Anti-resonance hollow-core optical fiber and application thereof

Abstract

The invention provides an anti-resonance hollow-core optical fiber and application thereof. The anti-resonance hollow-core optical fiber comprises a cladding and a fiber core, a protective tube is arranged outside the cladding, a plurality of single-layer resonant tubes and a plurality of double-layer nested tubes which are tangent to the cladding are arranged in the cladding, the single-layer resonant tubes are circumferentially and uniformly distributed by taking the circle center of the fiber core as the center, and one double-layer nested tube is arranged between every two single-layer resonant tubes; the diameter of the single-layer resonant tube is greater than that of the double-layer nested tube; the double-layer nesting pipe comprises an inner pipe and an outer pipe, and the inner pipe and the outer pipe are internally tangent. According to the invention, coupling of a fiber core LP11 mode and a cladding mode is realized through the single-layer resonant tube, so that the mode capability of a high-order mode is leaked to realize single-mode transmission of the optical fiber; and fiber core fundamental mode energy is locked in the fiber core through a double-layer nested tube arranged between the two single-layer resonant tubes, so that fiber fundamental mode low-loss transmission is realized. According to the invention, the fundamental mode limiting loss can be effectively reduced, and optical fiber single-mode transmission is realized through mode coupling.

Description

Technical Field

[0001] The present invention mainly relates to the field of fiber laser technology, and particularly to anti-resonant hollow-core fibers and their applications. Background Art

[0002] Hollow-core fibers (HCFs), as a special type of fiber, with their unique property of confining light waves to propagate in air, have characteristics such as low optical nonlinearity, low material absorption loss, high damage threshold, and low time delay. And such fibers are widely used in multiple fields, such as high-power transmission, fiber communication, and supercontinuum generation. Hollow-core fibers mainly include photonic bandgap hollow-core fibers (PBG-HCFs) and anti-resonant hollow-core fibers (AR-HCFs). However, compared with PBG-HCFs, AR-HCFs have a larger transmission bandwidth by reducing the interaction between the core light and the cladding material during transmission.

[0003] To achieve low-loss fundamental mode and excellent single-mode transmission characteristics of AR-HCFs, researchers have designed various novel anti-resonant hollow-core fiber structures. In 2016, S. Habib et al. proposed an anisotropic anti-resonant tube hollow-core fiber with a core diameter of 30 μm, achieving a high-order mode extinction ratio (HOMER) greater than 1000 in the spectral range of 1.0 - 1.65 μm, and the minimum confinement loss of the LP 01 mode was less than 5 dB / km at 1.06 μm. In 2018, S. Yan et al. proposed a novel double-ring anti-resonant hollow-core fiber with a core diameter of 70 μm, and the minimum confinement loss of the LP 01 mode was 0.29 dB / km, and the HOMER of this fiber exceeded 1000 in the spectral range of 2.5 - 3.3 μm. In 2019, S. Habib et al. developed a five-tube nested anti-resonant hollow-core fiber with a core diameter of 30.5 μm, and the HOMER reached a record of 1.2×10 4 at 1.55 μm, and in the spectral range of 1.33 - 1.66 μm, the minimum confinement loss of the LP 01 mode was 0.45 dB / km. In 2022, Y. Zhou et al. proposed a novel double-triangle symmetric anti-resonant hollow-core fiber with a core diameter of 50 μm. Simulations showed that the confinement loss of the LP 01 mode was less than 1 dB / km in the spectral range of 1 - 1.1 μm, and the HOMER exceeded 1000. It has been found that it is difficult to achieve low-loss fundamental mode transmission and single-mode transmission of anti-resonant hollow-core fibers while achieving high-power transmission at a relatively large core diameter. Summary of the Invention

[0004] In view of the deficiencies existing in the prior art, the present invention provides an anti-resonant hollow fiber and its applications.

[0005] To achieve the above object, the technical solution adopted by the present invention is as follows: On the one hand, the present invention provides an anti-resonant hollow fiber, including a cladding and a core; a protective tube is provided outside the cladding, and a plurality of single-layer resonant tubes and a plurality of double-layer nested tubes tangent to the cladding are provided inside the cladding. The single-layer resonant tubes are evenly distributed in a circle with the center of the 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 internally tangent to the outer tube.

[0006] Further, the gap between the double-layer nested tube and the two adjacent single-layer resonant tubes is equal.

[0007] Further, the tangent point of the internal tangency between the inner tube and the outer tube is located on the straight line connecting the tangent point of the outer tube and the cladding and the center of the core; the tangent point of the internal tangency between the inner tube and the outer tube is located on the side close to the cladding.

[0008] Further, the thickness of the protective tube is 10 μm.

[0009] Further, the number of the single-layer resonant tubes and the double-layer nested tubes is five.

[0010] Further, the thicknesses of the single-layer resonant tube, the outer tube, and the inner tube are all t , the diameter of the core is D core , the diameter of the single-layer resonant tube is d tube , the diameter of the outer tube is d 1 , based on COMSOL, a model of the anti-resonant hollow fiber is established. By optimizing t , D core , d tube and d 1 , the high-order mode suppression ratio is greater than 1000 in the spectral range of 1.3 μm - 1.7 μm, realizing single-mode transmission and simultaneously realizing low-loss transmission of the fundamental mode.

[0011] Further, the process of the optimization t includes: Fix the core diameter D core , the diameter of the single-layer resonant tube d tube , the diameter of the outer tube d 1 , the diameter of the inner tube d2 , optimize t , and obtain the curve graphs of the fundamental mode loss and the high-order mode confinement loss varying with t and the curve graph of the high-order mode suppression ratio varying with t , and determine the t preferred value.

[0012] Further, the process of the said optimization D core includes: Fix the ratio of the diameter of the single-layer resonant tube to the core diameter d tube / D core , the ratio of the outer tube diameter to the core diameter d 1 / D core , the ratio of the inner tube diameter to the core diameter d 2 / D core , the thicknesses of the single-layer resonant tube, the outer tube and the inner tube t , optimize D core , and obtain the curve graphs of the fundamental mode loss and the high-order mode confinement loss varying with D core and the curve graph of the high-order mode suppression ratio varying with D core , and determine the D core preferred value.

[0013] Further, the process of the said optimization d tube , d 1 includes: Fix the outer tube diameter d 1 , the inner tube diameter d 2 , the thicknesses of the single-layer resonant tube, the outer tube and the inner tube t , the core diameter D core , optimize d tube / D core , and obtain the curve graphs of the fundamental mode loss and the high-order mode confinement loss varying with d tube / D core and the curve graph of the high-order mode suppression ratio varying with d tube / D coreThe change curve diagram to determine d tube / D core The preferred value of; Fix d tube / D core As d tube / D core The preferred value of to optimize d 1 / D core and obtain the fundamental mode loss and high-order mode confinement loss as d 1 / D core The change curve diagram of and the high-order mode suppression ratio as d 1 / D core The change curve diagram to determine d 1 / D core The preferred value of.

[0014] On the other hand, the present invention also provides an application of an anti-resonant hollow fiber, using the above anti-resonant hollow fiber for optical fiber communication.

[0015] Compared with the prior art, the beneficial technical effects of the present invention are as follows: The anti-resonant hollow fiber and its application provided by the present invention can achieve low-loss transmission of the fundamental mode in the spectral range of 1.3 μm - 1.7 μm and an ultra-high high-order mode suppression ratio (HOMER) under the condition of a large mode field to achieve single-mode transmission. Specifically, the coupling between the core LP 11 mode and the cladding mode is realized through a single-layer resonant tube, so that the high-order mode ability leaks to achieve single-mode transmission of the optical fiber; then, the fundamental mode energy of the core is locked in the core by a double-layer nested tube arranged between two single-layer resonant tubes to achieve low-loss transmission of the fundamental mode of the optical fiber; through the cross-arrangement structure between the single-layer resonant tube and the double-layer nested tube, the fundamental mode confinement loss can be effectively reduced and single-mode transmission of the optical fiber can be achieved through mode coupling. Description of the Drawings

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.

[0017] Figure 1 Schematic cross-sectional view of an anti-resonant hollow fiber provided for an embodiment; Figure 2 Influence curve of the thickness of the single-layer resonant tube, outer tube and inner tube on the fundamental mode loss and high-order mode confinement loss provided for an embodiment; Figure 3 Influence curve of the thickness of the single-layer resonant tube, outer tube and inner tube on the high-order mode confinement loss ratio HOMER provided for an embodiment; Figure 4 Influence curve of the number of single-layer resonant tubes and double-layer nested tubes on the fundamental mode loss and high-order mode confinement loss ratio provided for an embodiment; Figure 5 Influence curve of the number of single-layer resonant tubes and double-layer nested tubes on the high-order mode confinement loss ratio HOMER provided for an embodiment; Figure 6 Influence curve of the core diameter on the fundamental mode loss and high-order mode confinement loss ratio provided for an embodiment; Figure 7 Influence diagram of the core diameter on the high-order mode confinement loss ratio HOMER and the mode field area provided for an embodiment; Figure 8 Influence curve of the effective refractive index of the core fundamental mode, high-order mode and cladding mode in the case of different ratios of the single-layer resonant tube diameter to the core diameter provided for an embodiment; Figure 9 Influence diagram of the core fundamental mode, high-order mode confinement loss and their ratio in the case of different ratios of the single-layer resonant tube diameter to the core diameter provided for an embodiment; Figure 10 Influence curve of the effective refractive index of the core fundamental mode, high-order mode and cladding mode in the case of different ratios of the outer tube diameter to the core diameter in different double-layer nested tubes provided for an embodiment; Figure 11 Influence diagram of the core fundamental mode, high-order mode confinement loss and their ratio in the case of different ratios of the outer tube diameter to the core diameter in different double-layer nested tubes provided for an embodiment; Figure 12 Influence diagram of the high-order mode, fundamental mode confinement loss and their ratio of the fiber core in the spectral range of 1.3 μm - 1.7 μm provided for an embodiment; Figure 13 The diagram of the mode field diameter and mode field area of the fundamental mode in the fiber core within the spectral range of 1.3 μm - 1.7 μm provided for an embodiment; Figure 14 For an embodiment, the fundamental mode and LP of the fiber within the spectral range of 1.3 μm - 1.7 μm with different degrees of collapse T values 11 Schematic diagram of the confinement loss spectrum; Figure 15 For an embodiment, the influence of different degrees of collapse of the fiber within the spectral range of 1.3 μm - 1.7 μm T values on the high - order mode confinement loss ratio HOMER; Curve graph Figure 16 For an embodiment, the fundamental mode and LP of the fiber within the spectral range of 1.3 μm - 1.7 μm with different offset angles θ values 11 Schematic diagram of the confinement loss spectrum; Figure 17 For an embodiment, the influence of different offset angles of the fiber within the spectral range of 1.3 μm - 1.7 μm θ values on the high - order mode confinement loss ratio HOMER; Curve graph

[0018] Annotation of the attached figure: 1. Single - layer resonant tube; 2. Double - layer nested tube; 3. Inner tube; 4. Outer tube; 5. Protective tube; 6. Fiber core. Specific implementation manner

[0019] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than 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 making creative efforts belong to the scope of protection of the present invention.

[0020] Referring to Figure 1 , an embodiment provides an anti - resonant hollow fiber, including a cladding and a fiber core 6; a protective tube 5 is provided outside the cladding, and a plurality of single - layer resonant tubes 1 and a plurality of double - layer nested tubes 2 tangent to the cladding are provided inside the cladding. The single - layer resonant tubes 1 are arranged in an array with the center of the fiber 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 is internally tangent to the outer tube 4.

[0021] The fiber core LP is realized through the single - layer resonant tube 11The mode is coupled with the cladding mode, so that the high-order mode power leaks to achieve single-mode transmission of the optical fiber; then, the fundamental mode power of the core is locked in the core by a double-layer sleeve arranged between two single-layer resonant tubes to achieve low-loss transmission of the fundamental mode of the optical fiber; through the cross-arrangement structure between the single-layer resonant tube and the double-layer sleeve, the confinement loss of the fundamental mode can be effectively reduced and single-mode transmission of the optical fiber can be achieved through mode coupling.

[0022] The thickness of the protective tube is 10 μm.

[0023] Refer to Figure 16 、 Figure 17 , in an embodiment, the LP 01 mode and the LP 11 mode at different bias angle θ values (0°, 1°, 2°, 3°, 4°) are calculated by simulation for the confinement loss spectrum and HOMER. It can be seen from the figure that when θ = 0°, the confinement losses of the LP 01 mode and the LP 11 mode are less than 0.27 dB / km and 3.36×10 3 dB / km respectively in the spectral region of 1.3 - 1.7 μm, and the HOMER reaches 3.13×10 4 ; when θ = 1°, the change in the confinement loss spectrum is almost negligible; when θ = 2°, the confinement loss spectra of the LP 01 and LP 11 modes increase and decrease respectively. When θ = 4° and the transmission band is 1.6 μm, the confinement loss of the LP 01 mode is 0.10 dB / km, the confinement loss of the LP 11 mode is 2.23×10 3 dB / km, and the HOMER is 2.2×10 4 . Although the bias angle θ of the double-layer sleeve reduces the confinement loss of the LP 11 mode, the optical fiber can still maintain low-loss transmission of the LP 01 mode and support single-mode transmission performance. It can be seen that the anti-resonant hollow-core optical fiber provided by the present invention can maintain low-loss transmission of the LP θ mode and support single-mode transmission performance when the bias angle 01 does not exceed 4°.

[0024] In a preferred embodiment, the gaps between the double-layer sleeve 2 and the two adjacent single-layer resonant tubes 1 are equal.

[0025] Refer to Figure 14, Figure 15 , in one embodiment, the LP 01 mode and the LP 11 mode at different collapse degrees T values (0 μm, 1 μm, 2 μm, 3 μm, 4 μm) of the confinement loss spectra and HOMER are calculated by simulation. It can be seen from the figure that T when 01 = 0 μm, in the spectral region of 1.3 μm - 1.7 μm, the confinement loss of the LP 11 mode is less than 27 dB / km, the confinement loss of the LP 3 mode exceeds 8.12×10 4 dB / km, and the HOMER reaches 3.13×10 T When the collapse degree is increased to 11 = 2 μm, the confinement loss of the fundamental mode increases to 0.49 dB / km, and the confinement loss of the LP 2 mode decreases to 2.27×10 11 dB / km and the HOMER is greater than 1000 in the spectral range of 1.3 μm - 1.7 μm. When the collapse degree further increases, the confinement losses of the fundamental mode and the LP T = 3 μm, at a wavelength of 1.5 μm, the confinement loss of the fundamental mode increases to 0.35 dB / km, and the confinement loss of the LP 11 mode decreases to 1.60×10 2 dB / km and the HOMER is 460. At this time, the optical fiber no longer has single-mode performance. It can be seen that the anti-resonant hollow-core optical fiber provided by the present invention has an anti-collapse tolerance of 0 - 2 μm.

[0026] In the embodiment, the tangent point where the inner tube 3 is internally tangent to 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 core 6; the tangent point where the inner tube 3 is internally tangent to the outer tube 4 is located on the side near the cladding.

[0027] In one embodiment, the single-layer resonant tube 1, the double-layer nested tube 2, and the protective tube 5 are made of SiO 2 .

[0028] 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 the core 6 is D core , the diameter of the single-layer resonant tube 1 is d tube , the diameter of the outer tube 4 is d 1 , the anti-resonant hollow-core optical fiber is modeled based on COMSOL, and by optimizing t ,D core , d tube and d 1 such that the high - order mode suppression ratio is greater than 1000 in the spectral range of 1.3 μm - 1.7 μm, enabling single - mode transmission and simultaneously achieving low - loss transmission of the fundamental mode.

[0029] The said optimization t process includes: Fix the diameter of the core 6 D core , the diameter of the single - layer resonant tube 1 d tube , the diameter of the outer tube 4 d 1 , the diameter of the inner tube 3 d 2 , optimize t to obtain the variation curves of the fundamental - mode loss and the high - order - mode confinement loss with t and the variation curve of the high - order mode suppression ratio with t , and determine the preferred value of t .

[0030] In this embodiment, the diameter of the core 6 D core = 100 μm, the diameter of the single - layer resonant tube 1 d tube = 60 μm, the diameter of the outer tube 4 d 1 = 40 μm, the diameter of the inner tube 3 d 2 = 20 μm. Referring to Figure 2 , Figure 3 , it can be seen from the figure that when the thicknesses 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 ) are relatively small, in the short - wavelength band, the fundamental - mode loss of the core 6 is small; but in the long - wavelength band, the fundamental - mode loss of the core 6 increases significantly. For example, when t = 0.26 μm, the fundamental - mode loss of the core 6 can reach 7.35 dB / km. In this case, too much of the transmitted energy will leak. At this time, although the fiber confinement loss ratio is relatively stable, the value is small, all less than 50; when the resonant tube thickness t = 0.5 μm, in the entire transmission window, the fundamental - mode confinement loss of the core 6 is less than 0.45 dB / km. Especially in the long - wavelength band, although the fundamental - mode confinement loss of the core 6 increases, the amplitude is small; the loss spectrum of the high - order mode LP 11 of the core 6 is similar to the fundamental - mode loss spectrum, but as the resonant tube thickness tWith the continuous increase of t , the loss of the high-order mode first decreases and then increases, reaching a maximum of 29.75 dB / km. At this time, the confinement loss ratio is the most stable, all above 60. When the thickness of the resonant tube t is 0.56 μm, only the central band HOMER reaches 60. Therefore, when the thickness of the resonant tube t just satisfies the negative curvature anti-resonance condition, that is, when the thickness of the resonant tube t is 0.5 μm, the high-order mode of the core 6 couples with the cladding mode, resulting in a sharp increase in the loss of the high-order mode over the entire transmission window. At this time, the confinement loss ratio is the largest and the most stable. Therefore, in this preferred embodiment, the thicknesses of the single-layer resonant tube 1, the outer tube 4, and the inner tube 3

[0031] in the preferred value is 0.5 μm. D core In one embodiment, the optimization process includes: d tube / D core , fixing the ratio of the diameter of the single-layer resonant tube to the diameter of the core d 1 / D core , the ratio of the diameter of the outer tube to the diameter of the core d 2 / D core , the ratio of the diameter of the inner tube to the diameter of the core t , the thicknesses of the single-layer resonant tube, the outer tube, and the inner tube D core , optimizing D core to obtain the curve graphs of the fundamental mode loss and the high-order mode confinement loss with respect to D core and the curve graph of the high-order mode suppression ratio with respect to D core , and determining the preferred value of

[0032] In this embodiment, the diameter of the core 6 D core is 100 μm, the ratio of the diameter of the single-layer resonant tube 1 to the diameter of the core d tube = D core × a, the ratio of the diameter of the outer tube 4 to the diameter of the core d 1 = D core × b, the ratio of the diameter of the inner tube 3 to the diameter of the core d 2 = Dcore × c, where a = 0.6, b = 0.4, c = 0.2, and the thickness of the resonant tube t = 0.5 μm. Refer to Figure 6 、 Figure 7 , as the diameter of the core 6 increases, the mode field diameter also increases, the ability of the optical fiber to confine light is stronger, the losses of the fundamental mode and higher-order modes of the core 6 are both reduced, and the confinement loss and the diameter of the core 6 show D core -1 a power-law pattern; in the high-power laser transmission scenario, selecting an optical fiber with a smaller mode field area will cause significant nonlinear effects and may even damage the optical fiber. However, if a larger mode field area is selected, the confinement loss ratio of the higher-order modes of the optical fiber, HOMER, is too small, resulting in the inability of the optical fiber to perform single-mode transmission. Therefore, in this embodiment, the diameter of the core 6 is selected D core = 100 μm, at this time HOMER is 32, and the mode field area is 4754 μm 2 .

[0033] In a preferred embodiment, the number of the single-layer resonant tubes 1 and the double-layer nested tubes 2 is five; and the number of the single-layer resonant tubes 1 and the double-layer nested tubes 2 set is verified through simulation experiments.

[0034] Refer to Figure 4 、 Figure 5 , in this embodiment, in the spectral range of 1.2 μm - 2.0 μm, when the number of the single-layer resonant tubes 1 and the double-layer nested tubes 2 is five (i.e., five pairs of resonant tube structures), the confinement losses of the fundamental mode and higher-order modes during the optical fiber transmission are both small. The minimum fundamental mode loss is 0.12 dB / km. At this time, the LP 11 loss is 7.7 dB / km, which can lock the energy in the optical fiber to a large extent, and the confinement loss ratio is large. Therefore, the single-mode transmission characteristics are good; when there are four pairs of resonant tube structures, the light locking ability of the optical fiber is poor, and the maximum fundamental mode loss reaches 15.75 dB / km; when there are six pairs of resonant tube structures, the loss of the optical fiber is not much different from that of the five-pair resonant tube structure. However, from the perspective of single-mode characteristics, the HOMER value of the six-pair resonant tube structure is lower than that of the five-pair resonant tube structure, and the data fluctuation is large, and the system stability is poor. Therefore, in this embodiment, the number of the single-layer resonant tubes 1 and the double-layer nested tubes 2 is five.

[0035] In an embodiment, the optimization d tube 、 d 1 process includes: Fix the outer tube diameter d 1 , the inner tube diameter d2 The thicknesses of the single-layer resonant tube, the outer tube, and the inner tube t The core diameter D core Optimization d tube / D core To obtain the curve graphs of the fundamental mode loss and the high-order mode confinement loss versus d tube / D core and the curve graph of the high-order mode suppression ratio versus d tube / D core and determine the preferred values of d tube / D core ; Fix d tube / D core as the preferred value of d tube / D core and optimize d 1 / D core To obtain the curve graphs of the fundamental mode loss and the high-order mode confinement loss versus d 1 / D core and the curve graph of the high-order mode suppression ratio versus d 1 / D core and determine the preferred values of d 1 / D core .

[0036] In this embodiment, the diameter of the core 6 D core = 100 μm, the diameter of the single-layer resonant tube 1 d tube = D core ×a, the diameter of the outer tube 4 d 1 = D core ×b, the diameter of the inner tube 3 d 2 = D core ×c, where c = 0.2, the thickness of the resonant tube t= 0.5 μm. Refer to Figures 8 - 11 , when a = 0.71 (i.e., d tube = 71 μm) and b = 0.36 (i.e., d 1 = 36 μm), the mode coupling between the high-order mode LP 11 of the fiber core 6 and the cladding mode occurs, resulting in a sudden increase in LP 11 ; therefore, the point (0.71, 0.36) is the resonance coupling point sought. At this special point, the mode field distribution is as Figure 8 shown, and the figure clearly shows that the high-order mode LP 11 of the core 6 is connected to the cladding mode. At this time, the high-order mode loss is 6.55×10 3 dB / km, the fundamental mode loss is 0.19 dB / km, and the high-order mode loss ratio is 3.12×10 4 . The fiber has low fundamental mode loss and good single-mode transmission characteristics.

[0037] In one embodiment, refer to Figure 12 , the diameter of the core 6 D core = 100 μm, the diameter of the single-layer resonance tube 1 d tube = 71 μm, the diameter of the outer tube 4 d 1 = 36 μm, the diameter of the inner tube 3 d 2 = 20 μm, the thickness of the resonance tube t = 0.5 μm. The number of the single-layer resonance tube 1 and the double-layer nested tube 2 is five. In the spectral range of 1.3 μm - 1.7 μm, the confinement loss of the core fundamental mode is less than 0.27 dB / km, and at 1.4 μm, it is as low as 0.16 dB / km at minimum. The confinement loss of the high-order mode LP 11 is greater than 3.36×10 3 dB / km. The confinement loss ratio HOMER of the two is of the order of 10 4 , far exceeding the condition that HOMER is greater than 1000. Therefore, the anti-resonant hollow-core fiber in this embodiment can perform single-mode transmission.

[0038] In one embodiment, refer to Figure 13 , the diameter of the core 6 D core = 100 μm, the diameter of the single-layer resonance tube 1 d tube = 71 μm, the diameter of the outer tube 4 d 1 = 36 μm, the diameter of the inner tube 3 d 2= 20 μm, thickness of the resonant tube t = 0.5 μm. The number of single-layer resonant tubes 1 and double-layer nested tubes 2 is five. In the spectral range of 1.3 μm - 1.7 μm, the mode field area decreases with the increase of wavelength. At the short wavelength band (1.3 μm), the mode field area is 4808 μm 2 , and throughout the transmission window, the mode field area is greater than 4720 μm 2 , and the mode field diameter is greater than 77 μm. Therefore, the anti-resonant hollow-core fiber in this embodiment can be regarded as a large mode field negative curvature anti-resonant hollow-core fiber.

[0039] As can be seen from the above, for the anti-resonant hollow-core fiber provided in this embodiment within the transmission band of 1.3 μm - 1.7 μm, the fundamental mode LP of the fiber core 6 01 has a confinement loss lower than 0.27 dB / km, and the high-order mode LP 11 has a confinement loss greater than 3.36×10 3 dB / km; at 1.4 μm, the fundamental mode LP of the fiber core 01 has a minimum confinement loss of 0.16 dB / km, and the high-order mode LP 11 has a confinement loss of 4.2×10 3 dB / km, and the HOMER value is 2.6×10 4 , and the mode field area is 4785 μm 2 , realizing low-loss transmission of the fundamental mode of the fiber core under the condition of large mode field and the single-mode transmission characteristic of the optical fiber.

[0040] In one embodiment, the above anti-resonant hollow-core fiber is used for optical fiber communication.

[0041] Matters not described in detail in this invention are well-known technologies.

[0042] The technical features of the above embodiments can be combined arbitrarily. For the sake of brief description, 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, it should be considered as the scope described in this specification.

[0043] The above-described embodiments merely represent several implementation manners of this application. Their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of this application, several deformations and improvements can still be made, and these all belong to the protection scope of this application. Therefore, the protection scope of this application should be subject to the appended claims.

[0044] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An antiresonant hollow core optical fiber, characterized in that: It comprises a cladding and a fiber core; a protective tube is arranged outside the cladding, and a plurality of single-layer resonance tubes and a plurality of double-layer nested tubes tangent to the cladding are arranged inside the cladding, the single-layer resonance 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 resonance tubes; the diameter of the single-layer resonance tube is greater than the diameter of the double-layer nested tubes; the double-layer nested tubes comprise an inner tube and an outer tube, and the inner tube is internally cut into the outer tube.

2. The antiresonant hollow core optical fiber according to claim 1, wherein: The gap between the double-layer nested tube and two adjacent single-layer resonant tubes is equal.

3. The antiresonant hollow core optical fiber according to claim 1, wherein: The tangent point between the inner tube and the outer tube is located on the straight line formed by the tangent point between the outer tube and the cladding and the center of the fiber core; the tangent point between the inner tube and the outer tube is located on the side close to the cladding.

4. The antiresonant hollow core optical fiber according to claim 1, wherein: The thickness of the protective tube is 10 μm.

5. The antiresonant hollow core optical fiber according to claim 1, wherein: The number of the single-layer resonance tubes and double-layer nested tubes is five.

6. The antiresonant hollow core optical fiber according to claim 1, wherein: The thickness of the single-layer resonance tube, the outer tube and the inner tube are t , the diameter of the fiber core is D core , the diameter of a single-layer resonance tube is d tube , the outer tube diameter is d 1. Modeling of antiresonant hollow core fiber based on COMSOL, through optimization t , D core , d tube and d 1, so that the high-order mode suppression ratio is greater than 1000 in the 1.3 μm -1.7 μm spectral range, single-mode transmission is achieved, and low-loss transmission of the fundamental mode is achieved at the same time.

7. The antiresonant hollow core optical fiber according to claim 6, characterized in that: The optimization t The process includes: Fixed core diameter D core , single-layer resonance tube diameter d tube , outer tube diameter d 1. Inner tube diameter d 2. Optimization t , the fundamental mode loss and the higher-order mode limitation loss are obtained as t The change curve of the high-order mode suppression ratio t The change curve diagram of t The preferred value of .

8. The antiresonant hollow core optical fiber according to claim 6, wherein: The optimization D core The process includes: Fixed ratio of single-layer resonance tube diameter to fiber core diameter d tube / D core , the ratio of the outer tube diameter to the core diameter d 1 / D core , the ratio of the inner tube diameter to the core diameter d 2 / D core , the thickness of the single-layer resonance tube, outer tube and inner tube t ,optimization D core , the fundamental mode loss and the higher-order mode limitation loss are obtained as D core The change curve of the high-order mode suppression ratio D core The change curve diagram of D core The preferred value of .

9. The antiresonant hollow core optical fiber according to claim 6, wherein: The optimization d tube , d 1 The process includes: Fixed outer tube diameter d 1. Inner tube diameter d 2. The thickness of the single-layer resonance tube, outer tube and inner tube t , core diameter D core ,optimization d tube / D core , the fundamental mode loss and the higher-order mode limitation loss are obtained as d tube / D core The change curve of the high-order mode suppression ratio d tube / D core The change curve diagram of d tube / D core The preferred value of fixed d tube / D core for d tube / D core The preferred value of d 1 / D core , the fundamental mode loss and the higher-order mode limitation loss are obtained as d 1 / D core The change curve of the high-order mode suppression ratio d 1 / D core The change curve diagram of d 1 / D core The preferred value of .

10. Application of antiresonant hollow core optical fiber, characterized in that: Optical fiber communication is performed using the antiresonant hollow core optical fiber as claimed in any one of claims 1 to 9.

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