, for example, a regular pentagonal lattice. This allows the air hole core section 20D to be formed in the area surrounded by the tubular body 10D. The field FD indicates the field of light propagating through the air hole core section 20D. The wall thickness of the tubular body 10D is set according to the wavelength of the light propagating through the air hole core section 20D.

[0044] Moreover, the tubular body 10D is mechanically connected to the support body 30D or the outer tubular body 40 by welding or the like, and is supported by the support body 30D or the outer tubular body 40. Specifically, among the tubular bodies 10D, the tubular body 11D is connected to the outer tubular body 40, and among the tubular bodies 10D, the tubular body 12D is connected to the support body 30D. Moreover, the tubular bodies 10D include tubular bodies having different sizes, such as diameters, from each other.

[0045] The multi-core fiber 100D configured as above can achieve high performance or multiple functions similar to the multi-core fiber 100 according to embodiment 1 as described above. In particular, the multi-core fiber 100D has three air-hole core portions 20D, which is more than the multi-core fiber 100, and therefore can achieve higher performance or multiple functions than the multi-core fiber 100.

[0046] In the multi-core fiber 100D, the support 30D divides the internal space of the outer tubular body 40 into three sections, and the tubular body 10D forms air hole core portions 20D within the sections, and the air hole core portions 20D are arranged with relatively high symmetry.

[0047] Furthermore, in the multi-core fiber 100D, the tubular bodies 10D include tubular bodies having different sizes, such as diameters, so that there is a high degree of freedom in setting the size, position, and so on, of the hole core portions 20D.

[0048] (Embodiment 6) 6 is a schematic cross-sectional view in a plane perpendicular to the longitudinal direction of a multi-core fiber according to embodiment 6. The multi-core fiber 100E includes 20 tubular bodies 10E, four air-hole core portions 20E, 12 supports 30E, and an outer tubular body 40. The outer tubular body 40 accommodates the tubular bodies 10E, the air-hole core portions 20E, and the support 30E.

[0049] The twelve supports 30E are rod-shaped bodies with a circular cross section, and are made of a solid medium such as quartz glass. The twelve supports 30E are arranged to form four line segments in the cross section. The four line segments form approximately equal angles around the central axis and extend from the central axis to the outer tubular body 40. Four of the twelve supports 30E are mechanically connected to the inner wall of the outer tubular body 40 by welding or the like. In addition, the supports 30E adjacent to each other on the line segments are mechanically connected to each other by welding or the like. As a result, the supports 30E are directly or indirectly supported by the outer tubular body 40. In addition, the twelve supports 30E are arranged to divide the inner space of the outer tubular body 40 into four.

[0050] The 20 tubular bodies 10E are arranged in each of the four sections, five of them in each section. The five tubular bodies 10E in the same section are arranged to form a pentagonal lattice in cross section. The pentagonal lattice is, for example, a regular pentagonal lattice. This allows the air hole core section 20E to be formed in the area surrounded by the tubular body 10E. The field FE indicates the field of light propagating through the air hole core section 20E. The wall thickness of the tubular body 10E is set according to the wavelength of the light propagating through the air hole core section 20E.

[0051] Further, the tubular body 10E is mechanically connected to the support body 30E or the outer tubular body 40 by welding or the like. As a result, the tubular body 10E is supported by the support body 30E or the outer tubular body 40. Specifically, of the tubular body 10E, the tubular body 11E is mechanically connected to the outer tubular body 40, and of the tubular body 10E, the tubular body 12E is mechanically connected to the support body 30D.

[0052] The multi-core fiber 100E configured as above can achieve high performance or multiple functions similar to those of the multi-core fiber 100 according to the embodiment 1, as described above. In particular, since the multi-core fiber 100E has five air-hole core portions 20E, it can achieve even higher performance or multiple functions than the multi-core fiber 100.

[0053] In the multi-core fiber 100E, the support 30E divides the internal space of the outer tubular body 40 into four sections, and the tubular body 10E forms air hole core portions 20E within the sections, and the air hole core portions 20E are arranged with relatively high symmetry.

[0054] (Embodiment 7) 7 is a schematic cross-sectional view in a plane perpendicular to the longitudinal direction of a multi-core fiber according to embodiment 7. The multi-core fiber 100F includes 17 tubular bodies 10F, four air-hole core portions 20F, six supports 30F, and an outer tubular body 40. The outer tubular body 40 houses the tubular bodies 10F, the air-hole core portions 20F, and the support 30F.

[0055] The six supports 30F are rod-shaped bodies with a circular cross section, and are made of a solid medium such as quartz glass. The six supports 30F include rod-shaped bodies with different diameters. The six supports 30F include one support 31F, three supports 32F, and two supports 33F. The one support 31F is mechanically connected to and supported by the inner wall of the outer tubular body 40 by welding or the like, and is also mechanically connected to and supports the other support 33F by welding or the like. That is, the support 31F is an example of a support that is supported by the outer tubular body and supports at least one of the multiple tubular bodies. The three supports 32F are mechanically connected to and supported by the inner wall of the outer tubular body 40 by welding or the like. The two supports 33F have different diameters, and are mechanically connected to each other by welding or the like, and the one with the larger diameter is mechanically connected to the support 31F by welding or the like.

[0056] The 17 tubular bodies 10F include tubular bodies having different sizes such as diameters. The tubular bodies 10F include a tubular body 11F and a tubular body 12F. The tubular body 11F is mechanically connected to the outer tubular body 40 by welding or the like, and the tubular body 12F is mechanically connected to the support body 30F by welding or the like.

[0057] The four air hole core portions 20F include three air hole core portions 21F and one air hole core portion 22F. The three air hole core portions 21F are surrounded by five tubular bodies 10F each having a different size such as a diameter. In each of the air hole core portions 21F, a pentagonal field FF1 is formed, which is a field FF of propagating light. In each of the air hole core portions 21F, a quadrangular field FF2 is formed, which is a field FF of propagating light. The thickness of the tubular body 10F is set according to the wavelength of the light propagating in the air hole core portion 20F. The 17 tubular bodies 10F include a tubular body 10F shared between at least two of the plurality of air hole core portions 20F.

[0058] According to the multi-core fiber 100F configured as above, it is possible to realize high performance or multiple functions similar to those of the multi-core fiber 100 according to the first embodiment as described above. In particular, since the multi-core fiber 100F is configured by the tubular bodies 10F and the supports 30F having different sizes, the size, shape and arrangement of the four hole core portions 20F have a high degree of freedom. Moreover, since the multi-core fiber 100F includes the tubular body 10F shared between at least two of the multiple hole core portions 20F, the number of tubular bodies used and the cross-sectional area of ​​the multi-core fiber 100F are reduced.

[0059] (Embodiment 8) 8 is a schematic cross-sectional view in a plane perpendicular to the longitudinal direction of a multi-core fiber according to embodiment 8. The multi-core fiber 100G includes 17 tubular bodies 10G, four air-hole core portions 20G, nine supports 30G, and an outer tubular body 40. The outer tubular body 40 accommodates the tubular bodies 10G, the air-hole core portions 20G, and the supports 30G.

[0060] The nine supports 30G are rod-shaped bodies with a circular cross section, and are made of a solid medium such as quartz glass. The nine supports 30G include rod-shaped bodies with different sizes, such as diameters. The nine supports 30G include one support 31G, six supports 32G, and two supports 33G. The one support 31G is mechanically connected to and supported by the inner wall of the outer tubular body 40 by welding or the like, and is also mechanically connected to and supports the other support 33G by welding or the like. The six supports 32G are mechanically connected to and supported by the inner wall of the outer tubular body 40 by welding or the like. The two supports 33G have different diameters, and are mechanically connected to each other by welding or the like, and the one with the larger diameter is mechanically connected to the support 31G by welding or the like.

[0061] The 17 tubular bodies 10G include tubular bodies having different sizes such as diameters. The tubular bodies 10G include a tubular body 11G and a tubular body 12G. The tubular body 11G is mechanically connected to the outer tubular body 40 by welding or the like, and the tubular body 12G is mechanically connected to the support body 30G by welding or the like.

[0062] Moreover, the four air hole core portions 20G are surrounded by five tubular bodies 10G each having a different size, such as a diameter. In each of the air hole core portions 21G, a pentagonal field FG is formed, which is a field of propagating light. The wall thickness of the tubular body 10G is set according to the wavelength of the light propagating in the air hole core portion 20G. Moreover, the 17 tubular bodies 10G include a tubular body 10G shared between at least two of the plurality of air hole core portions 20G.

[0063] The multi-core fiber 100G configured as above can achieve high performance, multi-function, high degree of freedom in the size, shape and arrangement of the air-hole core portion 20G, reduction in the number of tubular bodies used and the cross-sectional area of ​​the multi-core fiber 100G, and the like, similar to the multi-core fiber 100F according to the seventh embodiment, as described above.

[0064] (Embodiment 9) 9 is a schematic cross-sectional view in a plane perpendicular to the longitudinal direction of a multi-core fiber according to embodiment 9. The multi-core fiber 100H includes fifteen tubular bodies 10H, three hole core portions 20H, three tubular supports 30H, and an outer tubular body 40. The outer tubular body 40 accommodates the tubular bodies 10H, the hole core portions 20H, and the tubular supports 30H.

[0065] The three tubular supports 30H have a cylindrical structure and are arranged to form a triangular lattice in cross section. The triangular lattice is, for example, a regular triangular lattice. The tubular supports 30H are, for example, quartz glass tubes having a predetermined thickness. The tubular supports 30H are mechanically connected to and supported by the inner wall of the outer tubular body 40 by welding or the like, and are also mechanically connected to each other by welding or the like.

[0066] Each of the three tubular supports 30H houses five tubular bodies 10H. The five tubular bodies 10H in each tubular support 30H are arranged to form a pentagonal lattice in cross section. The pentagonal lattice is, for example, a regular pentagonal lattice. As a result, in each tubular support 30H, a hole core portion 20H is formed in an area surrounded by the tubular bodies 10H. A field FH indicates a field of light propagating through the hole core portion 20H. The wall thickness of the tubular body 10H is set according to the wavelength of light propagating through the hole core portion 20H.

[0067] The multi-core fiber 100H configured as above can achieve high performance or multiple functions similar to those of the multi-core fiber 100 according to embodiment 1, as described above. Moreover, in the multi-core fiber 100H, the three structures, each of which is composed of one tubular support 30H and five tubular bodies 10H, have the same shape, so that in manufacturing, the base structures can be prepared by preparing one base structure that serves as a base material for the structures and cutting this into three.

[0068] (Embodiment 10) 10 is a schematic cross-sectional view in a plane perpendicular to the longitudinal direction of a multi-core fiber according to embodiment 10. The multi-core fiber 100I has a configuration in which fifteen tubular bodies 10I are added to the multi-core fiber 100H according to embodiment 9. The fifteen tubular bodies 10I are each housed in the tubular body 10H. The wall thickness of the tubular body 10I is also set so as to realize anti-resonant type light confinement according to the wavelength of light propagated in the air-hole core portion 20H.

[0069] In the multi-core fiber 100I, the tubular bodies 10H and 10I form an anti-resonant double light confinement structure for the air-hole core portion 20H.

[0070] The multi-core fiber 100I configured as above can achieve high performance or multiple functions similar to those of the multi-core fiber 100H according to embodiment 10 as described above. Furthermore, since the tubular bodies 10H, 10I form a double light confinement structure for the air hole core portion 20, the confinement loss in the air hole core portion 20H can be reduced more than in the multi-core fiber 100H.

[0071] (Embodiment 11) 11 is a schematic cross-sectional view in a plane perpendicular to the longitudinal direction of a multi-core fiber according to Embodiment 11. The multi-core fiber 100J includes three air-hole core portions 20J, an outer structure portion 50J, and a photonic bandgap structure 60J.

[0072] The outer structure 50J is a cylindrical structure that surrounds the periphery of the photonic bandgap structure 60J to form the outer peripheral surface of the multi-core fiber 100J. The outer structure 50J is made of, for example, silica-based glass.

[0073] The photonic bandgap structure 60J extends in the longitudinal direction of the multicore fiber 100J. The photonic bandgap structure 60J surrounds the periphery of the air-hole core portion 20J and is made of glass having a large number of air holes. The large number of air holes are arranged, for example, in a triangular lattice shape so as to form a photonic crystal with the air-hole core portion 20J as a crystal defect. The interval between the air holes is set according to the wavelength of the light propagating through the air-hole core portion 20J.

[0074] The three air hole core portions 20J are arranged to form a triangular lattice in cross section. The triangular lattice is, for example, a regular triangular lattice. A field FJ indicates a field of light propagating through the air hole core portions 20J.

[0075] In the multi-core fiber 100J configured as above, light is confined and propagated in the air-hole core portions 20J due to the photonic bandgap type light confinement effect.

[0076] According to the multi-core fiber 100J, it is possible to achieve high performance or multiple functions similar to those of the multi-core fiber 100 according to the first embodiment as described above.

[0077] (Embodiment 12) 12 is a schematic cross-sectional view in a plane perpendicular to the longitudinal direction of a multi-core fiber according to embodiment 12. The multi-core fiber 100K includes seven air-hole core portions 20K, an outer structure portion 50K, and a photonic bandgap structure 60K.

[0078] The outer structure 50K is a cylindrical structure that surrounds the periphery of the photonic bandgap structure 60K and forms the outer peripheral surface of the multi-core fiber 100K. The outer structure 50K is made of, for example, silica-based glass.

[0079] The photonic bandgap structure 60K extends in the longitudinal direction of the multicore fiber 100K. The photonic bandgap structure 60K surrounds the periphery of the air hole core portion 20K and is made of glass having a large number of air holes. The large number of air holes are arranged, for example, in a triangular lattice shape so as to form a photonic crystal with the air hole core portion 20K as a crystal defect. The interval between the air holes is set according to the wavelength of the light propagating through the air hole core portion 20K.

[0080] The seven air hole core portions 20K are arranged to form a triangular lattice in cross section. The triangular lattice is, for example, a regular triangular lattice. A field FK indicates a field of light propagating through the air hole core portions 20K.

[0081] In the multi-core fiber 100K configured as above, light is confined and propagated in the air-hole core portions 20K due to the photonic bandgap type light confinement effect.

[0082] The multi-core fiber 100K can achieve high performance or multiple functions similar to the multi-core fiber 100J according to embodiment 11 as described above. In particular, the multi-core fiber 100K has seven air-hole core portions 20K, which is more than the multi-core fiber 100J, and therefore can achieve higher performance or multiple functions than the multi-core fiber 100J.

[0083] In the multi-core fibers 100J and 100K, the number of photonic bandgap type air-hole core portions is 3 or 7, but the number is not limited to this and may be 19, for example.

[0084] In the above embodiment, the tubular body, the support, and the tubular support have a circular cross section, but the cross section may be polygonal or the like. The support may have another shape, such as a plate. The support may have a solid structure or a hollow structure, and is not particularly limited.

[0085] Furthermore, the present invention is not limited to the above-mentioned embodiment. The present invention also includes a configuration in which the above-mentioned components are appropriately combined. 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-mentioned embodiment, and various modifications are possible. [Explanation of symbols]

[0086] 10, 10A, 10D, 10E, 10F, 10G, 10H, 10I, 11, 11D, 11E, 11F, 11G, 12, 12D, 12E, 12F, 12G, 13: Tubular body 20, 20D, 20E, 20F, 20G, 20H, 20J, 20K, 21F, 21G, 22F: Hole core 30, 30B, 30D, 30E, 30F, 30G, 31F, 31G, 32F, 32G, 33F, 33G: Support 30H: Tubular support 40: Outer tubular body 50J, 50K: Outer structure 60J, 60K: Photonic band gap structure 100, 100A, 100B, 100C, 100D, 100E, 100F, 100G, 100H, 100I, 100J, 100K: Multi-core fiber F, FD, FE, FF, FF1, FF2, FG, FH, FJ, FK: Field

Claims

1. A plurality of cores are provided. The plurality of core portions are hole core portions. Multicore fiber.

2. The air hole core portion confines light by an antiresonant type light confinement effect. The multicore fiber according to claim 1 .

3. A plurality of tubular bodies are provided which surround the periphery of the air hole core portion and have the effect of confining light to the air hole core portion by the antiresonant phenomenon. The multicore fiber according to claim 2 .

4. At least one of the plurality of tubular bodies is shared between at least two of the plurality of air hole core portions. The multicore fiber according to claim 3 .

5. an outer tubular body that surrounds the plurality of tubular bodies and supports at least one of the plurality of tubular bodies; The multicore fiber according to claim 3 .

6. a support supported by the outer tubular body and supporting at least one of the plurality of tubular bodies; The multicore fiber according to claim 5 .

7. The support has a tubular structure that accommodates at least one of the plurality of tubular bodies. The multicore fiber according to claim 6.

8. The air hole core portion confines light by a photonic band gap type light confinement effect. The multicore fiber according to claim 1 .

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