Cladding nested anti-resonant tube with different wall thicknesses of low-loss hollow core optical fiber and application

Abstract

This invention relates to a low-loss hollow-core optical fiber with nested anti-resonant tubes of varying wall thicknesses and its applications. The fiber comprises an outer cladding and an inner cladding. The inner cladding is composed of anti-resonant structural units arranged circumferentially along and connected to the inner wall of the outer cladding. The central cavity enclosed by the inner cladding forms the fiber core. The key feature is that each anti-resonant structural unit comprises at least two layers of anti-resonant tubes with different radii and thicknesses, the thickness of which increases progressively from the outside to the inside. By establishing a gradually increasing wall thickness relationship between the anti-resonant tubes from the outside to the inside, this invention maintains the low-loss light-guiding characteristics of the hollow-core optical fiber with minimal impact on the low-loss bandwidth range. Ultimately, it effectively improves the tolerance of the hollow-core optical fiber to manufacturing tolerances and reduces the manufacturing difficulty of the hollow-core optical fiber.

Description

Technical Field

[0001] This invention relates to the field of hollow fiber technology, specifically to a low-loss hollow fiber with cladding nested anti-resonant tubes of different wall thicknesses and its applications. Background Technology

[0002] Since the invention of the first solid optical fiber, optical fiber technology has been widely applied in various fields, including communications, sensing, and medicine, after more than half a century of development. With the rapid development of society and the improvement of people's living standards, there is an urgent need for optical fibers with longer transmission distances, higher power, and larger capacity. However, the performance of traditional silica optical fibers has approached its theoretical limits, prompting people to explore more advanced optical fiber technologies to meet the ever-increasing demand for data transmission.

[0003] Hollow-core fiber, as a novel type of optical fiber, confines light waves within an air core, exhibiting intrinsic advantages such as low Rayleigh scattering, low nonlinearity, and tunable dispersion. It can theoretically achieve extremely low loss and provide a higher laser damage threshold, showing potential applications in high-power laser transmission, ultraviolet / mid-infrared light transmission, pulse compression, and optical soliton transmission. Furthermore, the air core possesses characteristics such as large mode area, single-mode operation, low nonlinearity, low dispersion, and low latency, potentially breaking the nonlinear Shannon limit of traditional optical fibers and providing a new transmission medium for next-generation high-capacity, long-distance optical communication systems.

[0004] Even though hollow-core fiber has unique and significant advantages in design and application, it also introduces more complex structures compared to ordinary single-mode fiber. In common multi-layer nested nodeless hollow-core fiber structures, the nested tubes within each resonant unit maintain the same wall thickness to center the low-loss transmission window at the required wavelength and maximize bandwidth. For example, the center wavelength of the second window in hollow-core fiber at 1550nm corresponds to a nested tube wall thickness of approximately 1.22µm.

[0005] In existing publicly available technologies, the structural design of hollow-core optical fibers often requires that the wall thickness of each nested tube be the same to achieve optimal attenuation and bandwidth. For example, Chinese patents CN115629444A, CN118795594A, CN115728863A, CN110333571A, US patents US12117646B2 and US20220011502A1 all require that the wall thickness of the nested tubes in each resonant unit be the same. However, in the actual fabrication process of hollow-core optical fibers, various other factors often affect the process, causing the wall thickness of the nested tubes to be almost impossible to keep the same. In this case, the hollow-core optical fiber will introduce additional attenuation, and the operating bandwidth will also be narrowed. Summary of the Invention

[0006] This invention provides a low-loss hollow-core optical fiber with cladding nested anti-resonant tubes of different wall thicknesses and its application, solving the problem in the prior art where the thickness of each glass reflective layer in the resonant unit cannot be kept the same due to process issues, thus maintaining low loss and wide bandwidth as much as possible.

[0007] The technical solution adopted by the present invention to solve the above-mentioned problems is as follows:

[0008] A low-loss hollow-core optical fiber with nested anti-resonant tubes of different wall thicknesses includes an outer cladding and an inner cladding. The inner cladding is composed of anti-resonant structural units, which are arranged circumferentially along the inner wall of the outer cladding and connected to the inner wall of the outer cladding. The central cavity covered by the inner cladding forms the fiber core. The characteristic feature is that the anti-resonant structural unit includes at least two layers of anti-resonant tubes with different radii and thicknesses, and the thickness of the anti-resonant tubes increases sequentially from the outside to the inside.

[0009] According to the above technical solution, the line connecting the curvature centers of each nested glass sleeve coincides with the extension line connecting the outer anti-resonant tube and the geometric center of the fiber core.

[0010] According to the above technical solution, the anti-resonant tube includes circular anti-resonant tubes with different radii, each circular anti-resonant tube is tangent to the others, and the outer anti-resonant tube is tangent to the inner cavity wall of the outer cladding.

[0011] According to the above technical solution, the various cutting points overlap with each other.

[0012] According to the above technical solution, the anti-resonant tube includes arc anti-resonant tubes and circular anti-resonant tubes with different radii, wherein each arc anti-resonant tube intersects with the inner wall of the outer cladding, and each circular anti-resonant tube is tangent to each other, or each circular anti-resonant tube is tangent to the inner wall of the outer cladding.

[0013] According to the above technical solution, the anti-resonant tube includes circular arc anti-resonant tubes with different radii, and each circular arc anti-resonant tube intersects with the inner wall of the outer cladding layer.

[0014] According to the above technical solution, the anti-resonance structure unit includes 2-5 layers of anti-resonance tubes with different radii.

[0015] According to the above technical solution, the inner cladding layer includes 4 to 6 anti-resonance structural units.

[0016] According to the above technical solution, the anti-resonance structure unit includes three layers of anti-resonance tubes with different radii, from the outside to the inside including an outer anti-resonance tube, a first inner anti-resonance tube, and a second inner anti-resonance tube. The wall thickness of the outer anti-resonance tube is 0.8 to 1.22 μm, the wall thickness of the first inner anti-resonance tube is 0.8 to 1.5 μm, and the wall thickness of the second inner anti-resonance tube is 1.22 to 1.5 μm.

[0017] According to the above technical solution, the ratio of the outer diameter of the outer anti-resonant tube, the first inner anti-resonant tube, and the second inner anti-resonant tube is 1:0.6~0.9:0.15~0.3.

[0018] According to the above technical solution, the ratio of the outer diameter of the outer anti-resonant tube, the first inner anti-resonant tube, and the second inner anti-resonant tube is 1:0.7~0.8:0.18~0.25.

[0019] According to the above technical solution, both the outer cladding and the inner wall are circular.

[0020] According to the above technical solution, the substrate materials of the outer cladding layer and the anti-resonance structural unit are both pure quartz glass.

[0021] According to the above technical solution, the core region and other cavities within the outer cladding are filled with gas.

[0022] According to the above technical solution, the gas is argon, nitrogen, helium, air, or a mixture of multiple gases.

[0023] According to the above technical solution, the LP01 mode loss of the optical fiber is less than 0.1 dB / km.

[0024] According to the above technical solution, the bandwidth of the optical fiber with a value of less than 0.1dB / km is greater than 200nm.

[0025] An application of low-loss hollow-core optical fibers with different wall thicknesses of cladding nested anti-resonant tubes as described above, characterized in that the low-loss hollow-core optical fibers are used in communication, laser, or sensing fields.

[0026] The beneficial effects of this invention are as follows:

[0027] 1. This invention maintains the low-loss light guiding characteristics of hollow optical fiber by setting the relationship between the anti-resonant tubes with the wall thickness gradually increasing from the outside to the inside, and has little impact on the low-loss bandwidth range. Ultimately, it effectively improves the tolerance of hollow optical fiber to manufacturing tolerances and reduces the manufacturing difficulty of hollow optical fiber.

[0028] 2. When the anti-resonant structure unit includes three layers of anti-resonant tubes with different radii, when the ratio of the outer diameter of the outer anti-resonant tube, the first inner anti-resonant tube, and the second inner anti-resonant tube is optimized to the best, the outer anti-resonant tube has the thinnest wall thickness, the second inner anti-resonant tube has the thickest wall thickness, and the first inner anti-resonant tube has a wall thickness between the two. This structure is the optimal choice when it is difficult to keep the wall thickness of the anti-resonant tubes completely the same during the actual fabrication of hollow optical fibers, thereby obtaining performance with small changes in attenuation and bandwidth, and significantly reducing the manufacturing difficulty of hollow optical fibers.

[0029] 3. Since the glass tube wall of the hollow fiber itself acts as a Fabry-Perot resonator, different wall thicknesses can make it in an anti-resonance state at the corresponding wavelength, and the light is reflected back to the fiber core. When the anti-resonator tube is thinner, it can reflect light of a shorter wavelength, and when the anti-resonator tube is thicker, it can reflect light of a longer wavelength. This invention can achieve complementary anti-resonance effects of different wavelengths of light by setting anti-resonator tubes with progressively thicker thicknesses from the outside to the inside, thereby achieving a better low-attenuation bandwidth. Attached Figure Description

[0030] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a radial cross-sectional diagram of a low-loss hollow fiber with different wall thicknesses for embodiment 1 of the present invention.

[0032] Figure 2 This is a partial enlarged view of a nested tube in Embodiment 1 of the present invention.

[0033] Figure 3 This is a graph showing the LP01 mode loss versus wavelength in the first embodiment of the present invention.

[0034] Figure 4 This is a partially enlarged view of a nested tube of a low-loss hollow fiber with different wall thicknesses, provided in Embodiment 2 of the present invention.

[0035] Figure 5 This is a graph showing the LP01 mode loss versus wavelength in the second embodiment of the present invention.

[0036] Figure 6 The radial cross-sectional structure of a low-loss hollow optical fiber containing two anti-resonant tubes is shown in the third embodiment of the present invention.

[0037] Figure 7 The radial cross-sectional structure of a low-loss hollow optical fiber containing four anti-resonant tubes is shown in the fourth embodiment of the present invention.

[0038] Figure 8 The radial cross-sectional structure diagram of a low-loss hollow optical fiber containing an arc-shaped nested tube is provided for the fifth embodiment of the present invention. Detailed Implementation

[0039] 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, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0040] Example 1:

[0041] The first embodiment of the invention is as follows: Figure 1 , 2 As shown, it includes an outer cladding layer 1 and an inner cladding layer. The inner cladding layer is composed of 5 anti-resonance structural units, which are arranged circumferentially along the inner wall of the outer cladding layer. Each anti-resonance structural unit includes 3 layers of anti-resonance tubes with different radii, including an outer anti-resonance tube 2, a first inner anti-resonance tube 3, and a second inner anti-resonance tube 4, forming an anti-resonance unit. Each anti-resonance tube includes 3 circular anti-resonance tubes with different radii, wherein the diameter of the outer anti-resonance tube is d1, the diameter of the first inner anti-resonance tube is d2, and the diameter of the second inner anti-resonance tube is d3. The wall thickness of the outer anti-resonance tube is h1, the wall thickness of the first inner anti-resonance tube is h2, and the wall thickness of the second inner anti-resonance tube is h3. The outer wall of the outer anti-resonance tube is tangent to the inner wall of the outer cladding layer, the outer wall of the first inner anti-resonance tube is tangent to the inner wall of the outer anti-resonance tube, and the outer wall of the second inner anti-resonance tube is tangent to the inner wall of the second nested tube. The three tangent points coincide with each other. The central cavity covered by the inner cladding forms the fiber core 8. The fiber core region and other internal spaces, including the outer anti-resonant tube cavity 5, the first inner anti-resonant tube cavity 6, and the second inner anti-resonant tube cavity 7, are filled with gas. The gas is argon, nitrogen, helium, air, or a mixture of multiple gases.

[0042] Specifically, the relevant parameters in this embodiment are as follows: the core diameter D is 31 μm, the outer diameter d1 of the outer anti-resonator is 31 μm, the outer diameter d2 of the first inner anti-resonator is 23 μm, the outer diameter d3 of the second inner anti-resonator is 7.7 μm, and the inner diameter of the cladding (outer cladding cavity diameter) is 93 μm. The wall thickness h1 of the outer anti-resonator is 1.18 μm, the wall thickness h2 of the first inner anti-resonator is 1.22 μm, and the wall thickness h3 of the second inner anti-resonator is 1.26 μm.

[0043] The relevant parameters for Comparative Example 1 are as follows: the core diameter D is 31 μm, the outer diameter d1 of the outer anti-resonator is 31 μm, the outer diameter d2 of the first inner anti-resonator is 23 μm, and the outer diameter d3 of the second inner anti-resonator is 7.7 μm; the inner diameter of the cladding (the diameter of the cladding cavity) is 93 μm. The wall thickness h1 of the outer anti-resonator is 1.22 μm, the wall thickness h2 of the first inner anti-resonator is 1.22 μm, and the wall thickness h3 of the second inner anti-resonator is 1.22 μm.

[0044] The relevant parameters for Comparative Example 2 are as follows: the core diameter D is 31 μm, the outer diameter d1 of the outer anti-resonator is 31 μm, the outer diameter d2 of the first inner anti-resonator is 23 μm, and the outer diameter d3 of the second inner anti-resonator is 7.7 μm; the inner diameter of the cladding (the diameter of the cladding cavity) is 93 μm. The wall thickness h1 of the outer anti-resonator is 1.26 μm, the wall thickness h2 of the first inner anti-resonator is 1.22 μm, and the wall thickness h3 of the second inner anti-resonator is 1.18 μm.

[0045] Figure 3 The simulation results of fiber attenuation for different structures show that the minimum attenuation and low attenuation bandwidth of the fiber in Example 1 and Comparative Example 1 are almost the same, while Comparative Example 2 does not use the wall thickness optimization scheme we provided, and both the minimum attenuation and low attenuation bandwidth are degraded.

[0046] In summary, this invention combines a reasonable and feasible nested structure with an optimized wall thickness relationship between anti-resonant tubes, resulting in the following combined technical effects: significantly improved tolerance and yield of hollow-core optical fibers to manufacturing tolerances, reduced manufacturing difficulty of hollow-core optical fibers, and minimal impact on loss and bandwidth. Figure 3 As shown, the lowest loss of the LP01 mode of the present invention is 0.0137dB / km, and the bandwidth of less than 0.1dB / km is about 300nm. Compared with the ideal case with the same anti-resonant tube wall thickness, the lowest loss of the LP01 mode is 0.131dB / km, and the bandwidth of less than 0.1dB / km is about 300nm, which is not much different.

[0047] This embodiment also provides an application of low-loss hollow optical fibers with different wall thicknesses of nested anti-resonant tubes, which can be used in communication, laser, or sensing fields.

[0048] Example 2:

[0049] Second embodiment of the present invention, for example Figure 4 As shown, the difference between it and the first embodiment is that, compared with the comparative example, embodiment 1 keeps the outer diameter of the anti-resonant tube unchanged and only changes the wall thickness of the anti-resonant tube; compared with comparative example 1, embodiment 2 keeps the radial cross-sectional glass surface area unchanged, the wall thickness of the anti-resonant tube is the same as that of embodiment 1, but the outer diameter of the anti-resonant tube is different, and the other structures are the same as the first embodiment.

[0050] Specifically, the relevant parameters in this embodiment are as follows: the fiber core diameter D is 31 μm, the outer diameter d1 of the outer anti-resonator is 31.96 μm, the outer diameter d2 of the first inner anti-resonator is 23 μm, and the outer diameter d3 of the second inner anti-resonator is 7.54 μm; the inner diameter of the cladding (outer cladding cavity diameter) is 93 μm. The wall thickness h1 of the outer anti-resonator is 1.18 μm, the outer diameter h2 of the first inner anti-resonator is 1.22 μm, and the outer diameter h3 of the second inner anti-resonator is 1.26 μm. This invention combines a reasonable and feasible nested structure with optimized wall thickness relationships between anti-resonator tubes, resulting in the following technical effects: significantly improved tolerance and yield of hollow-core optical fibers to manufacturing tolerances, reduced manufacturing difficulty of hollow-core optical fibers, and minimal impact on loss and bandwidth. Figure 5 As shown, the lowest loss of the LP01 mode of the present invention is 0.0133dB / km, and the bandwidth of less than 0.1dB / km is about 300nm. Compared with the ideal case with the same anti-resonant tube wall thickness, the lowest loss of the LP01 mode is 0.131dB / km, and the bandwidth of less than 0.1dB / km is about 300nm, which is not much different.

[0051] Example 3:

[0052] A third embodiment of the present invention, for example Figure 6 As shown, its difference from the first embodiment is that the anti-resonance structure unit includes two layers of anti-resonance tubes with different radii and wall thicknesses, namely an outer anti-resonance tube and a first inner anti-resonance tube. The two glass tubes are circular, and the preferred wall thickness relationship is that the outer anti-resonance tube < the first inner anti-resonance tube.

[0053] Example 4:

[0054] A third embodiment of the present invention, for example Figure 7 As shown, its difference from the first embodiment is that the anti-resonance structure unit includes four layers of anti-resonance tubes with different radii and wall thicknesses, namely an outer anti-resonance tube, a first inner anti-resonance tube, a second inner nested tube, and a third inner anti-resonance tube. The preferred wall thickness relationship is outer anti-resonance tube < first inner anti-resonance tube < second inner anti-resonance tube < third inner anti-resonance tube.

[0055] Example 5:

[0056] Third embodiment of the present invention Figure 8 As shown, it differs from the first embodiment in that the anti-resonance structure unit includes an outer anti-resonance tube, a first inner anti-resonance tube, and a second inner anti-resonance tube. The outer anti-resonance tube is arc-shaped and intersects with the inner wall of the outer cladding. Each circular anti-resonance tube is tangent to the others, and the tangent points coincide. The preferred wall thickness relationship is outer anti-resonance tube < first inner anti-resonance tube < second inner anti-resonance tube.

[0057] The embodiments described above are some, but not all, of the embodiments of this application. The detailed description of the embodiments of this application is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

Claims

1. A low-loss hollow-core optical fiber with nested anti-resonant tubes of different wall thicknesses, comprising an outer cladding and an inner cladding, wherein the inner cladding is composed of anti-resonant structural units, the anti-resonant structural units being 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 forming the fiber core, characterized in that: The anti-resonance structure unit includes at least two layers of anti-resonance tubes with different radii and thicknesses, with the thickness of the anti-resonance tubes increasing sequentially from the outside to the inside.

2. The low-loss hollow-core optical fiber with different wall thicknesses of nested anti-resonant tubes according to claim 1, characterized in that: The line connecting the curvature centers of each nested glass tube coincides with the extension of the line connecting the outer anti-resonant tube and the geometric center of the fiber core.

3. The low-loss hollow-core optical fiber with different wall thicknesses of the cladding nested anti-resonant tube as described in claim 1 or 2, characterized in that: The anti-resonant tube includes circular anti-resonant tubes with different radii, all of which are tangent to each other, and the outer anti-resonant tube is tangent to the inner wall of the outer cladding.

4. The low-loss hollow-core optical fiber with different wall thicknesses of nested anti-resonant tubes according to claim 3, characterized in that: The tangent points overlap with each other.

5. The low-loss hollow-core optical fiber with different wall thicknesses of the cladding nested anti-resonant tubes according to claim 1 or 2, characterized in that: The anti-resonant tubes include arc-shaped anti-resonant tubes and circular anti-resonant tubes with different radii. Each arc-shaped anti-resonant tube intersects with the inner wall of the outer cladding, and each circular anti-resonant tube is tangent to each other or to the inner wall of the outer cladding.

6. The low-loss hollow-core optical fiber with different wall thicknesses of the cladding nested anti-resonant tubes according to claim 1 or 2, characterized in that: The anti-resonant tubes include arc-shaped anti-resonant tubes with different radii, and each arc-shaped anti-resonant tube intersects with the inner wall of the outer cladding.

7. The low-loss hollow-core optical fiber with different wall thicknesses of nested anti-resonant tubes according to claim 1 or 2, characterized in that: The anti-resonance structure unit includes 2-5 layers of anti-resonance tubes with different radii.

8. The low-loss hollow-core optical fiber with different wall thicknesses of the cladding nested anti-resonant tubes according to claim 1 or 2, characterized in that: The inner cladding layer includes 4 to 6 anti-resonant structural units.

9. The low-loss hollow-core optical fiber with different wall thicknesses of the cladding nested anti-resonant tubes according to claim 1 or 2, characterized in that: The anti-resonance structure unit includes three layers of anti-resonance tubes with different radii. From the outside to the inside, it includes an outer anti-resonance tube, a first inner anti-resonance tube, and a second inner anti-resonance tube. The wall thickness of the outer anti-resonance tube is 0.8 to 1.22 μm, the wall thickness of the first inner anti-resonance tube is 0.8 to 1.5 μm, and the wall thickness of the second inner anti-resonance tube is 1.22 to 1.5 μm.

10. The low-loss hollow-core optical fiber with different wall thicknesses of nested anti-resonant tubes according to claim 9, characterized in that: The ratio of the outer diameter of the external anti-resonant tube, the first internal anti-resonant tube, and the second internal anti-resonant tube is 1:0.6~0.9:0.15~0.

3.

11. The low-loss hollow-core optical fiber with different wall thicknesses of nested anti-resonant tubes according to claim 10, characterized in that: The ratio of the outer diameter of the external anti-resonant tube, the first internal anti-resonant tube, and the second internal anti-resonant tube is 1:0.7~0.8:0.18~0.

25.

12. The low-loss hollow-core optical fiber with different wall thicknesses of nested anti-resonant tubes according to claim 1 or 2, characterized in that: Both the outer cladding and the inner wall are circular.

13. The low-loss hollow-core optical fiber with different wall thicknesses of the cladding nested anti-resonant tubes according to claim 1 or 2, characterized in that: The substrate materials for both the outer cladding layer and the anti-resonance structural unit are pure quartz glass.

14. The low-loss hollow-core optical fiber with different wall thicknesses of the cladding nested anti-resonant tubes according to claim 1 or 2, characterized in that: The core region and other cavities within the outer cladding are filled with gas.

15. The low-loss hollow-core optical fiber with different wall thicknesses of the cladding nested anti-resonant tubes according to claim 14, characterized in that: The gas is argon, nitrogen, helium, air, or a mixture of multiple gases.

16. The low-loss hollow-core optical fiber with different wall thicknesses of the cladding nested anti-resonant tubes according to claim 1 or 2, characterized in that: The LP01 mode loss of the optical fiber is less than 0.1 dB / km.

17. The low-loss hollow-core optical fiber with different wall thicknesses of the cladding nested anti-resonant tubes according to claim 1 or 2, characterized in that: The optical fiber has a bandwidth of more than 200 nm and a strength of less than 0.1 dB / km.

18. An application of a low-loss hollow-core optical fiber with cladding nested anti-resonant tubes of different wall thicknesses as described in any one of claims 1 to 17, characterized in that, The low-loss hollow fiber is used in communication, laser, or sensing fields.

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