Multi-mode hollow-core anti-resonance optical fiber

Abstract

The invention provides a multi-mode hollow-core anti-resonance optical fiber. The multi-mode hollow-core anti-resonance optical fiber comprises a tubular outer wrapping layer, an inner wrapping layer and an outer wrapping layer, the plurality of tubular anti-resonance structures are uniformly distributed on the inner wall of the outer cladding; the anti-resonance structure comprises at least two tubular sub-anti-resonance structures which are nested in sequence; in the same anti-resonance structure, the sub-anti-resonance structure on the innermost layer is tangent to the inner wall of the outer cladding layer, the tubular side wall of at least the sub-anti-resonance structure on the outermost layer is provided with an opening extending in the length direction, and the opening is fixed to the inner wall of the outer cladding layer. The anti-resonance structure formed by the at least two tubular sub-anti-resonance structures which are sequentially nested can form a multi-layer anti-resonance reflection interface, the leakage of a fundamental mode and a high-order mode of the optical fiber is limited, the transmission loss is reduced, the sub-anti-resonance structure on the innermost layer is tangent to the inner wall of the outer cladding layer, and a tangent point is formed. And the tangent point is not in contact with the intersection point of the opening fixed on the inner wall of the outer cladding, so that a flatter broadband transmission spectrum is provided for the optical fiber.

Description

Technical Field

[0001] The present application relates to the field of optics and laser optoelectronics technology, and more specifically, to a multimode hollow core anti-resonant optical fiber. Background Art

[0002] Hollow-core optical fiber based on air core light guidance combines the ideal transmission environment of air with the flexible fiber of optical fiber, providing nearly free-space propagation conditions for light waves, breaking through the intrinsic limitations of traditional solid-core optical fiber core materials. It has a series of advantages such as extremely low transmission delay, ultra-low backscattered light intensity, negligible dispersion and extremely low nonlinear coefficient, and is expected to promote the further development of multiple optical fields such as optical fiber communications, optical fiber lasers, and optical fiber sensing.

[0003] As a branch of hollow core fiber, hollow core antiresonant fiber guides light based on the antiresonant reflecting optical waveguide (ARROW) mechanism, breaking through the strict restrictions on the material composition of traditional solid core fiber and not relying on the core material with a high refractive index. The light field transmitted in the air core is mainly determined by the glass wall thickness in the cladding. When the wavelength of light meets the resonance condition under the glass wall thickness, the light will be significantly leaked, while other wavelengths of light that do not meet the resonance condition can be effectively transmitted in the core. At the same time, combined with the grazing incidence of light and the radial multi-layer antiresonant reflection interface, the leakage of the light field in the air core to the cladding is greatly suppressed, achieving low-loss and stable transmission of light.

[0004] Most existing hollow-core anti-resonant fiber designs only support low-loss transmission in the fundamental mode, but have high transmission losses in higher-order modes, and cannot achieve stable multi-mode low-loss transmission. This will lead to problems such as coupling difficulties and low overall transmission efficiency when transmitting high-power multi-mode lasers, greatly limiting the application of hollow-core anti-resonant fibers in multi-mode laser generation and transmission scenarios. Therefore, there is still a lack of novel multi-mode ultra-low-loss hollow-core anti-resonant fiber designs in this field. Summary of the invention

[0005] In view of this, the present application provides a multimode hollow core anti-resonant optical fiber, the scheme is as follows:

[0006] A multimode hollow core antiresonant optical fiber, comprising:

[0007] Tubular outer covering;

[0008] A plurality of tubular anti-resonance structures uniformly distributed on the inner wall of the outer cladding; the anti-resonance structure comprises at least two tubular sub-anti-resonance structures nested in sequence;

[0009] Among them, in the same anti-resonance structure, the innermost sub-anti-resonance structure is tangent to the inner wall of the outer cladding, and at least the tubular side wall of the outermost sub-anti-resonance structure has an opening extending in the length direction, and the opening is fixed to the inner wall of the outer cladding.

[0010] Preferably, in the multimode hollow-core anti-resonant optical fiber introduced above, the anti-resonant structure includes N sub-anti-resonant structures, and in the direction from the outside to the inside, the N sub-anti-resonant structures are sequentially the 1st sub-anti-resonant structure to the Nth sub-anti-resonant structure, and N is a positive integer greater than 2; the 1st sub-anti-resonant structure to the N-1th sub-anti-resonant structure all have the opening, and there is a spacing between two adjacent openings on the inner wall of the outer cladding.

[0011] Preferably, in the multimode hollow core anti-resonant optical fiber introduced above, for the sub-anti-resonant structure having the opening, the radial cross section is a partial circle or a partial ellipse having the opening;

[0012] For the sub-antiresonance structure without the opening, the radial cross section is a circle or an ellipse tangent to the inner wall of the outer cladding.

[0013] Preferably, in the multi-mode hollow-core anti-resonant optical fiber introduced above, the angle of the opening corresponding to the center point of the sub-anti-resonant structure is less than 60°.

[0014] Preferably, in the multimode hollow-core anti-resonant optical fiber described above, the anti-resonant structure includes N sub-anti-resonant structures, and in the direction from the outside to the inside, the N sub-anti-resonant structures are sequentially a first sub-anti-resonant structure to an Nth sub-anti-resonant structure, and N is a positive integer greater than 2;

[0015] The side wall thickness of the ath sub-antiresonant structure is t a , a is a positive integer not greater than N;

[0016] The minimum distance between two adjacent anti-resonance structures is g;

[0017] Among them, 2t a <g<10t a .

[0018] Preferably, in the multimode hollow-core anti-resonant optical fiber introduced above, in the same anti-resonant structure, the refractive index of the sub-anti-resonant structures is the same, and the refractive index of the sub-anti-resonant structures is greater than 1.3 and less than 2.5.

[0019] Preferably, in the multimode hollow-core anti-resonant optical fiber introduced above, the anti-resonant structure includes N sub-anti-resonant structures, and in the direction from the outside to the inside, the N sub-anti-resonant structures are sequentially the 1st sub-anti-resonant structure to the Nth sub-anti-resonant structure, and N is a positive integer greater than 2; the 1st sub-anti-resonant structure to the N-1th sub-anti-resonant structure all have the opening, and two adjacent openings are fixed at the same position on the inner wall of the outer cladding.

[0020] Preferably, in the multimode hollow-core anti-resonant optical fiber introduced above, the radial cross-section of the outer cladding is circular, and the side of all the anti-resonant structures facing the center of the circle is located on the same circumscribed circle.

[0021] Preferably, in the multimode hollow-core anti-resonant optical fiber described above, the anti-resonant structure includes N sub-anti-resonant structures, and in the direction from the outside to the inside, the N sub-anti-resonant structures are sequentially a first sub-anti-resonant structure to an Nth sub-anti-resonant structure, and N is a positive integer greater than 2;

[0022] The side wall thickness of the ath sub-antiresonant structure is t a , a is a positive integer not greater than N; the diameter of the circumscribed circle is D;

[0023] Among them, 20t a <D<100t a .

[0024] Preferably, in the multi-mode hollow-core anti-resonant optical fiber introduced above, the number of the anti-resonant structures is 8-12.

[0025] Based on the above introduction, the present application provides a multimode hollow core anti-resonant optical fiber, comprising: a tubular outer cladding; a plurality of tubular anti-resonant structures uniformly distributed on the inner wall of the outer cladding; the anti-resonant structure comprises at least two tubular sub-anti-resonant structures nested in sequence; wherein, in the same anti-resonant structure, the innermost sub-anti-resonant structure is tangent to the inner wall of the outer cladding, and at least the tubular side wall of the outermost sub-anti-resonant structure has an opening extending in the length direction, and the opening is fixed to the inner wall of the outer cladding. The anti-resonant structure composed of at least two tubular sub-anti-resonant structures nested in sequence can form a multi-layer anti-resonant reflection interface, thereby limiting the leakage of the fundamental mode and high-order modes of the optical fiber, reducing the transmission loss, and the innermost sub-anti-resonant structure is tangent to the inner wall of the outer cladding to have a tangent point, and the tangent point does not touch the intersection point where the opening is fixed on the inner wall of the outer cladding, thereby providing a flatter broadband transmission spectrum for the optical fiber. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the related technologies, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0027] The structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification so as to facilitate understanding and reading by persons familiar with this technology. They are not used to limit the conditions under which this application can be implemented, and therefore have no substantive technical significance. Any structural modification, change in proportion or adjustment of size, without affecting the effects and purposes that can be achieved by this application, should still fall within the scope of the technical contents disclosed in this application.

[0028] Figure 1 A radial cross-sectional view of a multimode hollow-core anti-resonant optical fiber provided in an embodiment of the present application;

[0029] Figure 2 for Figure 1 Schematic diagram of the performance of a multimode hollow core antiresonant fiber shown;

[0030] Figure 3 A radial cross-sectional view of another multimode hollow-core anti-resonant optical fiber provided in an embodiment of the present application;

[0031] Figure 4 for Figure 3 Schematic diagram of the performance of a multimode hollow core antiresonant fiber shown;

[0032] Figure 5 A radial cross-sectional view of another multimode hollow core anti-resonant optical fiber provided in an embodiment of the present application;

[0033] Figure 6 A radial cross-sectional view of another multimode hollow core anti-resonant optical fiber provided in an embodiment of the present application;

[0034] Figure 7 A radial cross-sectional view of another multimode hollow-core antiresonant optical fiber provided in an embodiment of the present application. DETAILED DESCRIPTION

[0035] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the embodiments in the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0036] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0037] Combination Figure 1 and Figure 2 As shown, Figure 1 A radial cross-sectional view of a multimode hollow-core antiresonant optical fiber provided in an embodiment of the present application, Figure 2 for Figure 1 The performance diagram of the multimode hollow core antiresonant fiber is shown in Figure 1. Figure 1 A multimode hollow core anti-resonant optical fiber is shown, comprising: a tubular outer cladding 10; a plurality of tubular anti-resonant structures 11 uniformly distributed on the inner wall of the outer cladding 10; the anti-resonant structure 11 comprises at least two tubular sub-anti-resonant structures 111 nested in sequence; wherein, in the same anti-resonant structure 11, the innermost sub-anti-resonant structure 111 is tangent to the inner wall of the outer cladding 10, and at least the tubular side wall of the outermost sub-anti-resonant structure 111 has an opening extending in the length direction, and the opening is fixed to the inner wall of the outer cladding 10. It is easy to know that the length direction is the length direction of the multimode hollow core anti-resonant optical fiber.

[0038] exist Figure 1 In the illustrated manner, each anti-resonance structure 11 includes two tubular sub-anti-resonance structures 111 nested in sequence. The inner sub-anti-resonance structure 111 of the same anti-resonance structure 11 is tangent to the inner wall of the outer cladding 10, and the tubular side wall of the outer sub-anti-resonance structure 111 has an opening extending in the length direction, and the opening is fixed to the inner wall of the outer cladding 10.

[0039] The antiresonance structure 11 composed of at least two tubular sub-antiresonance structures 111 nested in sequence can form a multi-layer antiresonance reflection interface, thereby limiting the leakage of the optical fiber fundamental mode and high-order modes, reducing transmission loss, and the innermost sub-antiresonance structure 111 has a tangent point when tangent to the inner wall of the outer cladding 10, and the tangent point does not contact the intersection point where the opening is fixed on the inner wall of the outer cladding 10, thereby providing a flatter broadband transmission spectrum for the optical fiber. In the multimode hollow-core antiresonance optical fiber, the radial cross-sectional area of ​​the innermost sub-antiresonance structure 111 and the outermost sub-antiresonance structure 111 can also be adjusted to change the effective refractive index of the air mode in the antiresonance structure 11, so that the multimode hollow-core antiresonance optical fiber forms a phase mismatch of the high-order mode, thereby reducing the transmission loss of the optical fiber high-order mode.

[0040] In the multi-mode hollow-core anti-resonant optical fiber described above, the number of anti-resonant structures 11 is 8-12.

[0041] When the number of anti-resonance structures 11 is between 8 and 12, the phase mismatch of the multimode hollow core anti-resonance optical fiber in the high-order mode can be improved, and the coupling loss in the high-order mode can be suppressed, thereby realizing the ultra-low loss transmission of the optical fiber in the high-order mode. At the same time, the multimode hollow core anti-resonance optical fiber provided in the present application is mainly to improve the ultra-low loss transmission of the high-order mode, and its specific number needs to be set according to the wavelength, mode, loss and other conditions of the light to be transmitted, and the number of anti-resonance structures 11 is usually between 8 and 12. In an embodiment of the present application, the number of anti-resonance structures 11 and the area ratio of the sub-anti-resonance structure inside a single anti-resonance structure 11 can be adjusted at the same time, so as to realize the phase mismatch between the high-order mode in the central area of ​​the multimode hollow core anti-resonance optical fiber and the air mode in the anti-resonance structure 11, thereby realizing the ultra-low loss transmission of the high-order mode of the multimode hollow core anti-resonance optical fiber.

[0042] refer to Figure 2 From the data, we can see that Figure 1 The multimode hollow core anti-resonant optical fiber provided can significantly reduce the transmission loss of the optical fiber fundamental mode and higher-order modes, and supports LP 01 LP 11 LP 21 LP 02 Ultra-low loss transmission of multiple mode groups in the wavelength range of 800nm-1200nm. Among them, the multimode hollow core anti-resonant fiber is in LP 01 In the LP mode, when the wavelength is 1020nm, the loss is the lowest, only 0.04dB / km. In the wavelength range of 910nm-1080nm, the loss is less than 0.1dB / km, and in the wavelength range of 820nm-1130nm, the loss is less than 1dB / km. 11 In this mode, the minimum loss is only 0.078dB / km at 1020nm, and the loss is less than 1dB / km in the wavelength range of 850nm-1100nm. 21 In LP mode, the loss is the lowest at 1040nm, only 0.2dB / km, and the loss is less than 1dB / km in the wavelength range of 870nm-1070nm. 02 In this mode, the minimum loss is only 0.23dB / km at 1020nm, and the loss is less than 1dB / km in the wavelength range of 875nm-1110nm. At the same time, the multimode hollow core anti-resonant fiber has a wavelength range of 820nm-1200nm, LP 11 LP 21 LP 02 Mode Group and LP 01 The minimum loss ratio of the mode group is less than 10, so ultra-low loss transmission of multiple modes can be achieved.

[0043] Based on the above data, it can be seen that the number of outer cladding 10 and internal antiresonance structure 11 in the multimode hollow core antiresonance optical fiber provided in the embodiment of the present application and the combination of the air region formed by the sub-antiresonance structure 111 inside it can significantly reduce the transmission loss of the optical fiber fundamental mode and the higher-order mode of the multimode hollow core antiresonance optical fiber, thereby realizing the multi-mode ultra-low loss stable transmission of the optical fiber.

[0044] refer to Figure 3 , Figure 3 A radial cross-sectional view of another multimode hollow-core anti-resonant optical fiber provided in an embodiment of the present application, wherein the anti-resonant structure in the multimode hollow-core anti-resonant optical fiber includes N sub-anti-resonant structures 111, and in the direction from the outside to the inside, the N sub-anti-resonant structures 111 are sequentially a first sub-anti-resonant structure 111 to an Nth sub-anti-resonant structure 111, where N is a positive integer greater than 2; the first sub-anti-resonant structure 111 to the N-1th sub-anti-resonant structure 111 all have openings, and there is a spacing between two adjacent openings on the inner wall of the outer cladding 10.

[0045] When the antiresonance structure 11 includes more than two sub-antiresonance structures 111, and only the innermost sub-antiresonance structure 111 does not have an opening, as the number of sub-resonance structures increases, the phase mismatch between the high-order mode in the central region of the multimode hollow-core antiresonance optical fiber and the air mode in the antiresonance structure 11 can be further enhanced. There is a spacing between the inner walls of the outer cladding 10 of two adjacent antiresonance structures 111, which is conducive to obtaining a flat broadband transmission spectrum and can also reduce the leakage loss of the optical signal during transmission.

[0046] In the embodiments provided in the present application, for the sub-antiresonance structure 111 with an opening, the radial cross-section is a partial circle or partial ellipse with the opening; for the sub-antiresonance structure 111 without an opening, the radial cross-section is a circle or an ellipse tangent to the inner wall of the outer cladding 10.

[0047] like Figure 1 The sub-anti-resonance structure 111 with an opening is partially circular, and the sub-anti-resonance structure 111 without an opening is elliptical. Figure 3 The sub-anti-resonance structure 111 with an opening is partially circular, and the sub-anti-resonance structure 111 without an opening is circular. Figure 5 The sub-anti-resonance structure 111 with an opening is partially elliptical, and the sub-anti-resonance structure 111 without an opening is elliptical. It can be seen that the shapes of the sub-anti-resonance structure 111 with an opening and the sub-anti-resonance structure 111 without an opening can be arbitrarily combined in this application, and this application does not limit this, and it is only necessary to ensure that there is a spacing between the sub-anti-resonance structure 111 with an opening and the sub-anti-resonance structure 111 without an opening.

[0048] refer to Figure 4-Figure 6 , Figure 4 A radial cross-sectional view of another multimode hollow core anti-resonant optical fiber provided in an embodiment of the present application; Figure 5 for Figure 4 Schematic diagram of the performance of a multimode hollow core antiresonant fiber shown; Figure 6 A schematic radial cross-sectional view of another multimode hollow-core antiresonant optical fiber provided in an embodiment of the present application.

[0049] exist Figure 4 In the multimode hollow core anti-resonant optical fiber shown, the sub-anti-resonant structure 111 located on the outside is partially circular, and the sub-anti-resonant structure 111 inside is circular, and in this embodiment, the thickness of the outer sub-anti-resonant structure 111 is inconsistent with that of the inner sub-anti-resonant structure 111. Among them, the equivalent diameter of the radial section of the outer sub-anti-resonant structure 111 is 22.67μm, and the side wall thickness is 0.75μm, and the diameter of the radial section of the inner sub-anti-resonant structure 111 is 10.2μm, and the side wall thickness is 0.75μm. Based on the side wall thickness and radial cross-sectional diameter introduced above, the anti-resonance condition in the anti-resonant reflection optical waveguide principle (ARROW) is met, the anti-resonant reflection effect can be exerted, the coherent cancellation of the leakage light field is achieved, and the loss of the transmission mode is reduced.

[0050] It should be noted that, for the multimode hollow-core anti-resonant optical fiber provided in the embodiment of the present application, for different sub-anti-resonant structures 111 in the same anti-resonant structure 11, the radial structure can be circular or elliptical, and the corresponding anti-resonant structure 111 with an opening is a circular or elliptical shape with an opening. In the same anti-resonant structure 11, the radial cross-section of each sub-anti-resonant structure 111 can be a circular ring, an elliptical ring, a circular ring with an opening, or an open elliptical shape. The above-mentioned shapes can all form a radial anti-resonant reflection interface. At the same time, the performance difference brought by the selection of sub-anti-resonant structures 111 of different shapes to the multi-mode hollow-core anti-resonant optical fiber is small and can be ignored. Therefore, the present application does not limit this.

[0051] In each anti-resonance structure 11 in the same multi-mode hollow-core anti-resonance optical fiber, the structures of the sub-anti-resonance structures 111 contained therein are correspondingly the same, that is, the structures of each anti-resonance structure 11 are the same, thereby reducing the differences between the anti-resonance structures 11, so that the performance differences at various positions inside the multi-mode hollow-core anti-resonance optical fiber are minimized.

[0052] The size of the ellipse or circle corresponding to the shape of the radial cross section of the outermost sub-antiresonance of the antiresonance structure 11 can be determined according to the size of the core region required for propagating the optical signal. The core region is usually a circle, and the core region is circumscribed to one side of any antiresonance structure 11 toward the center of the outer cladding 10.

[0053] Combination Figure 5 It can be seen that Figure 4 The multimode hollow core antiresonant fiber shown also supports LP 01 LP 11 LP 21 LP 02 The multimode hollow core anti-resonant fiber has ultra-low loss transmission in the 800nm-1200nm wavelength range. 01 In the LP mode, when the wavelength is 1020nm, the loss is the smallest, only 0.04dB / km, in the 920nm-1130nm wavelength range the loss is less than 0.1dB / km, in the 830nm-1185nm wavelength range the loss is less than 1dB / km. 11 In LP mode, the minimum loss is only 0.07dB / km at 1040nm, and the loss is less than 1dB / km in the wavelength range of 860nm-1150nm. 21 In LP mode, the minimum loss is only 0.24dB / km at 1020nm, and the loss is less than 1dB / km in the wavelength range of 880nm-1180nm. 02 In this mode, when the wavelength is 1020nm, the loss is the lowest, only 0.33dB / km, and the loss is less than 1dB / km in the wavelength range of 890nm-1140nm. At the same time, the multimode hollow core anti-resonant fiber has a wavelength range of 840nm-1200nm, LP 11 LP 21 LP 02 The pattern group and LP 01 The loss ratio of the mode group is less than 10, so it has the characteristics of ultra-low loss transmission in multiple modes. Based on the above data, it can be seen that the combination of the outer cladding 10, the internal anti-resonance structure 11 and the remaining air area in the multi-mode hollow core anti-resonant optical fiber can significantly reduce the transmission loss of the optical fiber fundamental mode and high-order mode, thereby achieving ultra-low loss stable transmission in multiple modes.

[0054] refer to Figure 6The radial cross-sectional structure diagram of the multimode hollow-core antiresonant optical fiber shown in the figure shows that the antiresonant structures 11 inside the fiber are evenly distributed in the outer cladding 10 and do not touch each other. In the same antiresonant structure 11, the sub-antiresonant structure 111 with an opening is an ellipse with an opening, and the sub-antiresonant structure 111 inside without an opening is an ellipse. For the multimode hollow-core antiresonant optical fiber of this structure, the equivalent diameter of the circumscribed circle circumscribed to the side of all antiresonant structures 11 toward the center of the circle is 50 μm, the wall thickness of the sub-antiresonant structure 111 with an opening is 0.75 μm, the major axis distance is 46 μm, and the minor axis distance is 26 μm. The wall thickness of the sub-antiresonant structure 111 without an opening is 0.75 μm, the major axis distance is 24 μm, and the minor axis distance is 13.56 μm.

[0055] In the multi-mode hollow core anti-resonant optical fiber described above, the angle between the opening of the sub-anti-resonant structure 111 and the center point of the sub-anti-resonant structure 111 is less than 60°.

[0056] Among them, when the radial cross section of the sub-antiresonance structure 111 is a partial circle, the center point represents the center point of the circle, and when the radial cross section of the sub-antiresonance structure 111 is a partial ellipse, the center point represents the midpoint of the major axis of the ellipse. When there is a smaller opening, the opening of any sub-antiresonance structure 111 in the antiresonance structure 11 is smaller, and the central angle corresponding to the radial cross section is larger, so that the surface area of ​​the antiresonance reflection cross section formed is larger, and the utilization efficiency is higher. At the same time, the opening can avoid the connection of adjacent sub-antiresonance structures 111, improve the utilization efficiency of the antiresonance reflection interface, and reduce the transmission loss.

[0057] In the multimode hollow core antiresonant optical fiber described above, the antiresonant structure 11 includes N sub-antiresonant structures 111. In the direction from the outside to the inside, the N sub-antiresonant structures 111 are sequentially the first sub-antiresonant structure 111 to the Nth sub-antiresonant structure 111, where N is a positive integer greater than 2; the side wall thickness of the ath sub-antiresonant structure 111 is t a , a is a positive integer not greater than N; the minimum distance between two adjacent anti-resonance structures 11 is g; wherein, 2t a <g<10t a .

[0058] In the embodiments of the present application, in the same anti-resonant structure 11, the side wall thickness t of each sub-anti-resonant structure 111 may be the same, or at least two sub-anti-resonant structures 111 with different side wall thicknesses t may be provided in the same anti-resonant structure 11. The side wall thickness t of the sub-anti-resonant structure 111 needs to satisfy 2t < g < 10t, so as to prevent light waves from escaping significantly along the radial cross-section of the optical fiber, thereby reducing the transmission loss of the optical fiber and improving the transmission efficiency. When the anti-resonant structure 11 has two sub-anti-resonant structures 111, 2t < g < 10t also needs to be satisfied.

[0059] In the same anti-resonant structure 11, the refractive indices of the sub-anti-resonant structures 111 are the same, and the refractive index of the sub-anti-resonant structure 111 is greater than 1.3 and less than 2.5.

[0060] In the same anti-resonant structure 11, when the refractive indices of each sub-anti-resonant are the same and satisfy the above conditions, the spectral bandwidth of the optical fiber prepared based on the anti-resonant structure 11 can be improved, the complexity of the structure can be reduced, and the preparation difficulty can be reduced. At the same time, when the refractive index is between 1.3 and 2.5, the coupling difficulty of the laser during transmission can be reduced, the transmission loss can be reduced, and the transmission efficiency can be improved.

[0061] Reference Figure 7 , Figure 7 Another multi-mode hollow anti-resonant optical fiber provided by the embodiments of the present application, the anti-resonant structure in the optical fiber includes N sub-anti-resonant structures 111. In the direction from the outside to the inside, the N sub-anti-resonant structures 111 are the first sub-anti-resonant structure 111 to the Nth sub-anti-resonant structure 111 in sequence, and N is a positive integer greater than 2; the first sub-anti-resonant structure 111 to the N-1th sub-anti-resonant structure 111 all have openings, and adjacent two openings are fixed at the same position on the inner wall of the outer cladding 10.

[0062] In this embodiment, only the innermost sub-anti-resonant structure 111 has a spacing from other anti-resonant structures 11, while the other sub-anti-resonant structures 111 are all fixed at the same position on the inner wall of the outer cladding 10. At this time, the correlation between the outer sub-anti-resonant structures 111 can be improved. At the same time, the existence of multiple sub-anti-resonant structures 111 can improve the anti-resonant effect of the anti-resonant structure 11. At the same time, the inner sub-anti-resonant structure 111 is set separately, which is convenient for obtaining a flatter broadband transmission spectrum, so as to realize ultra-low loss transmission of multiple modes.

[0063] In the embodiments of the present application, the radial cross-section of the outer cladding 10 is circular, and one side of all the anti-resonant structures 11 facing the center of the circle of the circular radial cross-section of the outer cladding 10 is located on the same circumscribed circle. The circumscribed circle and the circle where the inner wall of the outer cladding 10 is located are two concentric circles. The outermost anti-resonant structure 111 of each anti-resonant structure 11 is tangent to the circumscribed circle.

[0064] The circumscribed circle is concentric with the outer cladding 10, and the internal region it covers is the position where the optical signal propagates inside the optical fiber under normal conditions, which is usually called the core region.

[0065] In the anti-resonant optical fiber introduced above, the anti-resonant structure 11 includes N sub-anti-resonant structures 111. In the direction from the outside to the inside, the N sub-anti-resonant structures 111 are successively the first sub-anti-resonant structure to the Nth sub-anti-resonant structure, and N is a positive integer greater than 2; the side wall thickness of the a-th sub-anti-resonant structure is t a , where a is a positive integer not greater than N; the diameter of the circumscribed circle is D; among them, 20t a < D < 100t a .

[0066] As described above, in the same anti-resonant structure 11, the side wall thicknesses t of the respective sub-anti-resonant structures 111 may be the same, or there are at least two sub-anti-resonant structures 111 with different side wall thicknesses t in the same anti-resonant structure 11. Setting the side wall thickness t of the sub-anti-resonant structure 111 all needs to satisfy 20t < D < 100t. When the anti-resonant structure 11 has two sub-anti-resonant structures 111, it also needs to satisfy 20t < D < 100t.

[0067] Among them, for the same anti-resonant structure 11, for any two adjacent sub-anti-resonant structures 111, the ratio of the radial cross-sectional area of the inner sub-anti-resonant structure 111 to the cross-sectional area of the outer sub-anti-resonant structure 111 is less than 0.5. It should be noted that the phase mismatch between the transmission of the high-order mode in the multi-mode hollow anti-resonant optical fiber and the air mode in the anti-resonant structure 11 can be achieved by adjusting the radial cross-sectional area of the inner sub-anti-resonant structure 111 and the cross-sectional area composed of the outer sub-anti-resonant structure 111 and the outer cladding 10, so as to achieve low-loss transmission of the high-order mode in the multi-mode hollow anti-resonant optical fiber.

[0068] In this specification, each embodiment is described in a progressive, or parallel, or a combination of progressive and parallel manners. Each embodiment focuses on the differences from other embodiments, and the same or similar parts among the embodiments can be referred to each other.

[0069] It should be noted that in the description of the present application, the description of the drawings and embodiments is illustrative rather than restrictive. The same reference numerals throughout the embodiments of the specification identify the same structure. In addition, for the sake of understanding and ease of description, the drawings may exaggerate the thickness of some layers, films, panels, regions, etc. It is also understood that when an element such as a layer, film, region or substrate is referred to as "on" another element, the element may be directly on the other element or there may be an intermediate element. In addition, "on" refers to positioning an element on or below another element, but does not essentially refer to positioning on the upper side of another element according to the direction of gravity.

[0070] The terms "upper", "lower", "top", "bottom", "inner", "outer", etc. indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present application. When a component is considered to be "connected" to another component, it may be directly connected to the other component or there may be a centrally arranged component at the same time.

[0071] It should also be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprises", "comprising" or any other variants thereof are intended to cover non-exclusive inclusion, so that an article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such article or device. In the absence of further restrictions, the elements defined by the sentence "comprising a ..." do not exclude the existence of other identical elements in the article or device including the above elements.

[0072] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A multimode hollow core antiresonant optical fiber, characterized in that: include: Tubular outer covering; A plurality of tubular anti-resonance structures uniformly distributed on the inner wall of the outer cladding; the anti-resonance structure comprises at least two tubular sub-anti-resonance structures nested in sequence; Among them, in the same anti-resonance structure, the innermost sub-anti-resonance structure is tangent to the inner wall of the outer cladding, and at least the tubular side wall of the outermost sub-anti-resonance structure has an opening extending in the length direction, and the opening is fixed to the inner wall of the outer cladding.

2. The multimode hollow core antiresonant optical fiber according to claim 1, characterized in that: The anti-resonance structure comprises N sub-anti-resonance structures, and in the direction from the outside to the inside, the N sub-anti-resonance structures are sequentially a 1st sub-anti-resonance structure to an Nth sub-anti-resonance structure, where N is a positive integer greater than 2; the 1st sub-anti-resonance structure to the N-1th sub-anti-resonance structure all have the opening, and there is a spacing between two adjacent openings on the inner wall of the outer cladding.

3. The multimode hollow core antiresonant optical fiber according to claim 1, characterized in that: For the sub-antiresonance structure having the opening, the radial cross section is a partial circle or a partial ellipse having the opening; For the sub-antiresonance structure without the opening, the radial cross section is a circle or an ellipse tangent to the inner wall of the outer cladding.

4. The multimode hollow core antiresonant optical fiber according to claim 1, characterized in that: The angle of the opening corresponding to the center point of the sub-anti-resonance structure is less than 60°.

5. The multimode hollow core antiresonant optical fiber according to claim 1, characterized in that: The anti-resonance structure includes N sub-anti-resonance structures, and in the direction from the outside to the inside, the N sub-anti-resonance structures are sequentially a first sub-anti-resonance structure to an Nth sub-anti-resonance structure, where N is a positive integer greater than 2; The side wall thickness of the ath sub-antiresonant structure is t a , a is a positive integer not greater than N; The minimum distance between two adjacent anti-resonance structures is g; Among them, 2t a <g<10t a .

6. The multimode hollow core antiresonant optical fiber according to claim 1, characterized in that: In the same anti-resonance structure, the sub-anti-resonance structures have the same refractive index, and the refractive index of the sub-anti-resonance structure is greater than 1.3 and less than 2.

5.

7. The multimode hollow core antiresonant optical fiber according to claim 1, characterized in that: The anti-resonance structure comprises N sub-anti-resonance structures, and in the direction from the outside to the inside, the N sub-anti-resonance structures are sequentially a 1st sub-anti-resonance structure to an Nth sub-anti-resonance structure, where N is a positive integer greater than 2; the 1st sub-anti-resonance structure to the N-1th sub-anti-resonance structure all have the opening, and two adjacent openings are fixed at the same position on the inner wall of the outer cladding.

8. The multimode hollow core antiresonant optical fiber according to claim 1, characterized in that: The radial cross section of the outer cladding is circular, and the sides of all the anti-resonance structures facing the center of the circle are located on the same circumscribed circle.

9. The multimode hollow core anti-resonant optical fiber according to claim 8, characterized in that: The anti-resonance structure includes N sub-anti-resonance structures, and in the direction from the outside to the inside, the N sub-anti-resonance structures are sequentially a first sub-anti-resonance structure to an Nth sub-anti-resonance structure, where N is a positive integer greater than 2; The side wall thickness of the ath sub-antiresonant structure is t a , a is a positive integer not greater than N; the diameter of the circumscribed circle is D; Among them, 20t a <D<100t a .

10. The multimode hollow core antiresonant optical fiber according to claim 1, characterized in that: The number of the anti-resonance structures is 8-12.

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