A novel high-birefringence polarization-maintaining hollow anti-resonant optical fiber

Abstract

The application discloses a novel high-birefringence polarization maintaining hollow anti-resonant optical fiber, which comprises a base layer, a cladding layer and an air core, and the inside of the base layer is a hollow structure; the air core is arranged in the inner center of the base layer and forms an annular mounting space between the air core and the inner sidewall of the base layer, the cladding layer comprises a first cladding layer structure and a second cladding layer structure which are arranged in the annular mounting space in an array, the first cladding layer structure and the second cladding layer structure are respectively provided with at least two groups with the axis of the base layer as the symmetry center to form the cladding layer area of the hollow anti-resonant optical fiber in the annular mounting space; wherein the first cladding layer structure and the second cladding layer structure are arranged along the X direction and the Y direction of the cross section of the base layer respectively; the first cladding layer structure and the second cladding layer structure both comprise a cladding tube and a plurality of nested tubes which are arranged in the cladding tube in sequence and away from the air core, and the number and thickness of the nested tubes in the first cladding layer structure and the second cladding layer structure are different, so that the wideband high-birefringence is realized and the confinement loss is reduced.

Description

Technical Field

[0001] This invention relates to the field of microstructured light design technology, specifically to a novel high birefringence polarization-maintaining hollow-core anti-resonant optical fiber. Background Technology

[0002] Currently, almost all commercially available traditional polarization-maintaining fibers are solid-core fibers. Although the fabrication process is becoming increasingly mature, traditional polarization-maintaining fibers still suffer from some inherent defects of solid-core fibers, mainly manifested as significant nonlinear effects, unavoidable chromatic dispersion, low damage threshold, and large material absorption loss. Hollow-core fibers have received widespread attention in recent years due to their distinct advantages. Through the design of precise microstructures, the optical field can be efficiently confined within the air core, and the overlap between its mode field and the quartz cladding microstructure can be controlled to below 1%.

[0003] Based on their light guiding mechanisms, hollow-core fibers can be classified into hollow-core photonic bandgap fibers (HC-PBGFs) and hollow-core anti-resonant fibers (HC-ARFs). While the photonic bandgap effect effectively confines the light field within the air core, these fibers still face three key technical bottlenecks: narrow transmission bandwidth, low mode purity, and significant surface scattering loss. In contrast, HC-ARFs suppress the coupling between the core and cladding modes, thus confining the light field to the air core region. These fibers, with their superior optical properties (including low dispersion, low delay, low nonlinearity, and wider transmission bandwidth), have become a research hotspot in the field of optical fibers.

[0004] Introducing birefringence into HC-ARFs to achieve high-refractive-index polarization-maintaining hollow-core antiresonant fibers would have significant scientific implications and enormous engineering application potential. However, to date, research on achieving high birefringence in HC-ARFs has yielded only a limited number of theoretical explorations and experimental verifications. For example, in 2016, Mousavi et al. first proposed an HC-ARF with a four-tube cladding and multiple nested tubes, achieving high birefringence and single polarization characteristics. Their results showed that at a wavelength of 1.55 µm, the birefringence and polarization extinction ratio (PER) of this fiber reached 1.5 × 10⁻⁶. -4The fiber exhibits a confinement loss of 0.043 dB / m and a core size of 1000 nm, while maintaining a confinement loss of 0.043 dB / m. It is noteworthy that this fiber has a complex structure and a relatively small core size (14 µm). In 2021, MD. SELIM HABIB et al. proposed a design scheme for HC-ARFs based on a quartz / silicon hybrid cladding structure, which enables single-polarization, single-mode, and high birefringence transmission. It demonstrates excellent performance at a wavelength of 1064 nm: a confinement loss of 0.05 dB / m and a birefringence of 0.5 × 10⁻⁶. -4 The polarization extinction ratio is >300, but its operating wavelength is far from the low-loss window of optical fibers. In 2025, Xiao et al. proposed a stadium-shaped nested antiresonant fiber, achieving a polarization extinction ratio of 1.39 × 10⁻⁶ at a wavelength of 1.38 µm. -4 Birefringence and 26.5 dB / km confinement loss; achieving 1.28 × 10⁻⁶ at 1.55 µm wavelength. -4 Birefringence and 2.64 dB / km limiting loss.

[0005] However, existing HC-ARFs still do not meet the high-performance requirements of practical engineering applications, such as high bandwidth, low loss, simple structure, and operation within the low-loss window of optical fiber communication. Summary of the Invention

[0006] In view of this, the purpose of this invention is to provide a novel high birefringence polarization-maintaining hollow-core anti-resonant optical fiber to solve the technical problems mentioned in the prior art.

[0007] A novel high birefringence polarization-maintaining hollow-core antiresonant optical fiber, comprising:

[0008] The base layer has a hollow internal structure.

[0009] An air fiber core is disposed at the inner center of the base layer and forms an annular installation space between it and the inner sidewall of the base layer;

[0010] The cladding includes a first cladding structure and a second cladding structure arrayed within the annular mounting space. The first cladding structure and the second cladding structure are respectively arranged in at least two sets with the axis of the base layer as the center of symmetry, so as to form the cladding region of the hollow anti-resonant optical fiber within the annular mounting space. The first cladding structure is arranged along the X direction of the cross-section of the base layer, and the second cladding structure is arranged along the Y direction of the cross-section of the base layer.

[0011] Both the first cladding structure and the second cladding structure include a cladding tube and a plurality of nested tubes arranged sequentially inside the cladding tube away from the air fiber core, and the number and thickness of the nested tubes in the first cladding structure and the second cladding structure are different.

[0012] Optionally, the annular mounting space has a wall thickness of equal thickness.

[0013] Optionally, the cladding region is composed of two sets of first cladding structures and four sets of second cladding structures, with the four sets of second cladding structures symmetrically distributed on opposite sides of the central connecting line of the two sets of first cladding structures.

[0014] Optionally, the number of nested tubes in the first cladding structure is set to 1 layer, and the number of nested tubes in the second cladding structure is set to 2 layers.

[0015] Optionally, the outer wall of the cladding tube is tangent to the inner wall of the base layer and / or the outer wall of the air core.

[0016] Optionally, the first cladding structure includes:

[0017] The first cladding tube has a thickness of 755~765nm and a diameter of 21.6~22μm.

[0018] The first nested tube is located inside the first cladding tube. The thickness of the first nested tube is set to 376~384nm, and the diameter of the first nested tube is set to 15.6~16.4μm.

[0019] Optionally, the second cladding structure includes:

[0020] The second cladding tube has a thickness of 376~384nm and a diameter of 21.6~22μm.

[0021] The second nested tube is located inside the second cladding tube. The thickness of the second nested tube is set to 376~384nm, and the diameter of the second nested tube is set to 15~16μm.

[0022] A third nested tube is located inside the second nested tube. The thickness of the third nested tube is set to 376~384nm, and the diameter of the third nested tube is set to 8.6~9.4μm.

[0023] Optionally, the diameter of the air fiber core is set to 25.2~25.6μm.

[0024] Optionally, the base layer, the cladding tube, and the nested tube are all made of silicon dioxide.

[0025] The beneficial effects that this invention can produce include:

[0026] 1. The present invention provides a novel high birefringence polarization-maintaining hollow-core antiresonant optical fiber, wherein an air core is disposed at the center of a substrate, and a cladding is disposed between the air core and the substrate. The cladding includes a first cladding structure and a second cladding structure, and the cladding region of the polarization-maintaining hollow-core antiresonant optical fiber is composed of a circular array of six nested units centered at the center of the substrate. By simultaneously breaking the symmetry of the cladding structure in two dimensions—the number of nested units and the wall thickness—a large birefringence is generated, and the hollow-core antiresonant optical fiber reduces the confinement loss of light waves, thus achieving both broadband high birefringence and reduced confinement loss.

[0027] 2. The optical fiber provided by this invention has a birefringence of up to 9.17 × 10⁻⁶ at a working wavelength of 1550 nm. -4 The confinement loss for the x-polarization mode is 0.232 dB / m, and the confinement loss for the y-polarization mode is 0.65 dB / m. While meeting the requirement of confinement loss <1 dB / m, the birefringence is >1.0 × 10⁻⁶. -4 The bandwidth is 105nm. In addition, the fiber has good bending characteristics, maintaining a bending loss of <1dB / m with a bandwidth of 125nm when the bending radius is 7cm. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the cross-sectional structure of the novel high birefringence polarization-maintaining hollow-core anti-resonant optical fiber of the present invention;

[0029] Figure 2 In (a), the relative effective refractive index of the novel high birefringence polarization-maintaining hollow-core antiresonant fiber of the present invention is ( The curve showing the variation of birefringence with the thickness of the first cladding tube;

[0030] Figure 2 (b) shows the confinement loss curve of the novel high birefringence polarization-maintaining hollow antiresonant fiber of the present invention as a function of the thickness of the first cladding tube;

[0031] Figure 3 In (a), the relative effective refractive index of the novel high birefringence polarization-maintaining hollow-core antiresonant fiber of the present invention is ( The curves showing the variation of birefringence with the thickness of the first nested tube, the thickness of the second cladding tube, the thickness of the second nested tube, and the thickness of the third nested tube;

[0032] Figure 3 (b) shows the confinement loss curve of the novel high birefringence polarization-maintaining hollow anti-resonant fiber of the present invention as a function of the thickness of the first nested tube, the thickness of the second cladding tube, the thickness of the second nested tube, and the thickness of the third nested tube.

[0033] Figure 4 In (a), the relative effective refractive index of the novel high birefringence polarization-maintaining hollow-core antiresonant fiber of the present invention is ( The curve showing the variation of birefringence with the diameter of the air-filled fiber core;

[0034] Figure 4 (b) shows the confinement loss curve of the novel high birefringence polarization-maintaining hollow-core antiresonant optical fiber of the present invention as a function of air core diameter;

[0035] Figure 5 In (a), the relative effective refractive index of the novel high birefringence polarization-maintaining hollow-core antiresonant fiber of the present invention is ( The curves showing the variation of birefringence with the diameters of the first and second cladding tubes;

[0036] Figure 5 (b) shows the confinement loss curve of the novel high birefringence polarization-maintaining hollow-core antiresonant fiber of the present invention as a function of the diameter of the first cladding tube and the diameter of the second cladding tube.

[0037] Figure 6 In (a), the relative effective refractive index of the novel high birefringence polarization-maintaining hollow-core antiresonant fiber of the present invention is ( ), the curve of birefringence as a function of the diameter of the first nested tube;

[0038] Figure 6 (b) shows the curve of confinement loss of the novel high birefringence polarization-maintaining hollow antiresonant fiber of the present invention as a function of the diameter of the first nested tube;

[0039] Figure 7 In (a), the relative effective refractive index of the novel high birefringence polarization-maintaining hollow-core antiresonant fiber of the present invention is ( The curve showing the variation of birefringence with the diameter of the second nested tube;

[0040] Figure 7 (b) shows the curve of confinement loss of the novel high birefringence polarization-maintaining hollow-core antiresonant fiber of the present invention as a function of the diameter of the second nested tube;

[0041] Figure 8 In (a), the relative effective refractive index of the novel high birefringence polarization-maintaining hollow-core antiresonant fiber of the present invention is ( ), the curve of birefringence as a function of the diameter of the third nested tube;

[0042] Figure 8 (b) shows the confinement loss curve of the novel high birefringence polarization-maintaining hollow-core antiresonant fiber of the present invention as a function of the diameter of the third nested tube;

[0043] Figure 9 (a) shows the mode field distribution of the x-polarization mode of the novel high birefringence polarization-maintaining hollow-core anti-resonant fiber of the present invention at a working wavelength of 1550 nm.

[0044] Figure 9(b) shows the mode field distribution of the y-polarization mode of the novel high birefringence polarization-maintaining hollow-core anti-resonant fiber of the present invention at a working wavelength of 1550 nm.

[0045] Figure 10 (a) shows the birefringence of the novel high birefringence polarization-maintaining hollow-core antiresonant optical fiber of the present invention as a function of wavelength.

[0046] Figure 10 Figure (b) shows the relationship between the confinement loss and wavelength of the novel high birefringence polarization-maintaining hollow-core antiresonant fiber of the present invention.

[0047] Figure 11 (a) shows the curve of the bending loss of the x-polarization mode of the novel high birefringence polarization-maintaining hollow-core anti-resonant fiber of the present invention as a function of the bending radius;

[0048] Figure 11 (b) shows the relationship between the bending loss of the x-polarization mode and the wavelength when the bending radius is 7 cm in the novel high birefringence polarization-maintaining hollow-core antiresonant fiber of the present invention.

[0049] In the diagram: 1. Base layer, 2. Air fiber core, 3. Annular installation space, 4. First cladding structure, 41. First cladding tube, 42. First nested tube, 5. Second cladding structure, 51. Second cladding tube, 52. Second nested tube, 53. Third nested tube. Detailed Implementation

[0050] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0051] Please see Figure 1This invention provides a novel high birefringence polarization-maintaining hollow anti-resonant optical fiber, comprising a base layer 1, a cladding, and an air core 2. The base layer 1 has a hollow internal structure. The air core 2 is disposed at the inner center of the base layer 1, forming an annular mounting space 3 between itself and the inner sidewall of the base layer 1. The annular mounting space 3 has a uniform wall thickness. The cladding includes a first cladding structure 4 and a second cladding structure 5 arrayed within the annular mounting space 3. At least two sets of the first cladding structure 4 and the second cladding structure 5 are respectively arranged with the axis of the base layer 1 as the center of symmetry, to form an annular mounting space. The cladding region of the hollow anti-resonant optical fiber is formed within the base layer 1. The first cladding structure 4 is arranged along the X direction of the cross-section of the base layer 1, and the second cladding structure 5 is arranged along the Y direction of the cross-section of the base layer 1. Both the first cladding structure 4 and the second cladding structure 5 include a cladding tube and several nested tubes arranged sequentially inside the cladding tube away from the air core 2. The number and thickness of the nested tubes in the first cladding structure 4 and the second cladding structure 5 are different, so as to break the symmetry of the traditional structure to improve birefringence and make it highly flexible in the control of optical fiber performance.

[0052] In this embodiment, as Figure 1 As shown, the cladding region consists of two sets of first cladding structures 4 and four sets of second cladding structures 5, with the four sets of second cladding structures 5 symmetrically distributed in pairs on opposite sides of the central connecting line of the two sets of first cladding structures 4. In the above, the structural parameters of a novel high birefringence polarization-maintaining hollow-core anti-resonant optical fiber of the present invention are configured as follows: the number of nested tubes in the first cladding structure 4 is set to 1 layer, and the number of nested tubes in the second cladding structure 5 is set to 2 layers; the outer wall of the cladding tube is tangent to the inner wall of the base layer 1 and / or the outer wall of the air core 2. The first cladding structure 4 includes a first cladding tube 41 and a first nested tube 42. The thickness of the first cladding tube 41 is set to 755~765nm, and the diameter of the first cladding tube 41 is set to 21.6~22μm; the first nested tube 42 is located inside the first cladding tube 41, and the thickness of the first nested tube 42 is set to 376~384nm, and the diameter of the first nested tube 42 is set to 15.6~16.4μm. The second cladding structure 5 includes a second cladding tube 51, a second nested tube 52, and a third nested tube 53. The thickness of the second cladding tube 51 is set to 376~384nm, and the diameter of the second cladding tube 51 is set to 21.6~22μm. The second nested tube 52 is located inside the second cladding tube 51, and the thickness of the second nested tube 52 is set to 376~384nm, and the diameter of the second nested tube 52 is set to 15~16μm. The third nested tube 53 is located inside the second nested tube 52, and the thickness of the third nested tube 53 is set to 376~384nm, and the diameter of the third nested tube 53 is set to 8.6~9.4μm. The diameter of the air core 2 is set to 25.2~25.6μm.

[0053] Specifically, by simultaneously breaking the structural symmetry in both the horizontal and vertical directions in terms of the number and wall thickness of the nested tubes within the nested unit—that is, one layer of circular nested tubes in the horizontal direction and two layers of circular nested tubes in the vertical direction—and by setting the wall thickness of the nested tubes in the first cladding structure 4 in the horizontal direction close to the resonant thickness, and the wall thickness of the nested tubes in the second cladding structure 5 in the vertical direction far from the resonant thickness, a greater birefringence is generated. The design of the air core 2 helps reduce scattering and absorption losses during light transmission, improving light transmission efficiency. This facilitates the realization of more advanced functions in fields such as optical communication, sensing, or signal processing. Furthermore, the hollow-core antiresonant fiber reduces the confinement loss of light waves, further improving the birefringence of the polarization-maintaining hollow-core antiresonant fiber and reducing confinement loss during transmission. By adjusting the structural parameters of the cladding (such as the size, position, and number of nested units), the optical performance of the fiber can be flexibly adjusted to adapt to different application requirements.

[0054] Example 1:

[0055] The parameters of a novel high birefringence polarization-maintaining hollow-core antiresonant fiber are set as follows: the thicknesses of the first nested tube 42, the second cladding tube 51, the second nested tube 52, and the third nested tube 53 are all set to 0.38 nm; the diameter of the air core 2 is set to 25.4 μm; the diameters of the first cladding tube 41 and the second cladding tube 51 are both set to 21.8 μm; the diameter of the second nested tube 52 is set to 15.5 μm; the diameter of the third nested tube 53 is set to 9 μm; and the diameter of the first nested tube 42 is set to 16 μm. The thickness of the first cladding tube 41 ranges from 755 to 765 nm, with a step size of 0.01 nm, thus obtaining the following... Figure 2 The diagram illustrates the relationship between birefringence and confinement loss as a function of the thickness of the first cladding tube 41. Specifically, it shows the changes in x-polarization mode and y-polarization mode as the thickness of the first cladding tube 41 increases from 755 nm to 765 nm. Both the confinement loss and birefringence decrease with increasing thickness of the first cladding tube 41. On the other hand, as the thickness of the first cladding tube 41 increases, the confinement loss of the x-polarized mode fluctuates from 0.2 dB / m to 0.36 dB / m, while the confinement loss of the y-polarized mode fluctuates from 1.279 dB / m, first decreasing then fluctuating to 0.91 dB / m. At a thickness of 759 nm, the confinement loss of the y-polarized mode reaches a near minimum of 0.65 dB / m. At this point, the confinement loss of the x-polarized mode is 0.232 dB / m, and the birefringence is 9.17 × 10⁻⁶. -4At a thickness of 761 nm in the first nested tube 42, the confinement loss of the y-polarization mode reaches a minimum of 0.55 dB / m, while the confinement loss of the x-polarization mode is 0.243 dB / m, and the birefringence is 8.2 × 10⁻⁶. -4 To achieve greater birefringence, the thickness of the first cladding tube 41 is preferably 759 nm.

[0056] Example 2:

[0057] The parameters of a novel high birefringence polarization-maintaining hollow-core antiresonant fiber are set as follows: the thickness of the first cladding tube 41 is set to 759 nm, the diameter of the air core 2 is set to 25.4 μm, the diameters of both the first cladding tube 41 and the second cladding tube 51 are set to 21.8 μm, the diameter of the second nested tube 52 is set to 15.5 μm, the diameter of the third nested tube 53 is set to 9 μm, and the diameter of the first nested tube 42 is set to 16 μm; the thicknesses of the first nested tube 42, the second cladding tube 51, the second nested tube 52, and the third nested tube 53 are all within the range of 375-385 nm, with a step size of 0.01 nm, thus obtaining the following... Figure 3 The diagram illustrates the synchronous variation of birefringence and confinement loss with the thicknesses of the first nested tube 42, the second cladding tube 51, the second nested tube 52, and the third nested tube 53. The x-polarization mode... As the thickness of the first nested tube 42, the second cladding tube 51, the second nested tube 52, and the third nested tube 53 increases synchronously from 7.072 × 10⁻⁶, the thickness of the third nested tube 53 increases. -4 Decreased to 7.045×10 -4 y-polarization mode The thickness of the first nested tube 42, the second cladding tube 51, the second nested tube 52, and the third nested tube 53 are increased synchronously and maintained at 1.62 × 10⁻⁶. -3 Nearby, therefore, the birefringence increases from 9.174 × 10⁻⁶ with the simultaneous increase of the thicknesses of the first nested tube 42, the second cladding tube 51, the second nested tube 52, and the third nested tube 53. -4 Decreased to 9.149×10 -4 On the other hand, as the thicknesses of the first nested tube 42, the second cladding tube 51, the second nested tube 52, and the third nested tube 53 increase synchronously, the confinement loss of the x-polarization mode fluctuates from 0.22 dB / m to 0.24 dB / m, and the confinement loss of the y-polarization mode fluctuates from 0.64 dB / m to 0.66 dB / m. To simultaneously satisfy the requirements of relatively high birefringence and relatively low confinement loss, the thicknesses of the first nested tube 42, the second cladding tube 51, the second nested tube 52, and the third nested tube 53 are preferably 380 nm.

[0058] Example 3:

[0059] The parameters of a novel high birefringence polarization-maintaining hollow-core antiresonant fiber are set as follows: the thicknesses of the first nested tube 42, the second cladding tube 51, the second nested tube 52, and the third nested tube 53 are all 380 nm; the thickness of the first cladding tube 41 is set to 759 nm; the diameters of the first cladding tube 41 and the second cladding tube 51 are set to 21.8 μm; the diameter of the second nested tube 52 is set to 15.5 μm; the diameter of the third nested tube 53 is set to 9 μm; and the diameter of the first nested tube 42 is set to 16 μm. The diameter of the air core 2 ranges from 25 to 26 μm, with a step size of 10 nm, thus obtaining the following... Figure 4 The diagram illustrates the relationship between birefringence and confinement loss as a function of the diameter of the air core 2. As the diameter of the air core 2 increases from 25 μm to 26 μm, the x-polarization mode... As the diameter of the air core 2 increases from 7.3 × 10⁻⁶, -4 Decreased to 6.7×10 -4 y-polarization mode As the diameter of the air core 2 increases from 1.69 × 10⁻⁶, -3 Decreased to 1.54 × 10 -3 On the other hand, the confinement loss of the x-polarization mode fluctuates within the range of 0.18 dB / m and 0.24 dB / m as the diameter of the air core 2 increases, while the confinement loss of the y-polarization mode first decreases and then increases from 0.86 dB / m to 1.69 dB / m and then decreases again to 1.2 dB / m as the diameter of the air core 2 increases. In order to obtain high birefringence and avoid excessive loss, the diameter of the air core 2 is preferably 25.4 μm.

[0060] Example 4:

[0061] The parameters of a novel high birefringence polarization-maintaining hollow-core antiresonant fiber are set as follows: the thicknesses of the first nested tube 42, the second cladding tube 51, the second nested tube 52, and the third nested tube 53 are all 380 nm; the thickness of the first cladding tube 41 is set to 759 nm; the diameter of the air core 2 is 25.4 μm; the diameter of the second nested tube 52 is set to 15.5 μm; the diameter of the third nested tube 53 is set to 9 μm; and the diameter of the first nested tube 42 is set to 16 μm. The diameters of the first cladding tube 41 and the second cladding tube 51 range from 21 to 22 μm, with a step size of 10 nm, thus obtaining the following... Figure 5 The diagram illustrates the relationship between birefringence and confinement loss as a function of the diameters of the first cladding tube 41 and the second cladding tube 51. As the diameters of the first cladding tube 41 and the second cladding tube 51 increase synchronously, the x-polarization mode and the y-polarization mode... Both birefringence and the diameter of the first cladding tube 41 and the second cladding tube 51 decrease synchronously. On the other hand, with other parameters unchanged, the synchronous increase in the diameter of the first cladding tube 41 and the second cladding tube 51 allows light to be better confined in the air core 2. The confinement loss of the x-polarization mode remains basically unchanged, while the confinement loss of the y-polarization mode generally decreases and then increases in a fluctuating manner as the diameter of the first cladding tube 41 and the second cladding tube 51 increases synchronously. The confinement loss of the y-polarization mode is the lowest when the diameter of the first cladding tube 41 and the second cladding tube 51 is 21.82 μm. However, in order to achieve both low confinement loss and higher birefringence, the diameters of the first cladding tube 41 and the second cladding tube 51 are ultimately selected to be 21.8 μm.

[0062] Similarly, such as Figure 6 , Figure 7 , Figure 8 The figures show the variations in birefringence and confinement loss with the diameters of the first nested tube 42, the second nested tube 52, and the third nested tube 53, respectively. As can be seen from the figures, if only sufficiently high birefringence is considered, the confinement loss may not be optimal, and vice versa. However, for the designed polarization-maintaining hollow-core antiresonant fiber, it is necessary to comprehensively consider both birefringence and confinement loss to meet the requirements. Therefore, in some implementations, the diameters of the first nested tube 42 (16 μm), the second nested tube 52 (15.5 μm), and the third nested tube 53 (9 μm) are ultimately chosen. Meanwhile, since increasing the diameter of the third nested tube 53 does not significantly contribute to breaking the cross-sectional symmetry of the fiber, its diameter has a relatively small impact on birefringence. Based on the above analysis, the thicknesses of the first nested tube 42 and the second cladding tube 51 are ultimately selected. 、 The thickness of the second nested tube 52 and the third nested tube 53 are both 380 nm, the thickness of the first cladding tube 41 is 759 nm, the diameter of the air core 2 is 25.4 μm, the diameter of the first cladding tube 41 and the second cladding tube 51 are both 21.8 μm, the diameter of the second nested tube 52 is 15.5 μm, the diameter of the third nested tube 53 is 9 μm, and the diameter of the first nested tube 42 is 16 μm. This design achieves good birefringence performance at 1550 nm.

[0063] In some embodiments, the base layer 1, the cladding tube, and the nested tube are all made of silicon dioxide (SiO2). It should be noted that the refractive index of silicon dioxide in the C-band (1530nm to 1565nm) is approximately 1.444.

[0064] Specifically, such as Figure 9The figure shows the mode field distribution of the x-polarization mode and y-polarization mode of the novel high birefringence polarization-maintaining hollow-core antiresonant fiber provided by this invention at a working wavelength of 1550 nm; wherein, Figure 9 In the middle (a), the mode field distribution of the x-polarization mode is shown; Figure 9 In (b), the mode field distribution of the y-polarization mode is shown; by Figure 9 It is evident that both the x-polarization mode and the y-polarization mode are effectively confined within the air core 2.

[0065] Specifically, Figure 10 Figures (a) and (b) show the relationship between birefringence and confinement loss as a function of wavelength for a novel high-birefringence polarization-maintaining hollow-core antiresonant fiber. Specifically, near the initial wavelength of the S-band, there are three wavelength ranges (1452-1456 nm, 1461-1465 nm, and 1478-1485 nm) where the birefringence is >1.0 × 10⁻⁶. -4 Furthermore, the birefringence is >1.0×10⁻⁶ in both the full C-band and part of the L-band (1565-1581nm). -4 At 1550 nm, the birefringence can reach as high as 9.17 × 10⁻⁶. -4 The confinement loss of both x-polarization and y-polarization modes is relatively high at the short wavelength edge, then decreases to below 1 dB / m at 1531 nm and tends to stabilize. At 1550 nm, the confinement loss of x-polarization mode is as low as 0.232 dB / m, and the confinement loss of y-polarization mode is as low as 0.65 dB / m. The results show that the designed optical fiber can function normally.

[0066] Specifically, Figure 11 Figure (a) shows the relationship between the bending loss of the x-polarization mode of a polarization-maintaining hollow-core anti-resonant fiber and the bending radius when the operating wavelength is 1550 nm. When the fiber structure parameters are set as follows: the thicknesses of the first nesting tube 42, the second cladding tube 51, the second nesting tube 52, and the third nesting tube 53 are all 380 nm; the thickness of the first cladding tube 41 is 759 nm; the diameter of the air core 2 is 25.4 μm; the diameters of the first and second cladding tubes 41 and 51 are both 21.8 μm; the diameter of the second nesting tube 52 is 15.5 μm; the diameter of the third nesting tube 53 is 9 μm; and the diameter of the first nesting tube 42 is 16 μm, it can be seen that the bending loss first decreases sharply with the increase of the bending radius and then tends to stabilize. At bending radii of 3 cm and above, extremely low bending loss (<0.5 dB / m) is maintained. When the bending radius is 7 cm, the bending loss is 0.35 dB / m. Figure 11 Figure (b) shows the relationship between bending loss and wavelength in hollow antiresonant fiber with a bending radius of 7 cm. The results show that the bending loss remains below 0.5 dB / m in the wavelength range of 1525 nm to 1650 nm.

[0067] In this invention, an air core 2 is positioned at the center of a base layer 1, and a cladding is positioned between the air core 2 and the base layer 1. The cladding includes a first cladding structure 4 and a second cladding structure 5, and the cladding region of the polarization-maintaining hollow-core anti-resonant fiber is composed of a circular array of six nested units centered on the center of the base layer 1. This invention breaks the symmetry of the cladding structure simultaneously in terms of the number of nested tubes and the tube wall thickness, thereby generating greater birefringence. Furthermore, the hollow-core anti-resonant fiber reduces the confinement loss of the light wave, achieving both broadband high birefringence and reduced confinement loss. The fiber provided exhibits a birefringence as high as 9.17 × 10⁻⁶ at a working wavelength of 1550 nm. -4 The confinement loss for the x-polarization mode is 0.232 dB / m, and the confinement loss for the y-polarization mode is 0.65 dB / m. While meeting the requirement of confinement loss <1 dB / m, the birefringence is >1.0 × 10⁻⁶. -4 The bandwidth is 105nm. In addition, the fiber has good bending characteristics, maintaining a bending loss of <1dB / m with a bandwidth of 125nm when the bending radius is 7cm.

Claims

1. A novel high-birefringence polarization-maintaining hollow-core antiresonant optical fiber, characterized in that, include: The base layer (1) has a hollow internal structure; An air fiber core (2) is disposed in the inner center of the base layer (1) and forms an annular installation space (3) between it and the inner sidewall of the base layer (1). The cladding includes a first cladding structure (4) and a second cladding structure (5) arrayed within the annular mounting space (3). The first cladding structure (4) and the second cladding structure (5) are respectively arranged in at least two sets with the axis of the base layer (1) as the center of symmetry, so as to form the cladding region of the hollow anti-resonant optical fiber within the annular mounting space (3). The first cladding structure (4) is arranged along the X direction of the cross-section of the base layer (1), and the second cladding structure (5) is arranged along the Y direction of the cross-section of the base layer (1). Both the first cladding structure (4) and the second cladding structure (5) include a cladding tube and a plurality of nested tubes arranged sequentially inside the cladding tube away from the air core (2). The number of nested tubes in the first cladding structure (4) and the second cladding structure (5) are different, and the thickness of the cladding tube in the first cladding structure (4) and the second cladding structure (5) is different. The cladding region is composed of two sets of first cladding structures (4) and four sets of second cladding structures (5), and the four sets of second cladding structures (5) are symmetrically distributed on opposite sides of the central connecting line of the two sets of first cladding structures (4). The number of nested tubes in the first cladding structure (4) is set to 1 layer, and the number of nested tubes in the second cladding structure (5) is set to 2 layers.

2. The novel high birefringence polarization-maintaining hollow-core antiresonant optical fiber according to claim 1, characterized in that, The annular installation space (3) has a wall thickness of equal thickness.

3. The novel high birefringence polarization-maintaining hollow-core antiresonant optical fiber according to claim 1, characterized in that, The outer wall of the cladding tube is tangent to the inner wall of the base layer (1) and / or the outer wall of the air core (2).

4. The novel high birefringence polarization-maintaining hollow-core antiresonant optical fiber according to claim 1, characterized in that, The first cladding structure (4) includes: The first cladding tube (41) has a thickness of 755~765nm and a diameter of 21.6~22μm. The first nested tube (42) is located inside the first cladding tube (41). The thickness of the first nested tube (42) is set to 376~384nm, and the diameter of the first nested tube (42) is set to 15.6~16.4μm.

5. A novel high-birefringence polarization-maintaining hollow-core antiresonant optical fiber according to claim 1, characterized in that, The second cladding structure (5) includes: The second cladding tube (51) has a thickness of 376~384nm and a diameter of 21.6~22μm. The second nested tube (52) is located inside the second cladding tube (51). The thickness of the second nested tube (52) is set to 376~384nm, and the diameter of the second nested tube (52) is set to 15~16μm. The third nested tube (53) is located inside the second nested tube (52). The thickness of the third nested tube (53) is set to 376~384nm, and the diameter of the third nested tube (53) is set to 8.6~9.4μm.

6. The novel high birefringence polarization-maintaining hollow-core antiresonant optical fiber according to claim 1, characterized in that, The diameter of the air fiber core (2) is set to 25.2~25.6μm.

7. The novel high birefringence polarization-maintaining hollow-core antiresonant optical fiber according to claim 1, characterized in that, The base layer (1), the cladding tube, and the nested tube are all made of silicon dioxide.

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