Hollow core optical fiber and optical cable

Abstract

The application relates to a hollow optical fiber and an optical cable, the hollow optical fiber comprising a cladding region and a core region; the cladding region comprising, from outside to inside, an outer cladding and an anti-resonance layer; the core region comprising a region surrounded by the boundary of the anti-resonance layer and the outer cladding; wherein the anti-resonance layer comprises a plurality of rotationally symmetric distributed nested units, the nested units comprising a first nested ring and a second nested ring nested in the first nested ring, the first nested ring being connected to the inner wall of the outer cladding with a first arc length, and the second nested ring being connected to the inner wall of the first nested ring at the position where the first nested ring is connected to the inner wall of the outer cladding with a second arc length. The application can solve the problem of poor stability of the nested ring structure of the hollow optical fiber in the prior art, which is easily deformed by external stress.

Description

Technical Field

[0001] This application relates to the field of optical communication technology, and in particular to a hollow optical fiber and optical cable. Background Technology

[0002] The one-dimensional planar anti-resonant reflective optical waveguide (ARROW) theoretical model allows light to propagate in a core medium with a lower refractive index. This differs significantly from the traditional optical fiber theory, which relies on a high core refractive index and a low cladding refractive index to achieve total internal reflection, thus transmitting light through a high-refractive-index core. When light propagates in the air core of hollow optical fiber, it travels nearly 30% faster than in the high-refractive-index core of silica optical fiber. Therefore, hollow optical fiber communication systems offer a 30% lower latency advantage compared to traditional silica optical fiber communication systems. This significant advantage has attracted considerable attention. Furthermore, hollow optical fiber also possesses low nonlinearity, low dispersion, and maintains its original transmission characteristics even under irradiation, making it highly advantageous for long-distance, high-capacity transmission, ultrafast lasers, data centers, and space communications. For over 30 years since its inception, it has remained a hot research topic.

[0003] Since the introduction of Kagome-structured hollow-core fiber, while the attenuation of hollow-core fiber has been continuously decreasing, it has remained difficult to break through the level of less than 0.150 dB / km. In recent years, researchers have developed negative curvature core structures to achieve even lower losses, and subsequently developed the nested tube structure HC-ARF. In 2022, researchers reported a double-nested antiresonant hollow-core fiber. This fiber's loss in the C-band is comparable to that of commercial solid-core fiber (0.174 dB / km). Hollow-core fibers for short-wavelength transmission from 200 nm to 800 nm and hollow-core fibers for widely applicable mid-infrared transmission are also under development.

[0004] However, in practical research, it has been found that hollow-core optical fibers are highly susceptible to external stress, leading to increased attenuation. This is because existing structures rely heavily on maintaining the nested ring shape, meaning the nested rings theoretically maintain their shape through tangential contact. To achieve a better shape, the thickness of each nested ring is on the order of micrometers. This combination of a tiny structure and tangential contact results in poor stability of the nested rings, making them highly susceptible to deformation due to external influences. When the nested rings deform under stress, the fitted circle located at the center and tangent to all the nested rings will deform, no longer being a regular shape. This will cause changes in the effective mode field region of the light, resulting in a sharp increase in attenuation. Therefore, on the one hand, new structures need to be designed to resist the adverse effects of this deformation; on the other hand, the final product form of the optical fiber, optical cable, needs to be developed to better protect the fiber from external interference. Thus, existing optical fiber structures need to be more robust to adapt to the performance degradation caused by the large control fluctuations in actual manufacturing processes. Summary of the Invention

[0005] This application provides a hollow optical fiber and optical cable to solve the problems of poor stability and easy deformation of the nested ring structure of hollow optical fibers in related technologies.

[0006] In a first aspect, a hollow optical fiber is provided, the hollow optical fiber comprising a cladding region and a core region;

[0007] The cladding region includes an outer cladding layer and an anti-resonance layer arranged sequentially from the outside to the inside;

[0008] The fiber core region includes the area surrounded by the boundary between the anti-resonance layer and the outer cladding layer;

[0009] The anti-resonance layer includes multiple rotationally symmetrically distributed nested units. Each nested unit includes a first nested ring and a second nested ring nested within the first nested ring. The first nested ring is connected to the inner wall of the outer cladding layer with a first arc length, and the second nested ring is connected to the inner wall of the first nested ring with a second arc length at the position where the first nested ring is connected to the inner wall of the outer cladding layer.

[0010] In some embodiments, the central angle formed by the first arc length and the center point P1 of the first nested ring is θ1, and the value of θ1 / π ranges from 6% to 16%.

[0011] And / or, the central angle formed by the second arc length and the center point P2 of the second nested ring is θ2, and the value of θ2 / π ranges from 8% to 24%;

[0012] And / or, the ratio k1 of the outer radius R2 of the second nested ring to the inner radius r1 of the first nested ring ranges from 0.45 to 0.6;

[0013] And / or, the range of values ​​for the ratio k2 of the wall thickness t2 of the second nested ring to the wall thickness t1 of the first nested ring is as follows:

[0014]

[0015] Where N is the number of the first nested rings, and n is the refractive index of the material used in the hollow fiber.

[0016] In some embodiments, the anti-resonance layer further includes an auxiliary resonant ring disposed between two adjacent nested units, the outer wall of the auxiliary resonant ring being tangent to the inner wall of the outer cladding layer.

[0017] In some embodiments, the nested unit further includes a third nested ring, which is nested within the second nested ring, and the third nested ring is connected to the inner wall of the second nested ring at a position where the second nested ring is connected to the inner wall of the first nested ring by a third arc length.

[0018] In some embodiments, the central angle formed by the first arc length and the center point P1 of the first nested ring is θ1, and the value of θ1 / π ranges from 6% to 16%.

[0019] And / or, the central angle formed by the second arc length and the center point P2 of the second nested ring is θ2, and the value of θ2 / π ranges from 8% to 20%;

[0020] And / or, the central angle formed by the third arc length and the center point P3 of the third nested ring is θ3, and the value of θ3 / π ranges from 6% to 15%;

[0021] And / or, the ratio k1 of the outer radius R2 of the second nested ring to the inner radius r1 of the first nested ring ranges from 0.7 to 0.9;

[0022] And / or, the wall thickness t2 of the second nested ring ranges from 0.3um to 1.0um;

[0023] And / or, the ratio of the outer radius R3 of the third nested ring to the inner radius r1 of the first nested ring ranges from 0.2 to 0.4;

[0024] And / or, the wall thickness t3 of the third nested ring ranges from 0.2um to 0.5um.

[0025] In some embodiments, the anti-resonance layer further includes an auxiliary resonant ring disposed between two adjacent nested units, the outer wall of the auxiliary resonant ring being tangent to the inner wall of the outer cladding layer.

[0026] In some embodiments, the ratio of the outer radius R6 of the auxiliary resonant ring to the inner radius r1 of the first nested ring ranges from 0 to 0.4 and is not 0;

[0027] And / or, the wall thickness t6 of the auxiliary resonant ring ranges from 0.2µm to 0.5µm.

[0028] In some embodiments, the core region includes an effective core, which is a circular region formed by virtual circles simultaneously circumscribed in each of the first nested rings;

[0029] When the light transmission wavelength λ is between 1200 nm and 1600 nm, the radius r0 of the effective fiber core satisfies:

[0030] r0 = k0 × (r - 2 × R1);

[0031] Where r is the inner radius of the outer cladding layer, R1 is the outer radius of the first nested ring, and k0 is the transmission coefficient, with the following value range:

[0032]

[0033] θ1 is the central angle formed by the first arc length and the center point P1 of the first nested ring;

[0034] When the light transmission wavelength λ is 2um to 11um, the effective fiber core radius r0 ranges from 25um to 250um.

[0035] When the light transmission wavelength λ is 200nm to 1100nm, the effective fiber core radius r0 ranges from 5um to 200um.

[0036] In some embodiments, there is a spacing x between two adjacent first nested rings, and x > 0.

[0037] In some embodiments, the wall thickness t1 of the first nested ring is R1-r1, where R1 is the outer radius of the first nested ring and r1 is the inner radius of the first nested ring.

[0038] When the wall thickness t1 of the first nested ring is less than 1 μm, the value range of the spacing x is: X ~ 2X;

[0039] in,

[0040] When the wall thickness t1 of the first nested ring is ≥ 1 μm, the value range of the spacing x is: Y ~ 2Y;

[0041] in,

[0042] r is the inner radius of the outer cladding, N is the number of the first nested rings, and n is the refractive index of the material used in the hollow fiber.

[0043] In some embodiments, the central angle formed by the first arc length and the center point P1 of the first nested ring is θ1;

[0044] When θ1 / π≤8%, the range of values ​​for the wall thickness t1 of the first nested ring is:

[0045]

[0046] When θ1 / π > 8%, the wall thickness t1 of the first nested ring ranges from 0.2λ to 0.8λ, where λ is the wavelength of light transmission.

[0047] In some embodiments, the hollow optical fiber is made of quartz, and a resin protective layer is coated on the outer cladding. A sleeve layer is disposed outside the resin protective layer, and a sheath layer is disposed outside the sleeve layer.

[0048] In some embodiments, the resin protective layer includes an inner layer and an outer layer, wherein the inner layer has a modulus of 0.1 MPa to 1.2 MPa and the outer layer has a modulus greater than 500 MPa.

[0049] In some embodiments, the material of the sleeve layer includes polyurethane (TPU), polyester (PBT), polyethylene (PE), polypropylene (PP), ethylene-tetrafluoroethylene (ETFE), or polyetheretherketone (PEEK).

[0050] In some embodiments, an auxiliary reinforcement is also provided between the sleeve layer and the sheath layer.

[0051] In some embodiments, the auxiliary reinforcement includes aramid yarn and / or glass yarn.

[0052] In some embodiments, the hollow optical fiber is made of polymer or glass.

[0053] In some embodiments, the polymeric material includes polystyrene (PS), polymethyl methacrylate (PMMA), polycarbonate (PC), polyester (PBT), polyethylene (PE), ethylene-tetrafluoroethylene (ETFE), or polyether ether ketone (PEEK).

[0054] In some embodiments, the glass comprises chalcogenide glass or fluoride glass.

[0055] In a second aspect, an optical cable is provided, comprising hollow optical fibers as described in any of the above.

[0056] The beneficial effects of the technical solution provided in this application include:

[0057] The hollow-core optical fiber provided in this application does not use the existing tangent contact method for the nested rings contained in its nested unit. Instead, they are connected with a certain arc length and are also connected to the outer cladding with a certain arc length. The arc length connection increases the contact surface and ensures the stability between the nested rings and between the nested rings and the outer cladding. Even when affected by external stress, the high stability between the nested rings and between the nested rings and the outer cladding makes the fitted circle located at the center and tangent to each nested ring less prone to deformation. This improves its ability to maintain a regular shape and avoids the situation where the attenuation increases sharply due to changes in the effective mode field region of the light. Attached Figure Description

[0058] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0059] Figure 1 A cross-sectional view of a hollow optical fiber (N=5) provided for an embodiment of this application;

[0060] Figure 2 A cross-sectional view of a hollow optical fiber (N=6) provided for an embodiment of this application;

[0061] Figure 3 A cross-sectional view of a hollow optical fiber (N=4) provided for an embodiment of this application;

[0062] Figure 4 A schematic diagram of a hollow optical fiber provided in an embodiment of this application;

[0063] Figure 5 The attenuation curve of the hollow fiber provided in the embodiments of this application near 1550nm.

[0064] In the figure: 1. Outer cladding layer; 2. Anti-resonance layer; 21. First nested ring; 22. Second nested ring; 23. Third nested ring; 24. Auxiliary resonant ring; 3. Effective fiber core; 4. Resin protective layer; 5. Sleeve layer; 6. Sheath layer. Detailed Implementation

[0065] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0066] See Figure 1 , Figure 2 and Figure 3 As shown, this application embodiment provides a hollow-core optical fiber, which includes a cladding region and a core region. The cladding region includes an outer cladding layer 1 and an anti-resonance layer 2 arranged sequentially from the outside to the inside. The core region includes a region surrounded by the boundary between the anti-resonance layer 2 and the outer cladding layer 1. The anti-resonance layer 2 includes a plurality of rotationally symmetric nested units. Each nested unit includes a first nested ring 21 and a second nested ring 22 nested within the first nested ring 21. The first nested ring 21 is connected to the inner wall of the outer cladding layer 1 with a first arc length. The second nested ring 22 is connected to the inner wall of the first nested ring 21 with a second arc length at the position where the first nested ring 21 is connected to the inner wall of the outer cladding layer 1. It can be understood that there is a virtual circle in the region surrounded by the boundary between the anti-resonance layer 2 and the outer cladding layer 1. This virtual circle is circumscribed by each of the first nested rings 21, such that the region where the virtual circle is located forms the effective core 3 of the core region.

[0067] The hollow-core optical fiber provided in this application does not use the existing tangent contact method for the nested rings contained in its nested unit. Instead, they are connected with a certain arc length and are also connected to the outer cladding with a certain arc length. The arc length connection increases the contact surface and ensures the stability between the nested rings and between the nested rings and the outer cladding. Even when affected by external stress, the high stability between the nested rings and between the nested rings and the outer cladding makes the fitted circle located at the center and tangent to each nested ring less prone to deformation. This improves its ability to maintain a regular shape and avoids the situation where the attenuation increases sharply due to changes in the effective mode field region of the light.

[0068] For ease of understanding, this application uniformly stipulates the following:

[0069] The effective fiber core 3 and the outer cladding 1 share the same center, denoted as point P0. The radius of the effective fiber core 3 is r0. The inner radius of the outer cladding 1 is r, and the outer radius of the outer cladding 1 is R.

[0070] The number of nested units contained in the anti-resonance layer 2 is the same as the number of the first nested ring 21. Specifically, the number of the first nested ring 21 is denoted as N, which can be 3, generally 4 and 5, or 6 or more.

[0071] The center of the first nested ring 21 is point P1, the inner radius is r1, the outer radius is R1, the wall thickness is t1, and t1 = R1 - r1. The central angle formed by the first arc length and the center point P1 is θ1.

[0072] The center of the second nested ring 22 is point P2, the inner radius is r2, the outer radius is R2, the wall thickness is t2, and t2 = R2 - r2. The central angle formed by the second arc length and the center point P2 is θ2.

[0073] The center of the third nested ring 23 is point P3, the inner radius is r3, the outer radius is R3, the wall thickness is t3, and t3 = R3 - r3. The central angle formed by the third arc length and the center point P3 is θ3.

[0074] The auxiliary resonant ring 24 has an inner radius of r6, an outer radius of R6, and a wall thickness of t6, where t6 = R6 - r6.

[0075] To minimize the attenuation of the light waves transmitted in the effective core 3 of the hollow fiber, the first nested rings 21 are distributed at equal intervals, so that the first nested rings 21 are arranged in an equilateral polygon with point P0 as the center.

[0076] Based on the first nested ring 21 and the second nested ring 22 of this application, a nested ring can be further set within the second nested ring 22. Specifically, the nested unit also includes a third nested ring 23, which is nested within the second nested ring 22. The third nested ring 23 is connected to the inner wall of the second nested ring 22 at a position where the second nested ring 22 is connected to the inner wall of the first nested ring 21 with a third arc length.

[0077] It is understandable that when the nested unit has only the first nested ring 21 and the second nested ring 22, the center point P0 of the outer layer 1 is collinear with the center point P1 of the first nested ring 21 and the center point P2 of the second nested ring 22.

[0078] When the nested unit includes a first nested ring 21, a second nested ring 22, and a third nested ring 23, the center point P0 of the outer cladding layer 1 is collinear with the center point P1 of the first nested ring 21, the center point P2 of the second nested ring 22, and the center point P3 of the third nested ring 23.

[0079] To better form anti-resonance and reduce attenuation within the effective fiber core 3, the anti-resonance layer 2 also includes an auxiliary resonant ring 24 disposed between two adjacent nested units, the outer wall of the auxiliary resonant ring 24 being tangent to the inner wall of the outer cladding layer 1.

[0080] When the nested unit consists only of the first nested ring 21 and the second nested ring 22, the central angle formed by the first arc length and the center point P1 of the first nested ring 21 is θ1, and the value of θ1 / π ranges from 6% to 16%; the central angle formed by the second arc length and the center point P2 of the second nested ring 22 is θ2, and the value of θ2 / π ranges from 8% to 24%; the ratio k1 of the outer radius R2 of the second nested ring 22 to the inner radius r1 of the first nested ring 21 ranges from 0.45 to 0.6; the value range of k2 of the ratio t2 of the wall thickness t2 of the second nested ring 22 to the wall thickness t1 of the first nested ring 21 is as follows:

[0081]

[0082] Where N is the number of the first nested rings 21, and n is the refractive index of the material used in the hollow optical fiber.

[0083] It is understandable that the refractive index of the material used in hollow optical fiber is the same as the refractive index of the hollow optical fiber. The material used in hollow optical fiber can be quartz, glass, or polymer materials. Glass is usually a mixture, while quartz is pure silicon dioxide. If the hollow optical fiber uses quartz, the refractive index is the refractive index of quartz. If the hollow optical fiber uses polymer materials, the refractive index is the refractive index of the polymer materials.

[0084] It is understandable that the structures contained in hollow optical fibers, such as the cladding and anti-resonance layer, are generally made of the same material.

[0085] When the nested unit has only the first nested ring 21 and the second nested ring 22, if an auxiliary resonant ring 24 is also provided, the ratio of the outer radius R6 of the auxiliary resonant ring 24 to the inner radius r1 of the first nested ring 21 is in the range of 0 to 0.4 and is not 0; the wall thickness t6 of the auxiliary resonant ring 24 is in the range of 0.2um to 0.5um.

[0086] When the nested unit has only the first nested ring 21 and the second nested ring 22, the number of the first nested ring 21 can be 5 or 6, etc. Similarly, if there is an auxiliary resonant ring 24, the number of the auxiliary resonant ring 24 can be 5 or 6, etc.

[0087] When the nested unit includes a first nested ring 21, a second nested ring 22, and a third nested ring 23, the central angle formed by the first arc length and the center point P1 of the first nested ring 21 is θ1, and the value of θ1 / π ranges from 6% to 16%; the central angle formed by the second arc length and the center point P2 of the second nested ring 22 is θ2, and the value of θ2 / π ranges from 8% to 20%; the central angle formed by the third arc length and the center point P3 of the third nested ring 23 is θ3, and the value of θ3 / π ranges from 8% to 20%. The range is 6% to 15%; the ratio k1 of the outer radius R2 of the second nested ring 22 to the inner radius r1 of the first nested ring 21 ranges from 0.7 to 0.9; the wall thickness t2 of the second nested ring 22 ranges from 0.3 μm to 1.0 μm; the ratio of the outer radius R3 of the third nested ring 23 to the inner radius r1 of the first nested ring 21 ranges from 0.2 to 0.4; the wall thickness t3 of the third nested ring 23 ranges from 0.2 μm to 0.5 μm.

[0088] When the nested unit includes a first nested ring 21, a second nested ring 22, and a third nested ring 23, if an auxiliary resonant ring 24 is also provided, the ratio of the outer radius R6 of the auxiliary resonant ring 24 to the inner radius r1 of the first nested ring 21 is in the range of 0 to 0.4 and is not 0; the wall thickness t6 of the auxiliary resonant ring 24 is in the range of 0.2um to 0.5um.

[0089] When the nested unit includes a first nested ring 21, a second nested ring 22, and a third nested ring 23, the number of first nested rings 21 can be 4, 5, or 6, etc. Similarly, if there is an auxiliary resonant ring 24, the number of auxiliary resonant rings 24 can be 4, 5, or 6, etc.

[0090] The fiber core region includes an effective fiber core 3, which is a circular region formed by virtual circles that are simultaneously circumscribed by each of the first nested rings 21.

[0091] When the light transmission wavelength λ is 1200nm~1600nm, the radius r0 of the effective fiber core 3 satisfies: r0=k0×r-2×R1.

[0092] Where r is the inner radius of the outer cladding layer 1, R1 is the outer radius of the first nested ring 21, and k0 is the transmission coefficient, with the following value range:

[0093]

[0094] Wherein, θ1 is the central angle formed by the first arc length and the center point P1 of the first nested ring 21.

[0095] It is understandable that, because hollow fiber has a certain loss, in order to express the impact of this loss on the effective core size, a transmission coefficient k0 is introduced, and the value of this coefficient is limited by θ1.

[0096] When the nested unit consists only of the first nested ring 21 and the second nested ring 22, when the light transmission wavelength λ is 1200nm to 1600nm, the corresponding minimum attenuation is about 0.045dB / km, and the dispersion range is 1.0ps / (nm·km) to 5.0ps / (nm·km).

[0097] When the nested unit includes a first nested ring 21, a second nested ring 22, and a third nested ring 23, when the light transmission wavelength λ is 1200nm to 1600nm, the corresponding minimum attenuation is about 0.030dB / km, and the dispersion range is 3.0ps / (nm·km) to 5.0ps / (nm·km).

[0098] When the nested unit consists only of the first nested ring 21 and the second nested ring 22, or when the nested unit includes the first nested ring 21, the second nested ring 22 and the third nested ring 23, and when the light transmission wavelength λ is 2um to 11um, the radius r0 of the effective fiber core 3 ranges from 25um to 250um; the average attenuation is less than 3dB / km, and the minimum attenuation is less than 0.3dB / km.

[0099] When the nested unit consists only of the first nested ring 21 and the second nested ring 22, or when the nested unit includes the first nested ring 21, the second nested ring 22 and the third nested ring 23, and when the light transmission wavelength λ is 200nm to 1100nm, the radius r0 of the effective fiber core 3 ranges from 5um to 200um, the average attenuation is less than 5dB / km, and the minimum attenuation is less than 0.5dB / km.

[0100] To form an anti-resonant hollow fiber with a gap node type, there is a spacing x between two adjacent first nested rings 21, and x > 0.

[0101] When the wall thickness t1 of the first nested ring 21 is less than 1 μm, the value range of the spacing x is: X ~ 2X;

[0102] in,

[0103] When the wall thickness t1 of the first nested ring 21 is ≥ 1 μm, the value range of the spacing x is: Y ~ 2Y;

[0104] in,

[0105] r is the inner radius of the outer cladding 1, N is the number of the first nested rings 21, and n is the refractive index of the material used in the hollow optical fiber.

[0106] The wall thickness t1 of the first nested ring 21 is determined based on the size of the central angle θ1 formed by the first arc length and the center point P1 of the first nested ring 21.

[0107] When θ1 / π≤8%, the range of values ​​for the wall thickness t1 of the first nested ring 21 is:

[0108]

[0109] When θ1 / π > 8%, the wall thickness t1 of the first nested ring 21 ranges from 0.2λ to 0.8λ, where λ is the wavelength of light transmission.

[0110] The transmission wavelength λ can typically be 1.0 μm, 1.5 μm, 3.0 μm, 6.0 μm, 10.0 μm, etc.; the first nested ring 21, the second nested ring 22, the third nested ring 23, the auxiliary resonant ring 24, and the region between the first nested ring 21 and the outer cladding 1 are all filled with dry gas, with a water vapor content of ppm or even below ppb.

[0111] In this application, the hollow optical fiber can be made of quartz. In this case, a coating is required, and then the optical cable is manufactured using a low-stress optical cable process.

[0112] The hollow optical fiber can also be made of polymer materials or glass, and can be used directly as an optical cable.

[0113] For example, see Figure 4 As shown, the hollow optical fiber is made of quartz. The outer cladding 1 is coated with a resin protective layer 4. A sleeve layer 5 is disposed outside the resin protective layer 4. A sheath layer 6 is disposed outside the sleeve layer 5.

[0114] The resin protective layer 4 includes an inner layer and an outer layer, with the inner layer having a modulus of 0.1 MPa to 1.2 MPa and the outer layer having a modulus greater than 500 MPa.

[0115] The material of the sleeve layer 5 includes polyurethane TPU, polyester PBT, polyethylene PE, polypropylene PP, ethylene-tetrafluoroethylene ETFE, or polyether ether ketone PEEK.

[0116] Furthermore, an auxiliary reinforcement is provided between the sleeve layer 5 and the sheath layer 6.

[0117] The auxiliary reinforcement includes aramid yarn and / or glass yarn.

[0118] For example, the hollow optical fiber may be made of polymer or glass.

[0119] The polymeric materials include polystyrene (PS), polymethyl methacrylate (PMMA), polycarbonate (PC), polyester (PBT), polyethylene (PE), ethylene-tetrafluoroethylene (ETFE), or polyether ether ketone (PEEK).

[0120] The glass includes chalcogenide glass or fluoride glass.

[0121] See Figure 5 As shown, the attenuation curve of the hollow fiber near 1550nm is shown. It can be seen that the attenuation is basically below 0.5d / km, indicating that the hollow fiber provided in this application has low attenuation characteristics due to its stable structure.

[0122] The following detailed description, in conjunction with the accompanying drawings, illustrates some embodiments of this application:

[0123] Implementation Plan 1:

[0124] When there are only a first nested ring and a second nested ring, and the material constituting the optical fiber is quartz, the following examples are shown in Table 1:

[0125] Table 1

[0126]

[0127]

[0128] The final form of the optical fiber cable is a single-core hollow optical fiber cable. This hollow optical fiber cable consists of hollow optical fibers, a resin protective layer surrounding the hollow optical fibers, a sheath layer, and finally a protective layer. The resin protective layer is made of UV-curable resin, preferably polyacrylic acid resin, and is coated in two layers. The resin protective layer has an inner layer and an outer layer. The inner layer has a modulus between 0.1 MPa and 1.2 MPa, while the outer layer has a modulus greater than 500 MPa. A low-stress cable-making process is used for protection. Afterward, a sheath layer made of polymer material is extruded onto the coated optical fiber. Because the diameter of the optical fiber is larger than that of conventional solid single-mode optical fiber, to reduce the additional attenuation caused by stress and excess length during the loose-tube process, the sheath layer is preferably made of a polymer extrusion material with a modulus lower than 2000 MPa. The sheath layer material is modified polypropylene, with an outer diameter of 2.0 mm and an inner diameter of 1.3 mm. The outer layer of the sheath is the outermost layer, preferably polyethylene. The final outer diameter of the optical cable is 3.0 mm, and the wall thickness is 0.4 mm. When the optical cable needs to withstand greater tensile force, an auxiliary reinforcement can be placed between the sheath and the outermost layer, preferably non-metallic yarn, such as aramid yarn or fiberglass yarn.

[0129] As can be seen from the above 10 embodiments, this application redesigns the structure of hollow optical fiber. For hollow optical fiber made of quartz material, even if the nesting unit has only two nesting rings, the attenuation can be as low as 0.041dB / km and the dispersion can be as low as 1.0ps / (nm·km).

[0130] Implementation Plan 2:

[0131] When there are only a first nested ring and a second nested ring, and the materials constituting the optical fiber are polymer materials or glass directly, the following examples are shown in Table 2:

[0132] Table 2

[0133]

[0134] Optical fibers made in this way can be used directly. The materials that make up the optical fiber can be selected from polymer materials such as polystyrene (PS), polymethyl methacrylate (PMMA), and polycarbonate (PC), or rigid materials such as PBT, PE, ETFE, and PEEK to make hollow optical fibers. The glass that can be selected includes chalcogenide glass and fluoride glass.

[0135] As can be seen from the above eight embodiments, this application redesigns the structure of hollow optical fibers. For hollow optical fibers made of polymer materials or glass, even if the nesting unit has only two nesting rings, the attenuation can be as low as 0.041dB / km and the dispersion can be as low as 1.0ps / (nm·km).

[0136] Implementation Plan 3:

[0137] When there are first nested rings, second nested rings, and third nested rings, and the materials constituting the optical fiber are made of polymer materials or glass directly, the following examples are shown in Table 3:

[0138] Table 3

[0139]

[0140]

[0141] Optical fibers made in this way can be used directly. The materials that make up the optical fiber can be selected from polymer materials such as polystyrene (PS), polymethyl methacrylate (PMMA), and polycarbonate (PC), or rigid materials such as PBT, PE, ETFE, and PEEK to make hollow optical fibers. The glass that can be selected includes chalcogenide glass and fluoride glass.

[0142] As can be seen from the above eight embodiments, this application redesigns the structure of hollow optical fiber. For hollow optical fibers made of polymer materials or glass, the nesting unit includes three nesting rings, and the attenuation can be as low as 0.021dB / km, and the dispersion can be as low as 3.0ps / (nm·km).

[0143] Implementation Plan 4:

[0144] When there are first nested rings, second nested rings, and third nested rings, and the material constituting the optical fiber is quartz, the following examples are shown in Table 4:

[0145] Table 4

[0146]

[0147]

[0148] The hollow-core optical fiber cable consists of hollow-core optical fibers, a resin protective layer surrounding the hollow-core optical fibers, a sleeve layer, and a sheath layer. The resin protective layer is made of UV-curable resin, preferably polyacrylic acid resin, and is applied in a double-layer coating. The resin protective layer has an inner layer and an outer layer; the inner layer has a modulus between 0.1 MPa and 1.2 MPa, while the outer layer has a modulus greater than 500 MPa. A low-stress cable-making process is used for protection. After coating, a sleeve layer made of a polymer material is extruded over the coated optical fiber. Because the diameter of the optical fiber is larger than that of conventional solid-core single-mode optical fibers, to reduce the additional attenuation caused by stress and excess length during the loose-tube process, the sleeve layer is preferably made of a polymer extrusion material with a modulus lower than 2000 MPa. The sleeve layer material is modified polypropylene, with an outer diameter of 2.0 mm and an inner diameter of 1.3 mm. The outer layer of the sleeve layer is the sheath layer, preferably made of polyethylene. The final outer diameter of the optical cable is 3.0 mm, and the wall thickness is 0.4 mm. When optical cables need to withstand large tensile forces, auxiliary reinforcements can be placed between the sheath layer and the protective sheath layer. These reinforcements are preferably non-metallic yarns, such as aramid yarn or fiberglass yarn.

[0149] As can be seen from the above eight embodiments, this application redesigns the structure of hollow optical fiber. For hollow optical fiber made of quartz material, the nesting unit includes three nesting rings, and the attenuation can be as low as 0.016dB / km and the dispersion as low as 3.0ps / (nm·km).

[0150] In the description of this application, it should be noted that the terms "upper," "lower," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Unless otherwise expressly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two elements. For those skilled in the art, the specific meaning of the above terms in this application can be understood according to the specific circumstances.

[0151] It should be noted that in this application, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0152] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A hollow-core optical fiber, characterized in that: The hollow optical fiber includes a cladding region and a core region; The cladding region includes an outer cladding layer (1) and an anti-resonance layer (2) arranged sequentially from the outside to the inside. The fiber core region includes the area surrounded by the boundary between the anti-resonance layer (2) and the outer cladding layer (1); The anti-resonance layer (2) includes multiple rotationally symmetrically distributed nested units. Each nested unit includes a first nested ring (21) and a second nested ring (22) nested within the first nested ring (21). The first nested ring (21) is connected to the inner wall of the outer cladding layer (1) with a first arc length. The second nested ring (22) is connected to the inner wall of the first nested ring (21) with a second arc length at the position where the first nested ring (21) is connected to the inner wall of the outer cladding layer (1). The central angle formed by the first arc length and the center point P1 of the first nested ring (21) is θ1, and the value of θ1 / π ranges from 6% to 16%. The central angle formed by the second arc length and the center point P2 of the second nested ring (22) is θ2, and the value range of θ2 / π is 8% to 24%. The ratio k1 of the outer radius R2 of the second nested ring (22) to the inner radius r1 of the first nested ring (21) ranges from 0.45 to 0.

6. The range of values ​​for the ratio k2 of the wall thickness t2 of the second nested ring (22) to the wall thickness t1 of the first nested ring (21) is as follows: Where N is the number of the first nested rings (21) and n is the refractive index of the material used in the hollow fiber.

2. The hollow-core optical fiber as described in claim 1, characterized in that: The anti-resonance layer (2) also includes an auxiliary resonant ring (24) disposed between two adjacent nested units, the outer wall of the auxiliary resonant ring (24) being tangent to the inner wall of the outer cladding layer (1).

3. The hollow-core optical fiber as described in claim 1, characterized in that: The nested unit further includes a third nested ring (23), which is nested inside the second nested ring (22). The third nested ring (23) is connected to the inner wall of the second nested ring (22) at a position where the second nested ring (22) is connected to the inner wall of the first nested ring (21) with a third arc length.

4. The hollow-core optical fiber as described in claim 3, characterized in that: The central angle formed by the first arc length and the center point P1 of the first nested ring (21) is θ1, and the value of θ1 / π ranges from 6% to 16%. The central angle formed by the second arc length and the center point P2 of the second nested ring (22) is θ2, and the value of θ2 / π ranges from 8% to 20%. The central angle formed by the third arc length and the center point P3 of the third nested ring (23) is θ3, and the value range of θ3 / π is 6% to 15%. The ratio k1 of the outer radius R2 of the second nested ring (22) to the inner radius r1 of the first nested ring (21) ranges from 0.7 to 0.

9. The wall thickness t2 of the second nested ring (22) ranges from 0.3um to 1.0um; The ratio of the outer radius R3 of the third nested ring (23) to the inner radius r1 of the first nested ring (21) ranges from 0.2 to 0.

4. The wall thickness t3 of the third nested ring (23) ranges from 0.2um to 0.5um.

5. The hollow-core optical fiber as described in claim 3, characterized in that: The anti-resonance layer (2) also includes an auxiliary resonant ring (24) disposed between two adjacent nested units, the outer wall of the auxiliary resonant ring (24) being tangent to the inner wall of the outer cladding layer (1).

6. The hollow-core optical fiber as described in claim 2 or 5, characterized in that: The ratio of the outer radius R6 of the auxiliary resonant ring (24) to the inner radius r1 of the first nested ring (21) ranges from 0 to 0.4 and is not 0. And / or, the wall thickness t6 of the auxiliary resonant ring (24) ranges from 0.2um to 0.5um.

7. The hollow-core optical fiber as described in claim 1, characterized in that: The hollow optical fiber is made of quartz. The outer cladding (1) is coated with a resin protective layer (4). A sleeve layer (5) is provided outside the resin protective layer (4). A sheath layer (6) is provided outside the sleeve layer (5).

8. The hollow-core optical fiber as described in claim 7, characterized in that: The resin protective layer (4) includes an inner layer and an outer layer, with the inner layer having a modulus of 0.1 MPa to 1.2 MPa and the outer layer having a modulus greater than 500 MPa.

9. The hollow-core optical fiber as described in claim 7, characterized in that: The materials of the sleeve layer (5) include polyurethane TPU, polyester PBT, polyethylene PE, polypropylene PP, ethylene-tetrafluoroethylene ETFE or polyether ether ketone PEEK.

10. The hollow-core optical fiber as described in claim 7, characterized in that: An auxiliary reinforcement is also provided between the sleeve layer (5) and the sheath layer (6).

11. The hollow-core optical fiber as described in claim 10, characterized in that: The auxiliary reinforcement includes aramid yarn and / or glass yarn.

12. The hollow-core optical fiber as described in claim 1, characterized in that: The hollow optical fiber is made of polymer or glass.

13. The hollow-core optical fiber as described in claim 12, characterized in that: The polymeric materials include polystyrene (PS), polymethyl methacrylate (PMMA), polycarbonate (PC), polyester (PBT), polyethylene (PE), ethylene-tetrafluoroethylene (ETFE), or polyether ether ketone (PEEK).

14. The hollow-core optical fiber as described in claim 12, characterized in that: The glass includes chalcogenide glass or fluoride glass.

15. An optical cable, characterized in that, It includes hollow optical fibers as described in any one of claims 1-14.

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