A composite structure hollow anti-resonant optical fiber

Abstract

This invention discloses a composite hollow anti-resonant optical fiber, comprising an outer cladding layer, a doped layer, and an anti-resonant layer arranged sequentially from the outside to the inside. The anti-resonant layer includes multiple glass nested tubes evenly distributed circumferentially and tangent to the doped layer, with gaps between them. These glass nested tubes surround and form an air core. Each glass nested tube includes a circular outer nested tube and an elliptical inner nested tube located within the outer nested tube. The minor axis of the inner nested tube is arranged radially along the optical fiber, and the outer circle of the inner nested tube, away from the air core, is tangent to the inner circle of the outer nested tube, also away from the air core. This invention employs a multi-layer nested structure, optimizing the anti-resonance effect through the combination of the doped layer and the specially structured anti-resonant layer.

Description

Technical Field

[0001] This invention relates to the field of optical fibers, and more particularly to a composite structure hollow anti-resonant optical fiber. Background Technology

[0002] Conventional solid-core optical fibers, such as step-index fibers, use a high-refractive-index material for the core and a low-refractive-index material for the cladding to guide light through total internal reflection. However, the inherent defects of widely used solid-core fibers, such as nonlinearity, dispersion, photodamage, and lack of light transmission in the ultraviolet and mid-infrared range, significantly limit their application in certain fields, including communication data transmission. Furthermore, traditional optical fibers have limitations in high-power transmission, high-sensitivity sensing, and broadband optics applications. Especially during high-power beam transmission, traditional fibers are prone to signal distortion due to nonlinear effects. With the increasing demand for higher bandwidth, faster transmission speeds, and longer transmission distances, existing fiber designs are insufficient to meet these requirements, necessitating a new type of optical fiber capable of overcoming these technical bottlenecks.

[0003] The Hollow-core Anti-resonant Fiber (HC-ARF) was developed to address these challenges. This technology utilizes a hollow structure design, where light transmission within the fiber core is primarily achieved through the anti-resonant effect in the cladding, significantly reducing absorption and scattering losses in the fiber material. Compared to traditional solid-core fibers, HC-ARF exhibits lower nonlinear effects, higher power capacity, and low loss across a wide spectral range. These characteristics make HC-ARF a significant advantage in applications such as high-power laser transmission, ultrafast optical pulse transmission, and optical sensing. Furthermore, the design of HC-ARF offers flexibility and adjustability; by adjusting the core structure and anti-resonant bandwidth, efficient transmission of light across different wavelength ranges can be achieved. This flexibility not only makes it highly promising in traditional optical communications but also opens new possibilities for emerging fields such as quantum communication, terahertz transmission, and nonlinear optics.

[0004] However, current hollow antiresonant fibers typically employ a single geometric structure to achieve their function, which limits the fiber's performance and results in poor adaptability and performance in a variety of applications. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by proposing a composite hollow anti-resonant optical fiber, thereby providing high bandwidth, low loss, and excellent optical performance in different application scenarios.

[0006] The technical solution to achieve the objective of this invention is:

[0007] A composite hollow anti-resonant optical fiber includes an outer cladding layer, a doped layer, and an anti-resonant layer arranged sequentially from the outside to the inside. The anti-resonant layer includes a plurality of glass nested tubes evenly distributed circumferentially and tangent to the doped layer, with gaps between them. The plurality of glass nested tubes surround and form an air core. The glass nested tubes include a circular outer nested tube and an elliptical inner nested tube disposed within the outer nested tube. The minor semi-axis of the inner nested tube is arranged radially along the optical fiber, and the outer circle of the inner nested tube away from the air core is tangent to the inner circle of the outer nested tube away from the air core.

[0008] Furthermore, a compensation tube tangentially disposed between adjacent glass nested composite tubes is provided.

[0009] Furthermore, the cross-section of the compensation tube is circular.

[0010] Furthermore, the number of the glass nested composite tubes is 4 to 8.

[0011] Furthermore, the inner diameter of the outer nested tube is 35–40 μm, the major axis of the inner nested tube is 25–30 μm, the minor axis is 15–20 μm, the inner diameter of the compensation tube is 15–20 μm, and the thickness of the outer nested tube, the inner nested tube, and the compensation tube is 0.2–1.5 μm, with consistent thickness to ensure the stability and uniformity of the entire structure.

[0012] Furthermore, the inner diameter of the outer cladding layer is 110–130 μm and the thickness is 50–60 μm, and the inner diameter of the doped layer is 100–110 μm and the thickness is 5–10 μm.

[0013] Furthermore, the inner diameter of the outer nested tube is 1.4 to 1.6 times the long axis of the inner nested tube to ensure effective light transmission and reduce reflection loss.

[0014] Furthermore, the short axis of the inner nested tube should be less than half the inner diameter of the outer nested tube to ensure sufficient space to form an effective air core.

[0015] Furthermore, the gap between the adjacent nested glass tubes and the compensation tube is 10% to 20% of the diameter of the inner nested tube, thereby optimizing the light propagation path and preventing light leakage.

[0016] Furthermore, the ratio of the inner diameter of the compensation tube to the minor axis of the inner nested tube should be 1:1.5 to 1:2, which can better achieve compensation in terms of anti-resonance effect.

[0017] Furthermore, the inner diameter of the outer cladding layer, approximately 110–130 μm, should be matched with the inner diameter of the doped layer, which is 100–110 μm. It is recommended that the ratio of the inner diameter of the outer cladding layer to the inner diameter of the doped layer be 1:1 to 1.1:1 to ensure the effective structural stability of the optical fiber.

[0018] Furthermore, the anti-resonance layer is made of glass with a refractive index of 1.46 to 1.48.

[0019] Furthermore, the doped layer is a silicon dioxide-based glass material with one or more dopants such as fluorine, germanium, phosphorus, boron, or ytterbium added, so that the refractive index of the doped layer reaches 1.42 to 1.48.

[0020] Furthermore, the outer cladding layer is made of pure silicon dioxide or germanium-doped silicon dioxide, so that the refractive index of the outer cladding layer is 1.38 to 1.42.

[0021] Furthermore, the refractive index difference between the doped layer and the cladding layer is 0.02 to 0.08.

[0022] By adopting the above technical solution, the present invention has the following beneficial effects:

[0023] (1) This invention employs a multi-layer nested structure. Through the combination of a doped layer and a specially structured anti-resonance layer, the anti-resonance effect is optimized. The glass nested tubes are uniformly arranged circumferentially, enhancing the mechanical stability of the optical fiber and improving its resistance to environmental disturbances, allowing the optical fiber to maintain good transmission performance under different environmental conditions. By tangentially embedding the elliptical inner nested tube into the circular outer nested tube, the special structure of the inner nested tube generates asymmetric photon confinement in different directions, thereby better controlling the photon propagation path and reducing optical loss. Furthermore, the tangent point between the inner and outer nested tubes is close to the doped layer, causing the light to be mainly confined to the air core region. In addition, it innovatively... The short semi-axis of the nested tube is aligned radially with the optical fiber. Firstly, this arrangement reduces optical loss. By adjusting the anti-resonance conditions at the inner and outer interfaces of the nested tube, radial reflection loss is minimized, improving fiber transmission efficiency. This is particularly beneficial in anti-resonant fibers, effectively reducing optical signal leakage. Furthermore, hollow anti-resonant fibers are typically sensitive to bending, while the nested tube's flattened elliptical structure, with its short semi-axis aligned radially, effectively suppresses mode mismatch and leakage caused by bending, reducing bending loss and making it suitable for applications requiring high bending performance. Simultaneously, the flattened elliptical shape provides a directional distribution, allowing the short semi-axis to better withstand external mechanical stress in the radial direction. This configuration enhances the fiber's stability under external forces and strengthens its stress resistance, making it particularly suitable for applications requiring high mechanical stability. Secondly, it optimizes the mode field distribution. This geometry helps control the mode field distribution within the fiber. Because the short semi-axis is aligned radially, the light field can be guided more effectively to the core region of the hollow anti-resonant fiber, thereby improving mode field confinement and enhancing optical transmission quality. This multi-layer structure can more effectively suppress light leakage from the fiber core, improve the transmission efficiency of optical fiber over a wide wavelength range, and thus provide high bandwidth, low loss and excellent optical performance in different application scenarios.

[0024] (2) By adding a compensation tube and cooperating with the glass nested combined tube, the present invention can form effective anti-resonance conditions in multiple wavelength ranges. In particular, the specific analysis of realizing multi-wavelength anti-resonance conditions is as follows:

[0025] Optimize refractive index distribution:

[0026] Compensating tubes can achieve anti-resonance effects by adjusting their material and thickness to create a specific refractive index distribution. When used in conjunction with nested glass tubes, they can effectively control the propagation path and mode of light.

[0027] Enhance light transmission efficiency:

[0028] Compensating tubes can reduce light scattering and reflection in optical fibers, optimize light propagation characteristics, and improve transmission efficiency. Especially in multi-wavelength signal transmission, they can more effectively maintain signal quality.

[0029] Reduce modal interference:

[0030] The design of the compensating tube helps reduce intermodal interference, especially in multimode fiber. Through effective structural design, better mode selectivity can be achieved, improving signal clarity.

[0031] Provide structural support:

[0032] The compensation tube provides structural support for the nested composite tube, ensuring the mechanical strength and stability of the optical fiber in various environments and avoiding performance degradation due to external pressure or bending.

[0033] (3) The cross-section of the compensation tube of the present invention is circular, which has the following advantages:

[0034] Uniform optical properties:

[0035] The circular cross-section is symmetrical in all directions, which allows light to propagate in a uniform manner when passing through the compensating tube, reducing light distortion and scattering.

[0036] Simplify manufacturing process:

[0037] The circular cross-section design is easier to implement in the production process, especially in mass production, reducing production costs and complexity.

[0038] Strengthening structural strength:

[0039] The circular structure performs better under internal and external pressure, effectively resisting bending and compressive forces, thereby improving the durability and stability of optical fibers.

[0040] (4) The doped layer of this invention can be doped with different materials to adjust the refractive index of each layer, which can precisely control the width of the photonic bandgap, enabling the optical fiber to adapt to a wider wavelength range, thereby further optimizing the anti-resonance effect. By doping with different elements such as fluorine, germanium, and phosphorus, the optical properties of the optical fiber can be adjusted, giving it better transmission performance at specific wavelengths. At the same time, doping can reduce the loss of the optical fiber and improve the signal transmission efficiency, which is especially important in high-power laser applications. The doping elements can also improve the heat resistance of the optical fiber, enhance its stability in high-temperature environments, and extend the service life of the optical fiber. By doping, the nonlinear optical properties of the optical fiber can be controlled, thereby optimizing the laser amplification and optical transmission characteristics and improving the overall performance of the system. In summary, the optical fiber with the doped layer can maintain a stable photonic bandgap width under different experimental conditions (such as temperature changes and light intensity changes), improving the adaptability and multi-wavelength transmission capability of the optical fiber.

[0041] (5) This invention ensures effective reflection and transmission of optical signals by controlling the refractive index difference between the doped layer and the outer cladding layer, thereby achieving effective coupling. Attached Figure Description

[0042] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein:

[0043] Figure 1 This is a schematic diagram of the structure of Example 1;

[0044] Figure 2 The effective refractive index curve of the composite hollow anti-resonant optical fiber of Example 1 as a function of wavelength;

[0045] Figure 3 The confinement loss curve of the composite hollow antiresonant fiber in Example 1 as a function of wavelength;

[0046] Figure 4 The bending loss curve of the composite hollow anti-resonant optical fiber in Example 1 varies with the bending radius;

[0047] Figure 5 The curve of the higher-order mode ratio of the hollow anti-resonant fiber in Example 1 as a function of wavelength is shown.

[0048] The labels in the attached diagram are:

[0049] Outer cladding layer 1, doped layer 2, glass nested composite tube 3, outer nested tube 3-1, inner nested tube 3-2, air fiber core 4, compensation tube 5. Detailed Implementation

[0050] To better understand the above technical solutions, the following will provide a detailed explanation of the technical solutions in conjunction with the accompanying drawings and specific implementation methods.

[0051] (Example 1)

[0052] like Figure 1The composite hollow anti-resonant optical fiber shown includes an outer cladding layer 1, a doped layer 2, and an anti-resonant layer arranged sequentially from the outside to the inside. The anti-resonant layer includes multiple glass nested tubes 3 evenly distributed circumferentially and tangent to the doped layer 2, with gaps between them. These multiple glass nested tubes 3 surround and form an air core 4. The positional distribution of the glass nested tubes 3 not only enhances the mechanical stability of the optical fiber but also improves its resistance to environmental disturbances, enabling the optical fiber to maintain good transmission performance under different environmental conditions. The glass nested tubes 3 include a circular outer nested tube 3-1 and an elliptical inner nested tube 3-2 disposed within the outer nested tube 3-1. The minor axis of the inner nested tube 3-2 is arranged radially along the optical fiber, and the outer circle of the inner nested tube 3-2 away from the air core 4 is tangent to the inner circle of the outer nested tube 3-1 away from the air core 4. By embedding an elliptical inner nested tube 3-2 tangentially within a circular outer nested tube 3-1, the unique structure of the inner nested tube generates asymmetric photon confinement in different directions, thereby better controlling the photon propagation path and reducing optical loss. Furthermore, the tangent point between the inner nested tube 3-2 and the outer nested tube 3-1 is close to the doped layer 2, optimizing the reflection path and confining light primarily to the air core region. In addition, the short semi-axis of the inner nested tube is innovatively positioned radially along the fiber. This multilayer structure more effectively suppresses light leakage from the fiber core, improving the fiber's transmission efficiency over a wide wavelength range, thus providing high bandwidth, low loss, and excellent optical performance in various application scenarios.

[0053] Specifically, the number of glass nested composite tubes should be 4 to 8. If the number of glass nested composite tubes is less than 4, the anti-resonance effect is insufficient. A smaller number of composite tubes cannot effectively achieve the anti-resonance effect, leading to reduced fiber transmission efficiency, performance below expectations, and increased loss. Light is more prone to reflection and scattering during propagation, further increasing loss. Furthermore, flexibility is insufficient; too few composite tubes limit the flexibility of fiber design, making it unable to adapt to different application requirements and environments. If the number of glass nested composite tubes exceeds 8, manufacturing complexity increases, production difficulty rises, and higher precision requirements are needed in the manufacturing process, leading to increased costs. Space utilization efficiency is also low; too many tubes occupy too much space, resulting in a less compact overall fiber structure, affecting its applicability, and increasing loss. Too many composite tubes increase scattering within the fiber, thus increasing optical signal loss and affecting transmission performance.

[0054] This embodiment features five nested glass tubes 3. A compensation tube 5, tangentially positioned to the doped layer 2, is positioned between adjacent nested glass tubes 3. Working in conjunction with the nested glass tubes 3, it forms effective anti-resonance conditions across multiple wavelength ranges. The compensation tube has a circular cross-section. To ensure excellent anti-resonance performance, the inner diameter of the outer nested tube 3-1 is 35–40 μm, the major axis of the inner nested tube 3-2 is 25–30 μm, the minor axis is 15–20 μm, and the inner diameter of the compensation tube 5 is 15–20 μm. Furthermore, the thicknesses of the outer nested tube, inner nested tube, and compensation tube are all 0.2–1.5 μm. In this embodiment, the inner diameter of the outer nested tube 3-1 is 40 μm, the major axis of the inner nested tube 3-2 is 30 μm, the minor axis is 15 μm, the inner diameter of the compensation tube is 15 μm, and the thicknesses of the outer nested tube 3-1, inner nested tube 3-2, and compensation tube 5 are all 1 μm. All are made of glass with a refractive index of 1.47.

[0055] The outer cladding layer 1 is made of pure silicon dioxide or germanium-doped silicon dioxide to achieve a refractive index of 1.38–1.42. In this embodiment, the refractive index of the outer cladding layer is 1.4. The doping layer 2 is doped with one or more of fluorine, germanium, phosphorus, boron, or ytterbium to achieve a refractive index of 1.42–1.48. By adjusting the refractive index of each layer through doping with different materials, the width of the photonic bandgap can be precisely controlled, enabling the optical fiber to adapt to a wider wavelength range, thereby further optimizing the anti-resonance effect. In this embodiment, the refractive index of the doped layer 2 is 1.45, and the refractive index difference between the doped layer 2 and the outer cladding layer 1 is 0.05. The inner diameter of the outer cladding layer 1 is 110–130 μm, and the thickness is 50–60 μm. The inner diameter of the doped layer 2 is 100–110 μm, and the thickness is 5–10 μm. In this embodiment, the inner diameter of the outer cladding layer is 120 μm and the thickness is 60 μm, and the inner diameter of the doped layer 2 is 110 μm and the thickness is 10 μm.

[0056] In the design of this composite hollow anti-resonant fiber, the refractive index of the anti-resonant layer plays a crucial role in the overall performance, while also having a synergistic effect with the refractive indices of the cladding and doping layers. The main function of the anti-resonant layer is to limit the propagation path of photons in the fiber core through reflection, achieving an anti-resonance effect and thus reducing light loss and scattering. The closer the refractive index of the anti-resonant layer is to that of the fiber cladding, the lower the transmission loss can be maintained over a wider wavelength range. In this embodiment, the refractive index of the anti-resonant layer is 1.47, which is lower than that of the doping and cladding layers. This makes it easier for light to be reflected back into the hollow fiber core from the doping layer, achieving effective light confinement and reducing loss. The refractive index of the doping layer is 1.45, similar to that of the anti-resonant layer, which increases light reflection in the doping layer and effectively reduces light leakage in the anti-resonant layer. The doping layer acts like a tuning layer for anti-resonance, improving photon reflection through fine-tuning of its refractive index. The outer cladding has a relatively low refractive index of 1.42, which creates a refractive index difference with the doped layer, making the light reflection more concentrated and thus further enhancing the confinement and propagation of light within the fiber core.

[0057] By precisely configuring the refractive index distribution, optical fibers can achieve excellent anti-resonance performance across different wavelength ranges. This synergistic effect of refractive indices is a fundamental condition for low-loss multi-wavelength transmission. Furthermore, the refractive index difference between the doped layer and the cladding layer ensures stability and low nonlinear loss under high-power conditions.

[0058] Using a wavelength of 1550nm as the operating wavelength, the structure of this embodiment was simulated using the finite element method. The outer diameter of the outer cladding layer 1 is 230μm, the inner diameter is 120μm, and the outer cladding layer thickness is 55μm; the outer diameter of the doped layer 2 is 120μm, the inner diameter is 100μm, and the thickness is 10μm. The inner diameter of the circular outer nested tube is 36μm; the major axis of the elliptical inner nested tube is 28μm, the minor axis is 16μm, and the inner diameter of the circular compensation tube is 16μm.

[0059] See Figure 2 The hollow-core antiresonant optical fiber provided by this invention has an effective refractive index close to 1, meaning that transmission within the hollow core has a transmission refractive index close to 1. See also... Figure 3 At 1550 nm, the confinement loss of the fundamental mode in hollow antiresonant fiber is less than 0.005 dB / km. See also Figure 4 The bending loss measured by the bending test with a bending radius of 20cm is less than 0.06dB / km, which means that the present invention has low fundamental mode loss and low bending loss at the working wavelength.

[0060] In addition, see Figure 3The limiting loss corresponding to the transmission wavelength of 1300-1700nm is less than 0.011dB / km, and the transmission wavelength with a limiting loss of less than 0.01dB / km (the part <1300nm) actually has broadband low-loss transmission characteristics in the range of 1300-1700nm.

[0061] See Figure 5 Hollow-core antiresonant fiber has a higher-order mode ratio (the ratio of fundamental mode loss to the lowest loss of higher-order modes) than 100, exhibiting good single-mode characteristics.

[0062] (Comparative Example 1)

[0063] The structure of this embodiment is the same as that of embodiment 1, except that the refractive index of the anti-resonant layer is 1.47, the refractive index of the outer cladding layer 1 is 1.35, the refractive index of the doped layer 2 is 1.4, and the difference in refractive index between the outer cladding layer 1 and the doped layer 2 is 0.05.

[0064] (Comparative Example 2)

[0065] The structure of this embodiment is the same as that of embodiment 1, except that the refractive index of the anti-resonant layer is 1.47, the refractive index of the outer cladding layer 1 is 1.35, the refractive index of the doped layer 2 is 1.5, and the difference in refractive index between the outer cladding layer 1 and the doped layer 2 is 0.15.

[0066] (Comparative Example 3)

[0067] The structure of this embodiment is the same as that of embodiment 1, except that the refractive index of the anti-resonant layer is 1.47, the refractive index of the outer cladding layer 1 is 1.35, the refractive index of the doped layer 2 is 1.42, and the difference in refractive index between the outer cladding layer 1 and the doped layer 2 is 0.07.

[0068] (Comparative Example 4)

[0069] The structure of this embodiment is the same as that of embodiment 1, except that the refractive index of the anti-resonant layer is 1.47, the refractive index of the outer cladding layer 1 is 1.45, the refractive index of the doped layer 2 is 1.5, and the difference in refractive index between the outer cladding layer 1 and the doped layer 2 is 0.05.

[0070] (Comparative Example 5)

[0071] The structure of this embodiment is the same as that of embodiment 1, except that the refractive index of the anti-resonant layer is 1.47, the refractive index of the outer cladding layer 1 is 1.45, the refractive index of the doped layer 2 is 1.47, and the difference in refractive index between the outer cladding layer 1 and the doped layer 2 is 0.02.

[0072] (Comparative Example 6)

[0073] The structure of this embodiment is the same as that of embodiment 1, except that the refractive index of the anti-resonant layer is 1.47, the refractive index of the outer cladding layer 1 is 1.45, the refractive index of the doped layer 2 is 1.4, and the refractive index difference between the outer cladding layer 1 and the doped layer 2 is -0.05.

[0074] Using a wavelength of 1550nm as the working wavelength, finite element simulations were performed on the structures of Comparative Examples 1 to 6. The results are shown in the table below, where the bending loss performance is the result under a bending radius of 20cm:

[0075] Effective refractive index Limiting loss dB / km Bending loss dB / km Comparative Example 1 0.99952 0.0049 0.46 Comparative Example 2 1.02952 0.0229 0.68 Comparative Example 3 1.00952 0.0085 0.52 Comparative Example 4 1.01952 0.0178 0.74 Comparative Example 5 0.99952 0.0121 0.58 Comparative Example 6 1.03952 0.0532 0.92

[0076] This invention employs a multi-layer nested structure, optimizing the anti-resonance effect through the combination of doped layers and specially structured anti-resonance layers, thereby enhancing the mechanical stability of the optical fiber. This allows the optical fiber to maintain good transmission performance under different environmental conditions, reducing optical loss, improving transmission efficiency, and lowering bending loss. By precisely setting the refractive index distribution, the optical fiber can achieve excellent anti-resonance effects in different wavelength ranges. This synergistic effect of refractive index is a fundamental condition for multi-wavelength low-loss transmission. Furthermore, the refractive index difference between the doped layer and the cladding layer can ensure stability and low nonlinear loss under high power conditions.

[0077] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A composite hollow anti-resonant optical fiber, characterized in that: The fiber comprises an outer cladding layer, a doped layer, and an anti-resonance layer arranged sequentially from the outside to the inside. The anti-resonance layer includes multiple glass nested tubes evenly distributed circumferentially and tangent to the doped layer. The multiple glass nested tubes surround and form an air core. The glass nested tubes include a circular outer nested tube and an elliptical inner nested tube disposed within the outer nested tube. The minor semi-axis of the inner nested tube is arranged radially along the fiber, and the outer circle of the inner nested tube away from the air core is tangent to the inner circle of the outer nested tube away from the air core.

2. The composite hollow anti-resonant optical fiber according to claim 1, characterized in that: A compensation tube, which is tangential to the doped layer, is provided between adjacent glass nested tubes.

3. The composite hollow anti-resonant optical fiber according to claim 2, characterized in that: The cross-section of the compensation tube is circular.

4. The composite hollow anti-resonant optical fiber according to claim 3, characterized in that: The number of the glass nested composite tubes is 4 to 8.

5. The composite hollow anti-resonant optical fiber according to claim 3, characterized in that: The outer nested tube has an inner diameter of 35–40 μm, the inner nested tube has a major axis of 25–30 μm and a minor axis of 15–20 μm, the compensation tube has an inner diameter of 15–20 μm, and the outer nested tube, inner nested tube, and compensation tube all have a thickness of 0.2–1.5 μm.

6. The composite hollow anti-resonant optical fiber according to claim 3, characterized in that: The outer cladding layer has an inner diameter of 110–130 μm and a thickness of 50–60 μm, and the doped layer has an inner diameter of 100–110 μm and a thickness of 5–10 μm.

7. The composite hollow anti-resonant optical fiber according to claim 1, characterized in that: The anti-resonance layer is made of glass with a refractive index of 1.46 to 1.

48.

8. The composite hollow anti-resonant optical fiber according to claim 1, characterized in that: The doped layer is a silicon dioxide-based glass material with one or more of fluorine, germanium, phosphorus, boron, or ytterbium added to achieve a refractive index of 1.42 to 1.

48.

9. The composite hollow anti-resonant optical fiber according to claim 1, characterized in that: The outer cladding layer is made of pure silicon dioxide or germanium-doped silicon dioxide, so that the refractive index of the outer cladding layer is 1.38 to 1.

42.

10. A composite hollow anti-resonant optical fiber according to claim 1, characterized in that: The refractive index difference between the doped layer and the outer cladding layer is 0.02 to 0.08.

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