A counter resonant hollow core optical fiber

Abstract

This disclosure relates to an antiresonant hollow optical fiber, comprising: an outer sheath having an inner surface; and cladding elements located within the outer sheath and including a plurality of first cladding elements arranged around the inner surface, wherein any two adjacent first cladding elements are in contact with each other and define an intermediate air region of the antiresonant hollow optical fiber, wherein the core fundamental mode field of the antiresonant hollow optical fiber is defined within the intermediate air region; wherein any two adjacent first cladding elements have a contact point closest to the center point of the core fundamental mode field, and the ratio between the distance D1 from the closest contact point to the nearest boundary of the core fundamental mode field and the distance D2 from the nearest boundary to the center point of the core fundamental mode field has the following relationship: D1 / D2>0.46, wherein each first cladding element further includes at least one first main nested element.

Description

Technical Field

[0001] This disclosure relates to the field of hollow optical fibers, and more specifically to an anti-resonant hollow optical fiber. Background Technology

[0002] Depending on the optical guiding mechanism, hollow optical fibers can typically include hollow photonic bandgap fibers and anti-resonant hollow optical fibers.

[0003] Antiresonant hollow-core optical fiber is characterized by its simple structure, hollow-core light guiding, and wide transmission spectrum, making it suitable for important applications in fields such as light-filled material interactions, nonlinear optics, gas detection, gas laser generation, and optofluidics. Furthermore, its hollow-core light guiding properties, including ultra-low Rayleigh scattering, low nonlinear coefficient, and tunable dispersion, can provide a higher laser damage threshold, making it a potential candidate for high-power laser transmission, ultraviolet / mid-infrared light transmission, pulse compression, and optical soliton transmission.

[0004] Furthermore, the ultra-low loss, low dispersion, low nonlinearity, and near-light speed of propagation of anti-resonant hollow fiber enable the development of hollow fiber communication transmission and communication devices, laying the foundation for the construction and development of next-generation ultra-high capacity, low latency, and high-speed optical communication systems. Summary of the Invention

[0005] According to a first aspect of this disclosure, an anti-resonant hollow-core optical fiber is provided. The anti-resonant hollow-core optical fiber includes: an outer sheath having an inner surface; and cladding elements located within the outer sheath and including a plurality of first cladding elements arranged around the inner surface, wherein any two adjacent first cladding elements of the plurality of first cladding elements are in contact with each other and define an intermediate air region of the anti-resonant hollow-core optical fiber, wherein a core fundamental mode field of the anti-resonant hollow-core optical fiber is defined within the intermediate air region; wherein any two adjacent first cladding elements have a contact point closest to the center point of the core fundamental mode field, and the ratio between the distance D1 from the closest contact point to the nearest boundary of the core fundamental mode field and the distance D2 from the nearest boundary to the center point of the core fundamental mode field has the following relationship: D1 / D2 > 0.46; wherein the boundary of the core fundamental mode field is formed by an intensity of 1 / e of the intensity of the center point of the core fundamental mode field. 2 The center point of the square of the fundamental mode electric field strength of the fiber core is defined as the peak point of the square of the fundamental mode electric field strength; wherein each of the first cladding elements also has at least one first main nested element.

[0006] It will be understood that, with the anti-resonant hollow fiber of this disclosure, since adjacent first cladding elements are in contact with each other, the requirements for drawing the hollow fiber can be reduced compared to existing non-contact structures, while the limitation of the range of D1 / D2 can ensure that the confinement loss of the anti-resonant hollow fiber is maintained at a satisfactory level.

[0007] In some embodiments, each of the first cladding elements is selected from a full tube, an arc, a straight wall, or a combination thereof.

[0008] In some embodiments, each of the first cladding elements is a first arcuate element with an opening facing the inner surface and having the same or similar dimensions to each other, and the number of the first cladding elements is 3, 4, or 5. In some embodiments, D1 / D2 is greater than 0.5, 0.6, 0.8, or 1. In these embodiments, the confinement loss of the antiresonant hollow fiber can be further optimized by further limiting the number of first cladding elements and the range of D1 / D2 values.

[0009] In some embodiments, the first primary nesting element is fully or partially nested within the first cladding element. In some embodiments, the first primary nesting element is selected from any of a full tube, a second arcuate element with its opening facing the inner surface, or a straight wall.

[0010] In some embodiments, when the first primary nested element is a full tube or the second arc-shaped element, each of the first primary nested elements also has at least one second primary nested element that is fully nested or partially nested therein.

[0011] In some embodiments, when the first primary nested element is a straight wall, each of the first primary nested elements further has at least one second primary nested element nested between the first primary nested element and the inner surface.

[0012] In some embodiments, the anti-resonant hollow fiber further includes a third main nesting element, which is nested within the second main nesting element or between the second main nesting element and the inner surface.

[0013] In some embodiments, the plurality of first cladding elements include first cladding master elements and first cladding layer elements, wherein at least one corresponding first cladding layer element is present between any two adjacent first cladding master elements, wherein at least some of the first cladding master elements are arranged to contact the largest virtual inscribed circle in the intermediate air region, while all the first cladding layer elements do not contact the largest virtual inscribed circle at all.

[0014] In some embodiments, the corresponding at least one first cladding hierarchical element includes a corresponding one first cladding hierarchical element, and the corresponding one first cladding hierarchical element is respectively in contact with two adjacent first cladding main elements.

[0015] In some embodiments, the corresponding at least one first cladding hierarchical element includes two corresponding first cladding hierarchical elements in contact with each other, and the two corresponding first cladding hierarchical elements are also respectively in contact with an adjacent first cladding main element.

[0016] In some embodiments, there is a spacing d between any two adjacent first cladding main elements, the radius of the maximum virtual inscribed circle is a, and the following relationship exists between the spacing d and a: 0.1 < d / a < 1.5. In these embodiments, the above numerical range of d / a can also be used to further optimize the preparation of the anti-resonant hollow-core optical fiber.

[0017] In some embodiments, the shapes and sizes of each of the first cladding main elements are the same or similar, and are full tubes or nearly full tubes.

[0018] In some embodiments, the shape of each of the first cladding hierarchical elements is the same or similar to the shape of the first cladding main element.

[0019] In some embodiments, the shape of each of the first cladding hierarchical elements is different from the shape of the first cladding main element, and is selected from any one of an arc-shaped element and a straight wall.

[0020] In some embodiments, the first cladding main element includes at least one main nested element, and the at least one main nested element is selected from any one of a full tube, an arc-shaped element, and a straight wall.

[0021] In some embodiments, when the first cladding hierarchical element is a full tube or an arc-shaped element with an opening facing the inner surface, the first cladding hierarchical element includes at least one first nested element.

[0022] In some embodiments, when the first cladding hierarchical element is a straight wall, the first cladding hierarchical element is further configured with at least one first nested element located between the first cladding hierarchical element and the inner surface.

[0023] In some embodiments, the number of the first cladding main elements and the number of the first cladding hierarchical elements are the same, and are 3, 4, 5, or 6.

[0024] In some embodiments, all the wall thicknesses of the first cladding elements are substantially the same.

[0025] In some embodiments, the first cladding element includes different first cladding elements in orthogonal directions, and the wall thicknesses of the first cladding elements in the orthogonal directions are different.

[0026] In some embodiments, the anti-resonant hollow fiber supports effective single-mode or multi-mode transmission.

[0027] In some embodiments, the loss ratio between the lowest-loss high-order mode in the core and the fundamental mode in the core is at least one order of magnitude, or at least two orders of magnitude, or at least three orders of magnitude.

[0028] In some embodiments, for all wall thicknesses t of the first cladding element and all nested elements, the anti-resonant condition is satisfied:

[0029]

[0030] where λ m is the resonant wavelength, m is the order of the anti-resonant layer, and n is the refractive index of the material of the component constituting the first cladding element.

[0031] In some embodiments, the ratio of the radius of the maximum virtual inscribed circle of the core to the optical wavelength guided by the hollow fiber is between 3 and 40, or between 4.5 and 20.

[0032] According to a second aspect of the present disclosure, an anti-resonant hollow fiber is provided. The anti-resonant hollow fiber includes: an outer protective sleeve having an inner surface; and a cladding element located within the outer protective sleeve and including a plurality of first cladding elements arranged around the inner surface, any two adjacent first cladding elements of the plurality of first cladding elements being in contact with each other and defining an intermediate air region of the anti-resonant hollow fiber, wherein the core mode field of the anti-resonant hollow fiber is defined within the intermediate air region; wherein the plurality of first cladding elements includes a first cladding main element and a first cladding sub-element, wherein there is at least one corresponding first cladding sub-element between any two adjacent first cladding main elements, wherein at least some of the first cladding main elements are arranged to contact the maximum virtual inscribed circle within the intermediate air region, and all of the first cladding sub-elements do not contact the maximum virtual inscribed circle, wherein there is a spacing d between any two adjacent first cladding main elements, the radius of the maximum virtual inscribed circle is a, and the following relationship exists between the spacing d and a: 0.1 < d / a < 1.5; wherein the distance D3 from the contact point closest to the center point of the maximum virtual inscribed circle between the first cladding main element and the first cladding sub-element to the maximum virtual inscribed circle and the radius a of the maximum virtual inscribed circle have the following relationship: D3 / a > 0.6; wherein the first cladding main element includes at least one first main nested element.

[0033] It will be understood that in the anti-resonant hollow-core optical fiber of this second aspect, since the adjacent first cladding elements are in contact with each other, the requirements for drawing the hollow-core optical fiber can also be reduced compared to the existing non-contact structure. In addition, by defining the parameters of both d / a and D3 / a, the confinement loss of the anti-resonant hollow-core optical fiber can also be controlled at a satisfactory level.

[0034] In some embodiments, the first main nested element is selected from any one of a full tube, an arc-shaped element, and a straight wall, and the first main nested element is fully nested or partially nested within the first cladding main element.

[0035] In some embodiments, the corresponding at least one first cladding sub-element includes a corresponding one first cladding sub-element, and the corresponding one first cladding sub-element is in contact with two adjacent first cladding main elements respectively.

[0036] In some embodiments, the corresponding at least one first cladding sub-element includes two corresponding first cladding sub-elements in contact with each other, and the two corresponding first cladding sub-elements are also each in contact with a neighboring first cladding main element.

[0037] In some embodiments, the shape and size of each first cladding main element are the same, and it is a full tube or nearly a full tube or an arc-shaped element.

[0038] In some embodiments, D3 / a > 0.8. In some embodiments, D3 / a > 1. In some embodiments, the following relationship exists between the spacing d and a: 0.15 < d / a < 1.3. In some embodiments, the following relationship exists between the spacing d and a: 0.15 < d / a < 1. In these embodiments, by further defining the numerical ranges of D3 / a and d / a, the loss level of the anti-resonant hollow-core optical fiber can be further optimized.

[0039] In some embodiments, the shape of each of the first cladding sub-elements is the same as the shape of the first cladding main element.

[0040] In some embodiments, the shape of each of the first cladding sub-elements is different from the shape of the first cladding main element, and is selected from a full tube, an arc-shaped element, a straight wall, or a combination thereof.

[0041] In some embodiments, a second main nested element is further provided within each of the first main nested elements, and the second main nested element is fully or partially nested within the first main nested element.

[0042] In some embodiments, a third main nested element is further provided within each of the second main nested elements.

[0043] In some embodiments, where the first layered element is a full tube or an arcuate element with an opening facing the inner surface, the first layered element includes at least one first nested element.

[0044] In some embodiments, where the first layered element is a straight wall, the first layered element is further configured with at least one first nested element located between the first layered element and the inner surface.

[0045] In some embodiments, each first package hierarchical element further includes a first nested element, and each first nested element further includes a second nested element.

[0046] In some embodiments, the number of the first cladding master element and the first cladding layer element is the same, and is 3, 4, 5 or 6.

[0047] In some embodiments, all wall thicknesses of the first cladding main element are substantially the same.

[0048] In some embodiments, the first cladding main element includes different first cladding main elements in orthogonal directions, and the different first cladding main elements have different wall thicknesses.

[0049] In some embodiments, the anti-resonant hollow fiber supports effective single-mode or multi-mode transmission.

[0050] In some embodiments, the loss ratio between the lowest-loss higher-order mode and the fundamental mode within the fiber core is at least one order of magnitude, or at least two orders of magnitude, or at least three orders of magnitude.

[0051] In some embodiments, all wall thicknesses t of the first cladding main element satisfy the anti-resonance condition:

[0052] Where λ m λ is the resonant wavelength, m is the order of the anti-resonant layer, and n is the refractive index of the material of the component constituting the first cladding element.

[0053] In some embodiments, the ratio of the maximum inscribed circle radius of the fiber core to the wavelength of the light guided by the hollow fiber is between 3 and 40, or between 4.5 and 20.

[0054] It should also be understood that the description in the Summary of the Invention is not intended to limit the key or essential features of the embodiments of this disclosure, nor is it intended to restrict the scope of this disclosure. Other features of the embodiments of this disclosure will become readily apparent from the following description. Attached Figure Description

[0055] The above and other features, advantages, and aspects of the embodiments of this disclosure will become more apparent from the accompanying drawings and the following detailed description. In the drawings, the same or similar reference numerals denote the same or similar elements, wherein:

[0056] Figure 1 The conventional Kagome configuration of anti-resonant hollow fiber is shown;

[0057] Figure 2 The conventional single-turn non-contact configuration of anti-resonant hollow fiber is shown;

[0058] Figure 3 The conventional contact nesting configuration of anti-resonant hollow fiber is shown;

[0059] Figure 4 The conventional non-contact nested configuration of anti-resonant hollow fiber is shown;

[0060] Figure 5 A schematic diagram is shown illustrating the drawing of preforms into a non-contact nested configuration;

[0061] Figure 6a A schematic diagram of a typical structure of an anti-resonant hollow optical fiber according to a first exemplary embodiment of the present disclosure is shown;

[0062] Figure 6b An example of altering the structure of an anti-resonant hollow fiber by adjusting the distance between the closest contact point and the inner surface of the outer sheath is shown, where from Figure 6b In (a) to (c), the size of the core mold field remains unchanged, the distance D1 from the closest contact point to the nearest boundary of the core base mold field and the distance D2 from the nearest boundary to the center point of the core base mold field both remain unchanged, the curvature of the first arc-shaped element also remains unchanged, while the distance between the closest contact point and the inner surface of the outer sheath tube gradually increases, and the size of both the nested tube and the outer sheath tube increases accordingly.

[0063] Figure 6c It shows in Figure 6a Simulation plot of the limiting loss of anti-resonant hollow fiber with varying D1 / D2, taking the first cladding element with different radii of curvature as an example under a four-tube contact structure layout.

[0064] Figure 6d A simulation plot of the limiting loss as a function of wavelength is shown for a given D1 / D2;

[0065] Figure 6e It shows in Figure 6a Simulation drawing of the limiting loss as the ratio of D1 / D2 changes under a four-tube contact structure layout with given predetermined structural parameters.

[0066] Figure 6f It shows in Figure 6a Simulation plot of the limiting loss as the ratio of D1 / D2 changes under a four-tube contact structure layout, taking another given predetermined structural parameters as an example.

[0067] Figure 6g It shows in Figure 6a Simulation drawing of the effect of changing the ratio between the distance l from the nearest contact point to the outer sheath and the radius a of the largest virtual inscribed circle on limiting losses under the four-tube contact structure layout, while keeping D1 / D2 fixed.

[0068] Figure 6h (a) to (e) in the text show Figure 6a Example of a structural variation in an anti-resonant hollow fiber where the ratio k of the radius of the first main nested element within the first cladding element to the radius of the inscribed circle of the fiber core gradually increases.

[0069] Figure 6i Simulation plots are shown showing the limiting loss as a function of the ratio k of the radius of the first main nested element to the radius of the inscribed circle of the fiber core under different D1 / D2 conditions;

[0070] Figure 6j This shows a simulation plot of the limiting loss as a function of D1 / D2 under different size ratios k of the first main nested element relative to the radius of the inscribed circle of the fiber core;

[0071] Figure 6k A simulation plot is shown showing the limiting loss as a function of the size ratio k of the first main nested element relative to the radius of the inscribed circle of the fiber core at D1 / D2 = 0.93;

[0072] Figure 6l A simulation plot is shown showing the limiting loss as a function of the size ratio k of the first main nested element relative to the radius of the inscribed circle of the fiber core at D1 / D2 = 0.69;

[0073] Figure 7a This illustrates a structural example of an anti-resonant hollow optical fiber of the present disclosure, in which there is a gap region between the closest contact point of two adjacent first cladding elements and the inner surface of the outer sheath.

[0074] Figure 7b Simulation plots show the effect of different filling materials (e.g., air and quartz) on the loss of anti-resonant hollow fiber in the gap region between the closest contact point of two adjacent first cladding elements and the inner surface of the outer sheath.

[0075] Figure 8 The simulation plot of the limiting loss of the four-tube contact structure as a function of wavelength under different bending radii BR is shown.

[0076] Figure 9a It shows Figure 6a A schematic diagram of a modified embodiment of an anti-resonant hollow-core optical fiber;

[0077] Figure 9b It shows Figure 6a Example simulation plot of confinement loss as a function of wavelength under the structural layout of a variant embodiment of antiresonant hollow fiber;

[0078] Figure 10a A schematic diagram of the structure of an anti-resonant hollow optical fiber according to a second exemplary embodiment of the present disclosure is shown;

[0079] Figure 10b It shows in Figure 10a Example simulation plot of the limitation loss as a function of wavelength under a three-tube contact structure layout;

[0080] Figure 10c It shows Figure 10a Example of a variation of the three-tube contact structure;

[0081] Figure 10d It shows in Figure 10a Example simulation plot of the confined loss of antiresonant hollow fiber as D1 / D2 varies, taking the first nested component of a given predetermined size as an example under a three-tube contact structure layout.

[0082] Figure 10e It shows in Figure 10a Simulation plot of the confined loss of an anti-resonant hollow fiber as a function of D1 / D2, taking a first nested component of a given predetermined size as an example, under a three-tube contact structure layout.

[0083] Figure 10f It shows in Figure 10a Simulation plot of the limiting loss of anti-resonant hollow fiber with varying D1 / D2, taking the first cladding element with different radii of curvature as an example under the three-tube contact structure layout.

[0084] Figure 11 It shows in Figure 10a Simulation plot of the limiting loss of antiresonant hollow fiber under a three-tube contact structure layout as the radius of the inscribed circle of the fiber core changes.

[0085] Figure 12 It shows in Figure 10a Simulation plot of the confinement loss of anti-resonant hollow optical fibers with different D1 / D2 ratios as a function of wavelength under a three-tube contact structure layout.

[0086] Figure 13 It shows in Figure 10aSimulation plot of surface scattering loss of antiresonant hollow fiber with wavelength under a three-tube contact structure layout.

[0087] Figure 14 It shows in Figure 10a Simulation plot of bending loss of antiresonant hollow fiber with different bending radii under different bending curvatures as a function of wavelength in a three-tube contact structure layout.

[0088] Figure 15 It shows in Figure 10a Simulation plot of the coupling efficiency between an anti-resonant hollow fiber and a Gaussian beam under different core inscribed circle radii in a three-tube contact structure layout.

[0089] Figure 16a A schematic diagram of the structure of an anti-resonant hollow optical fiber according to a third exemplary embodiment of the present disclosure is shown;

[0090] Figure 16b It shows in Figure 16a Simulation plot of the limiting loss as a function of D1 / D2 under a five-tube contact structure layout;

[0091] Figure 17a A schematic diagram of a typical structure of an anti-resonant hollow-core optical fiber according to a fourth exemplary embodiment of the present disclosure is shown;

[0092] Figure 17b , Figure 17c , Figure 17d and Figure 17e It shows Figure 17a Variations of the embodiments;

[0093] Figure 17f A schematic diagram of a structure is shown, showing two corresponding first cladding layer elements between any two adjacent first cladding layer main elements;

[0094] Figure 17g It shows in Figure 17a Simulation drawing of the limiting loss under the contact structure layout as the ratio of D1 / D2 changes;

[0095] Figure 17h It shows in Figure 17a Simulation plot of the limitation loss as a function of wavelength under the contact structure layout;

[0096] Figure 17i It shows in Figure 17g Simulation plot of the limitation loss as a function of wavelength under the contact structure layout;

[0097] Figure 18a It shows Figure 17a A schematic diagram of a variant structure of the typical structure of the fourth example embodiment;

[0098] Figure 18b exist Figure 18a Simulation drawing of loss limitation under structural layout with D1 / D2 ratio variation

[0099] Figure 19a A schematic diagram of a structure in which the first cladding master element and the first cladding layer element of an anti-resonant hollow optical fiber according to a fifth exemplary embodiment of the present disclosure each have only one layer of nested elements (i.e., a single-layer nested structure);

[0100] Figure 19b It shows Figure 19a Simulation plot of the confinement loss of antiresonant hollow fiber as a function of wavelength;

[0101] Figure 20a A schematic diagram of a structure is shown for an anti-resonant hollow fiber according to a fifth exemplary embodiment of the present disclosure, in which both the first cladding master element and the first cladding layer element have double-layer nested elements (i.e., double-layer nested structure) and the dimensions of the first cladding master element and the first cladding layer element are different from each other.

[0102] Figure 20b It shows Figure 20a Simulation plot of the confinement loss of antiresonant hollow fiber as a function of d / a;

[0103] Figure 20c It shows Figure 20a Simulation plot of the confinement loss of antiresonant hollow fiber as a function of D3 / a;

[0104] Figure 20d It shows Figure 20a A schematic diagram illustrating the confinement loss of an antiresonant hollow fiber as a function of wavelength.

[0105] Figure 21a A schematic diagram of a structure is shown for an anti-resonant hollow fiber according to a fifth exemplary embodiment of the present disclosure, in which both the first cladding master element and the first cladding layer element have double-layer nested elements (i.e., double-layer nested structure) and the dimensions of the first cladding master element and the first cladding layer element are the same.

[0106] Figure 21b It shows Figure 21a Simulation plot of the confinement loss of antiresonant hollow fiber as a function of d / a;

[0107] Figure 21c It shows Figure 21a Simulation plot of the confinement loss of antiresonant hollow fiber as a function of D3 / a;

[0108] Figure 21d It shows Figure 21aA schematic diagram showing the variation of confinement loss of antiresonant hollow fiber with wavelength under different spacing d.

[0109] Figure 22a An anti-resonant hollow-core optical fiber according to a fifth exemplary embodiment of this disclosure is shown. Figure 20a The structure (where the dimensions of the first cladding main elements are the same, and the dimensions of the first cladding layer elements are different). Figure 21a The structure (where the first cladding main element and the first cladding layer element are of the same size) and Figure 22b Comparative simulation plot of the limiting loss of a four-tube non-contact structure without a first cladding element as a function of d / a.

[0110] Figure 22b A schematic diagram of a four-tube non-contact structure without a first cladding element is shown for comparison.

[0111] Figure 22c An anti-resonant hollow fiber according to a fifth exemplary embodiment of this disclosure is shown. Figure 20a The structure (where the dimensions of the first cladding main elements are the same, and the dimensions of the first cladding layer elements are different). Figure 21a The structure (where the first cladding main element and the first cladding layer element are of the same size) and Figure 22b Comparative simulation plot of the limiting loss of a four-tube non-contact structure without a first cladding element as a function of D3 / a.

[0112] Figure 23a and Figure 23b Schematic diagrams of structures with strong and weak contact between two adjacent first cladding elements are shown respectively.

[0113] Figure 23c A comparative simulation plot of the confinement loss as a function of d / a for an anti-resonant hollow fiber in a fifth exemplary embodiment of the present disclosure under strong and weak contact conditions is shown.

[0114] Figure 23d A comparative simulation plot of the confinement loss of the anti-resonant hollow fiber according to the fifth exemplary embodiment of this disclosure as a function of D3 / a under strong and weak contact conditions is shown.

[0115] Figure 23e A comparative simulation plot of the confinement loss as a function of d / a for an anti-resonant hollow fiber with different core radii according to a fifth exemplary embodiment of the present disclosure is shown.

[0116] Figure 23f A comparative simulation plot of the confinement loss as a function of D3 / a for an anti-resonant hollow fiber with different core radii according to a fifth exemplary embodiment of the present disclosure is shown.

[0117] Figure 24a A schematic diagram of a variant embodiment of the anti-resonant hollow-core optical fiber according to the present disclosure is shown;

[0118] Figure 24b It shows that according to Figure 24a The confinement loss of the antiresonant hollow fiber is plotted as d / a.

[0119] Figure 24c according to Figure 24a The confinement loss of the antiresonant hollow fiber is shown in the simulation plot of D3 / a.

[0120] Figure 24d A schematic diagram of another variant embodiment of the anti-resonant hollow-core optical fiber according to this disclosure is shown;

[0121] Figure 24e It shows that according to Figure 24d Simulation plot of the confinement loss of antiresonant hollow fiber as a function of wavelength;

[0122] Figure 25a (a), (b), and (c) in the figure show schematic diagrams of the structure of the first cladding main element and the first cladding layer element of the anti-resonant hollow fiber of the present disclosure, which each have two nested elements in the first cladding layer element.

[0123] Figure 25b It shows Figure 25a Simulation comparison plot of the confinement loss of the core fundamental mode and higher-order modes of anti-resonant hollow fiber as the size ratio m of the first main nested element to the first cladding main element varies.

[0124] Figure 25c It shows Figure 25a Simulation plot of the high-order mode suppression ratio of anti-resonant hollow fiber as a function of the size ratio m of the first main nested element relative to the first cladding main element;

[0125] Figure 25d It shows Figure 25a A simulation comparison plot of the effective refractive index of the core fundamental mode, higher-order modes, and inter-tube cavity region modes of an anti-resonant hollow fiber as a function of the size ratio m of the first main nested element relative to the first cladding main element.

[0126] Figure 26a , Figure 26b and Figure 26c Schematic diagrams of some other variations of the anti-resonant hollow fiber according to this disclosure are shown.

[0127] Figure 26d A schematic diagram of an existing anti-resonant hollow fiber consisting of cladding elements composed of four sets of circular tube units is shown.

[0128] Figure 26e It shows that according to Figures 26a to 26d The confinement loss of the anti-resonant hollow fiber is compared with d / a in the simulation plot.

[0129] Figure 26f It shows that according to Figures 26a to 26c The confinement loss of antiresonant hollow fiber is compared with D3 / a in simulation plots.

[0130] Figure 26g It shows that according to Figure 26a Simulation plot of confinement loss of antiresonant hollow fiber with wavelength under different d / a conditions;

[0131] Figure 26h It shows that according to Figure 26a Simulation plot of the confinement loss of antiresonant hollow fiber with wavelength under different D3 / a conditions;

[0132] Figure 27a It shows Figure 25a The possible deformation of the structure during the actual drawing process;

[0133] Figure 27b It shows Figure 27a Simulation plot of the effect of the aforementioned contact point thickening on the limiting loss in the case of anti-resonant hollow fiber.

[0134] Figure 27c It shows in Figure 27a Simulation plot of the limitation loss versus wavelength in the case of anti-resonant hollow fiber with varying thickness of a portion of the tube wall (e.g., the thickness dimension of the first main nested element relative to the first cladding main element).

[0135] Figure 27d It shows in Figure 27a In the case of anti-resonant hollow fiber, the simulation plot shows the effect of changing the ratio m of the size of the first main nested element to the size of the first cladding main element on the confinement loss of the fiber core fundamental mode and higher-order modes.

[0136] Figure 27e It shows in Figure 27a A simulation plot of the high-order mode suppression ratio as a function of the ratio m of the size of the first main nested element to the size of the first cladding main element in the case of anti-resonant hollow fiber.

[0137] Figure 27f It shows in Figure 27a In the case of anti-resonant hollow fiber, the simulation plot shows the effect of changing the ratio m of the size of the first main nested element to the size of the first cladding main element on the effective refractive index of the fiber core fundamental mode and higher-order modes.

[0138] Figure 28a It shows in Figure 27a Simulation plot of the effect of changing the size ratio n1 of the first nested element relative to the first cladding layer element on the fiber core fundamental mode and higher-order modes in the case of anti-resonant hollow fiber.

[0139] Figure 28b It shows in Figure 27a A simulation plot of how the higher-order mode suppression ratio changes with the ratio n1 of the size of the first nested element to the size of the first cladding layer element in the case of anti-resonant hollow fiber.

[0140] Figure 28c It shows in Figure 27a Simulation plot of the effect of changing the size ratio n1 of the first nested element to the first cladding layer element on the effective refractive index of the fiber core fundamental mode, higher-order modes and inter-tube cavity region modes in the case of anti-resonant hollow fiber.

[0141] Figure 29a A schematic diagram of the structure of the first cladding master element of the anti-resonant hollow fiber of this disclosure having different thicknesses in the orthogonal directions is shown; and

[0142] Figure 29b It shows Figure 29a A simulation diagram showing the phase birefringence of the structure as a function of wavelength. Detailed Implementation

[0143] Embodiments of this disclosure will now be described in more detail with reference to the accompanying drawings. While some embodiments of this disclosure are shown in the drawings, it should be understood that this disclosure can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of this disclosure. It should be understood that the accompanying drawings and embodiments of this disclosure are for illustrative purposes only and are not intended to limit the scope of protection of this disclosure.

[0144] As mentioned earlier, antiresonant hollow-core fiber has significant application prospects in many fields, especially in optical fiber communication. A review of the development history of antiresonant hollow-core fiber reveals that it has evolved from... Figure 1 Kagome configuration to Figure 2 The single-loop non-contact configuration, and then to Figure 3 From the contact nesting configuration to Figure 4 The development process of non-contact nested configurations.

[0145] In the existing configurations described above, when there are contact points between tubes within the optical fiber, Fano oscillations occur at these contact points. These Fano oscillations couple with the fundamental mode field of the fiber core, resulting in oscillation peaks in the loss spectrum. The Kagome configuration described above is a contact structure, where the contact points are some distance from the fiber core to reduce loss, but the loss is still 40 dB / km, failing to achieve a loss below 1 dB / km. The single-turn non-contact configuration described above has too few anti-resonant layers, resulting in a loss of around 10 dB / km. In the contact nested configuration described above, the contact points are too close to the fiber core, resulting in more oscillation peaks and a loss greater than 1 dB / km. Only the non-contact nested configuration described above, where the ratio between the spacing between tube units and the fiber core radius is less than 0.4, can reduce the loss to below 0.1 dB / km.

[0146] However, in their research on the fluid dynamics of actual fiber drawing, the inventors discovered that mass production of non-contact structures with small inter-tube gaps is quite challenging. This is due to the mid-draw contraction problem during the drawing process—that is, when entering the high-temperature furnace, the capillaries are small and wide, requiring expansion through gas pressure to form a non-contact structure with small gaps. Specifically, in the initial stage of the drawing process, gas pressure dominates, causing the capillary structure to expand. However, in the latter part of the drawing process, surface tension begins to dominate, leading to capillary contraction. If the capillaries have already made contact in the middle of the high-temperature furnace, they cannot separate as they move downwards. If they remain non-contact, the capillaries will shrink further as the temperature decreases, increasing the gap. Therefore, drawing non-contact structures requires very high tension, frequently resulting in fiber breakage. Furthermore, the larger the ratio of the preform to the fiber size (draw-down ratio), the larger the gap between the capillaries, and the draw-down ratio directly determines the yield. Due to factors such as fiber breakage, preform size, and the requirement for small gaps, the current maximum actual output is 15 kilometers. Some articles predict a maximum output of 100 kilometers, but this is far from the output of traditional optical fibers, which ranges from thousands to tens of thousands of kilometers. Figure 5 A schematic diagram is shown of drawing preforms into a non-contact nested configuration.

[0147] To solve the above-mentioned problems in drawing and to ensure that the anti-resonant hollow fiber has a sufficiently low loss, the present disclosure proposes a novel anti-resonant hollow fiber, which includes: an outer protective sleeve having an inner surface; and a cladding element located within the outer protective sleeve and including a plurality of first cladding elements arranged around the inner surface, any two adjacent first cladding elements in the plurality of first cladding elements being in contact with each other and defining an intermediate air region of the anti-resonant hollow fiber, wherein the core fundamental mode field of the anti-resonant hollow fiber is defined within the intermediate air region; and one of the following applies: there is a contact point closest to the center point of the core fundamental mode field between any two adjacent first cladding elements, and the ratio between the distance D1 from the closest contact point to the nearest boundary of the core fundamental mode field and the distance D2 from the nearest boundary to the center point of the core fundamental mode field has the following relationship: D1 / D2 > 0.46, wherein the boundary of the core fundamental mode field is defined by 1 / e of the intensity of the center point of the core fundamental mode field 2 defined, and the center point of the square of the core fundamental mode field intensity is the peak point of the square of the fundamental mode electric field intensity; or the plurality of first cladding elements includes a first main cladding element and a first sub-cladding element, there being at least one corresponding first sub-cladding element between any two adjacent first main cladding elements, the first main cladding elements being arranged to be in contact with the largest virtual inscribed circle within the intermediate air region simultaneously, while the first sub-cladding elements are not in contact with the largest virtual inscribed circle, there being a spacing d between any two adjacent first main cladding elements, the radius of the largest virtual inscribed circle being a, and the relationship between the spacing d and a being as follows: 0.1 < d / a < 1.5, and the relationship between the distance D3 from the contact point closest to the center point of the core mode field between the first main cladding element and the first sub-cladding element to the largest virtual inscribed circle and the radius a of the largest virtual inscribed circle being as follows: D3 / a > 0.6; at least one nested element is included within the first cladding element or the first main cladding element.

[0148] It will be understood that by making any two adjacent first cladding elements in the cladding elements defining the core contact each other, the drawing difficulty is greatly reduced. In addition, by defining the ratio between D1 and D2, the ratio between the spacing d and the radius a of the largest virtual inscribed circle, and / or the ratio between D3 and the radius a of the largest virtual inscribed circle, the anti-resonant hollow fiber can have a sufficiently low loss.

[0149] Various exemplary embodiments of the anti-resonant hollow fiber according to the concept of the present disclosure will be described below with reference to the accompanying drawings.

[0150] First Example Implementation

[0151] Figure 6a A schematic diagram of a typical structure of an anti-resonant hollow fiber according to a first exemplary embodiment of the present disclosure is shown.

[0152] like Figure 6a As shown, the anti-resonant hollow fiber 1 may include an outer sheath tube 2 and a cladding element located inside the outer sheath tube 2.

[0153] The outer sheath 2 has an inner surface 21, and the aforementioned cladding elements may include a plurality of first cladding elements 31 arranged around the inner surface 21.

[0154] According to the design of this disclosure, any two adjacent first cladding elements 31 are in contact with each other and define an intermediate air region 10 of the anti-resonant hollow fiber 1, wherein the core fundamental mode field (e.g., including the core fundamental mode and higher-order core modes) of the anti-resonant hollow fiber is confined within the intermediate air region 10. Each first cladding element 31 may also have at least one first main nested element 32.

[0155] According to some embodiments of this disclosure, the first cladding elements 31 are all first arc-shaped elements with openings facing the inner surface, and have the same or similar dimensions. In particular, the number of first cladding elements 31 can be 3, 4, or 5.

[0156] As an example only, in Figure 6a Four first cladding elements 31 are shown, each of which is a first arc-shaped element with an opening facing the inner surface, and all are identical in size. Therefore, Figure 6a The first example embodiment can also be referred to as a four-tube contact structure.

[0157] In a further embodiment of this disclosure, as an example, the first main nested element may be a full tube, a second arc-shaped element with its opening facing the inner surface, or a straight wall. Figure 6a In the example, the first primary nested element 32 is a full tube, and each first cladding element 31 has two first primary nested elements 32.

[0158] Furthermore, in the first main nested element 32, which is a full tube (e.g., see...), Figure 6a When the first main nested element 32 is a straight wall (e.g., see below), or a second arc-shaped element, the first main nested element 32 may also have at least one second main nested element 33 nested therein; and when the first main nested element 32 is a straight wall (e.g., see below), the first main nested element 32 may also have at least one second main nested element 33 nested therein; Figure 9a In this case, the first main nested element 32 may also have at least one second main nested element 33 nested between the first main nested element 32 and the inner surface 21. The second main nested element 33 may still be selected from a full tube, an arc-shaped element, or a straight wall. For example, in Figure 6aIn the example, the second main nested element 33 is still a full tube, as will be described later. Figure 9a In the example, the second main nested element 33 can be a straight wall.

[0159] It should be understood that the nesting arrangement (including the number of layers and the shape of the nested elements) within the first cladding element 31 is selected according to the needs of the anti-resonance design. Therefore, those skilled in the art can select an appropriate nesting arrangement (including the number of layers, the shape and size of the nested elements) according to actual needs. For example, in some embodiments, the number of nested layers within the first cladding element 31 may be more or less than two layers.

[0160] Furthermore, since any two adjacent first cladding elements 31 are in contact with each other, any two adjacent first cladding elements 31 can have a contact point closest to the center point O of the core matrix field. For example, in Figure 6a In the example, any two adjacent first cladding elements 31 of the four first cladding elements 31 are in contact with each other and have four contact points closest to the center point O of the core matrix field, such as C1, C2, C3, and C4.

[0161] According to the design of this disclosure, the ratio between the distance D1 from the nearest contact point (e.g., C1, C2, C3, C4) to the nearest boundary of the core matrix field and the distance D2 from the nearest boundary to the center point of the core matrix field can have the following relationship: D1 / D2 > 0.46, wherein the boundary of the core matrix field is formed by a strength equal to 1 / e of the strength of the center point of the core matrix field. 2 Defined as follows: the center point of the square of the fundamental mode field strength of the fiber core is the peak point of the square of the fundamental mode electric field strength. Note: The nearest boundary of the aforementioned fundamental mode field can be, for example, derived from the following... Figure 6b The common endpoints of D1 and D2 in (a) to (c) are more clearly visible.

[0162] Simulation results show that the ratio of D1 / D2 > 0.46 can effectively limit the Fano oscillation caused by the contact between two adjacent first cladding elements to a sufficiently low level, thereby ensuring that the anti-resonant hollow fiber has a sufficiently low loss (e.g., a limit loss as low as 1 dB / km), while effectively utilizing the contact between any two adjacent first cladding elements to reduce the difficulty of drawing.

[0163] In some embodiments, the ratio of D1 / D2 and / or the limitation loss can be adjusted by adjusting the specific structural parameters of the anti-resonant hollow fiber (including but not limited to, the distance from the nearest contact point to the inner surface of the outer sheath, the diameter of the largest virtual inscribed circle in the intermediate air region, the wall thickness of each component in the cladding element, the curvature of the first arc-shaped element, the size of the first main nested element relative to the first cladding element, etc.) and the specific structural layout (including but not limited to, nesting arrangement, the number of anti-resonant layers, etc.).

[0164] Figure 6b An example of altering the structure of an anti-resonant hollow fiber by adjusting the distance between the closest contact point and the inner surface of the outer sheath is shown, where from Figure 6b In (a) to (c), the size of the core mold field remains unchanged, the distance D1 from the closest contact point to the nearest boundary of the core mold field and the distance D2 from the nearest boundary to the center point of the core mold field remain unchanged, the curvature of the first arc-shaped element also remains unchanged, while the distance between the closest contact point and the inner surface of the outer sheath tube gradually increases, and the size of both the nested tube and the outer sheath tube increases accordingly.

[0165] In some embodiments, the ratio of D1 / D2 can be changed by simply adjusting the distance between the nearest contact point and the inner surface of the outer sheath, while keeping other structural parameters constant.

[0166] Figure 6c It shows in Figure 6a A simulation drawing of the loss limitation under a four-tube contact structure layout as the ratio of D1 / D2 changes is presented. The distance between the nearest contact point and the inner surface of the outer sheath is adjusted by changing the curvature of the first arc-shaped element, thereby changing the D1 / D2 ratio. When D1 / D2 = 0.5, the loss limitation is less than 1 dB / km. Correspondingly, Figure 6d A simulation plot of the limiting loss as a function of wavelength is shown when D1 / D2 = 0.63. From... Figure 6d As can be seen, within the desired wavelength range (e.g., 1350 nm to 1700 nm), the antiresonant hollow-core fiber of this disclosure can maintain a low confinement loss level, for example, below 1 dB / km. Although the antiresonant hollow-core fiber of this disclosure forms fano resonance and causes oscillations, the amplitude is on the order of <0.1 dB / km.

[0167] For comparison, see back. Figure 1 Kagome configuration and Figure 3 The contact nesting configuration, as measured, Figure 1 The ratio of D1 / D2 in the equation is approximately 0.32, while... Figure 3The ratio of D1 / D2 in the equation is approximately 0.37, and neither of them can effectively reduce the losses caused by Fano oscillations.

[0168] Although the above description of the effect of the D1 / D2 ratio on the confinement loss of antiresonant hollow fiber has been presented, it should be understood that, in addition to the aforementioned D1 / D2 ratio, individual adjustments to other structural parameters of the antiresonant hollow fiber (including but not limited to, the distance from the nearest contact point to the inner surface of the outer sheath, the diameter of the largest virtual inscribed circle in the intermediate air region, the wall thickness of each component in the cladding element, the size of the first main nesting element relative to the first cladding element, etc.) and specific structural layouts (including but not limited to, nesting arrangement, the number of antiresonant layers) will also affect the loss of the core fundamental mode field (e.g., core fundamental mode) in the antiresonant hollow fiber.

[0169] Figure 6e It shows in Figure 6a A simulation drawing of the loss limitation as the ratio of D1 / D2 changes under a four-tube contact structure layout with given predetermined structural parameters is presented. The maximum virtual inscribed circle diameter of the central air region of the anti-resonant hollow fiber is 30 μm, and the wall thickness of each tube in the cladding element is 1.1 μm. The change in D1 / D2 is caused by moving the contact point towards the fiber core. Figure 6e In the above, when D1 / D2 = 0.62, the loss can be reduced to 1 dB / km, and the loss can be gradually reduced as D1 / D2 increases.

[0170] Figure 6f It shows in Figure 6a The simulation plot of the loss limitation as the ratio of D1 / D2 changes under a four-tube contact structure layout, taking another given predetermined structural parameters as an example, is shown. The diameter of the maximum virtual inscribed circle in the middle air region of the anti-resonant hollow fiber is 30 μm, and the wall thickness of each component in the cladding element is 1.2 μm. The D1 / D2 ratio changes by moving the contact point towards the fiber core. Figure 6f In the study, when D1 / D2 = 0.62, the loss can be reduced to 1 dB / km, and as D1 / D2 increases, the loss can gradually decrease. However, when D1 / D2 = 0.73, the loss slightly rebounds to more than 1 dB / km.

[0171] Figure 6g It shows in Figure 6aThis simulation plot illustrates the effect of varying the ratio of the distance *l* from the nearest contact point to the outer sheath to the radius *a* of the largest virtual inscribed circle on loss limitation in a four-tube contact structure layout, while keeping D1 / D2 constant. Here, *l / a* = 0 indicates that the distance *l* from the nearest contact point to the outer sheath is zero, typically representing the case where the closest contact point between two adjacent first cladding elements contacts near the inner surface of the outer sheath. A larger value for *l / a* indicates a larger distance *l* from the nearest contact point to the outer sheath relative to the radius *a* of the largest virtual inscribed circle. Figure 6g As shown, as the ratio of l / a increases, it first gradually decreases and then gradually increases. In particular, with D1 / D2 kept constant, the confinement loss of the anti-resonant hollow fiber will be at its lowest level when l / a is in the range of 0.2 to 1.6.

[0172] Figure 6h (a) to (e) in the text show Figure 6a Example of a structural variant in an anti-resonant hollow fiber where the ratio k of the size of the first main nested element within the first cladding element to the size of the first cladding element gradually increases.

[0173] Figure 6i Simulation plots are shown showing the limiting loss as the size ratio k of the first main nested element relative to the first cladding element varies under different D1 / D2 conditions. Figure 6j This presents a simulation plot showing the limitation of loss as a function of D1 / D2 under different size ratios k of the first main nested element relative to the first cladding element.

[0174] from Figure 6i and Figure 6j It can be seen that in embodiments where the D1 / D2 ratio is small (e.g., 0.46 < D1 / D2 < 0.59), as the size ratio k of the first main nested element relative to the first cladding element increases, the confinement loss gradually decreases, and typically the confinement loss can be controlled to around 1 dB / km or below. That is, when D1 / D2 is small, the larger the first main nested element is relative to the first cladding element, the better. Furthermore, from... Figure 6j It can be seen that by selecting an appropriate size ratio k of the first primary nested element to the first cladding element, for example, k greater than 0.7, it is possible to ensure that the limiting loss is around 1 dB / km or below, even when the ratio of D1 / D2 is as low as close to 0.46.

[0175] In addition, in embodiments where the ratio of D1 / D2 is large (e.g., D1 / D2 > 0.6), it may be preferable to select a ratio k of the size of the first main nested element relative to the first cladding element that is in the middle (e.g., 0.55 < k < 0.68). Figure 6kA simulation plot is shown showing the limiting loss as a function of the size ratio of the first primary nested element to the first cladding element when D1 / D2 = 0.93. Figure 6k As shown, as the size ratio k is greater than 0.68, the confinement loss increases sharply. Figure 6l A simulation plot is shown showing the limiting loss as a function of the size ratio k of the first main nested element relative to the first cladding element when D1 / D2 = 0.69. (See diagram.) Figure 6l As shown, when the size ratio k is less than 0.55, the limiting loss increases sharply.

[0176] Ideally, the closest contact point between two adjacent first cladding elements will be in close contact with the inner surface of the outer sheath, meaning there will be no air gap. However, in the actual drawing process, such as... Figure 7a As shown, the gap region 11 between the closest contact point of two adjacent first cladding elements and the inner surface of the outer sheath may be filled with air or a tube wall material such as quartz. Simulations show that the filling material of the aforementioned gap region 11 also affects the loss of the antiresonant hollow fiber.

[0177] Figure 7b A simulation plot shows the effect of different filling materials (e.g., air and quartz) on the loss of an antiresonant hollow fiber in the gap region between the closest contact point of two adjacent first cladding elements and the inner surface of the outer sheath. Figure 7b As shown, in the wavelength range of 1300 nm to 1500 nm, the gap region filled with air can have lower loss compared to the gap region filled with, for example, quartz.

[0178] Furthermore, through the above Figure 6a The study of bending loss in the structure also revealed that there was no significant difference in loss under different bending radii (e.g., 6 cm, 8 cm, and 10 cm) in antiresonant hollow fiber, which shows... Figure 6a The example structure exhibits excellent bending loss stability. Figure 8 Simulation plots showing the limitation loss as a function of wavelength under different curvature radii BR are presented.

[0179] Figure 9a It shows Figure 6a A schematic diagram of a modified embodiment of the antiresonant hollow-core optical fiber. (Compared to...) Figure 6a The difference lies in that the first main nesting element 32 has a straight wall. In addition, the second main nesting element 33 between the first main nesting element 32 and the inner surface 21 of the outer sheath 2 also has a straight wall. Figure 9b It shows that according to Figure 9a A schematic diagram illustrating the limitation of loss as a function of wavelength for an exemplary structure. Figure 9bAs shown, this structure can also maintain the limiting loss at around 1 dB / km or below within the desired wavelength range (e.g., 1350 nm to 1700 nm).

[0180] Second Example Implementation

[0181] Figure 10a A schematic diagram of the structure of an anti-resonant hollow fiber according to a second exemplary embodiment of the present disclosure is shown.

[0182] Figure 10a The second example embodiment and Figure 6a The first example embodiment is similar, except that: Figure 10a The cladding elements consist only of three first cladding elements 31 arranged around the inner surface 21 of the outer sheath 2 (therefore, Figure 10a The second example embodiment can also be referred to as a three-tube contact structure. It should be noted here that, unless the context explicitly contradicts itself, the above description of... Figure 6a The description and effects of the first example embodiment can also be extrapolated to the present disclosure. Figure 10a The second example embodiment.

[0183] They will also understand, relative to Figure 6a Regarding the four-tube contact structure, Figure 10a The three-tube contact structure allows the core matrix mode field to be designed to be relatively farther from the nearest contact point, which is beneficial for limiting... Figure 10a The Fano oscillation at the contact point is highly advantageous. In some embodiments, Figure 10a The loss limitation of the three-tube contact structure can even be adjusted to below 0.1 dB / km. Furthermore, Figure 10a In the three-tube contact structure, the curvature and angle of the first cladding element have little impact on the loss. Therefore, relative to Figure 6a Regarding the four-tube contact structure, Figure 10a The design of the three-tube contact structure has greater drawback.

[0184] As an example, Figure 10b It shows in Figure 10a An example simulation plot of the limiting loss as a function of wavelength under a three-tube contact structure layout. From Figure 10b It can be seen that the loss limitation level of less than 0.1 dB / km can be achieved in the range of 1300 nm to 1550 nm.

[0185] Figure 10c It shows Figure 10a A variation of the three-tube contact structure, wherein the curvature of the tube wall of the first cladding element defining the intermediate air region or fiber core is relative to... Figure 10aThis is somewhat reduced, and at the same time, the closest contact point between two adjacent first cladding elements 31 is designed to be closer to the center point O of the core matrix mode field. Assuming other conditions remain unchanged, this means the ratio of D1 / D2 is reduced. As an example, Figure 10c The ratio of D1 / D2 can be, for example, 0.7.

[0186] It should be understood that, similar to the four-tube contact structure described above, the limiting loss of the three-tube contact structure can be related not only to the ratio of D1 / D2, but also to other structural parameters of the anti-resonant hollow fiber (including, but not limited to, the distance from the closest contact point to the inner surface of the outer sheath, the diameter of the largest virtual inscribed circle in the intermediate air region, the wall thickness of each component in the cladding element, the curvature of the first arc-shaped element, the size and shape of the first main nested element relative to the first cladding element, etc.) and the specific structural layout (including, but not limited to, the nesting arrangement, the number of anti-resonant layers, etc.). Therefore, the limiting loss of the three-tube contact structure can be optimized, for example, by adjusting the specific structural parameters and / or the specific structural layout of the anti-resonant hollow fiber.

[0187] Figure 10d It shows in Figure 10a An example simulation drawing of the limiting loss of an antiresonant hollow fiber as a function of D1 / D2, using a first nested element of a given predetermined size as an example, under a three-tube contact structure layout. The first main nested element 32 is relatively small relative to the size within the first cladding element 31, and the variation of D1 / D2 is caused by changing the radius of curvature of the first cladding element. Figure 10d It can be seen that the loss can be kept below 1 dB / km. Figure 10e It shows in Figure 10a The simulation plot shows the limiting loss of an anti-resonant hollow fiber as a function of D1 / D2, taking a first nested component of a given predetermined size as an example, under a three-tube contact structure layout. The first main nested element 32 is designed to be relatively large relative to the size within the first cladding element 31, and the structural intersection points between the first cladding elements are varied by changing the radius of curvature of the first cladding element, thereby causing a change in the contact point and thus a change in D1 / D2. Through... Figure 10e Data analysis will reveal that the smaller the radius of curvature of the first cladding element and the farther the contact point, the lower the loss will be.

[0188] Through the Figure 10d and Figure 10e The comparison shows that by increasing the size of the first main nested element 32 relative to the first cladding element 31, the confinement loss of the anti-resonant hollow fiber can be significantly reduced. For example, the confinement loss can be reduced to 0.1 dB / km.

[0189] Figure 10f It shows in Figure 10a Simulation plot of the confinement loss of an antiresonant hollow fiber with varying D1 / D2, using first cladding elements with different radii of curvature as examples, under a three-tube contact structure layout. From Figure 10f It can be seen that anti-resonant hollow-core optical fibers exhibit different confinement losses under different radii of curvature R. Specifically, as the radius of curvature of the first cladding element increases (i.e., the first cladding element, acting as the first arc-shaped element, becomes flatter), the confinement loss can be relatively reduced. Furthermore, considering the actual contact point thickness, even without changing the curvature, as long as the contact point position is within the specified range, a low-loss standard can still be achieved. For structures with larger radii of curvature, the lower limit of the specified range can be even lower.

[0190] Figure 11 It shows in Figure 10a Simulation plot of the limiting loss of antiresonant hollow fiber with varying radius of the inscribed circle under a three-tube contact structure layout. From Figure 11 It can be seen that, given other conditions remaining constant, the confinement loss can be effectively reduced as the radius of the virtual inscribed circle of the fiber core gradually increases. Therefore, in practice, the confinement loss can be effectively reduced by selecting the appropriate radius of the inscribed circle of the fiber core.

[0191] Figure 12 It shows in Figure 10a Simulation plots showing the confinement loss of antiresonant hollow-core optical fibers with different D1 / D2 ratios varying with wavelength under a three-tube contact structure layout. From... Figure 12 It can be seen that, under different D1 / D2 ratios, anti-resonant hollow fiber exhibits low confinement loss across the entire wavelength range of 1300 to 1700 nm.

[0192] Figure 13 It shows in Figure 10a Simulation plot of the surface scattering loss of antiresonant hollow fiber with wavelength under a three-tube contact structure layout. Figure 13 Simulation results show that the Fano oscillations caused by the contact point do not affect the surface scattering loss of the anti-resonant hollow fiber.

[0193] Figure 14 It shows in Figure 10a Simulation plot of bending loss of antiresonant hollow fiber with different bending radii under different bending radii as a function of wavelength under a three-tube contact structure layout. Figure 14 Simulation results show that, under the same bending radius of curvature, the bending loss of the three-tube contact structure is significantly lower than that of the three-tube contact structure. Figure 6a The bending loss of the four-tube contact structure is greater, but it is still within a relatively low loss level range.

[0194] Figure 15 It shows in Figure 10a Simulation plot of the coupling efficiency between an anti-resonant hollow fiber and a Gaussian beam under different core inscribed circle radii in a three-tube contact structure layout. Figure 15 Simulation results show that: Figure 10a The anti-resonant hollow fiber with a three-tube contact structure can achieve an optical coupling efficiency of over 90% with a Gaussian beam.

[0195] Third Example Implementation

[0196] Figure 16a A schematic diagram of the structure of an anti-resonant hollow fiber according to a third exemplary embodiment of the present disclosure is shown.

[0197] Figure 16a The third example embodiment and Figure 6a The first example embodiment is similar, except that: Figure 16a The cladding elements include five first cladding elements 31 arranged around the inner surface 21 of the outer sheath 2 (therefore, Figure 16a The third example embodiment can also be referred to as a five-tube contact structure. It should be noted here that, unless the context explicitly contradicts each other, the above description of... Figure 6a The description and effects of the first example embodiment can also be extrapolated to the third example embodiment of FIG16 of this disclosure.

[0198] Similar to the four-tube contact structure described above, the limiting loss of the five-tube contact structure is related not only to the D1 / D2 ratio but also to the specific structural parameters of the anti-resonant hollow fiber (including but not limited to, the distance from the closest contact point to the inner surface of the outer sheath, the diameter of the largest virtual inscribed circle in the intermediate air region, the wall thickness of each component in the cladding element, the curvature of the first arc-shaped element, and the size and shape of the first main nested element relative to the first cladding element) and the specific structural layout (including but not limited to, the nesting arrangement and the number of anti-resonant layers). Therefore, the limiting loss of the five-tube contact structure can be optimized, for example, by adjusting the specific structural parameters and / or the specific structural layout of the anti-resonant hollow fiber.

[0199] As an example, Figure 16b It shows in Figure 16a The simulation plot shows the limitation loss as a function of D1 / D2 under a five-tube contact structure layout. The change in D1 / D2 is caused by filling the contact points with quartz, which moves the closest contact point towards the fiber core. Figure 16b As can be seen in this example, when D1 / D2 > 0.54, the limiting loss can be kept below 1 dB / km.

[0200] Fourth Example Implementation

[0201] Figure 17a A schematic diagram of a typical structure of an anti-resonant hollow fiber according to a fourth exemplary embodiment of the present disclosure is shown.

[0202] The fourth exemplary embodiment of this disclosure differs slightly in concept from the first, second, and third exemplary embodiments described above. Similar to the first, second, and third exemplary embodiments described above, such as... Figure 17a As shown, the anti-resonant hollow fiber 1 also includes an outer sheath tube 2 and a cladding element located within the outer sheath tube 2, wherein the outer sheath tube 2 has an inner surface 21, and the cladding element may include a plurality of first cladding elements 31 arranged around the inner surface 21.

[0203] However, unlike the concepts of the first, second, and third example embodiments above, the plurality of first cladding elements 31 in the fourth example embodiment can be divided into first cladding main elements 31-1 and first cladding layer elements 31-2. According to the design of this disclosure, at least one corresponding first cladding layer element 31-2 is present between any two adjacent first cladding main elements 31-1 and first cladding layer elements 31-2, wherein at least some of the first cladding main elements 31-1 are in contact with the largest virtual inscribed circle within the intermediate air region 10, while all the first cladding layer elements are not in contact with the largest virtual inscribed circle.

[0204] For example, when the fiber core is roughly circular, all the first cladding main elements 31-1 will simultaneously contact the largest virtual inscribed circle within the intermediate air region 10. However, when the fiber core is slightly elliptical, only some of the first cladding main elements 31-1 may contact the largest virtual inscribed circle within the intermediate air region 10.

[0205] In the above arrangement, any two adjacent first cladding master elements will have a spacing d, where the spacing d is defined by the shortest distance between the two adjacent first cladding master elements. Typically, the first cladding element 31-2 between two adjacent first cladding master elements 31-1 is further away from the center point of the core matrix field relative to the first cladding master element 31-1.

[0206] In some embodiments, each first cladding main element 31-1 has the same or similar shape and size, and is a full tube or near-full tube. Furthermore, each first cladding main element 31-1 may also include at least one main nested element 34-1, and each main nested element 34-1 may be selected from any of full tubes, arc-shaped elements, and straight walls.

[0207] Each first-layer element 31-2 may also be a full tube or a near-full tube. Furthermore, each first-layer element 31-2 may include at least one first-nested element 34-2, which may be selected from any of a full tube, an arc-shaped element, and a straight wall.

[0208] In some embodiments, the shape of each first layer element may differ from the shape of the first layer main element and is selected from either an arcuate element or a straight wall. Specifically, in the case where the first layer element is an arcuate element or a straight wall with an opening facing the inner surface, the first layer element may include at least one secondary nested element 34-2, which is located between the first layer element 31-2 and the inner surface 21. In some embodiments, each primary nested element may also contain at least one secondary nested element.

[0209] In some embodiments, any two adjacent first cladding main elements 31-1 may have only one corresponding first cladding layer element 31-2, thereby the first cladding main elements 31-1 and the first cladding layer elements 31-2 alternate with each other and are the same in number. Typically, the number of first cladding main elements 31-1 and first cladding layer elements 31-2 may both be 3, 4, 5 or 6.

[0210] As an example, Figure 17a Four first cladding main elements 31-1 and four first cladding layer elements 31-2 are shown, and both the first cladding main elements 31-1 and the four first cladding layer elements 31-2 are full tubes. In addition, the size of each first cladding layer element 31-2 is much smaller than that of the first cladding main elements 31-1. Figure 17b , Figure 17c , Figure 17d and Figure 17e It shows Figure 17a A variant embodiment, wherein with Figure 17a compared to, Figure 17b , Figure 17c , Figure 17d and Figure 17e The dimensions of the four first-layer elements 31-2 have been increased. Furthermore, Figure 17d The outer contours of the cladding elements form a square arrangement within the outer sheath, while Figure 17e The outer contours of the cladding elements form a circular arrangement.

[0211] In some embodiments, any two adjacent first cladding main elements 31-1 may have a plurality of corresponding first cladding layer elements 31-2, and these plurality of corresponding first cladding layer elements 31-2 may be in contact with each other. As an example, Figure 17fA schematic diagram is shown showing a structure with two corresponding first cladding layer elements 31-2 between any two adjacent first cladding layer main elements 31-1, wherein the two corresponding first cladding layer elements 31-2 are in contact with each other and are also in contact with a neighboring first cladding layer main element.

[0212] Furthermore, according to the design of this disclosure, the first cladding main element 31-1 and / or the first cladding layer element 31-2 can be arranged to contact or not contact the inner surface of the outer sheath, which can be a regular shape (e.g., circular or square) or an irregular shape. For example, Figure 17a , Figure 17b and Figure 17c The inner surface of the outer sheath is irregularly shaped. Figure 17d The inner surface of the outer sheath is square, while Figure 17e and Figure 17f The inner surface of the outer sheath is circular. Furthermore, Figure 17f The first cladding main element is arranged so as not to contact the inner surface of the outer sheath.

[0213] In some embodiments, when the first cladding main element 31-1 and / or the first cladding layer element 31-2 can be arranged to not contact the inner surface of the outer sheath, they can be supported or attached to the inner surface of the outer sheath by, for example, a support 35 (e.g., a straight wall or arcuate element or a columnar element).

[0214] Similar to the first, second, and third example embodiments described above, in this fourth example embodiment, adjacent first cladding elements 31 (here, between adjacent first cladding main elements 31-1 and first cladding layer elements 31-2) will also have the closest contact points, for example... Figure 17a The numbers C1, C2, C3, C4, C5, C6, C7, and C8 are also relevant. Similarly, the confinement loss of the antiresonant hollow fiber will vary with D1 / D2.

[0215] Figure 17g It shows in Figure 17a Simulation drawing of the limiting loss under the contact structure layout as the ratio of D1 / D2 changes. For example... Figure 17g As shown, the loss can be reduced as the value of D1 / D2 increases. Figure 17h It shows in Figure 17a Simulation plots of the confinement loss versus wavelength under the contact structure layout show that the confinement loss can be limited to below 1 dB / km, or even below 0.1 dB / km, in the range of 1200 nm to 1750 nm. Figure 17i It shows in Figure 17g Simulation plot of the limitation loss versus wavelength under the contact structure layout, from which... Figure 17i It can be seen that, Figure 17g The contact structure can also keep the confinement loss below 0.1 dB / km.

[0216] Similar to the above first, second, and third exemplary embodiments, the confinement loss of the anti-resonant hollow-core fiber is related not only to the ratio of D1 / D2 but also to other structural parameters of the anti-resonant hollow-core fiber (including but not limited to, the distance from the closest contact point to the inner surface of the outer jacket, the diameter of the largest virtual inscribed circle in the intermediate air region, the wall thickness of each component in the cladding element, the size of the first cladding sub-element relative to the first cladding main element, the size and shape of the first main nested element relative to the first cladding main element, the size and shape of the first nested element relative to the first cladding sub-element, etc.) and the specific structural layout (including but not limited to, the nested arrangement, the number of layers of the anti-resonant layer arrangement, etc.). Therefore, the confinement loss of the anti-resonant hollow-core fiber can be optimized by adjusting the above specific structural parameters and / or specific structural layout of the anti-resonant hollow-core fiber.

[0217] Figure 18a shows Figure 17a a schematic diagram of a variant structure of the typical structure of the fourth exemplary embodiment. Figure 18a The variant structure of Figure 17a differs from the structure of Figure 18b in that the first cladding sub-element 31-2 is formed with a straight wall, thus being completely different from the shape of the 31-1 of the first cladding main element. Figure 18b shows Figure 18a a simulation plot of the confinement loss varying with the ratio of D1 / D2 under the contact structure layout of Figure 18b As Figure 17g shown, in this example, as the ratio of D1 / D2 increases, the loss decreases, thus showing similar characteristics to

[0218] Fifth Example Implementation

[0219] Although the confinement loss of the anti-resonant hollow-core fiber is mainly studied with reference to D1 / D2 above. However, for the above fourth exemplary embodiment, it is also found that the confinement loss of the anti-resonant hollow-core fiber can also be characterized by the ratio d / a between the distance d between any two adjacent first cladding main elements and the radius a of the largest virtual inscribed circle in the core, and / or the ratio D3 / a between the distance D3 from the contact point closest to the center point of the core fundamental mode field between the adjacent first cladding main element and the first cladding sub-element to the largest virtual inscribed circle and the radius a of the largest virtual inscribed circle. In particular, it is particularly advantageous that the following relationships exist between the distance d and a and between the distance D3 and a: 0.15 < d / a < 1 and / or D3 / a > 0.6.

[0220] Figure 19aA schematic diagram is shown of a structure in which the first cladding master element and the first cladding layer element of an antiresonant hollow optical fiber according to a fifth exemplary embodiment of the present disclosure each have only one layer of nested elements (i.e., a single-layer nested structure). Figure 19a In the structure shown, the cladding element is approximately square, and the first cladding main element and the first cladding layer element have the same size. Figure 19b It shows Figure 19a The confinement loss of antiresonant hollow fiber is plotted as a function of wavelength using simulation. From Figure 19b It can be seen that the overall loss of a single-layer nested structure is relatively high.

[0221] Figure 20a A schematic diagram is shown of a structure in which both the first cladding master element and the first cladding layer element of an antiresonant hollow optical fiber according to a fifth exemplary embodiment of this disclosure have double-layer nested elements (i.e., a double-layer nested structure). Similar to... Figure 19a In the structure shown, the structure of the cladding element is also roughly square. The size of the first cladding main element can vary according to the spacing d between the first cladding main elements. At the same time, the size of the first cladding layer element can be less than, equal to or greater than the size of the first cladding main element.

[0222] Figure 20b It shows Figure 20a Simulation plot of the confinement loss of antiresonant hollow fiber as a function of d / a. Simulation results show that when the ratio of spacing d to a is in the range of 0.15 to 0.87, the confinement loss can be limited to within 1 dB / km, and even below 0.1 dB / km. Figure 20c It shows Figure 20a Simulation plots of the confinement loss of antiresonant hollow fiber as a function of D3 / a are presented. Simulation results show that when the ratio of D3 to a is greater than 1.2 and less than 3.5, the confinement loss can be effectively controlled at a low level, even below 0.1 dB / km or 0.01 dB / km. Furthermore, Figure 20d It shows Figure 20a A schematic diagram showing the confinement loss of an antiresonant hollow fiber as a function of wavelength at D3 / a = 2.21227. From... Figure 20d It can be seen that the limiting loss can be controlled to below 0.1 dB / km in the band range from 1300 nm to 1700 nm.

[0223] Figure 21a A schematic diagram of a variant structure is shown, in which both the first cladding master element and the first cladding layer element of the antiresonant hollow optical fiber according to a fifth exemplary embodiment of this disclosure have double-layer nested elements (i.e., a double-layer nested structure). Figure 20a The example structure is different, Figure 21a The inner surface of the outer sheath of the anti-resonant hollow fiber is irregular, wherein the size of the first cladding main element can vary according to the spacing d between the first cladding main elements, and the size of the first cladding layer element is the same as the size of the first cladding main element.

[0224] Figure 21b It shows Figure 21a Simulation plot of the confinement loss of antiresonant hollow fiber as a function of d / a. Simulation results show that when the ratio between spacing d and a is in the range of 0.15 to 0.87, the confinement loss can be essentially limited to within 1 dB / km, and even below 0.1 dB / km. Figure 21c It shows Figure 21a Simulation plots of the confinement loss of antiresonant hollow fiber as a function of D3 / a are presented. Simulation results show that when the ratio of D3 to a is greater than 1.2 and less than 3.5, the confinement loss can be effectively controlled at a low level, even below 0.1 dB / km or 0.01 dB / km. Furthermore, Figure 21d It shows Figure 21a A schematic diagram illustrating the confinement loss of antiresonant hollow fiber as a function of wavelength for different spacings d, where d is 10 μm and 9 μm, respectively. Figure 21d Simulations show that a slight increase in spacing d does not substantially affect the limiting loss. In particular, in the case of only three first cladding main elements in the anti-resonant hollow fiber, the ratio requirement can be further relaxed when the fiber core is increased, for example, d / a < 1, or even d / a < 1.3, or even d / a < 1.5.

[0225] It should be understood that the above Figures 19a to 21d The presence of the first cladding layer element allows for a wider spacing d between two adjacent first cladding layer main elements, thereby increasing the redundancy of the spacing d between two adjacent first cladding layer main elements. This reduces the drawing requirements for the anti-resonant hollow fiber of this disclosure.

[0226] In contrast. Figure 22a An anti-resonant hollow-core optical fiber according to a fifth exemplary embodiment of this disclosure is shown. Figure 20a The structure (where the dimensions of the first cladding main elements are the same, and the dimensions of the first cladding layer elements are different). Figure 21a The structure (where the first cladding main element and the first cladding layer element are of the same size) and Figure 22b Comparative simulation plot of the limiting loss of a four-tube non-contact structure without a first cladding element as a function of d / a. Figure 22c An anti-resonant hollow-core optical fiber according to a fifth exemplary embodiment of this disclosure is shown. Figure 20aThe structure (where the dimensions of the first cladding main elements are the same, and the dimensions of the first cladding layer elements are different). Figure 21a The structure (where the first cladding main element and the first cladding layer element are of the same size) and Figure 22b A comparative simulation plot showing the limiting loss of a four-tube non-contact structure without a first cladding element as a function of D3 / a. It should be noted here that... Figure 22b A schematic diagram of a four-tube non-contact structure without a first cladding element is shown for comparison, wherein... Figure 20a and Figure 21a The structure is similar, Figure 22b The structure has four first cladding main elements, each with a double-nested structure, but the four-tube non-contact structure does not have a first cladding element; in addition, there are multiple solid quartz rods between adjacent first cladding main elements. Figure 22a and Figure 22c It can be seen that, with Figure 22b Compared to the confinement loss of the four-tube non-contact antiresonant hollow-core fiber, the confinement loss of the antiresonant hollow-core fiber in the fifth exemplary embodiment of this disclosure can be maintained substantially below 1 dB / km. In contrast, Figure 2 The confinement loss of non-contact antiresonant hollow fiber increases significantly after d / a is greater than 0.6 or D3 / a is less than 2.

[0227] Figure 23a and Figure 23b The diagrams show structural schematics of strong and weak contact between two adjacent first cladding elements, respectively. The term "weak contact" is defined as the two adjacent first cladding elements just making contact, while the term "strong contact" is defined as the contact area between two adjacent first cladding elements being relatively large, in contrast to "weak contact".

[0228] Figure 23c A comparative simulation plot of the confinement loss as a function of d / a for an anti-resonant hollow fiber in a fifth exemplary embodiment of the present disclosure under strong and weak contact conditions is shown. Figure 23d A comparative simulation plot of the confinement loss of an anti-resonant hollow fiber according to a fifth exemplary embodiment of the present disclosure as a function of D3 / a under strong and weak contact conditions is shown. Figure 23c and Figure 23d Simulation results show that strong and weak contact have no significant impact on the confinement loss of the antiresonant hollow fiber disclosed in this paper. This is highly advantageous for the actual drawing process, as it relaxes the requirements for the drawing process.

[0229] Furthermore, as an example of research on the influence of different core radii on confinement loss, Figure 23eA comparative simulation plot of the confinement loss of an antiresonant hollow-core optical fiber according to a fifth exemplary embodiment of the present disclosure as a function of d / a at different core radii is shown; and Figure 23f A comparative simulation plot of the confinement loss as a function of D3 / a for an antiresonant hollow-core optical fiber with different core radii according to a fifth exemplary embodiment of this disclosure is shown. Figure 23e and Figure 23f It can be seen that different core radii (e.g., core radii a shown in the figure are 23 μm, 19 μm, and 15 μm, respectively) can also have a corresponding impact on the confinement loss, with a larger core radius resulting in better confinement effect. Therefore, in some cases, the confinement loss of the optical fiber can be adjusted by increasing the core radius of the antiresonant hollow fiber of this disclosure.

[0230] Other example embodiments

[0231] Figure 24a A schematic diagram of a variant embodiment of the anti-resonant hollow fiber according to the present disclosure is shown, wherein the cladding elements in the anti-resonant hollow fiber include three first cladding main elements 31-1 and three first cladding layer elements 31-2, wherein the size of the first cladding main elements is much smaller than that of the first cladding layer elements. Figure 24b It shows that according to Figure 24a The confinement loss of the antiresonant hollow fiber is plotted as d / a. Figure 24c according to Figure 24a The confinement loss of the antiresonant hollow fiber was plotted with respect to D3 / a in a simulation, where the core radius was chosen to be 20 μm. The simulation results show that by selecting appropriate antiresonant hollow fiber structure and related parameters, such as 1 < d / a < 1.4, and / or 1.25 < D3 / a < 3, the confinement loss can be controlled at a suitable level, such as below 1 dB / km.

[0232] Figure 24d A schematic diagram of another variant embodiment of the anti-resonant hollow fiber according to the present disclosure is shown, wherein the cladding elements in the anti-resonant hollow fiber include five first cladding main elements 31-1 and five first cladding layer elements 31-2, wherein the first cladding main elements and the first cladding layer elements are identical in shape and size. Figure 24e It shows that according to Figure 24d Simulation plot of the confinement loss of antiresonant hollow fiber as a function of wavelength. From Figure 24e It can be seen that in the 1250nm to 1600nm band range, the limiting loss can be controlled at a relatively good level of 0.1dB / km.

[0233] Figure 25aIn (a), (b), and (c), schematic diagrams of the structure where both the first cladding main element and the first cladding sub - element of the anti - resonant hollow fiber of the present disclosure have two layers of nested elements are shown. The ratio m of the size of the first main nested element to the size of the first cladding main element varies. Specifically, in (a) m = 0.5, in (b) m = 0.7, and in (c) m = 0.9.

[0234] Figure 25b shows Figure 25a simulation comparison plots of the confinement losses of the core fundamental mode and high - order modes of the anti - resonant hollow fiber varying with the size ratio m of the first main nested element to the first cladding main element; Figure 25c shows Figure 25a simulation plots of the high - order mode suppression ratio of the anti - resonant hollow fiber varying with the size ratio m of the first main nested element to the first cladding main element; Figure 25d shows Figure 25a simulation comparison plots of the effective refractive indices of the core fundamental mode, high - order modes, and the inter - tube cavity region mode of the anti - resonant hollow fiber varying with the size ratio m of the first main nested element to the first cladding main element. From Figure 25b and Figure 25c it can be seen that by changing the ratio of the size of the first main nested element to the first cladding element, the confinement losses of the high - order modes and the high - order mode suppression ratio of the [[ID=…]] Figure 25a anti - resonant hollow fiber can be adjusted to an appropriate range; from Figure 25d it can be seen that changing the size ratio m of the first main nested element to the first cladding main element has a greater impact on the effective refractive index of the cavity region between the nested tubes of the anti - resonant hollow fiber, while having little impact on the effective refractive indices of the fundamental mode LP01 and the high - order mode LP11 of the anti - resonant hollow fiber. Specifically, as m changes, for example, when 0.5 < m < 0.65, the cavity area between the first main nested element and the second main nested element nested within the first cladding main element gradually decreases, causing the effective refractive index of the fundamental mode at this cavity to gradually approach the effective refractive index of the high - order mode LP11. At the intersection point where m = 0.58, the high - order mode LP11 and the fundamental mode at the cavity are phase - matched, resulting in LP11 leaking from the cavity, increasing the loss, and thus increasing the high - order mode suppression ratio; when 0.7 < m < 0.9, the cavity area between the second main nested element and the third main nested element nested within the first cladding main element gradually increases, and the effective refractive index gradually increases, approaching LP11. At the intersection point where m = 0.82, the high - order mode P11 and the fundamental mode at the cavity are phase - matched, causing LP11 to leak from the cavity, increasing the loss, and thus increasing the high - order mode suppression ratio.

[0235] Figure 26a 、 Figure 26b and Figure 26cSchematic diagrams of several other variations of the anti-resonant hollow-core optical fiber according to this disclosure are shown, wherein... Figure 26a The cladding elements include four primary cladding elements that are essentially circular tubes and four secondary cladding elements consisting of only one straight wall. Figure 26b and Figure 26a The difference is Figure 26b Between the first layer of the straight-walled tube and the outer sheath, there is also a nested element that serves as the straight wall. Figure 26c and Figure 26b The difference is Figure 26c The cladding elements in this paper consist of only three primary cladding elements that are essentially circular tubes. In contrast, Figure 26d A schematic diagram of an existing anti-resonant hollow fiber consisting of cladding elements composed of four sets of circular tube units is shown.

[0236] Figure 26e It shows that according to Figures 26a to 26d The confinement loss of the anti-resonant hollow fiber is compared with d / a in the simulation plot. Figure 26f It shows that according to Figures 26a to 26c The confinement loss of the anti-resonant hollow fiber is compared with the simulation plot of D3 / a. Figure 26g It shows that according to Figure 26a Simulation plot of confinement loss of antiresonant hollow fiber with wavelength under different d / a conditions; Figure 26h It shows that according to Figure 26a Simulation plots of the confinement loss of antiresonant hollow fiber with wavelength under different D3 / a conditions. From Figure 26e It can be seen that: despite Figures 26a to 26c There are contact points between adjacent first cladding elements, but by optimizing the ratio between d and a, the confinement loss of the antiresonant hollow fiber can still be limited to a good range, such as 1 dB / km, or even within the range of 0.1 dB / km. Figure 26g and Figure 26h As can be seen, it can be done by selecting Figure 26a The appropriate ratio of d / a and D3 / a in the anti-resonant hollow fiber ensures that the confinement loss of the anti-resonant hollow fiber is limited to a low loss level.

[0237] It should be noted that the various structures of the antiresonant hollow fiber disclosed herein, as illustrated above, are ideal structures. In the actual drawing process, the structure of the antiresonant hollow fiber may deform under pressure.

[0238] As an example, Figure 27a It shows Figure 25aThe structure may deform during the actual drawing process. The first cladding main element 31-1 and the first cladding layer element 31-2, which are essentially full-tube shapes, may become irregularly circular. This is because the tube wall between the contact points of adjacent first cladding elements 31 will straighten during drawing. Furthermore, since supports 35 (e.g., quartz pillars) may be arranged between the inner surfaces of the first cladding main element and the outer sheath, the four supports 35 may be tangent to the corresponding inner surfaces 21 of the first cladding main element and the outer sheath. In this case, the tube wall between the contact points and the supports may also straighten during drawing. Simultaneously, the contact points between adjacent first cladding elements may also thicken due to compression during drawing.

[0239] Figure 27b It shows Figure 27a The simulation plot shows the effect of thickening the contact point on the confinement loss in the case of antiresonant hollow fiber. The simulation results show that thickening the contact point has no substantial impact on the confinement loss.

[0240] During the drawing process, the thickness of the tube wall may change in some local areas. Figure 27c It shows in Figure 27a A simulation plot of the limitation loss versus wavelength in the case of antiresonant hollow fiber, where the thickness of a portion of the tube wall is changed (e.g., the thickness of the first main nested element relative to the first cladding main element). Plot: Although the actual structure differs from the ideal structure, it still exhibits good fundamental mode loss performance.

[0241] Figure 27d It shows in Figure 27a In the case of anti-resonant hollow fiber, the simulation plot shows the effect of changing the ratio m of the size of the first main nested element to the size of the first cladding main element on the fiber core fundamental mode and higher-order modes. Figure 27e It shows in Figure 27a A simulation plot showing the variation of the higher-order mode suppression ratio (HDR) with the ratio *m* of the size of the first master nested element to the size of the first cladding master element in the case of an anti-resonant hollow fiber. Figure 27d It can be seen that changing the ratio m has a significant impact on the fundamental mode loss. When 0.65 < m < 0.75, the loss is ≤ 0.01 dB / km. However, in some embodiments, simply changing the value of m may not effectively filter out higher-order modes. For example, when 0.65 < m < 0.75, the higher-order mode suppression ratio is ≤ 100, meaning that the filtering effect of higher-order modes is poor. Figure 27f It shows in Figure 27a In the case of anti-resonant hollow fiber, simulation plots are shown to illustrate the effect of changing the ratio *m* of the size of the first master nested element to the size of the first cladding master element on the effective refractive index of the core fundamental mode, higher-order modes, and inter-tube cavity region modes. Furthermore, from... Figure 27fFrom the simulation drawing of the effective refractive index, it can be seen that the effective refractive index of the cavity in the first cladding main element is also far from the effective refractive index of the higher-order mode of the fiber core.

[0242] In some embodiments, the aforementioned higher-order mode suppression ratio can be suppressed by adjusting the size of the first nested element relative to the first nested element. Figure 28a It shows in Figure 27a Simulation plot of the effect of changing the size ratio n1 of the first nested element to the first cladding layer element on the limiting loss of the fiber core fundamental mode and higher-order modes in the case of anti-resonant hollow fiber. Figure 28b It shows in Figure 27a A simulation plot of how the higher-order mode suppression ratio changes with the ratio n1 of the size of the first nested element to the size of the first cladding layer element in the case of anti-resonant hollow fiber. Figure 28c It shows in Figure 27a Simulation plot of the effect of changing the size ratio n1 of the first nested element relative to the first cladding layer element on the effective refractive index of the fiber core fundamental mode, higher-order modes and inter-tube cavity region modes in the case of anti-resonant hollow fiber.

[0243] from Figure 28a and Figure 28b It can be seen that changing the size ratio n1 of the first nested tube relative to the first layered element has a relatively small impact on the fundamental mode loss; for example, the fundamental mode loss can be less than 0.01 dB / km. However, changing this ratio can effectively match the higher-order modes of the fiber core with the effective refractive index of the cavity within the first layered element, thereby changing the higher-order mode loss and achieving a higher higher-order mode suppression ratio. For example, Figure 28b This shows that at n=0.53, the higher-order mode suppression ratio can reach 2093. Furthermore, from... Figure 28c From the simulation plot of the effective refractive index, the effective refractive index of the cavity between the first layer element and the first nested element is also similar to the effective refractive index of the higher-order mode of the fiber core, for example, Δn. eff ≈0.00001.

[0244] Therefore, higher-order modes within the fiber core can be suppressed by alternating arrangements of multiple first cladding master elements and multiple first cladding layer elements, especially by nested arrangements within the first cladding layer elements.

[0245] Various embodiments of the antiresonant hollow fiber of this disclosure have been described above. It should be understood that, since adjacent first cladding elements in the antiresonant hollow fiber of this disclosure are in contact with each other, the requirements for drawing are reduced compared to existing non-contact structures. At the same time, by optimizing the specific structural parameters (especially the ratios of D1 / D2, d / a, and / or D3 / a) and / or the specific layout of the antiresonant hollow fiber of this disclosure, the confinement loss of the antiresonant hollow fiber can be maintained at a satisfactory level.

[0246] Typically, all wall thicknesses t of the first cladding element of this disclosure can satisfy the anti-resonance condition:

[0247] Where λm is the resonant wavelength, m is the order of the anti-resonant layer, and n is the refractive index of the material of the component constituting the first cladding element.

[0248] Specifically, in some embodiments, all wall thicknesses of the first cladding element may be substantially the same. In still other embodiments, the first cladding element may include different first cladding elements (or first cladding master elements) in orthogonal directions, and the wall thicknesses of these different first cladding elements (or first cladding master elements) in orthogonal directions may be different from each other. As an example, Figure 29a A schematic diagram of the structure of the first cladding master element of the antiresonant hollow fiber of this disclosure with different thicknesses in orthogonal directions is shown. For example, as Figure 29a As shown, the first cladding main element has a thickness of 1.3 μm in the first direction and only 1.1 μm in the second direction orthogonal to the first direction. With the wall thicknesses in these orthogonal directions being inconsistent, the anti-resonant hollow fiber can cause different effective refractive indices of the mode fields in the orthogonal directions within the fiber core, thereby generating birefringence and achieving the polarization-maintaining effect. Figure 29b It shows Figure 29a A simulation diagram showing the phase birefringence of the structure as a function of wavelength.

[0249] In some other embodiments, the ratio of the radius of the largest virtual inscribed circle of the fiber core to the wavelength of the light guided by the hollow fiber is between 3 and 40, or between 4.5 and 20. Furthermore, the antiresonant hollow fiber of this disclosure can support effective single-mode or multimode transmission, wherein the loss ratio between the lowest-loss higher-order mode and the fundamental mode within the fiber core can be at least one order of magnitude, or at least two orders of magnitude, or at least three orders of magnitude.

[0250] Furthermore, it should be understood that, without contradiction, the features of the above embodiments can be combined with each other, and the description of the above embodiments can be applied to other embodiments.

[0251] While the invention has been detailed and described in the accompanying drawings and foregoing description, these descriptions and descriptions should be considered illustrative or exemplary rather than restrictive; the invention is not limited to the disclosed embodiments. Other variations of the disclosed embodiments will be understood and practiced by those skilled in the art in practicing the claimed invention through study of the drawings, disclosure, and appended claims.

[0252] In the claims, the word "comprising" does not exclude other elements, and the indefinite articles "a" or "an" do not exclude a plurality. A single element or other component may fulfill the function of multiple items set forth in the claims. The mere fact that certain features are recited only in dissimilar embodiments or dependent claims does not imply that combinations of these features cannot be advantageously used. Without departing from the spirit and scope of this application, the scope of protection of this application covers any possible combination of the various features recited in the various embodiments or dependent claims.

[0253] Furthermore, any reference numerals in the claims should not be construed as limiting the scope of the invention.

Claims

1. An anti-resonant hollow-core optical fiber, comprising: Outer sheath with an inner surface; as well as A cladding element, located within the outer sheath and comprising a plurality of first cladding elements arranged around the inner surface, wherein any two adjacent first cladding elements are in contact with each other and define an intermediate air region of the anti-resonant hollow fiber, wherein the core fundamental mode field of the anti-resonant hollow fiber is confined within the intermediate air region. Between any two adjacent first cladding elements, there is a contact point closest to the center point of the core matrix field. The ratio between the distance D1 from the closest contact point to the nearest boundary of the core matrix field and the distance D2 from the nearest boundary to the center point of the core matrix field has the following relationship: D1 / D2 > 0.

46. The boundary of the core matrix mode field is defined by a strength equal to 1 / e of the strength at the center point of the core matrix mode field. 2 By definition, the center point of the square of the fundamental mode electric field strength of the fiber core is the peak point of the square of the fundamental mode electric field strength; Each of the first cladding elements further includes at least one first main nested element.

2. The anti-resonant hollow optical fiber according to claim 1, wherein each of the first cladding elements is selected from a full tube, a circular arc, a straight wall, or a combination thereof.

3. The anti-resonant hollow optical fiber according to claim 1, wherein each of the first cladding elements is a first arc-shaped element with an opening facing the inner surface and having the same or similar dimensions to each other, and the number of the first cladding elements is 3, 4 or 5.

4. The anti-resonant hollow fiber according to claim 1, wherein D1 / D2 is greater than 0.5, 0.6, 0.8 or 1.

5. The anti-resonant hollow fiber according to claim 1, wherein the first main nesting element is fully or partially nested in the first cladding element.

6. The anti-resonant hollow optical fiber according to claim 1, wherein the first main nesting element is selected from any one of a full tube, a second arc-shaped element with its opening facing the inner surface, or a straight wall.

7. The anti-resonant hollow fiber according to claim 6, wherein when the first main nesting element is a full tube or the second arc-shaped element, each of the first main nesting elements further comprises at least one second main nesting element that is fully or partially nested therein.

8. The anti-resonant hollow fiber according to claim 6, wherein when the first main nesting element is a straight wall, each of the first main nesting elements further comprises at least one second main nesting element nested between the first main nesting element and the inner surface.

9. The anti-resonant hollow optical fiber according to claim 7 or 8 further includes a third main nesting element, the third main nesting element being nested within the second main nesting element or between the second main nesting element and the inner surface.

10. The anti-resonant hollow fiber according to claim 1, wherein the plurality of first cladding elements comprises first cladding master elements and first cladding layer elements, wherein at least one corresponding first cladding layer element is present between any two adjacent first cladding master elements, wherein at least some of the first cladding master elements are arranged to contact the largest virtual inscribed circle in the intermediate air region, while all the first cladding layer elements are not in contact with the largest virtual inscribed circle at all.

11. The anti-resonant hollow-core optical fiber according to claim 10, wherein the corresponding at least one first cladding layer element includes a corresponding first cladding layer element, and the corresponding first cladding layer element is in contact with two adjacent first cladding main elements respectively.

12. The anti-resonant hollow fiber according to claim 10, wherein the corresponding at least one first cladding layer element comprises two corresponding first cladding layer elements in contact with each other, and each of the two corresponding first cladding layer elements is in contact with an adjacent first cladding main element.

13. The anti-resonant hollow-core optical fiber according to claim 10, wherein any two adjacent first cladding principal elements are spaced by a distance d, the radius of the largest virtual inscribed circle is a, and the distance d and a have the following relationship: 0.1 <d / a<1.5。 14. The anti-resonant hollow fiber according to claim 10, wherein each of the first cladding master elements has the same or similar shape and size, and is a full tube or nearly a full tube.

15. The anti-resonant hollow fiber according to claim 10, wherein the shape of each of the first cladding layer elements is the same as or similar to the shape of the first cladding main element.

16. The anti-resonant hollow fiber according to any one of claims 10 to 15, wherein the shape of each of the first cladding layer elements is different from the shape of the first cladding master element, and is selected from either arc-shaped elements and straight walls.

17. The anti-resonant hollow-core optical fiber according to any one of claims 10 to 15, wherein the first cladding master element comprises at least one master nested element, the at least one master nested element being selected from any one of a full tube, an arc-shaped element, and a straight wall.

18. The anti-resonant hollow fiber according to any one of claims 10 to 15, wherein in the case where the first cladding layer element is a full tube or an arc-shaped element with an opening facing the inner surface, the first cladding layer element includes at least one sub-nested element.

19. The anti-resonant hollow fiber according to any one of claims 10 to 15, wherein, in the case where the first cladding layer element is a straight wall, the first cladding layer element is further configured with at least one sub-nested element located between the first cladding layer element and the inner surface.

20. The anti-resonant hollow fiber according to any one of claims 10 to 15, wherein the number of the first cladding main element and the number of the first cladding layer elements are the same, and are 3, 4, 5 or 6.

21. The anti-resonant hollow fiber according to any one of claims 1-8 and 10-15, wherein all wall thicknesses of the first cladding element are substantially the same.

22. The anti-resonant hollow fiber according to any one of claims 1-8 and 10-15, wherein the first cladding element comprises different first cladding elements in orthogonal directions, the first cladding elements in the orthogonal directions having different wall thicknesses.

23. The anti-resonant hollow fiber according to any one of claims 1-8 and 10-15, wherein the anti-resonant hollow fiber supports effective single-mode or multimode transmission.

24. The anti-resonant hollow-core optical fiber according to any one of claims 1-8 and 10-15, wherein the loss ratio between the lowest loss higher-order mode in the core and the fundamental mode in the core is at least one order of magnitude, or at least two orders of magnitude, or at least three orders of magnitude.

25. The anti-resonant hollow-core optical fiber according to any one of claims 1-8 and 10-15, wherein all wall thicknesses t of the first cladding element and all nested elements satisfy the anti-resonance condition: Where λ m λ is the resonant wavelength, m is the order of the anti-resonant layer, and n is the refractive index of the material of the component constituting the first cladding element.

26. The anti-resonant hollow-core optical fiber according to any one of claims 1-8 and 10-15, wherein the ratio of the radius of the largest virtual inscribed circle of the fiber core to the wavelength of the light guided by the hollow-core optical fiber is between 3 and 40, or between 4.5 and 20.

27. An anti-resonant hollow optical fiber, comprising: Outer sheath with an inner surface; as well as A cladding element, located within the outer sheath and comprising a plurality of first cladding elements arranged around the inner surface, wherein any two adjacent first cladding elements are in contact with each other and define an intermediate air region of the anti-resonant hollow fiber, wherein the core mode field of the anti-resonant hollow fiber is confined within the intermediate air region. The plurality of first cladding elements includes first cladding main elements and first cladding layer elements, wherein at least one corresponding first cladding layer element is present between any two adjacent first cladding main elements, wherein at least some of the first cladding main elements are arranged to contact the largest virtual inscribed circle in the intermediate air region, while none of the first cladding layer elements are in contact with the largest virtual inscribed circle. The first cladding master element is spaced d apart from any two adjacent elements, and the radius of the largest virtual inscribed circle is a. The spaced d and a are related as follows: 0.1 <d / a<1.5; The distance D3 between the contact point closest to the center of the largest virtual inscribed circle and the first cladding main element and the first cladding layer element, and the radius a of the largest virtual inscribed circle, has the following relationship: D3 / a>0.6; The first cladding master element includes at least one first master nested element.

28. The anti-resonant hollow optical fiber according to claim 27, wherein the first main nesting element is selected from any one of a full tube, an arc-shaped element, and a straight wall, and the first main nesting element is fully nested or partially nested within the first cladding main element.

29. The anti-resonant hollow-core optical fiber according to claim 27, wherein the corresponding at least one first cladding layer element includes a corresponding first cladding layer element, and the corresponding first cladding layer element is in contact with two adjacent first cladding main elements respectively.

30. The anti-resonant hollow fiber according to claim 27, wherein the corresponding at least one first cladding layer element comprises two corresponding first cladding layer elements in contact with each other, and each of the two corresponding first cladding layer elements is in contact with an adjacent first cladding main element.

31. The anti-resonant hollow fiber according to claim 27, wherein each first cladding master element has the same shape and size, and is a full tube or near-full tube or arc-shaped element.

32. The anti-resonant hollow optical fiber according to claim 27, wherein D3 / a>0.

8.

33. The anti-resonant hollow optical fiber according to claim 27, wherein D3 / a>1.

34. The anti-resonant hollow-core optical fiber according to claim 27, wherein the spacing d and a have the following relationship: 0.15 <d / a<1.3。 35. The anti-resonant hollow fiber according to claim 27, wherein the spacing d and a have the following relationship: 0.15 <d / a<1。 36. The anti-resonant hollow fiber according to any one of claims 27 to 35, wherein the shape of each of the first cladding layer elements is the same as the shape of the first cladding master element.

37. The anti-resonant hollow fiber according to any one of claims 27 to 35, wherein the shape of each of the first cladding layer elements is different from the shape of the first cladding master element, and is selected from full tube, arc-shaped element, straight wall or combination thereof.

38. The anti-resonant hollow fiber according to any one of claims 27 to 35, wherein each of the first main nesting elements is further provided with a second main nesting element, the second main nesting element being wholly or partially nested within the first main nesting element.

39. The anti-resonant hollow optical fiber according to claim 38, wherein each of the second main nested elements further comprises a third main nested element.

40. The anti-resonant hollow fiber according to any one of claims 27 to 35, wherein each first cladding layer element further comprises a first nested element.

41. The anti-resonant hollow fiber according to any one of claims 27 to 35, wherein each first nested element further comprises a second nested element.

42. The anti-resonant hollow fiber according to any one of claims 27 to 35, wherein in the case where the first cladding element is a full tube or an arcuate element with its opening facing the inner surface, the first cladding element includes at least one first nesting element.

43. The anti-resonant hollow fiber according to any one of claims 27 to 35, wherein, in the case where the first cladding layer element is a straight wall, the first cladding layer element is further configured with at least one first nested element located between the first cladding layer element and the inner surface.

44. The anti-resonant hollow fiber according to any one of claims 27 to 35, wherein the number of the first cladding main element and the number of the first cladding layer elements are the same, and are 3, 4, 5 or 6.

45. The anti-resonant hollow fiber according to any one of claims 27 to 35, wherein all wall thicknesses of the first cladding master element are substantially the same.

46. ​​The anti-resonant hollow-core optical fiber according to any one of claims 27 to 35, wherein the first cladding main element comprises different first cladding main elements in orthogonal directions, and the different first cladding main elements have different wall thicknesses.

47. The anti-resonant hollow fiber according to any one of claims 27 to 35, wherein the anti-resonant hollow fiber supports effective single-mode or multimode transmission.

48. The anti-resonant hollow-core optical fiber according to any one of claims 27 to 35, wherein the loss ratio between the lowest loss higher-order mode in the core and the fundamental mode in the core is at least one order of magnitude, or at least two orders of magnitude, or at least three orders of magnitude.

49. The anti-resonant hollow-core optical fiber according to any one of claims 27 to 35, wherein all wall thicknesses t of the first cladding principal element satisfy the anti-resonance condition: Where λ m λ is the resonant wavelength, m is the order of the anti-resonant layer, and n is the refractive index of the material of the component constituting the first cladding element.

50. The anti-resonant hollow optical fiber according to any one of claims 27 to 35, wherein the ratio of the maximum inscribed circle radius of the fiber core to the wavelength of the light guided by the hollow optical fiber is between 3 and 40, or between 4.5 and 20.

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