A high single mode ultra-low loss hollow core anti-resonant optical fiber

Abstract

This invention relates to a high single-mode performance, ultra-low loss hollow-core anti-resonant optical fiber, comprising an outer cladding and an inner cladding. The inner cladding is composed of nested structural units arranged circumferentially along the inner wall of the outer cladding and connected to the inner wall. The central cavity enclosed by the inner cladding forms the fiber core. The nested structural units are characterized by comprising three or more nested glass tubes of different radii, with at least one inner nested glass tube deflected to one side relative to its adjacent outer nested glass tube at an angle of 5–55°. This invention, through variations in the cladding structure, combines a reasonable and fabricable nested structural unit shape, optimized nesting size combinations, and the deflection of the inner nested glass tubes, significantly improving the leakage loss of the LP11 mode with minimal impact on the fundamental mode performance, ultimately effectively enhancing the single-mode performance of the optical fiber.

Description

Technical Field

[0001] This invention relates to the field of hollow-core optical fiber technology, specifically to a high single-mode ultra-low loss hollow-core anti-resonant optical fiber, belonging to the field of optical communication and transmission technology. Background Technology

[0002] Hollow-core antiresonant fiber possesses a unique microstructure design that confines transmitted light waves within an air core, making it crucial for applications in fields such as light-filled material interactions, nonlinear optics, gas detection, gas laser generation, and optofluidics. Due to its unique structure and light-guiding mechanism, it achieves ultra-low Rayleigh scattering, low nonlinear coefficients, and tunable dispersion, providing a higher laser damage threshold and potential applications in high-power laser transmission, ultraviolet / mid-infrared light transmission, pulse compression, and optical soliton transmission. The ultra-low loss, low dispersion, low nonlinearity, and near-light-speed propagation of the air core enable the development of hollow-core fiber communication transmission and communication devices, laying the foundation for the construction and development of next-generation ultra-high-capacity, low-latency, and high-speed optical communication systems.

[0003] Even though hollow-core optical fiber has unique and significant advantages in design and application, its inherent lack of higher-order mode cutoff means that higher-order modes cannot be effectively filtered out like those in solid-core single-mode fiber. This greatly limits its application in short-distance transmission scenarios. Recent research has shown that, through reasonable structural design, the leakage loss of higher-order modes can be improved to some extent, thus producing an effect similar to single-mode after a certain distance.

[0004] A commonly used method for filtering higher-order modes is to select a high-attenuation cladding mode and, through structural design, achieve a high phase match with the LP11 mode in the fiber core, thereby effectively improving the leakage loss of the LP11 mode. The key factors in this design method are the inherent attenuation of the cladding mode and its phase match with the LP11 mode. Generally, the higher the attenuation of the cladding mode and the greater the phase match with the LP11 mode, the greater the improvement in LP11 mode leakage loss and the better the single-mode performance.

[0005] US Patent 11733451B2 discloses a single-ring hollow anti-resonant fiber. This patent proposes utilizing a high-loss anti-resonant unit (ARE) mode with a high phase match between the core LP11 mode. The structure is very simple, relatively easy to draw, and can achieve an ultra-high higher-order mode suppression ratio. By maintaining a cladding tube to core size ratio of approximately 0.68, a high degree of single-mode bandwidth can be achieved, with LP11 mode attenuation reaching 10%. 2The attenuation is in the dB / m range. However, this structure is difficult to achieve ultra-low attenuation transmission. Currently, the lowest attenuation in the near-infrared band is 4.3 dB / km (1080 nm), and the attenuation is even higher in the communication band. It also has poor bending resistance, so it does not have much advantage in many applications in the near-infrared band.

[0006] Chinese patent CN110515152B discloses a single-nested tube nodeless hollow-core anti-resonant fiber (NANF) and a double-nested tube nodeless hollow-core anti-resonant fiber (DNANF). Both structures effectively reduce the transmission loss of the fundamental mode by increasing the number of anti-resonant layers. For NANF fiber, the lowest attenuation has reached 0.22 dB / km, while DNANF has broken the record for the lowest attenuation of traditional solid-core fiber, reaching 0.11 dB / km. However, while achieving ultra-low attenuation, both fibers also maintain a relatively low LP11 mode loss. When the NANF structure achieves optimal resonant leakage design for the LP11 mode, the theoretical LP11 attenuation is approximately 10. 2 ~10 3 The attenuation is in the dB / km range, and under actual fabrication and placement conditions, the highest current attenuation is 2.6 dB / m. The native attenuation of its cladding mode has decreased significantly with increasing structural layers, thus the attenuation of the LP11 mode cannot reach a sufficiently high level. This situation is even more severe in DNANF structures: firstly, the attenuation of the cladding mode in DNANF structures is further reduced; secondly, the cladding region of DNANF structures does not have enough space for the LP11 mode to achieve sufficient phase matching with the cladding mode, and the theoretical attenuation of the LP11 mode is already below 10 dB / km. 2 dB / km, which means that DNANF fiber cannot effectively filter out higher-order modes, seriously affecting signal transmission quality. Summary of the Invention

[0007] The problem to be solved by the present invention is to provide a high single-mode ultra-low loss hollow anti-resonant optical fiber that addresses the shortcomings of the prior art by improving the loss of higher-order modes through changes in the cladding structure, thereby achieving high-purity single-mode transmission.

[0008] The technical solution adopted by the present invention to solve the above-mentioned problems is as follows: it includes an outer cladding layer and an inner cladding layer. The inner cladding layer is composed of nested structural units. The nested structural units are arranged circumferentially along the inner wall of the outer cladding layer and are connected to the inner wall of the outer cladding layer. The central cavity covered by the inner cladding layer forms a fiber core. The nested structural unit includes three or more nested glass tubes of different radii. At least one inner nested glass tube, which has at least one inner nested glass tube, is deflected to one side relative to its adjacent outer nested glass tube, with a deflection angle of 5 to 55°.

[0009] According to the above scheme, the deflected inner nested glass tube is included in one or two layers of inner nested glass tubes.

[0010] According to the above scheme, the nested structure unit includes three layers of nested glass tubes with different radii. From the outside to the inside, it includes an outer nested glass tube, a first inner nested glass tube, and a second inner nested glass tube. The first inner nested glass tube is deflected to one side relative to the outer nested glass tube, or the second inner nested glass tube is deflected to one side relative to the first inner nested glass tube.

[0011] According to the above scheme, the nested structure unit includes three layers of nested glass tubes with different radii. From the outside to the inside, it includes an outer nested glass tube, a first inner nested glass tube, and a second inner nested glass tube. The first inner nested glass tube is deflected to one side relative to the outer nested glass tube, and the second inner nested glass tube is deflected to one side relative to the first inner nested glass tube.

[0012] According to the above scheme, the first inner nested glass tube is deflected to one side relative to the outer nested glass tube. That is, the line L2 connecting the curvature center O2 of the first inner nested glass tube and the curvature center O1 of the outer nested glass tube forms a deflection angle with the extension line L1 of the line connecting the curvature center O1 of the outer nested glass tube and the geometric center O of the fiber core.

[0013] According to the above scheme, the second inner nested glass tube is deflected to one side relative to the first inner nested glass tube. That is, the line L3 connecting the curvature center O3 of the second inner nested glass tube and the curvature center O2 of the first inner nested glass tube forms a deflection angle with the extension of the line L2 connecting the curvature center O2 of the first inner nested glass tube and the curvature center O1 of the outer nested glass tube.

[0014] According to the above scheme, the inner cladding layer includes 4 to 6 nested structural units.

[0015] According to the above scheme, the nested structural units are evenly distributed circumferentially along the inner wall of the outer cladding.

[0016] According to the above scheme, both the outer cladding and the inner wall are circular.

[0017] According to the above scheme, the nested glass tube includes circular nested glass tubes with different radii, each circular nested glass tube is tangent to the others, and the outer nested glass tube is tangent to the inner wall of the outer cladding layer.

[0018] According to the above scheme, the nested glass tubes include arc-shaped nested glass tubes and circular nested glass tubes with different radii. Each arc-shaped nested glass tube intersects with the inner wall of the outer cladding or with an adjacent outer nested glass tube. Each circular nested glass tube is tangent to each other or to the inner wall of the outer cladding.

[0019] According to the above scheme, the nested glass tubes include circular arc nested glass tubes with different radii, and each circular arc nested glass tube intersects with the inner wall of the outer cladding layer.

[0020] According to the above scheme, all the inner nested glass tubes in the first layer of the inner nested glass tubes are deflected to the same side relative to their adjacent outer nested glass tubes, and the deflection angles are the same or basically the same.

[0021] According to the above scheme, all the first inner nested glass tubes are deflected to the same side relative to the outer nested glass tubes, and the deflection angles are the same or basically the same, while all the second inner nested glass tubes are not deflected relative to the first inner nested glass tubes.

[0022] According to the above scheme, all the first inner nested tubes are deflected to the same side relative to the outer nested glass tubes, and the deflection angles are the same or basically the same. All the second inner nested tubes are deflected to the opposite side relative to the first inner nested glass tubes, and the deflection angles are the same or basically the same.

[0023] According to the above scheme, all the inner nested glass tubes of the first inner nested tube are deflected to the same side relative to the outer nested glass tube, and the deflection angles are the same or basically the same. All the inner nested glass tubes of the second inner nested tube are deflected to the same side relative to the first inner nested glass tube, and the deflection angles are the same or basically the same.

[0024] According to the above scheme, the second inner nested tube is a circular nested glass tube, the first inner nested tube is a circular nested glass tube or an arc-shaped nested glass tube, and the outer nested glass tube is an arc-shaped nested glass tube.

[0025] According to the above scheme, the second inner nested tube is an arc-shaped nested glass tube, the first inner nested tube is an arc-shaped nested glass tube or a circular nested glass tube, and the outer nested glass tube is an arc-shaped nested glass tube.

[0026] According to the above scheme, the deflection angle is 15-55°; further, the deflection angle is 25-50°; further, the deflection angle is 35-45°.

[0027] According to the above scheme, the base material of the outer cladding layer and the nested structural unit is pure quartz glass.

[0028] According to the above scheme, the wall thickness of the inner and outer nested glass tubes is 0.3 to 1.5 μm.

[0029] According to the above scheme, the ratio of the outer diameter of the outer nested glass tube to the outer diameter of the first inner nested glass tube is 1:0.5 to 0.65, and the ratio of the outer diameter of the first inner nested glass tube to the outer diameter of the second inner nested glass tube is 1:0.3 to 0.5.

[0030] According to the above scheme, the core region and other cavities within the outer cladding are filled with gas.

[0031] According to the above scheme, the gas is argon, nitrogen, helium, air, or a mixture of multiple gases.

[0032] According to the above scheme, the fundamental mode loss of the optical fiber is 0.05 to 0.5 dB / km, and further, the fundamental mode loss of the optical fiber is less than 0.15 dB / km.

[0033] According to the above scheme, the higher-order mode loss of the optical fiber is 3 to 20 dB / m, and further, the higher-order mode loss of the optical fiber is higher than 8 dB / m.

[0034] The beneficial effects of this invention are as follows: 1. In the structure of this invention, the inner cladding includes multiple layers of anti-resonant quartz walls and an air layer, effectively confining the transmitted fundamental mode within the fiber core, thus reducing confinement loss. This invention, through changes in the cladding structure, combines a reasonable and fabricable nested structure unit shape, optimized nesting size combinations, and the deflection of the inner nested glass tube, significantly improving the leakage loss of the LP11 mode with minimal impact on fundamental mode performance, ultimately effectively enhancing the single-mode performance of the optical fiber. The key to this invention is that, when optimizing the ratio of the outer diameter of the outer nested glass tube to the inner nested glass tube to the optimal value, the inner nested glass tube is deflected to one side within the outer nested glass tube. This structure can improve the leakage efficiency of the LP11 mode, thereby achieving higher single-mode performance. 2. This invention designs phase matching between the higher-order modes in the fiber core and the modes in the inner air region, and designs to increase the cladding mode loss, enabling more efficient leakage of higher-order modes and further improving higher-order mode attenuation, resulting in excellent single-mode transmission performance. 3. The single-mode performance of this invention does not exhibit wavelength selectivity, achieving high single-mode transmission within the operating wavelength range. This invention provides a hollow-core optical fiber that balances attenuation and single-mode characteristics, providing a high-performance transmission medium for fields such as high-speed communication, high-power transmission, gas lasers, and gas detection. Attached Figure Description

[0035] Figure 1 This is a radial cross-sectional structural diagram of the first embodiment of the present invention.

[0036] Figure 2 yes Figure 1 A magnified view of a nested tube.

[0037] Figure 3 This is a graph showing the variation of the loss of the fundamental mode and LP11 mode with the rotation angle in the first embodiment of the present invention.

[0038] Figure 4 This is a graph showing the variation of fundamental mode and LP11 mode loss with wavelength in the first embodiment of the present invention.

[0039] Figure 5 This is a radial cross-sectional structural diagram of the second embodiment of the present invention.

[0040] Figure 6 This is a radial cross-sectional structural diagram of the third embodiment of the present invention.

[0041] Figure 7 This is a radial cross-sectional structural diagram of the fourth embodiment of the present invention.

[0042] Figure 8 This is a radial cross-sectional structural diagram of the fifth embodiment of the present invention.

[0043] Figure 9 This is a graph showing the variation of fundamental mode and LP11 mode loss with wavelength in the fifth embodiment of the present invention. Detailed Implementation

[0044] The present invention will now be described in further detail with reference to the embodiments and accompanying drawings.

[0045] A common method for filtering higher-order modes in hollow-core optical fibers is to select a high-attenuation cladding mode and, through structural design, achieve a high phase match with the LP11 mode in the fiber core, thereby effectively improving the leakage loss of the LP11 mode. Generally, the attenuation of the designed LP11 mode depends on the native attenuation of the cladding mode and its phase match with the LP11 mode. Typically, the higher the attenuation of the cladding mode and the greater the phase match with the LP11 mode, the greater the improvement in LP11 mode leakage loss and the better the single-mode performance.

[0046] First embodiment of the invention, for example Figure 1 , 2As shown, it includes an outer cladding layer 1 and an inner cladding layer. The inner cladding layer consists of four nested structural units, which are spaced apart circumferentially along the inner wall of the outer cladding layer. Each nested structural unit includes three layers of nested glass tubes with different radii, from the outside to the inside: an outer nested glass tube 2, a first inner nested glass tube 3, and a second inner nested glass tube 4, forming an anti-resonance unit. The nested glass tubes include one arc-shaped nested glass tube and two circular nested glass tubes with different radii. The outer nested glass tube is an arc-shaped nested glass tube with a diameter of d1, while the first and second inner nested glass tubes are circular nested glass tubes with diameters of d2 and d3, respectively. The outer nested glass tube and the inner cladding layer... The walls intersect, and the first inner nested glass tube is tangent to the inner wall of the outer cladding and deflected to one side. Specifically, the line L2 connecting the curvature center (center) of the first inner nested glass tube and the curvature center (center) of the outer nested glass tube forms a deflection angle θ1 with the extension line L1 connecting the curvature center of the outer nested glass tube and the geometric center of the fiber core. The second inner nested glass tube is tangent to the first inner nested glass tube, with the tangency point located at the same point where the first inner nested glass tube is tangent to the inner wall of the outer cladding. The line L3 connecting the curvature center (center) of the first inner nested glass tube and the curvature center (center) of the second inner nested glass tube forms an opposite deflection angle θ2 with L2. All inner nested glass tubes deflect in the same direction. The central cavity covered by the inner cladding forms the fiber core 5, and the fiber core region and other internal spaces are filled with gas. The gas is argon, nitrogen, helium, air, or a mixture of multiple gases. Specifically, the relevant parameters in this embodiment are as follows: the fiber core diameter D is 29 μm, the outer diameter d1 of the outer nested glass tube is 44 μm, and the circumference of the arc is 245°; the outer diameter d2 of the first inner nested glass tube is 24 μm, and the ratio of its outer diameter to that of the outer nested glass tube is 0.55; the outer diameter d3 of the second inner nested glass tube is 10 μm, and the ratio of its outer diameter to that of the first inner nested glass tube is 0.41; the inner diameter of the outer cladding (the diameter of the outer cladding cavity) is 105 μm. In this embodiment, the wall thickness of each nested glass tube is 1.1 μm. When the wall thickness of each nested glass tube is approximately 0.95 μm, the second resonant operating band is extended to 1310 nm. When the first anti-resonant window is used as the communication operating band, the wall thickness of each nested glass tube is approximately 0.5 μm. Figure 3The optimization process of the rotation angle θ1 in this embodiment is demonstrated: when θ1 is 0°, no structure deflects, and the mode losses of LP01 and LP11 are 0.025dB / km and 2200dB / km (2.2dB / m), respectively; when θ1 is 15°, the mode losses of LP01 and LP11 are 0.026dB / km and 2500dB / km (2.5dB / m), respectively; when θ1 is 30°, the mode losses of LP01 and LP11 are 0.032dB / km and 3500dB / km (2.5dB / m), respectively. The single-mode performance of the optical fiber is 3.5 dB / m. When θ1 is 35°, the mode losses of LP01 and LP11 are 0.037 dB / km and 4500 dB / km (4.5 dB / m), respectively. When θ1 is 40°, the mode losses of LP01 and LP11 are 0.045 dB / km and 6300 dB / km (6.3 dB / m), respectively. When θ1 is 44°, the mode losses of LP01 and LP11 are 0.053 dB / km and 8300 dB / km (8.3 dB / m), respectively. Increasing the rotation angle θ1 significantly improves the single-mode performance of the optical fiber without significantly increasing the fundamental mode loss.

[0047] This invention combines a reasonable and fabricable nested structural unit shape, an optimized nested size combination, and the deflection of the inner nested glass tube, resulting in the following technical effects: significantly improved leakage loss in LP11 mode with minimal impact on fundamental mode performance, ultimately effectively enhancing the single-mode performance of optical fiber. Figure 4 This is the optimized attenuation spectrum curve for this embodiment, where the deflection angles of L1 and L2 are 44°, and the opposite deflection angles of L2 and L3 are 40°. Within a wide bandwidth, it exhibits the design effect of ultra-low attenuation and ultra-high single-mode performance.

[0048] Second embodiment of the present invention, for example Figure 5As shown, it differs from the first embodiment in that the inner cladding is composed of 5 nested structural units, the outer nested glass tube is a circular nested glass tube, the outer nested glass tube is tangent to the inner wall of the outer cladding, the first inner nested glass tube is tangent to the outer nested glass tube and does not deflect relative to the outer nested glass tube, that is, the line L2 connecting the curvature center (center) of the first inner nested glass tube and the curvature center (center) of the outer nested glass tube, and the extension line L of the line connecting the curvature center of the outer nested glass tube and the geometric center of the fiber core. 1. Overlap; the second inner nested glass tube is tangent to the first inner nested glass tube, and the second inner nested glass tube is deflected to one side relative to the point of tangency between the first inner nested glass tube and the inner wall of the outer cladding. That is, the line L3 connecting the curvature center (center) of the second inner nested glass tube and the curvature center (center) of the first inner nested glass tube has a deflection angle of 30° with the extension line L2 connecting the curvature center of the first inner nested glass tube and the curvature center of the outer nested glass tube; the deflection direction of all inner nested glass tubes is consistent.

[0049] Third embodiment of the present invention Figure 6 As shown, the difference between this embodiment and the second embodiment is that the outer nested glass tube is an arc-shaped nested glass tube with a circumferential angle of approximately 320°. The outer nested glass tube intersects with the inner wall of the outer cladding. The first inner nested glass tube is tangent to the inner wall of the outer cladding and deflects to one side. That is, the line L2 connecting the curvature center (center) of the first inner nested glass tube and the curvature center (center) of the outer nested glass tube forms a deflection angle of 35° with the extension line L1 connecting the curvature center of the outer nested glass tube and the geometric center of the fiber core. The second inner nested glass tube is tangent to the first inner nested glass tube, and the point of tangency is located at the same point where the first inner nested glass tube is tangent to the inner wall of the outer cladding. The line L3 connecting the curvature center (center) of the first inner nested glass tube and the curvature center (center) of the second inner nested glass tube forms an opposite deflection angle of 30° with L2.

[0050] Fourth embodiment of the present invention Figure 7 As shown, it differs from the second embodiment in that the second inner nested glass tube is a circular nested glass tube, the first inner nested glass tube is an arc-shaped nested glass tube, and the outer nested glass tube is an arc-shaped nested glass tube. Both the outer nested glass tube and the first inner nested glass tube intersect with the inner wall of the outer cladding. The first inner nested glass tube does not deflect relative to the outer nested glass tube, with a deflection angle of 0°. The second inner nested glass tube deflects to one side relative to the first inner nested glass tube; that is, the line L3 connecting the curvature centers of the second and first inner nested glass tubes forms a deflection angle of 35° with the extension of the line L2 connecting the curvature centers of the first and outer nested glass tubes.

[0051] Fifth embodiment of the present invention Figure 8 As shown, it differs from the first embodiment in that the outer nested glass tube and the first inner nested glass tube are arc-shaped nested glass tubes, and the second inner nested glass tube is a circular nested glass tube. The outer nested glass tube and the first inner nested glass tube intersect with the inner wall of the outer cladding layer, and the second inner nested glass tube is tangent to the inner wall of the outer cladding layer. All the first inner nested tubes are deflected to the same side relative to the outer nested glass tube, and the deflection angles are the same or substantially the same, that is, the curvature center (center of the circle) of the first inner nested glass tube and the curvature center (center of the circle) of the outer nested glass tube are connected. Line L2, together with the extension of line L1 connecting the center of curvature of the outer nested glass tube and the geometric center of the fiber core, forms a deflection angle of 28°. All the second inner nested tubes are deflected to the opposite side relative to the first inner nested glass tube, and the deflection angles are the same or substantially the same. That is, line L3 connecting the center of curvature of the second inner nested glass tube and the center of curvature of the first inner nested glass tube forms an opposite deflection angle of 24° with the extension of line L2 connecting the center of curvature of the first inner nested glass tube and the center of curvature of the outer nested glass tube. Specifically, the relevant parameters in this embodiment are as follows: the core diameter D is 29 μm; the outer diameter d1 of the outer nested glass tube is 44 μm, and the circumference angle of the arc is 245°; the outer diameter d2 of the first inner nested glass tube is 28 μm, and the ratio of its outer diameter to that of the outer nested glass tube is 0.64; the outer diameter d3 of the second inner nested glass tube is 10 μm, and the ratio of its outer diameter to that of the first inner nested glass tube is 0.36; the inner diameter of the outer cladding (the diameter of the outer cladding cavity) is 105 μm. In this embodiment, the wall thickness of each nested glass tube is 1.1 μm. Figure 9 The attenuation spectrum curve of this embodiment shows that, within a wide bandwidth, the LP11 mode attenuation can reach nearly 10,000 dB / km (10 dB / m), and the fundamental mode transmission loss is less than 0.1 dB / km.

Claims

1. A high single-mode, ultra-low-loss hollow-core anti-resonant optical fiber, comprising an outer cladding and an inner cladding, wherein the inner cladding is composed of nested structural units arranged circumferentially along the inner wall of the outer cladding and connected to the inner wall of the outer cladding, and the central cavity covered by the inner cladding forms the fiber core, characterized in that... The nested structural unit includes three or more nested glass tubes of different radii, and at least one inner nested glass tube is deflected to one side relative to its adjacent outer nested glass tube, with a deflection angle of 5 to 55°.

2. The high single-mode ultra-low loss hollow anti-resonant optical fiber according to claim 1, characterized in that... The deflecting inner nested glass tube is comprised of one or two layers of inner nested glass tubes.

3. The high single-mode ultra-low loss hollow anti-resonant optical fiber according to claim 2, characterized in that... The nested structure unit includes three layers of nested glass tubes with different radii. From the outside to the inside, it includes an outer nested glass tube, a first inner nested glass tube, and a second inner nested glass tube. The first inner nested glass tube is deflected to one side relative to the outer nested glass tube, or the second inner nested glass tube is deflected to one side relative to the first inner nested glass tube.

4. The high single-mode ultra-low loss hollow anti-resonant optical fiber according to claim 2, characterized in that... The nested structure unit includes three layers of nested glass tubes with different radii. From the outside to the inside, it includes an outer nested glass tube, a first inner nested glass tube, and a second inner nested glass tube. The first inner nested glass tube is deflected to one side relative to the outer nested glass tube, and the second inner nested glass tube is deflected to one side relative to the first inner nested glass tube.

5. The high single-mode ultra-low loss hollow anti-resonant optical fiber according to claim 3 or 4, characterized in that... The first inner nested glass tube is deflected to one side relative to the outer nested glass tube. That is, the line L2 connecting the curvature center O1 of the first inner nested glass tube and the curvature center O2 of the outer nested glass tube forms a deflection angle with the extension line L1 of the line connecting the curvature center O1 of the outer nested glass tube and the geometric center O of the fiber core.

6. The high single-mode ultra-low loss hollow anti-resonant optical fiber according to claim 3 or 4, characterized in that... The second inner nested glass tube is deflected to one side relative to the first inner nested glass tube. That is, the line L3 connecting the curvature center O3 of the second inner nested glass tube and the curvature center O2 of the first inner nested glass tube forms a deflection angle with the extension of the line L2 connecting the curvature center O2 of the first inner nested glass tube and the curvature center O1 of the outer nested glass tube.

7. The high single-mode ultra-low loss hollow anti-resonant optical fiber according to claim 1 or 2, characterized in that... The inner cladding layer comprises 4 to 6 nested structural units.

8. The high single-mode ultra-low loss hollow anti-resonant optical fiber according to claim 1 or 2, characterized in that... The nested structural units are evenly distributed circumferentially along the inner wall of the outer cladding layer.

9. The high single-mode ultra-low loss hollow anti-resonant optical fiber according to claim 1 or 2, characterized in that... Both the outer cladding and the inner wall are circular.

10. The high single-mode ultra-low loss hollow anti-resonant optical fiber according to claim 3 or 4, characterized in that... The nested glass tubes include circular nested glass tubes of different radii, all of which are tangent to each other, and the outer nested glass tube is tangent to the inner wall of the outer cladding layer.

11. The high single-mode ultra-low loss hollow anti-resonant optical fiber according to claim 3 or 4, characterized in that... The nested glass tubes include arc-shaped nested glass tubes and circular nested glass tubes with different radii. Each arc-shaped nested glass tube intersects with the inner wall of the outer cladding or with an adjacent outer nested glass tube. Each circular nested glass tube is tangent to each other or to the inner wall of the outer cladding.

12. The high single-mode ultra-low loss hollow anti-resonant optical fiber according to claim 3 or 4, characterized in that... The nested glass tubes include circular arc nested glass tubes with different radii, and each circular arc nested glass tube intersects with the inner wall of the outer cladding layer.

13. The high single-mode ultra-low loss hollow anti-resonant optical fiber according to claim 1 or 2, characterized in that... In the aforementioned nested glass tubes, all the nested glass tubes in the same layer are deflected to the same side relative to their adjacent outer nested glass tubes, and the deflection angles are the same.

14. The high single-mode ultra-low loss hollow anti-resonant optical fiber according to claim 3, characterized in that... All the first inner nested glass tubes deflect to the same side relative to the outer nested glass tubes, and the deflection angle is the same. All the second inner nested glass tubes do not deflect relative to the first inner nested glass tubes.

15. The high single-mode ultra-low loss hollow anti-resonant optical fiber according to claim 4, characterized in that... All the first inner nested glass tubes deflect to the same side relative to the outer nested glass tubes, and the deflection angle is the same. All the second inner nested glass tubes deflect to the opposite side relative to the first inner nested glass tubes, and the deflection angle is the same.

16. The high single-mode ultra-low loss hollow anti-resonant optical fiber according to claim 4, characterized in that... All the first inner nested glass tubes deflect to the same side relative to the outer nested glass tubes, and the deflection angle is the same. All the second inner nested glass tubes deflect to the same side relative to the first inner nested glass tubes, and the deflection angle is the same.

17. The high single-mode ultra-low loss hollow anti-resonant optical fiber according to claim 3 or 4, characterized in that... The second inner nested glass tube is a circular nested glass tube, the first inner nested glass tube is a circular nested glass tube or an arc-shaped nested glass tube, and the outer nested glass tube is an arc-shaped nested glass tube.

18. The high single-mode ultra-low loss hollow anti-resonant optical fiber according to claim 3 or 4, characterized in that... The second inner nested glass tube is an arc-shaped nested glass tube, the first inner nested glass tube is an arc-shaped nested glass tube or a circular nested glass tube, and the outer nested glass tube is an arc-shaped nested glass tube.

19. The high single-mode ultra-low loss hollow anti-resonant optical fiber according to claim 1 or 2, characterized in that... The deflection angle is 15~55°.

20. The high single-mode ultra-low loss hollow anti-resonant optical fiber according to claim 1 or 2, characterized in that... The deflection angle is 25~50°.

21. The high single-mode ultra-low loss hollow anti-resonant optical fiber according to claim 1 or 2, characterized in that... The deflection angle is 35~45°.

22. The high single-mode ultra-low loss hollow anti-resonant optical fiber according to claim 1 or 2, characterized in that... The base material for both the outer cladding layer and the nested structural unit is pure quartz glass.

23. The high single-mode ultra-low loss hollow anti-resonant optical fiber according to claim 3 or 4, characterized in that... The wall thickness of the inner and outer nested glass tubes is 0.3 to 1.5 μm.

24. The high single-mode ultra-low loss hollow anti-resonant optical fiber according to claim 3 or 4, characterized in that... The ratio of the outer diameter of the outer nested glass tube to the outer diameter of the first inner nested glass tube is 1:0.5~0.65, and the ratio of the outer diameter of the first inner nested glass tube to the outer diameter of the second inner nested glass tube is 1:0.3~0.

5.

25. The high single-mode ultra-low loss hollow anti-resonant optical fiber according to claim 1 or 2, characterized in that... The core region and other cavities within the outer cladding are filled with gas.

26. The high single-mode ultra-low loss hollow anti-resonant optical fiber according to claim 25, characterized in that... The gas is argon, nitrogen, helium, air, or a mixture of multiple gases.

27. The high single-mode ultra-low loss hollow anti-resonant optical fiber according to claim 1 or 2, characterized in that... The fundamental mode loss of the optical fiber is 0.05~0.5 dB / km.

28. The high single-mode ultra-low loss hollow anti-resonant optical fiber according to claim 1 or 2, characterized in that... The fundamental mode loss of the optical fiber is less than 0.15 dB / km.

29. The high single-mode ultra-low loss hollow anti-resonant optical fiber according to claim 1 or 2, characterized in that... The higher-order mode loss of the optical fiber is 3~20 dB / m.

30. The high single-mode ultra-low loss hollow anti-resonant optical fiber according to claim 1 or 2, characterized in that... The higher-order mode loss of the optical fiber is higher than 8 dB / m.

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