Polarization-maintaining hollow-core anti-resonance optical fiber suitable for laser transmission and broadband communication

Abstract

The invention relates to a polarization-maintaining hollow-core anti-resonance optical fiber suitable for laser transmission and broadband communication, which comprises an elliptical fiber core (1), an outermost sleeve (7) and a cladding area, and is characterized in that the elliptical fiber core (1) is filled with air; the cladding region comprises an x-direction structure and a y-direction structure, the x-direction structure comprises at least one first cladding, the y-direction structure is vertically symmetrical relative to the central axis of the x-direction structure and is divided into an upper half part and a lower half part, and each of the upper half part and the lower half part comprises at least one second cladding; the first cladding comprises a first cladding tube (2), a second nested cladding tube (3) and a third nested cladding tube (4); and the second cladding comprises an internally nested cladding tube (5) and an externally nested cladding tube (6). According to the invention, polarization and low-loss energy transmission can be realized in a 1080nm high-energy transmission wave band, and wide application prospects are realized in the aspects of communication, sensing, high-energy polarization laser transmission and the like.

Description

Technical Field

[0001] This invention relates to the field of optical fiber technology, and in particular to a polarization-maintaining hollow-core anti-resonant optical fiber suitable for laser transmission and broadband communication. Background Technology

[0002] Hollow-core fiber (HCF) represents an innovative approach to fiber optic technology, aiming to improve the information transmission efficiency of fiber optic communication and overcome the performance limitations of traditional fibers. This type of fiber mainly includes Bragg fiber, Kagome fiber, hollow-core photonic bandgap fiber, and hollow-core antiresonant fiber. They share the characteristic that the core is primarily filled with a low-refractive-index material, such as air, while the cladding employs a periodic or antiresonant structure and contains some air. These structures confine light propagation within the fiber core through photonic bandgap or antiresonant effects, thereby achieving excellent loss and dispersion characteristics.

[0003] Hollow-core antiresonant fiber is widely used in signal transmission, precision sensing, and fiber optic gyroscopes due to its advantages such as low loss, low delay, and low nonlinearity. Polarization-maintaining performance is a crucial characteristic of hollow-core antiresonant fiber, typically measured by phase birefringence, defined as the difference in effective refractive index between the two fundamental modes of polarization. The light-guiding band of an antiresonant fiber is generally affected by the cladding thickness; different cladding thicknesses will cause changes in the antiresonant reflection order, resulting in overlap of the antiresonant bands. Appropriately adjusting the cladding thickness in mutually perpendicular directions can alter the polarization modes in orthogonal directions, leading to mode field differences and thus high birefringence.

[0004] With the rapid development of fiber optic technology, the requirements for fiber performance are increasing. In industrial processing and medical aesthetics, fibers are needed to stably transmit high-power lasers (such as Yb lasers in the 1080 nm band). Simultaneously, in fiber optic communication (such as S, C, L, and U bands), as well as fiber optic sensing and quantum communication, not only are low-loss and wide-bandwidth characteristics required, but excellent polarization-maintaining capabilities are also often demanded to stabilize the polarization state of transmitted signals. Currently, the mainstream technology for achieving polarization maintenance in fibers is solid-core polarization-maintaining fiber, such as panda or bowtie fiber. However, its solid core structure has inherent technical bottlenecks. First, its material exhibits strong nonlinear effects, which can easily lead to nonlinear effects and even damage at high power, limiting power transmission capabilities. Second, its transmission loss is already close to the theoretical limit of the material, making further reduction extremely difficult. Furthermore, its bandwidth is usually limited, making it difficult to simultaneously cover the near-infrared high-power band and the communication band. Hollow-core antiresonant fiber (HC-ARF) overcomes the material limitations of traditional solid-core fiber because its optical field is primarily propagated in air. It exhibits extremely low nonlinear effects, a high damage threshold, and potentially ultra-low loss, making it an ideal solution for the aforementioned applications. Although research on polarization-maintaining hollow-core antiresonant fiber has made progress, existing designs are mostly limited to communication bands, resulting in limited functionality. Facing the application demands of high-power laser transmission and broadband communication integration, there is an urgent need for a fiber design scheme that can cover high-power bands such as 1080nm and S+C+L+U communication bands, while also considering low loss and high polarization-maintaining characteristics.

[0005] To address the aforementioned technical bottlenecks, this invention aims to provide a polarization-maintaining hollow-core antiresonant optical fiber. This fiber, through a synergistic scheme combining differentiated wall thickness design with a special cladding matrix arrangement, successfully achieves high polarization-maintaining characteristics, low transmission loss, and wide operating bandwidth in the 1080nm high-energy transmission band and the S, C, L, and U communication bands. Summary of the Invention

[0006] To overcome the aforementioned problems in the existing technology, this invention provides a polarization-maintaining hollow-core anti-resonant optical fiber suitable for laser transmission and broadband communication, comprising an elliptical core, a cladding region, and an outermost sheath. The elliptical core (1) is filled with air. The cladding region includes an x-direction structure and a y-direction structure. The x-direction structure is symmetrical with respect to the central axis of the y-direction structure. The x-direction structure includes a left half and a right half. The right half has the same structure as the left half and includes at least one first cladding. The y-direction structure is vertically symmetrical with respect to the central axis of the x-direction structure and is divided into an upper half and a lower half. The upper half and the lower half... The lower half of each part includes at least one second cladding layer; the first cladding layer includes three nested circular structures, each consisting of a first cladding tube, a second nested cladding tube, and a third nested cladding tube, arranged in a triangular symmetrical pattern to form three support points; the second cladding layer includes two nested circular structures, each consisting of an inner nested cladding tube and an outer nested cladding tube, the two nested circular structures being tangent to a point on the outermost sleeve; the wall thickness of any circular structure in the first and second cladding layers is the same; the cladding layers do not contact each other.

[0007] Preferably, the materials of the first cladding layer, the second cladding layer, and the outer cladding layer are quartz glass, fluoride glass, sulfide glass, or silicate glass.

[0008] Preferably, the thickness of the first cladding tube is 0.6-0.9µm; the thickness of the second and third nested cladding tubes is 0.3-0.5µm; and the thickness of the inner and outer nested cladding tubes is 0.3-0.55µm.

[0009] Preferably, the number of outermost sleeves is 2-3 layers.

[0010] Preferably, the diameter of the first cladding tube is larger than the diameter of the inner nested cladding tube.

[0011] Preferably, the refractive indices of the first cladding tube, the second nested cladding tube, and the third nested cladding tube are all equal.

[0012] Preferably, the first cladding tube and the inner nested cladding tube have a wall thickness difference, thereby introducing high birefringence.

[0013] Preferably, the major axis of the elliptical fiber core is Da, the minor axis is Db, and the ellipticity of the elliptical fiber core is η, where η = Db / Da and η is 0.3-0.9.

[0014] Preferably, the hollow anti-resonant optical fiber has a diameter of 90-120 µm and an outer cladding thickness of 12-18 µm.

[0015] This invention provides a polarization-maintaining hollow-core antiresonant fiber suitable for laser transmission and broadband communication. This hollow-core antiresonant fiber features low delay, low dispersion, and low nonlinearity, effectively confining optical signals within the fiber core for transmission. The three adjacent nested tube structures in the vertical direction effectively limit leakage light in the y-direction, enabling low-loss, polarization-maintaining transmission in both guidebands. The loss is as low as 2.3 × 10⁻³ dB / m at 1080 nm (1020-1250 nm, bandwidth 220 nm); and as low as 2.6 × 10⁻⁴ dB / m at 1420-1700 nm (bandwidth 280 nm). It exhibits excellent polarization-maintaining performance in the C and L bands, with both y-pol values ​​below 10⁻³ dB / m and birefringence exceeding 10⁻⁴. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0017] Figure 1 This invention provides a polarization-maintaining hollow-core anti-resonant optical fiber suitable for laser transmission and broadband communication.

[0018] Figure 2 This is a graph showing the loss and birefringence of the hollow anti-resonant optical fiber provided in the embodiment of the present invention as a function of wavelength in the range of 1020-1280nm;

[0019] Figure 3 This is a graph showing the effective refractive index of the hollow anti-resonant optical fiber provided in the embodiment of the present invention as a function of wavelength in the range of 1020-1280nm;

[0020] Figure 4 This is a graph showing the loss and birefringence of the hollow anti-resonant optical fiber provided in the embodiment of the present invention as a function of wavelength in the range of 1420-1700nm;

[0021] Figure 5 This is a graph showing the effective refractive index of the hollow anti-resonant optical fiber provided in the embodiment of the present invention as a function of wavelength in the range of 1420-1700nm;

[0022] Figure 6 This is a diagram of the X-polarization and Y-polarization modes at 1080nm in a hollow anti-resonant optical fiber provided in an embodiment of the present invention;

[0023] Figure 7 This is a diagram of the X-polarization and Y-polarization modes at 1550nm in a hollow anti-resonant optical fiber provided in an embodiment of the present invention. Detailed Implementation

[0024] To better understand the technical solution of the present invention, the following will provide a detailed and clear explanation of the technical solution with reference to the accompanying drawings. It should be noted that the described examples represent only some, not all, embodiments of the present invention. All other embodiments that can be derived by those skilled in the art based on these embodiments of the present invention without creative work are within the scope of protection of the present invention. Next, the present invention will be described in more detail with reference to the accompanying drawings.

[0025] like Figure 1 As shown, a hollow anti-resonant optical fiber has a structure including an elliptical core, an outermost sheath, and a cladding region. The core is filled with air, and the outermost cladding region has a relatively thick first cladding layer that extends vertically upwards and downwards in the y-direction, forming an elliptical core that introduces high birefringence. Three adjacent nested tubes inside effectively confine leaked light. The elliptical core contains air, and the hollow anti-resonant optical fiber exhibits a left-right symmetrical relationship with respect to the central axis from top to bottom.

[0026] The elliptical fiber core structure also has a structure that can effectively amplify the birefringence effect, which includes: four horizontal cladding tubes with quasi-fourfold symmetry, combined with two large tubes in the vertical direction to construct a quasi-fourfold symmetry structure. The quasi-fourfold symmetry means that it is based on complete fourfold symmetry.

[0027] The core strategy of this embodiment includes two main steps: First, an elliptical fiber core is constructed, causing differences in the coupling characteristics of the fundamental mode in the two orthogonal directions. Second, the wall thickness in these two directions is adjusted to break the degeneracy of the walls in the internal structure of the fiber, resulting in different intensities and wavelength positions of their anti-cross coupling with the core mode. This introduces a polarization-related effective refractive index change, thereby generating a birefringence effect. Finally, the special arrangement of the nested cladding and the difference in nested wall thickness are used to effectively constrain the leakage of signal and energy light. It can be understood that, within this design framework, by rationally selecting the core size, a hollow-core antiresonant fiber with high birefringence characteristics can be developed.

[0028] Specifically, previous studies have consistently held that only quasi-quadruple symmetry structures can introduce high birefringence. While other symmetry structures can produce birefringence, their birefringence is lower than that of quasi-quadruple symmetry structures under the same core size and wall thickness ratio. However, we have found that by increasing the diameter of the cladding tube in the y-direction, a quasi-quadruple symmetry similar to an elliptical core can be constructed, thereby introducing high birefringence. Therefore, this disclosure adopts our quasi-quadruple symmetry-like structure.

[0029] Specifically, the cladding region includes two nested cladding layers and an air layer, but is not limited to two layers; it can also have three layers, etc. Taking three layers as an example, the nested structure of the cladding region, in order from the inside out, includes a first cladding tube, a second nested cladding tube, and a third nested cladding tube. The two outermost cladding tubes are nested at a point to form a support point; the inner nested cladding tube and the outer nested cladding tube, wherein the left and right cladding tubes are nested together and tangent to the outermost sleeve at a point.

[0030] Specifically, the materials of the multi-layer nested cladding tube and the outermost sleeve are quartz materials, and alternatively, they can also be fluoride glass, sulfide glass or silicate glass, etc.

[0031] The diameter of the first cladding tube in the vertical direction is 29.9 μm, the diameter of the second nested cladding tube is 11.65 μm, and the diameter of the third nested cladding tube is 10.35 μm; in the horizontal direction: the diameter of the first cladding tube in the horizontal direction is 19.5 μm, the diameter of the outer nested cladding tube in the horizontal direction is 12.3 μm, and the diameter of the outermost sleeve is 105.3 μm.

[0032] Specifically, based on the optimal structural parameters, the entire wall thickness was changed to t=t1. Wavelength analysis revealed lower loss and higher birefringence in the 0.5-0.65μm and 1.35-1.45μm regions. Therefore, considering t=0.67μm as the scanning wavelength, with other parameters unchanged, the diameter of the large cladding tube was changed. As the diameter increased, the birefringence showed an increasing trend. This is because the y-direction continuously squeezes the fiber core fundamental mode, causing the birefringence in both directions to increase. eff As the difference increases, birefringence rises. Because the elliptical fiber core is compressed in the y-direction, leakage increases, leading to an upward trend in both x-pol and y-pol losses. This indicates that compressing the fiber core in a certain direction can introduce high birefringence, but it also increases loss in that direction. Therefore, a balance must be struck between loss and birefringence when determining the appropriate wall thickness and cladding tube diameter.

[0033] Specifically, when t1 = 0.67 μm, it means that a tube wall of this thickness will experience first-order resonance around 1390 nm, leading to losses. Its low-loss conduction band will then lie between the resonant wavelengths, resulting in lower losses in the 1000-1280 nm and greater than 1500 nm regions. The first-order resonance of a wall thickness of t2 = 0.34 μm occurs around 710 nm (visible light band), so for the infrared band, it mainly serves to broaden the bandwidth, suppress higher-order modes, and further confine the optical field. The first-order resonance of a horizontal cladding wall thickness of t4 / t5 = 0.45 μm occurs around 940 nm. Therefore, its low-loss conduction band will lie between the resonant wavelengths, for example, in a region above approximately 1100 nm. It is understandable that, due to the requirements of anti-resonance, parameters such as the diameter of the cladding tube, the diameter of the thin-walled nested tube, various wall thicknesses, and the core diameter can be adjusted according to the needs of anti-resonance. In addition, other parameters can be further adjusted to achieve different polarization-maintaining performance.

[0034] Specifically, an elliptical core structure and differentiated wall thickness are used in the design of hollow anti-resonant fiber. The fundamental mode in the x-direction is confined by four horizontal cladding tubes, reducing light loss by two orders of magnitude. In the y-direction, adding only one nesting layer leads to increased light leakage due to greater coupling. Therefore, two or three nesting layers are used to minimize loss. However, the ratio of the diameter of the inner nesting circle to the diameter of the large cladding in the y-direction cannot be too large; otherwise, the coupling of the fundamental mode to the air cladding in the y-direction will weaken, resulting in increased light loss. eff The difference between the two directions becomes smaller, which in turn reduces the value of birefringence. Furthermore, the coupling between the fundamental mode and the mode in the cladding is smaller in the x-direction, which further reduces the loss of the fundamental mode in the x and y polarization states.

[0035] Specifically, the losses of the x-polarized fundamental mode in the horizontal direction and the y-polarized fundamental mode in the vertical direction of the fiber core differ. This is due to the different mode coupling degrees caused by the introduction of the elliptical fiber core and the differential wall thickness. Our designed structure introduces an elliptical fiber core, but due to the constraint of three adjacent nested cladding layers, a multi-layer nested anti-resonance effect is introduced, reducing the loss of the two polarization states. The difference in vibration direction between the two polarization states leads to n... effThe difference lies in the fact that the y-polarized fundamental mode, due to the introduction of three adjacent nested cladding layers, restricts the light leakage from the first layer. Although the first layer leaks more light, this is to introduce greater birefringence. Combined with the multi-resonance effect of the inner two layers and the fact that this band belongs to the anti-resonance layer, the loss is further reduced. As the diameter of the large cladding tube in the y-direction increases, the birefringence of this structure shows a trend of first decreasing and then increasing. The smaller the core aspect ratio, the more drastic the change. The extreme value of birefringence of this structure also increases as the core elliptic aspect ratio decreases. When the core aspect ratio is less than η=0.4, on the one hand, the core symmetry changes, from the original C6v structure to a C2v structure, affecting the propagation constants of the two polarization directions, causing a change in the effective refractive index, thus introducing birefringence. On the other hand, the decrease in the core aspect ratio η (increased cladding tube diameter) weakens the suppression coupling between the core mode and the cladding mode, causing mode coupling between the core mode and the cladding mode, resulting in energy exchange, thus leading to an increase in birefringence.

[0036] In an optional embodiment of the present invention, when the longitudinal radius of the elliptical core is small, the core fundamental mode will couple significantly with the mode of the adjacent first air layer, resulting in high loss of the core fundamental mode. As the longitudinal radius of the core increases, the coupling between the x-polarized and y-polarized fundamental modes and the modes of the upper and lower first air layers weakens significantly, the loss decreases significantly, and the effective refractive index also decreases accordingly. This is because the ellipticity of the core decreases, and the phase birefringence begins to gradually decrease. When Db / Da > 0.3, the loss of both polarization states decreases. This is because the radius of the inner region of the outermost sleeve is fixed, which means that as the core becomes larger, the air layer becomes thinner, reducing the compression on the fundamental mode in the y-direction, thus affecting the difference in birefringence between the two directions, reducing loss, and decreasing birefringence.

[0037] Specifically, in the first low-loss conduction band (1000-1280nm), the 0.67μm thick wall in the vertical direction is located within its first low-loss window (far from its first-order resonant point of 1390nm). The 0.45μm thin wall in the horizontal direction is also located at the beginning of its first low-loss window (far from its first-order resonant point of 940nm). Therefore, in this band, the wall thicknesses in both vertical directions are in an anti-resonant state, effectively confining the light within the fiber core, thus forming a broad low-loss conduction band. This conduction band is particularly suitable for high-power laser transmission at 1080nm. In the second low-loss conduction band (1420-1710nm), as the wavelength increases above 1420nm, the 0.67μm thick wall in the vertical direction is approaching its first-order resonant point of 1390nm. Generally, the closer to the resonant point, the higher the loss begins to increase. Meanwhile, the 0.45 μm thin wall in the horizontal direction is in the optimal position of its low-loss window (far from its 940 nm resonant point and not yet reaching the second-order resonance).

[0038] In an optional embodiment of the invention, by adjusting the diameter ratio of the three nested tubes in the y-direction, a higher birefringence and a lower loss are introduced. When the size of the innermost cladding tube remains constant, a good anti-resonance effect on the fundamental mode is achieved when the diameter ratio of the nested layers to the innermost layer is 0.45 and 0.4, respectively. As the diameter of the nested cladding tube increases or decreases, the bright spot on the fiber core fundamental mode coupling either becomes more prominent or the light confinement is insufficient. Increasing the size of the second nested layer does not significantly change the birefringence, but it does have a certain impact on the loss; its diameter cannot be too small, otherwise the loss will decrease. The birefringence is significantly affected by the compression in the y-direction and shows a positive correlation with the difference in wall thickness in the x and y directions. It is worth noting that the air layer also affects the fiber performance.

[0039] In an optional embodiment of the present invention, by changing the difference in cladding wall thickness in the x and y directions, the transmission band can be adjusted to the range required by the present invention. At the same time, the outer nested wall thickness mainly restricts the light leaking into a certain direction again. However, when the thickness of the remaining cladding wall is located in the resonant region, the modes in the adjacent air layers will leak and synthesize new modes, thereby increasing the mode coupling loss.

[0040] The thickness t of all types of clad tubes meets the following requirements: Where t represents the thickness of the cladding tube, n represents the operating wavelength, n1 and n0 are the refractive indices of the cladding tube material and air, respectively, and m is a positive integer. In some embodiments, m can be selected as first-order or second-order.

[0041] In summary, the optical fiber structure of this invention is simple and reasonable, with high process feasibility, and can meet the requirements for high birefringence characteristics. Utilizing a three-adjacent nested shunt structure, leakage light in the y-direction can be effectively limited, enabling low-loss polarization-maintaining transmission in both guidebands. Low-loss bandwidth polarization maintenance is achieved at 1080nm (1020-1250nm, bandwidth 220nm), with a minimum polarization of 2.3 × 10⁻⁶. -3 dB / m; low-loss bandwidth with polarization maintenance in the 1420-1700nm (280nm) range, reaching a minimum of 2.6×10. -4 dB / m, y-pol is at 10 in both C and L bands. -3 Below dB / m, birefringence can exceed 10. -4 Furthermore, greater birefringence can be introduced by changing the size of the elliptical fiber core, but this comes at the cost of some loss. However, this approach is acceptable in certain applications requiring high birefringence. In some structures, even with high birefringence, losses can reach 0.24 dB / km, below 1 dB / km, and by adjusting parameters, birefringence can reach 1.8 × 10⁻⁶.-4 .

[0042] It should be noted that the introduction of different transmission bands and different anti-resonance wavelengths and bandwidths by changing different cladding wall thicknesses should not be construed as a limitation of the present invention.

[0043] This invention relates to a polarization-maintaining hollow-core antiresonant fiber suitable for laser transmission and broadband communication, based on an elliptical core and a multi-nested cladding structure with differentiated wall thickness. The elliptical core induces birefringence, achieving excellent birefringence performance without compromising loss and bandwidth. Simultaneously, the multi-nested cladding design generates a superior antiresonance effect, effectively confining the fundamental mode light in the core. Furthermore, the structural design of the hollow-core antiresonant fiber balances the effects of mode coupling and antiresonance, minimizing the impact of cladding mode coupling on the core fundamental mode. This design allows for compatibility with existing silica-core fibers and related devices, enabling applications in low-loss optical signal transmission.

[0044] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Those skilled in the art can modify the technical solutions described in the present invention, or make equivalent substitutions for some of the technical features, and these modifications or substitutions do not cause the corresponding technical solutions to deviate from the scope of the present invention.

Claims

1. A polarization-maintaining hollow-core anti-resonant optical fiber suitable for laser transmission and broadband communication, comprising an elliptical core (1), an outermost sheath (7), and a cladding region, characterized in that, The elliptical fiber core (1) is filled with air; The cladding region includes an x-direction structure and a y-direction structure. The x-direction structure is symmetrical with respect to the central axis of the y-direction structure. The x-direction structure includes a left half and a right half. The right half has the same structure as the left half and includes at least one first cladding layer. The y-direction structure is vertically symmetrical with respect to the central axis of the x-direction structure and is divided into an upper half and a lower half. Both the upper half and the lower half include at least one second cladding layer. The first cladding includes three nested circular structures, which include a first cladding tube (2), a second nested cladding tube (3), and a third nested cladding tube (4). The three nested circular structures are arranged in a triangular pattern to form three support points. The first cladding tube (2) and the third nested cladding tube (4) intersect at a point on the outermost sleeve (7). The second cladding includes two nested circular structures, which include an inner nested cladding tube (5) and an outer nested cladding tube (6). The two nested circular structures intersect at a point on the outermost sleeve (7). The cladding regions do not touch each other.

2. The polarization-maintaining hollow-core antiresonant optical fiber suitable for laser transmission and broadband communication according to claim 1, characterized in that, The materials of the first cladding, the second cladding and the outer cladding (7) are quartz glass, fluoride glass, sulfide glass or silicate glass.

3. The polarization-maintaining hollow-core antiresonant optical fiber suitable for laser transmission and broadband communication according to claim 1, characterized in that, The thickness of the first cladding tube (2) is 0.6-0.9µm; the thickness of the second nested cladding tube (3) and the third nested cladding tube (4) is 0.3-0.5µm; the thickness of the inner nested cladding tube (5) and the outer nested cladding tube (6) is 0.3-0.55µm.

4. The polarization-maintaining hollow-core antiresonant optical fiber suitable for laser transmission and broadband communication according to claim 1, characterized in that, The number of the outermost sleeve (7) is 2-3 layers.

5. A polarization-maintaining hollow-core antiresonant optical fiber suitable for laser transmission and broadband communication according to claim 1, characterized in that, The diameter of the first cladding tube (2) is larger than the diameter of the inner nested cladding tube (5).

6. The polarization-maintaining hollow-core antiresonant optical fiber suitable for laser transmission and broadband communication according to claim 1, characterized in that, The refractive indices of the first cladding tube (2), the second nested cladding tube (3), and the third nested cladding tube (4) are all equal.

7. The polarization-maintaining hollow-core antiresonant optical fiber suitable for laser transmission and broadband communication according to claim 1, characterized in that, The first cladding tube (2) and the inner nested cladding tube (5) have different wall thicknesses, thus introducing high birefringence.

8. A polarization-maintaining hollow-core antiresonant optical fiber suitable for laser transmission and broadband communication according to claim 1, characterized in that, The major axis of the elliptical fiber core (1) is Da, the minor axis is Db, and the ellipticity of the elliptical fiber core (1) is η, where η = Db / Da and η is 0.3-0.

9.

9. A polarization-maintaining hollow-core antiresonant optical fiber suitable for laser transmission and broadband communication according to claim 1, characterized in that, The hollow anti-resonant fiber has a diameter of 90-120 µm and an outer cladding (7) thickness of 12-18 µm.

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