Antiresonant hollow core fiber and applications thereof

Abstract

This invention provides an anti-resonant hollow-core optical fiber and its application, comprising a cladding and a core. The cladding is externally fitted with a sheath, and within the cladding are multiple single-layer resonant tubes and multiple double-layer nested tubes tangent to the cladding. The single-layer resonant tubes are evenly distributed circumferentially around the center of the core, with a double-layer nested tube positioned between every two single-layer resonant tubes. The diameter of each single-layer resonant tube is larger than the diameter of the double-layer nested tube. Each double-layer nested tube includes an inner tube and an outer tube, with the inner and outer tubes internally tangent. This invention achieves anti-resonant hollow-core optical fiber (LP) through single-layer resonant tubes. 11 The fundamental mode is coupled with the cladding mode, thereby allowing the higher-order mode capability to leak and achieve single-mode transmission in optical fiber. Then, a double-layer nested tube positioned between two single-layer resonant tubes locks the fundamental mode energy within the fiber core, achieving low-loss transmission of the fundamental mode. This invention effectively reduces fundamental mode confinement loss and achieves single-mode transmission in optical fiber through mode coupling.

Description

Technical Field

[0001] This invention relates primarily to the field of fiber laser technology, and more particularly to anti-resonant hollow fiber and its applications. Background Technology

[0002] Hollow-core optical fibers (HCFs), a special type of optical fiber, possess unique properties that confine light waves to the air for transmission, resulting in characteristics such as low optical nonlinearity, low material absorption loss, high damage threshold, and low latency. These fibers are widely used in various fields, including high-power transmission, optical fiber communication, and supercontinuum generation. Hollow-core optical fibers mainly include photonic bandgap hollow-core fibers (PBG-HCFs) and anti-resonant hollow-core fibers (AR-HCFs). However, compared to PBG-HCFs, AR-HCFs exhibit a larger transmission bandwidth by reducing the interaction between the core light and the cladding material during transmission.

[0003] To achieve low fundamental mode loss and excellent single-mode transmission characteristics in AR-HCFs, researchers have designed various novel anti-resonant hollow fiber structures. In 2016, S. Habib et al. proposed an anisotropic anti-resonant tube hollow fiber with a core diameter of 30 μm, achieving a high-order mode suppression ratio (HOMER) greater than 1000 in the 1.0–1.65 μm spectral range, and achieving a low LP loss at 1.06 μm. 01 The minimum limiting loss of the mode is less than 5 dB / km. In 2018, S. Yan et al. proposed a novel double-ring antiresonant hollow fiber with a core diameter of 70 μm and LP... 01 The minimum limiting loss of this mode is 0.29 dB / km, and the HOMER of this fiber exceeds 1000 in the 2.5–3.3 μm spectral range. In 2019, S. Habib et al. developed a five-tube nested antiresonant hollow fiber with a core diameter of 30.5 μm, achieving a record HOMER of 1.2 × 10⁻⁶ at 1.55 μm. 4 In the spectral range of 1.33–1.66 μm, LP 01 The minimum limiting loss for the mode is 0.45 dB / km. In 2022, Y. Zhou et al. proposed a novel double-triangular symmetric antiresonant hollow fiber with a core diameter of 50 μm. Simulations showed that the LP signal in the 1-1.1 μm spectral range... 01 The limiting losses of all modes are less than 1 dB / km, and the HOMER exceeds 1000. The study found that it is difficult to achieve both low-loss transmission of the fundamental mode and single-mode transmission of antiresonant hollow fiber with a large core diameter. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides an anti-resonant hollow optical fiber and its applications.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] On one hand, the present invention provides an anti-resonant hollow optical fiber, comprising a cladding and a core; the cladding is provided with a protective tube on its exterior, and the cladding contains a plurality of single-layer resonant tubes and a plurality of double-layer nested tubes tangent to the cladding. The single-layer resonant tubes are evenly distributed circumferentially around the center of the core, and a double-layer nested tube is arranged between every two single-layer resonant tubes; the diameter of the single-layer resonant tube is larger than the diameter of the double-layer nested tube; the double-layer nested tube includes an inner tube and an outer tube, and the inner tube is internally tangent to the outer tube.

[0007] Furthermore, the gap between the double-layer nested tube and the two adjacent single-layer resonant tubes is equal.

[0008] Furthermore, the point of tangency between the inner tube and the outer tube is located on the straight line connecting the point of tangency between the outer tube and the cladding and the center of the fiber core; the point of tangency between the inner tube and the outer tube is located on the side closer to the cladding.

[0009] Furthermore, the thickness of the protective tube is 10 μm.

[0010] Furthermore, the number of the single-layer resonant tube and the double-layer nested tube is five.

[0011] Furthermore, the thickness of the single-layer resonant tube, the outer tube, and the inner tube are all... t The diameter of the fiber core is D core The diameter of the single-layer resonant tube is d tube The outer tube diameter is d 1. Modeling anti-resonant hollow fiber based on COMSOL, and optimizing it. t , D core , d tube and d 1. This enables a higher-order mode suppression ratio greater than 1000 in the 1.3 μm - 1.7 μm spectral range, achieving single-mode transmission while simultaneously achieving low-loss transmission of the fundamental mode.

[0012] Furthermore, the optimization t The process includes:

[0013] Fixed fiber core diameter D core single-layer resonator diameter d tube outer tube diameter d 1. Inner tube diameter d 2. Optimizationt The fundamental mode loss and higher-order mode confinement loss are obtained by... t The change curve and the suppression ratio of higher-order modes as a function of t The change curve graph determines t The preferred value.

[0014] Furthermore, the optimization D core The process includes:

[0015] The ratio of the diameter of a fixed single-layer resonant tube to the diameter of the fiber core. d tube / D core The ratio of the outer tube diameter to the fiber core diameter d 1 / D core The ratio of the inner tube diameter to the fiber core diameter d 2 / D core The thickness of the single-layer resonant tube, outer tube, and inner tube t ,optimization D core The fundamental mode loss and higher-order mode confinement loss are obtained by... D core The change curve and the suppression ratio of higher-order modes as a function of D core The change curve graph determines D core The preferred value.

[0016] Furthermore, the optimization d tube , d The process of step 1 includes:

[0017] Fixed outer tube diameter d 1. Inner tube diameter d 2. Thickness of the single-layer resonant tube, outer tube, and inner tube t Core diameter D core ,optimization d tube / D core The fundamental mode loss and higher-order mode confinement loss are obtained by... d tube / D core The change curve and the suppression ratio of higher-order modes as a function of d tube / D core The change curve graph determines d tube / Dcore The preferred value;

[0018] fixed d tube / D core for d tube / D core The preferred value, optimization d 1 / D core The fundamental mode loss and higher-order mode confinement loss are obtained by... d 1 / D core The change curve and the suppression ratio of higher-order modes as a function of d 1 / D core The change curve graph determines d 1 / D core The preferred value.

[0019] On the other hand, the present invention also provides an application of anti-resonant hollow fiber, using the above-mentioned anti-resonant hollow fiber for optical fiber communication.

[0020] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0021] The anti-resonant hollow-core optical fiber and its applications provided by this invention can achieve low-loss transmission of the fundamental mode and ultra-high higher-order mode suppression ratio (HOMER) in the 1.3 μm-1.7 μm spectral range under large mode field conditions, thus achieving single-mode transmission. Specifically, the core LP is achieved through a single-layer resonant tube. 11 The mode is coupled with the cladding mode, thereby allowing the higher-order mode capability to leak and achieve single-mode transmission in the fiber. Then, the fundamental mode energy in the fiber core is locked in the fiber core by a double-nested tube set between two single-layer resonators, so as to achieve low-loss transmission of the fundamental mode in the fiber. Through the cross-arrangement of the single-layer resonators and the double-nested tubes, the fundamental mode confinement loss can be effectively reduced and single-mode transmission in the fiber can be achieved through mode coupling. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present 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 only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0023] Figure 1 A schematic cross-sectional view of an anti-resonant hollow fiber provided in one embodiment;

[0024] Figure 2 A graph showing the effect of the thickness of the single-layer resonant tube, outer tube, and inner tube on the fundamental mode loss and higher-order mode confinement loss in one embodiment.

[0025] Figure 3 A graph showing the effect of the thickness of the single-layer resonant tube, outer tube, and inner tube on the high-order mode confinement loss ratio HOMER in one embodiment;

[0026] Figure 4 A graph showing the effect of the number of single-layer resonant transistors and double-layer nested transistors on the fundamental mode loss and the higher-order mode confinement loss ratio in one embodiment;

[0027] Figure 5 A graph showing the effect of the number of single-layer resonant transistors and double-layer nested transistors on the high-order mode confinement loss ratio HOMER in one embodiment;

[0028] Figure 6 A graph showing the effect of fiber core diameter on fundamental mode loss and higher-order mode confinement loss ratio in one embodiment;

[0029] Figure 7 A graph showing the effect of fiber core diameter on higher-order mode confinement loss ratio (HOMER) and mode field area in one embodiment;

[0030] Figure 8 Effective refractive index curves of the fiber core fundamental mode, higher-order modes, and cladding modes under different ratios of single-layer resonator diameter to fiber core diameter, provided as an embodiment;

[0031] Figure 9 A diagram showing the effect of the fiber core fundamental mode and higher-order mode confinement losses and their ratios on different ratios of single-layer resonant tube diameter to fiber core diameter, as provided in one embodiment;

[0032] Figure 10 Effective refractive index curves of the fiber core fundamental mode, higher-order modes, and cladding modes under different ratios of outer tube diameter to fiber core diameter in a double-layer nested tube provided in one embodiment;

[0033] Figure 11 A diagram showing the influence of the fiber core's fundamental mode and higher-order mode limitation losses and their ratios on different ratios of the outer tube diameter to the fiber core diameter in a double-layer nested tube, as provided in one embodiment.

[0034] Figure 12 A diagram showing the confinement loss of higher-order modes and fundamental mode in the fiber core within the 1.3 μm-1.7 μm spectral range, and their ratios, provided for one embodiment;

[0035] Figure 13The diagram shows the mode field diameter and mode field area of ​​the fiber core fundamental mode in the 1.3 μm - 1.7 μm spectral range, as provided in one embodiment.

[0036] Figure 14 Different degrees of fiber collapse in the 1.3 μm-1.7 μm spectral range provided in one embodiment. T The fundamental model of the value, LP 11 Schematic diagram of mode-limited loss spectrum;

[0037] Figure 15 One embodiment provides different degrees of fiber collapse in the 1.3 μm - 1.7 μm spectral range. T The effect of the value on the higher-order mode-limited loss ratio HOMER is shown in the curve.

[0038] Figure 16 Different offset angles of optical fiber in the 1.3 μm - 1.7 μm spectral range provided in one embodiment. θ The fundamental model of the value, LP 11 Schematic diagram of mode-limited loss spectrum;

[0039] Figure 17 Different offset angles of optical fiber in the 1.3 μm - 1.7 μm spectral range provided in one embodiment. θ The curve showing the effect of the value on the higher-order mode-limited loss ratio HOMER.

[0040] Attached image captions:

[0041] 1. Single-layer resonant tube; 2. Double-layer nested tube; 3. Inner tube; 4. Outer tube; 5. Protective tube; 6. Fiber core. Detailed Implementation

[0042] 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 a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0043] Reference Figure 1 One embodiment provides an anti-resonant hollow optical fiber, including a cladding and a core 6; the cladding is provided with a sheath 5 on the outside, and a plurality of single-layer resonant tubes 1 and a plurality of double-layer nested tubes 2 are provided inside the cladding and tangent to the cladding. The single-layer resonant tubes 1 are arranged in an array with the center of the core 6 as the center, and a double-layer nested tube 2 is arranged between every two single-layer resonant tubes 1; the diameter of the single-layer resonant tube 1 is larger than the diameter of the double-layer nested tube 2; the double-layer nested tube 2 includes an inner tube 3 and an outer tube 4, and the inner tube 3 and the outer tube 4 are internally tangent.

[0044] Achieving fiber core LP through a single-layer resonant tube 11 The mode is coupled with the cladding mode, thereby allowing the higher-order mode capability to leak and achieve single-mode transmission in the fiber. Then, the fundamental mode energy in the fiber core is locked in the fiber core by a double-nested tube set between two single-layer resonators, so as to achieve low-loss transmission of the fundamental mode in the fiber. Through the cross-arrangement of the single-layer resonators and the double-nested tubes, the fundamental mode confinement loss can be effectively reduced and single-mode transmission in the fiber can be achieved through mode coupling.

[0045] The thickness of the protective tube is 10 μm.

[0046] Reference Figure 16 , Figure 17 In one embodiment, LP was calculated through simulation. 01 Patterns and LPs 11 Pattern at different offset angles θ The confined loss spectrum and HOMER at values ​​(0°, 1°, 2°, 3°, 4°). As can be seen from the figure, at... θ At 0°, LP 01 Patterns and LPs 11 The mode's confinement loss is less than 0.27 dB / km and 3.36 × 10⁻⁶ dB / km, respectively, in the spectral region of 1.3–1.7 μm. 3 HOMER achieved a dB / km of 3.13×10 4 ;when θ When the confinement loss spectrum is 1°, the change is almost negligible; θ At =2°, LP 01 and LP 11 The mode's confined loss spectrum increases and decreases, respectively. When θ =4°, transmission band of 1.6 μm, LP 01 The mode's limiting loss is 0.10 dB / km, LP 11 The mode's limiting loss is 2.23 × 10⁻⁶. 3 dB / km, HOMER is 2.2×10 4 The offset angle of the double-nested tube. θ Although it reduced LP 11 Mode-limited loss, but the fiber can still maintain LP 01 The mode exhibits low-loss transmission and supports single-mode transmission performance. It can be seen that the anti-resonant hollow-core fiber provided by this invention can achieve low-loss transmission at a bias angle. θ Keep LP at no more than 4° 01 It features low-loss transmission in various modes and supports single-mode transmission performance.

[0047] In a preferred embodiment, the gap between the double-layer nested tube 2 and the two adjacent single-layer resonant tubes 1 is equal.

[0048] Reference Figure 14 , Figure 15 In one embodiment, LP was calculated through simulation. 01 Patterns and LPs 11 Patterns at different degrees of collapse T The confinement loss spectrum and HOMER at values ​​(0 μm, 1 μm, 2 μm, 3 μm, 4 μm). As can be seen from the figure, T At 0 μm, LP is achieved in the 1.3 μm -1.7 μm spectral region. 01 The mode's limiting loss is less than 27 dB / km, LP 11 The mode's limiting loss exceeds 8.12 × 10⁻⁶. 3 HOMER achieved a dB / km of 3.13×10 4 When the degree of collapse increases to T At a depth of 2 μm, the fundamental mode confinement loss increases to 0.49 dB / km, LP 11 The mode-limited loss is reduced to 2.27 × 10⁻⁶. 2 dB / km and HOMER greater than 1000 in the 1.3 μm-1.7 μm spectral range. As the collapse increases further, the fundamental mode and LP... 11 The mode limits the continued increase and decrease of losses. T =3 μm, at a wavelength of 1.5 μm, the fundamental mode limiting loss increases to 0.35 dB / km, LP 11 The mode-limited loss is reduced to 1.60 × 10⁻⁶. 2 With a dB / km ratio and a HOMER of 460, the optical fiber no longer exhibits single-mode performance. It can be seen that the anti-resonant hollow-core optical fiber provided by this invention has a collapse tolerance of 0-2 μm.

[0049] In the embodiment, the tangent point between the inner tube 3 and the outer tube 4 is located on the straight line connecting the tangent point of the outer tube 4 and the cladding and the center of the fiber core 6; the tangent point between the inner tube 3 and the outer tube 4 is located on the side near the cladding.

[0050] In one embodiment, the single-layer resonant tube 1, the double-layer nested tube 2, and the protective tube 5 are made of SiO2.

[0051] In one embodiment, the thicknesses of the single-layer resonant tube 1, the outer tube 4, and the inner tube 3 are all... t The diameter of fiber core 6 is D core The diameter of the single-layer resonant tube 1 is d tube The outer tube has a diameter of 4. d 1. Modeling anti-resonant hollow fiber based on COMSOL, and optimizing it. t ,D core , d tube and d 1. This enables a higher-order mode suppression ratio greater than 1000 in the 1.3 μm - 1.7 μm spectral range, achieving single-mode transmission while simultaneously achieving low-loss transmission of the fundamental mode.

[0052] The optimization t The process includes:

[0053] Fixed fiber core 6 diameter D core Single-layer resonant tube diameter 1 d tube outer tube diameter 4 d 1. Inner tube diameter 3 d 2. Optimization t The fundamental mode loss and higher-order mode confinement loss are obtained by... t The change curve and the suppression ratio of higher-order modes as a function of t The change curve graph determines t The preferred value.

[0054] In this embodiment, the diameter of the fiber core 6 is... D core =100 μm, diameter of single-layer resonant tube 1 d tube =60 μm, outer tube diameter 4 d 1 = 40 μm, inner tube diameter 3 d 2 = 20 μm. (Refer to...) Figure 2 , Figure 3 As can be seen from the figure, when the thickness of the single-layer resonant tube 1, the outer tube 4, and the inner tube 3 (hereinafter referred to as the resonant tube thickness) t When the core loss is relatively small, its core 6 fundamental mode loss is relatively small in the short-wavelength band; however, in the long-wavelength band, its core 6 fundamental mode loss increases significantly, such as... t At a thickness of 0.26 μm, the fundamental mode loss of the fiber core can reach 7.35 dB / km. This leads to excessive energy leakage during transmission. While the fiber confinement loss ratio is relatively stable at this point, the value is small, consistently less than 50. When the resonant tube thickness... t At a wavelength of 0.5 μm, the fundamental mode confinement loss of core 6 is less than 0.45 dB / km throughout the entire transmission window. Especially in the long-wavelength band, although the fundamental mode confinement loss of core 6 increases, the magnitude is small. The higher-order modes LP of core 6... 11 The loss spectrum shows a similar trend to the fundamental mode loss spectrum, but with the increase of the resonant tube thickness... t As the thickness of the resonant tube increases, the higher-order mode loss first decreases and then increases, reaching a maximum of 29.75 dB / km, at which point the limiting loss ratio is most stable, consistently above 60; when the thickness of the resonant tube... tWhen the thickness is 0.56 μm, only the center band HOMER reaches 60; therefore, when the resonant tube thickness is... t When the negative curvature anti-resonance condition is just met, i.e., the thickness of the resonant tube... t =0.5 μm, the coupling between the higher-order modes of the core 6 and the cladding modes causes a sharp increase in the higher-order mode loss across the entire transmission window, at which point the loss limit ratio is at its maximum and most stable. Therefore, in this preferred embodiment, the thickness of the single-layer resonant tube 1, the outer tube 4, and the inner tube 3 is... t The preferred value is 0.5 μm.

[0055] In one embodiment, the optimization D core The process includes:

[0056] The ratio of the diameter of a fixed single-layer resonant tube to the diameter of the fiber core. d tube / D core The ratio of the outer tube diameter to the fiber core diameter d 1 / D core The ratio of the inner tube diameter to the fiber core diameter d 2 / D core The thickness of the single-layer resonant tube, outer tube, and inner tube t ,optimization D core The fundamental mode loss and higher-order mode confinement loss are obtained by... D core The change curve and the suppression ratio of higher-order modes as a function of D core The change curve graph determines D core The preferred value.

[0057] In this embodiment, the diameter of the fiber core 6 is... D core =100 μm, the ratio of the diameter of the single-layer resonator tube 1 to the diameter of the fiber core. d tube = D core ×a, the ratio of the outer tube diameter to the fiber core diameter. d 1= D core ×b, the ratio of the inner tube diameter to the fiber core diameter. d 2= D core ×c, where a=0.6, b=0.4, c=0.2, and the thickness of the resonant tube. t =0.5 μm. (Reference) Figure 6 , Figure 7As the diameter of core 6 increases, the mode field diameter also increases, resulting in stronger light confinement capability of the fiber. The losses of both the fundamental and higher-order modes in core 6 decrease, and the confinement loss shows a direct correlation with the diameter of core 6. D core -1 Power pattern; In high-power laser transmission scenarios, selecting fibers with small mode field areas will induce significant nonlinear effects and may even damage the fiber. However, if a larger mode field area is selected, the higher-order mode confinement loss of the fiber will be too small compared to HOMER, which would prevent the fiber from performing single-mode transmission. Therefore, in this embodiment, a fiber core diameter of 6 is selected. D core =100 μm, at which point HOMER is 32 and the mode field area is 4754 μm. 2 .

[0058] In a preferred embodiment, the number of single-layer resonant tube 1 and double-layer nested tube 2 is five; and the number of single-layer resonant tube 1 and double-layer nested tube 2 was verified by simulation experiment.

[0059] Reference Figure 4 , Figure 5 In this embodiment, within the 1.2 μm - 2.0 μm spectral range, when the number of single-layer resonant tube 1 and double-layer nested tube 2 is five (i.e., five pairs of resonant tube structures), the fundamental mode and higher-order mode confinement losses during fiber transmission are both relatively small, with the fundamental mode loss being as low as 0.12 dB / km. At this point, the LP... 11 With a loss of 7.7 dB / km, the optical fiber can effectively lock in energy and has a relatively large loss limit, resulting in good single-mode transmission characteristics. However, with a four-pair resonator structure, the optical fiber's light-locking capability is poor, and the fundamental mode loss reaches a maximum of 15.75 dB / km. While the loss of the six-pair resonator structure is not significantly different from that of the five-pair structure, the HOMER value of the six-pair structure is lower than that of the five-pair structure, and the data fluctuates more, leading to poorer system stability. Therefore, in this embodiment, the number of single-layer resonator 1 and double-layer nested tube 2 is five.

[0060] In one embodiment, the optimization d tube , d The process of step 1 includes:

[0061] Fixed outer tube diameter d 1. Inner tube diameter d 2. Thickness of the single-layer resonant tube, outer tube, and inner tube t Core diameter D core ,optimization d tube / Dcore The fundamental mode loss and higher-order mode confinement loss are obtained by... d tube / D core The change curve and the suppression ratio of higher-order modes as a function of d tube / D core The change curve graph determines d tube / D core The preferred value;

[0062] fixed d tube / D core for d tube / D core The preferred value, optimization d 1 / D core The fundamental mode loss and higher-order mode confinement loss are obtained by... d 1 / D core The change curve and the suppression ratio of higher-order modes as a function of d 1 / D core The change curve graph determines d 1 / D core The preferred value.

[0063] In this embodiment, the diameter of the fiber core 6 is... D core =100 μm, diameter of single-layer resonant tube 1 d tube = D core ×a, outer tube diameter 4 d 1= D core ×b, inner tube diameter 3 d 2= D core ×c, where c=0.2, is the thickness of the resonant tube. t =0.5 μm. (Reference) Figures 8-11 When a = 0.71 (i.e. d tube =71 μm) and b=0.36 (i.e. d The sixth higher-order mode LP of the fiber core occurred at 1=36 μm. 11 Coupled with cladding mode, resulting in LP 11The sudden increase; therefore, the point (0.71, 0.36) is the sought resonance coupling point, at which the mode field distribution is as follows. Figure 8 As shown in the figure, the higher-order mode LP of the fiber core 6 is clearly displayed. 11 Similar to the cladding mode, the higher-order mode loss is 6.55 × 10⁻⁶. 3 dB / km, fundamental mode loss is 0.19 dB / km, and higher-order mode loss ratio is 3.12×10 4 Optical fiber has low fundamental mode loss and good single-mode transmission characteristics.

[0064] In one embodiment, reference is made to Figure 12 Fiber core diameter 6 D core =100 μm, diameter of single-layer resonant tube 1 d tube =71 μm, outer tube diameter 4 d 1 = 36 μm, inner tube diameter 3 d 2 = 20 μm, resonant tube thickness t =0.5 μm, with five single-layer resonator tubes 1 and double-layer nested tubes 2. In the spectral range of 1.3 μm - 1.7 μm, the core fundamental mode confinement loss is less than 0.27 dB / km, and at 1.4 μm, it is as low as 0.16 dB / km. Higher-order modes LP... 11 The limiting losses are all greater than 3.36 × 10. 3 dB / km, resulting in a limiting loss ratio of 10 for HOMER. 4 The magnitude is far greater than the condition that HOMER is greater than 1000. Therefore, the anti-resonant hollow fiber in this embodiment can perform single-mode transmission.

[0065] In one embodiment, reference is made to Figure 13 Fiber core diameter 6 D core =100 μm, diameter of single-layer resonant tube 1 d tube =71 μm, outer tube diameter 4 d 1 = 36 μm, inner tube diameter 3 d 2 = 20 μm, resonant tube thickness t =0.5 μm, the number of single-layer resonator 1 and double-layer nested 2 is five. In the spectral range of 1.3 μm - 1.7 μm, the mode field area decreases with increasing wavelength. In the short-wavelength band (1.3 μm), the mode field area is 4808 μm. 2 Throughout the entire transmission window, the mode field area is greater than 4720 μm. 2Since the mode field diameters are all greater than 77 μm, the anti-resonant hollow fiber in this embodiment can be regarded as a large mode field negative curvature anti-resonant hollow fiber.

[0066] As can be seen from the above, the anti-resonant hollow-core optical fiber provided in this embodiment has a core 6-fundamental mode LP in the transmission band of 1.3 μm - 1.7 μm. 01 The losses are now all below 0.27 dB / km, and the high-order mode LP 11 The limiting losses are all greater than 3.36 × 10. 3 dB / km; at 1.4 μm, the core fundamental mode LP 01 With a minimum limiting loss of 0.16 dB / km, high-order mode LP 11 The limiting loss is 4.2 × 10⁻⁶. 3 dB / km, HOMER value is 2.6×10 4 The model area is 4785 μm. 2 This achieves low-loss transmission of the fiber core fundamental mode under large mode field conditions and fiber single-mode transmission characteristics.

[0067] In one embodiment, the aforementioned anti-resonant hollow fiber is used for optical fiber communication.

[0068] Matters not covered in this invention are common knowledge.

[0069] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0070] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

[0071] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An anti-resonant hollow-core optical fiber, characterized in that, It includes a cladding and a fiber core; the cladding is provided with a protective tube on the outside, and multiple single-layer resonant tubes and multiple double-layer nested tubes are provided inside the cladding and tangent to the cladding. The single-layer resonant tubes are evenly distributed in a circle with the center of the fiber core as the center, and a double-layer nested tube is arranged between every two single-layer resonant tubes; the diameter of the single-layer resonant tube is larger than the diameter of the double-layer nested tube; the double-layer nested tube includes an inner tube and an outer tube, and the inner tube is tangent to the outer tube. The number of the single-layer resonant tube and the double-layer nested tube is five; The thickness of the single-layer resonant tube, the outer tube, and the inner tube are all... t The diameter of the fiber core is D core The diameter of the single-layer resonant tube is d tube The outer tube diameter is d 1. Modeling anti-resonant hollow fiber based on COMSOL, and optimizing it. t , D core , d tube and d 1. This enables a higher-order mode suppression ratio greater than 1000 in the 1.3 μm - 1.7 μm spectral range, achieving single-mode transmission while simultaneously achieving low-loss transmission of the fundamental mode.

2. The anti-resonant hollow-core optical fiber as described in claim 1, characterized in that, The gap between the double-layer nested tube and the two adjacent single-layer resonant tubes is equal.

3. The anti-resonant hollow-core optical fiber as described in claim 1, characterized in that, The point of tangency between the inner tube and the outer tube lies on the straight line connecting the point of tangency between the outer tube and the cladding and the center of the fiber core; the point of tangency between the inner tube and the outer tube lies on the side closer to the cladding.

4. The anti-resonant hollow-core optical fiber as described in claim 1, characterized in that, The thickness of the protective tube is 10 μm.

5. The anti-resonant hollow-core optical fiber as described in claim 1, characterized in that, The optimization t The process includes: Fixed fiber core diameter D core single-layer resonator diameter d tube outer tube diameter d 1. Inner tube diameter d 2. Optimization t The fundamental mode loss and higher-order mode confinement loss are obtained by... t The change curve and the suppression ratio of higher-order modes as a function of t The change curve graph determines t The preferred value.

6. The anti-resonant hollow-core optical fiber as described in claim 1, characterized in that, The optimization D core The process includes: The ratio of the diameter of a fixed single-layer resonant tube to the diameter of the fiber core. d tube / D core The ratio of the outer tube diameter to the fiber core diameter d 1 / D core The ratio of the inner tube diameter to the fiber core diameter d 2 / D core The thickness of the single-layer resonant tube, outer tube, and inner tube t ,optimization D core The fundamental mode loss and higher-order mode confinement loss are obtained by... D core The change curve and the suppression ratio of higher-order modes as a function of D core The change curve graph determines D core The preferred value.

7. The anti-resonant hollow-core optical fiber as described in claim 1, characterized in that, The optimization d tube , d The process of step 1 includes: Fixed outer tube diameter d 1. Inner tube diameter d 2. Thickness of the single-layer resonant tube, outer tube, and inner tube. t Core diameter D core ,optimization d tube / D core The fundamental mode loss and higher-order mode confinement loss are obtained by... d tube / D core The change curve and the suppression ratio of higher-order modes as a function of d tube / D core The change curve graph determines d tube / D core The preferred value; fixed d tube / D core for d tube / D core The preferred value, optimization d 1 / D core The fundamental mode loss and higher-order mode confinement loss are obtained by... d 1 / D core The change curve and the suppression ratio of higher-order modes as a function of d 1 / D core The change curve graph determines d 1 / D core The preferred value.

8. Applications of anti-resonant hollow optical fiber, characterized in that, Optical fiber communication is performed using anti-resonant hollow optical fiber as described in any one of claims 1 to 7.

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