Bending-resistant all-solid-state microstructure optical fiber

Abstract

The invention relates to a bending-resistant all-solid-state microstructure optical fiber. The bending-resistant all-solid-state microstructure optical fiber comprises a fiber core region and an inner cladding, the fiber core area comprises a first filling round hole, a first annular fiber core and a first groove ring; the first filling circular hole is located in the center of the fiber core area and has a first refractive index. The first annular fiber core wraps the first filling round hole and has a second refractive index; the first groove ring wraps the first annular fiber core and has a third refractive index; the inner cladding wraps the fiber core area and has a fourth refractive index; a plurality of second filling circular holes are distributed in the inner cladding, and the second filling circular holes have a fifth refractive index; the first refractive index is higher than the second refractive index; the second refractive index is higher than the fourth refractive index; the fourth refractive index is higher than the third refractive index; the third refractive index is higher than the fifth refractive index. According to the invention, the technical problem of poor bending resistance on the premise of large-mode-field transmission in the prior art can be solved.

Description

Technical Field

[0001] This application relates to the field of microstructured optical fibers, and in particular to a bend-resistant all-solid-state microstructured optical fiber. Background Technology

[0002] In high-power fiber lasers and compact optical devices, achieving high power capacity and excellent beam quality requires fibers to support large mode area single-mode transmission; to adapt to complex deployments in confined spaces, fibers must possess excellent bending resistance. How to achieve these characteristics in a coordinated manner is the core challenge in the design of current specialty optical fibers.

[0003] In existing technologies, periodically symmetrically distributed high-refractive-index segments are introduced into the cladding of segmented cladding fibers. This enhances the cladding's ability to confine the optical field within the fiber core, thereby suppressing higher-order modes and ensuring single-mode operation. However, this structure lacks a mechanism sensitive to bending direction. When the fiber bends during practical applications due to deployment requirements, the internal stress and optical field distribution exhibit strong direction dependence. This structure cannot provide differentiated responses or compensations for this, thus lacking an internal structural mechanism capable of adaptive optical response to bending direction. Consequently, it cannot guarantee good bending resistance while ensuring large-mode-field single-mode transmission.

[0004] There is currently no effective solution to the technical problem of improving bending resistance under the premise of large-scale transmission in related technologies. Summary of the Invention

[0005] This application provides a bend-resistant all-solid-state microstructure optical fiber to solve the technical problem of poor bend resistance in the prior art under the premise of large mode field transmission.

[0006] This application provides a bend-resistant all-solid-state microstructure optical fiber, comprising a core region and an inner cladding. The core region includes a first filled circular hole, a first annular core, and a first grooved ring. The first filled circular hole is located at the center of the core region and has a first refractive index. The first annular core surrounds the first filled circular hole and has a second refractive index. The first grooved ring surrounds the first annular core and has a third refractive index. The inner cladding surrounds the core region and has a fourth refractive index. A plurality of second filled circular holes are distributed on the inner cladding, and the second filled circular holes have a fifth refractive index. The first refractive index is higher than the second refractive index. The second refractive index is higher than the fourth refractive index. The fourth refractive index is higher than the third refractive index. The third refractive index is higher than the fifth refractive index.

[0007] In some embodiments, the core region further includes a second annular core and a second grooved ring; the second annular core surrounds the first grooved ring and has the second refractive index and a second ring width; the first annular core has a first ring width, which is greater than the second ring width; the second grooved ring surrounds the second annular core and has the third refractive index.

[0008] In some further embodiments, the core region further includes a third annular core; the third annular core surrounds the second groove ring and has the second refractive index and a third ring width; the second ring width is greater than the third ring width; both the first groove ring and the second groove ring have a fourth ring width; the third ring width is greater than the fourth ring width.

[0009] In some embodiments, the inner cladding includes an annular region and a plurality of spoke regions; the plurality of spoke regions extend outward along the annular region and are uniformly arranged circumferentially along the annular region; a petal-shaped inner cladding is filled between every two adjacent spoke regions; the petal-shaped inner cladding has the third refractive index, and the radial width of the petal-shaped inner cladding is equal to the annular width of the spoke region.

[0010] In some further embodiments, the second filling holes are uniformly distributed circumferentially along the annular region of the inner cladding.

[0011] In some further embodiments, the annular region is further distributed with a plurality of third filling holes; the plurality of third filling holes correspond to the positions of the plurality of spoke regions; the second filling holes are distributed in the annular region of the inner cladding, and at least one second filling hole is located between every two adjacent third filling holes; the center of the third filling hole and the center of the second filling hole are both at a first distance from the center of the first filling hole; the third filling hole has a fifth diameter and a fifth refractive index; the second filling hole has a fourth diameter; the fifth diameter is larger than the fourth diameter.

[0012] In some embodiments, the system further includes a first annular outer cladding layer, a third grooved ring, and an outer cladding layer; the first annular outer cladding layer surrounds the inner cladding layer and has the second refractive index and a fifth ring width; the third grooved ring surrounds the first annular outer cladding layer and has the fifth refractive index and a sixth ring width; the sixth ring width is greater than the fifth ring width; the outer cladding layer is located outside the third grooved ring and has the third refractive index.

[0013] In some further embodiments, the ratio of the width of the fifth ring to the width of the sixth ring is 1.5:5.5.

[0014] In some further embodiments, a single first annular outer cladding layer and the third grooved ring constitute a set of outer cladding layer units; at least one set of the outer cladding layer units are also wrapped between the third grooved ring and the outer cladding layer.

[0015] In some embodiments, the third refractive index ranges from 1.80 to 1.86; the first refractive index difference between the first and third refractive indices is 0.004; the second refractive index difference between the second and third refractive indices is 0.002; the fourth refractive index difference between the fourth and third refractive indices is 0.001; and the fifth refractive index difference between the fourth and third refractive indices is -0.0015.

[0016] Compared with the prior art, the embodiments of this application have the following beneficial effects:

[0017] The bend-resistant microstructure optical fiber of this application embodiment effectively focuses and confines the fundamental mode energy through a first filling circular hole at the center of the core region with the highest refractive index; a first annular core surrounding it cooperates with it with a lower refractive index to maintain optical field guidance; and a first grooved ring surrounding the first annular core further expands the mode field area with an even lower refractive index, suppressing nonlinear effects; the inner cladding surrounds the entire core region with a refractive index between that of the core and the groove, and the periodically distributed second filling circular holes with an even lower refractive index inside it work together with the inner cladding body to confine the optical field diffusion in the radial and circumferential directions, suppressing energy leakage during bending. The above structures work together to significantly improve the multi-directional bend resistance of the optical fiber while maintaining single-mode large mode field transmission.

[0018] Details of one or more embodiments of this application are set forth in the following drawings and description to make other features, objects and advantages of this application more readily apparent. Attached Figure Description

[0019] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0020] Figure 1 This is a cross-sectional view of a bend-resistant all-solid-state microstructure optical fiber provided in an embodiment of this application;

[0021] Figure 2 This is a cross-sectional view of a multilayer annular core bend-resistant all-solid-state microstructure optical fiber provided in an embodiment of this application;

[0022] Figure 3 This is a cross-sectional view of a bend-resistant all-solid-state microstructure optical fiber with a spoke region and a third filling circular hole provided in an embodiment of this application;

[0023] Figure 4 This is a cross-sectional view of a bend-resistant all-solid-state microstructure optical fiber provided in a preferred embodiment of this application;

[0024] Figure 5 This is a schematic diagram of the structural parameters of a bend-resistant all-solid-state microstructure optical fiber provided in a preferred embodiment of this application;

[0025] Figure 6 This is a line graph showing the variation of fundamental mode leakage loss, minimum leakage loss of higher-order modes, and mode field area of ​​the fundamental mode with the bending direction of the optical fiber, according to an embodiment of this application.

[0026] Figure 7 This is a line graph showing the leakage loss ratio of higher-order modes to fundamental modes under different diameters of the first filling circular hole provided in an embodiment of this application, which varies with the fiber bending direction.

[0027] Figure 8 This is a line graph showing the variation of the mode field area of ​​the fundamental mode with the fiber bending direction under different diameters of the first filling circular hole according to an embodiment of this application;

[0028] Figure 9 This is a line graph showing the variation of the leakage loss ratio of higher-order modes and fundamental mode with the fiber bending direction under different fourth ring widths according to an embodiment of this application.

[0029] Figure 10 This is a line graph showing the ratio of higher-order mode to fundamental mode leakage loss with fiber bending direction under different diameters of the third refractive index filled circular hole according to an embodiment of this application.

[0030] Figure 11 This is a line graph showing the variation of the higher-order mode to the fundamental mode leakage loss ratio with the fiber bending direction under different ratios of the fifth ring width and the sixth ring width, according to an embodiment of this application.

[0031] Figure 12 This is a schematic diagram of the mode field distribution of the fundamental mode and the lowest loss higher-order mode under different bending directions provided in an embodiment of this application.

[0032] In the figure: 1. First filling circular hole; 2. First annular fiber core; 3. Second annular fiber core; 4. Third annular fiber core; 5. First grooved ring; 6. Second grooved ring; 7. Inner cladding; 8. Lobe-shaped inner cladding; 9. Second filling circular hole; 10. Third filling circular hole; 11. First annular outer cladding; 12. Third grooved ring; 13. Outer cladding. Detailed Implementation

[0033] To better understand the purpose, technical solution, and advantages of this application, the application is described and explained below in conjunction with the accompanying drawings and embodiments.

[0034] Unless otherwise defined, the technical or scientific terms used in this application shall have the general meaning understood by one of ordinary skill in the art to which this application pertains. Words such as “a,” “an,” “an,” “the,” “the,” and “these” used in this application do not indicate quantitative limitation and may be singular or plural. The terms “comprising,” “including,” “having,” and any variations thereof used in this application are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or device that comprises a series of steps or modules (units) is not limited to the listed steps or modules (units) but may include steps or modules (units) not listed, or may include other steps or modules (units) inherent to these processes, methods, products, or devices. Words such as “connected,” “linked,” and “coupled” used in this application are not limited to physical or mechanical connections but may include electrical connections, whether direct or indirect. “Multiple” used in this application refers to two or more. “And / or” describes the relationship between related objects, indicating that three relationships may exist; for example, “A and / or B” can represent: A alone, A and B simultaneously, and B alone. Normally, the character " / " indicates that the objects before and after it are in an "or" relationship. The terms "first," "second," "third," etc., used in this application are merely to distinguish similar objects and do not represent a specific order.

[0035] This embodiment provides a bend-resistant all-solid-state microstructure optical fiber. Please refer to [link / reference]. Figure 1 The bending-resistant all-solid-state microstructure optical fiber of this embodiment includes: a core region and an inner cladding 7.

[0036] The fiber core region includes a first filling circular hole 1, a first annular fiber core 2, and a first grooved ring 5. The first filling circular hole 1 is located at the center of the fiber core region and has a first refractive index. The first annular fiber core 2 surrounds the first filling circular hole 1 and has a second refractive index. The first grooved ring 5 surrounds the first annular fiber core 2 and has a third refractive index. The first refractive index is higher than the second refractive index, and the second refractive index is higher than the third refractive index.

[0037] Based on this structure, the core region forms a waveguide structure with a three-tiered radial refractive index decreasing from high to low. During operation, the first filling circular hole 1, with the highest refractive index, acts as a strong refractive index protrusion, effectively concentrating and strongly confining the transmitted fundamental mode energy in its vicinity, which is fundamental to achieving efficient single-mode excitation and transmission. The first annular core 2 surrounding it has a second refractive index, forming a smooth refractive index transition with the first filling circular hole 1 at the center, which has the first refractive index. This provides a guiding layer for the light field diffusing from the center, maintaining the stability of the light field's axial transmission while avoiding strong mode coupling caused by abrupt changes in refractive index. The first grooved ring 5 surrounding the first annular core 2 has a third refractive index lower than that of the first annular core 2, essentially acting as an energy leakage channel on the periphery of the optical waveguide. Based on wave optics principles, when the light field propagates into the region of the first grooved ring 5, its lateral confinement is weakened. Therefore, the lateral distribution of the light field, i.e., the mode field, tends to extend towards the region of the first grooved ring 5, effectively increasing the mode field area of ​​the fundamental mode. The large mode area directly reduces the power density within the fiber core, significantly suppressing nonlinear effects and creating conditions for high-power transmission. Simultaneously, the low-refractive-index first groove ring 5 can initially enhance the waveguide's resistance to external bending disturbances, as some of the optical energy extending to this region is more easily radiated during bending. However, the degree of influence of this radiation differs between the fundamental mode and higher-order modes; therefore, it can be combined with the inner cladding 7 to further strengthen resistance to external bending disturbances.

[0038] The inner cladding 7 surrounds the fiber core region and has a fourth refractive index. Several second filling circular holes 9 with a fifth refractive index are distributed on the inner cladding 7. Furthermore, the second refractive index is higher than the fourth refractive index, the fourth refractive index is higher than the third refractive index, and the third refractive index is higher than the fifth refractive index.

[0039] Based on the above structure, the inner cladding constitutes a composite optical field management region. First, the fourth refractive index of the inner cladding lies between the second refractive index of the first annular core and the third refractive index of the first grooved ring. This ensures that the inner cladding neither strongly confines the optical field (i.e., excessively compresses the mode field) nor excessively releases it; instead, it acts as a buffer or extending cladding, receiving the optical field extending from the core region and providing a relatively loose but still controlled lateral expansion space for the optical field. Furthermore, the second filling holes distributed within the inner cladding have the lowest fifth refractive index, thus forming several periodic local refractive index depressions. These second filling holes contrast with the background material of the inner cladding in refractive index, resulting in strong scattering and suppression of the propagating optical field. That is, when the optical field is about to pass through the region of these second filling holes, due to the large refractive index difference between the second filling holes and the inner cladding background, most of the energy is reflected back to the inner cladding and the core region, thereby simultaneously constraining the further diffusion of the optical field in both the radial and circumferential directions. Therefore, it can suppress light energy leakage loss under bending conditions, achieving multi-directional bending resistance. The light field mentioned here can refer to the fundamental mode energy that is shifted outward due to bending, as well as the higher-order mode energy that is more easily leaked.

[0040] It is important to note that the core region and the inner cladding do not work independently. The extended mode field facilitated by the first trench ring surrounding the core region can be seamlessly embedded into the buffer environment of the inner cladding, which has a fourth refractive index. This fourth refractive index is set higher than the third refractive index of the first trench ring but lower than the second refractive index of the first annular core. This allows the inner cladding to provide a controlled and gently varying extension space for the optical field extending from the first trench ring. Furthermore, the low-refractive-index lattice formed by several second filling holes in the inner cladding is positioned precisely to manage the optical field further diffusing from the first trench ring, particularly the energy of the optical field shifted in a specific direction due to bending. Therefore, based on the initial shaping and extended mode field of the core region, the inner cladding, through the synergistic cooperation of the background material and the lattice formed by the second filling holes, jointly suppresses fiber leakage.

[0041] Unlike related technologies that rely solely on a single high-refractive-index segment for symmetry constraint, this embodiment employs a structural design that converges the light field in the fiber core region, guides the light field distribution, and expands the mode field, thus creating conditions for single-mode large-mode-field transmission. Furthermore, by incorporating a buffer background and low-refractive-index scattering-filled circular holes in the inner cladding, the problem of light field leakage during bending is effectively solved. Specifically, the first filling circular hole, located at the very center and possessing the highest refractive index, locks the fundamental mode core energy. The outermost first annular fiber core and first grooved ring work together to expand the mode field and form a preliminary bending-sensitive region. Based on this structure, several second filling circular holes in the inner cladding, due to their distribution and low refractive index, can reflect the dissipated energy back to the inner cladding and even the fiber core region. Therefore, the structures of the inner cladding and the fiber core region can cooperate based on their respective optical properties and physical structures, enhancing the adaptive ability of the internal light field redistribution when the optical fiber is subjected to bending stress, effectively blocking energy leakage channels. Based on the above technical means, this embodiment, while reliably ensuring the basic performance of single-mode large mode field transmission, significantly enhances the fiber's ability to suppress bending loss through the synergistic cooperation of all-solid-state microstructures, thereby effectively solving the technical problem of poor bending resistance in the prior art under the premise of large mode field transmission.

[0042] In some embodiments, the cross-sectional structure of the optical fiber remains unchanged along its axis. The principle behind this is to ensure consistent and predictable optical and mechanical properties across any length. Axial uniformity eliminates additional mode coupling, resonance, or random scattering that could be caused by structural undulations or periodic modulation, resulting in more stable optical signal transmission. In practical cabling, any segment of fiber will exhibit consistent bending resistance and mode field characteristics.

[0043] In some of these embodiments, please refer to Figure 2 The fiber core region also includes a second annular fiber core 3 and a second grooved ring 6. The second annular fiber core 3 surrounds the first grooved ring 5, and the second grooved ring 6 surrounds the second annular fiber core 3. The first annular fiber core 2 mentioned in the previous embodiment has a first ring width, and the second annular fiber core 3 in this embodiment has a second ring width, with the first ring width being greater than the second ring width. Simultaneously, the second annular fiber core 3 has a second refractive index, and the second grooved ring 6 has a third refractive index.

[0044] In this embodiment, by adding a ring core and a grooved ring pair, and introducing a geometric relationship of decreasing ring width, and referencing the correspondence that the second refractive index is greater than the third refractive index, a gradient-evolving optical field management structure is constructed radially. From the perspective of ring width, the first ring core, as the innermost main guiding region, provides sufficient and stable transmission space for the fundamental mode optical field due to its larger ring width. Based on this characteristic, the second ring core adopts a smaller ring width, which relatively increases the energy density of the optical field in this region, enabling more efficient confinement of the extended optical field.

[0045] Combining the relationship between the second and third refractive indices, the two fiber core layers separated by the first grooved ring with a lower refractive index both have a higher second refractive index, thus forming a process of constraining, releasing, and reconstraining the optical field. The low refractive index characteristic of the first grooved ring causes the optical field to expand laterally for the first time, while the second ring-shaped fiber core, which is narrower in width and surrounds it, effectively converges and guides the expanded field secondaryly based on its higher refractive index, preventing energy from dissipating outward too quickly.

[0046] Furthermore, designing the refractive indices of the first annular core, the first grooved ring, and the second annular core, along with the corresponding ring widths, optimizes the mode field shape and bending response. The reduced ring width of the second annular core, combined with the larger refractive index difference between it and the second grooved ring, creates a refractive index contrast interface, resulting in a more pronounced optical isolation effect for the second grooved ring. When the fiber bends, the light field deflected outwards experiences stronger refraction or reflection as it passes through these annular cores with decreasing ring widths and layers with significant refractive index differences, effectively confining it within the core region and significantly suppressing leakage loss.

[0047] In view of this, in this embodiment, a first and second annular fiber core with decreasing ring width are used, along with the refractive index distribution of each structure, to further expand the mode field area through the cumulative effect of multiple grooves to suppress nonlinear effects. At the same time, the gradient waveguide structure with adjustable constraint strength from the inside to the outside significantly enhances the waveguide's ability to resist external bending disturbances, thereby expanding the mode field and improving multi-directional bending resistance.

[0048] In some further embodiments, please refer to... Figure 2 The core region also includes a third annular core 4, which surrounds the second grooved ring 6 and has a second refractive index and a third ring width. Both the first grooved ring 5 and the second grooved ring 6 have a fourth ring width. Furthermore, the second ring width is greater than the third ring width, and the third ring width is greater than the fourth ring width.

[0049] In this embodiment, the ring widths of the three annular fiber cores decrease layer by layer, and the annular fiber cores and grooved rings are alternately distributed, thus forming a gradient waveguide with minimized grooves and alternating high and low refractive indices. The three annular fiber cores with the same second refractive index have their ring widths gradually narrowing from the inside to the outside, which gradually enhances the lateral constraint of each annular fiber core on the optical field; while the two grooved rings with the same lowest third refractive index have narrower fourth ring widths, forming an efficient optical isolation band between the fiber core layers.

[0050] Therefore, when the light field expands from the center to the periphery, it needs to go through a controlled cycle of constraint and release. That is, each low-refractive-index groove ring promotes the mode field to expand appropriately to suppress nonlinear effects, while each high-refractive-index ring core timely converges and strengthens the constraint of the expanded field.

[0051] In view of this, this embodiment can significantly increase the mode field area. Furthermore, because higher-order modes are more likely to extend to the periphery, they will experience stronger leakage losses in the multilayer structure, thereby effectively suppressing higher-order modes. Simultaneously, when the fiber bends, the deflected optical field must traverse multiple constraint interfaces of alternating strength, and energy is dissipated layer by layer, thus enhancing omnidirectional bending resistance.

[0052] In some of these embodiments, please refer to Figure 3 The inner cladding 7 includes an annular region and several spoke regions, with the spoke regions extending outward along the annular region and uniformly arranged along the circumference of the annular region. A petal-shaped inner cladding 8 is filled between every two adjacent spoke regions. The petal-shaped inner cladding 8 has a third refractive index, and the radial width of the petal-shaped inner cladding 8 is equal to the annular width of the spoke region.

[0053] Based on the structural combination of the annular region, spoke region, and petal region described above, the circumferentially uniformly distributed spoke region provides stable radial structural support. The petal-shaped inner cladding, filling the spaces between the spoke regions, has the same third refractive index as the first groove ring 5, forming several low-refractive-index regions embedded within the inner cladding. The petal-shaped regions, combined with the background of the annular spoke region having a fourth refractive index, periodically modulate the equivalent refractive index of the inner cladding in the circumferential direction. On one hand, this structure further reduces the overall average refractive index of the inner cladding, which is beneficial for the expansion of the mode field in the fiber core. On the other hand, this structure makes the optical response direction-dependent; that is, when the fiber bends in different directions, the light field will shift into the local environment formed by different combinations of petal-shaped and spoke regions. Because the refractive indices and areas of these regions are different, they constitute a non-uniform microstructure, which can generate differentiated scattering and confinement of the shifted light field, thereby giving the fiber preliminary omnidirectional bending resistance. Furthermore, the width of the petal-shaped region is equal to the width of the spoke region, ensuring controllable and more closely fitting performance.

[0054] In some further embodiments, the fiber optic structure exhibits better omnidirectional bending resistance when eight spoke zones are provided.

[0055] In some further embodiments, the second filling holes are uniformly distributed circumferentially along the annular region of the inner cladding. This embodiment, by applying a circumferentially uniform constraint to the distribution of the second filling holes, arranges the random or localized low-refractive-index scattering points that may exist in the aforementioned embodiments in an ordered and symmetrical manner. This uniform distribution ensures that, within the annular region, inconsistencies in the scattering and constraint intensity of the light field caused by the arrangement of the second filling holes are avoided as much as possible. Therefore, based on the above structure, the annular region of this embodiment, with its arrangement of second filling holes, forms a continuous and uniform optical barrier. When the optical fiber bends, causing the light field to shift in any direction, it encounters scattering points of similar intensity, thereby improving the directional consistency of the bending resistance and contributing to achieving omnidirectional bending resistance.

[0056] In some further embodiments, please refer to... Figure 3 The annular region also contains a plurality of third filling holes 10, the positions of which correspond to those of the spoke regions. At this time, second filling holes 9 are also distributed in the annular region of the inner cladding 7, and at least one second filling hole 9 is located between every two adjacent third filling holes 10. The centers of the third filling holes 10 and the second filling holes 9 are equidistant from the center of the first filling hole 1. The third filling holes 10 have a fifth diameter and a fifth refractive index, and the second filling holes 9 have a fourth diameter, with the fifth diameter being larger than the fourth diameter.

[0057] In this embodiment, by introducing a third filling hole with a larger diameter and positioned corresponding to each spoke region, and alternating it with a second filling hole of smaller diameter, each equidistant from the center of the first filling hole 1, a dual-scale, highly correlated low-refractive-index structure can be constructed. The large-diameter third filling hole corresponding to the spoke region can more effectively modulate the mechanical stress distribution and optical field distribution along its radial outer region, resulting in a stronger leakage effect on higher-order modes with specific spatial distributions. The small-diameter second filling holes interspersed among them provide a denser network of refractive index perturbation points. Thus, the alternating arrangement of enhanced large-hole positioning and optimized small-hole filling results in a more complex and efficient refractive index modulation period in the circumferential direction of the optical fiber in this embodiment.

[0058] In view of this, this embodiment, through the synergy of two aperture sizes, can selectively enhance and suppress higher-order modes over a wider spectrum, and further optimize the inner cladding for complex optical field distribution under bending conditions, especially its constraint and leakage capabilities when shifted in different directions, thereby further improving the fiber's all-around bending resistance and single-mode selectivity.

[0059] In some further embodiments, please refer to Figure 4The core region has a first filling circular hole 1 at its center, which is surrounded by a first annular core 2. The first annular core 2 is surrounded by a first grooved ring 5. The first grooved ring 5 is surrounded by a second annular core 3. The second annular core 3 is surrounded by a second grooved ring 6. The second grooved ring 6 is surrounded by a third annular core 4. The ring widths of the first annular core 2, the second annular core 3, and the third annular core 4 decrease in that order. Based on this structure, combined with the structure of the second filling circular hole 9 and the third filling circular hole 10 in the previous embodiment, the core structure of this embodiment is constituted. The annular region of the inner cladding also has several third filling circular holes 10 distributed therein, and the positions of these third filling circular holes 10 correspond to the positions of several spoke regions. At this time, the second filling circular holes 9 are also distributed in the annular region of the inner cladding 7, and at least one second filling circular hole 9 is located between every two adjacent third filling circular holes 10. The center of the third filling circular hole 10 and the center of the second filling circular hole 9 are both equidistant from the center of the first filling circular hole 1. The third filling hole 10 has a fifth diameter and a fifth refractive index, and the second filling hole 9 has a fourth diameter, with the fifth diameter being larger than the fourth diameter.

[0060] In some of these embodiments, please refer further to Figure 4 It also includes a first annular outer cladding layer 11, a third grooved ring 12, and an outer cladding layer 13; the first annular outer cladding layer 11 surrounds the inner cladding layer 7 and has a second refractive index and a fifth ring width; the third grooved ring 12 surrounds the first annular outer cladding layer 11 and has a fifth refractive index and a sixth ring width; the sixth ring width is greater than the fifth ring width; the outer cladding layer 13 is located outside the third grooved ring 12 and has a third refractive index.

[0061] This embodiment constructs a mode-filtering unit consisting of a high-refractive-index annular outer cladding, a low-refractive-index grooved ring, and a background cladding around the inner cladding, adding an outer optical control interface to the optical fiber. The first annular outer cladding, with a higher second refractive index, guides the light field that may extend from the inner cladding, guiding higher-order modes easily excited during bending. Surrounding it is a third grooved ring with the lowest refractive index and a wider width than the first annular outer cladding, forming a distinct optical interface. When higher-order mode energy attempts to pass through this optical interface, it encounters a strong refractive index mismatch, resulting in significant radiation loss. The outer cladding, acting as an optical cutoff region, receives and dissipates this leaked energy.

[0062] In view of this, this embodiment, through the synergistic design of the guiding layer, the leakage layer and the cutoff layer, can selectively filter out higher-order modes under bending conditions, thereby ensuring the pure single-mode nature and stability of the output beam.

[0063] In some further embodiments, the ratio of the width of the fifth ring to the width of the sixth ring is 1.5:5.5. The sixth ring width of the third groove ring is much larger than the fifth ring width of the first annular cladding. Based on the above ratio, this embodiment can balance the guiding ability of the high-refractive-index first annular cladding with the guiding ability of the ring and the leakage efficiency of the low-refractive-index third groove ring. When the third groove ring is too narrow, i.e., the ratio of the two is too large, the leakage effect of the third groove ring is insufficient; when the groove ring is too wide, i.e., the ratio of the two is too small, the locality of the established mode may be destroyed. Under the above ratio, higher-order modes can be scattered and lost to a greater extent through the structure of this embodiment, while the transmission of the fundamental mode is less affected, thereby significantly reducing the correlation between the higher-order mode suppression ratio and the bending direction.

[0064] In some further embodiments, please refer to... Figure 4 Each first annular outer cladding layer 11 and the third grooved ring 12 form a set of outer cladding layer units; at least one set of outer cladding layer units are also wrapped between the third grooved ring 12 and the outer cladding layer 13.

[0065] This embodiment uses a single-layer first annular outer cladding layer and a third trench ring as a set of outer cladding layer units, and periodically stacks the outer cladding layer units to achieve multiple scattering and interference cancellation effects for a wider range of higher-order modes, greatly expanding the bandwidth of the effective filter mode and improving the suppression depth of higher-order modes.

[0066] Based on the cooperation between the above structures, even under extreme conditions of small bending radius and strong bending disturbance, by increasing the number of outer cladding units, the high-order mode energy coupled from the fiber core to the cladding can be filtered and fully dissipated layer by layer, thereby maintaining high single-mode purity under any bending state and significantly improving the reliability of fiber deployment.

[0067] In some embodiments, the third refractive index ranges from 1.80 to 1.86, primarily based on the stable and easily achievable optical properties of yttrium aluminum garnet (YAG) crystals within the applied wavelength range. Using this as a unified material and optical benchmark, precise control of doping allows for specific, minute shifts in the refractive index of other regions, thereby systematically constructing the desired series of local refractive index contrasts.

[0068] Furthermore, the first refractive index difference between the first and third refractive indices is 0.004; the second refractive index difference between the second and third refractive indices is 0.002; the fourth refractive index difference between the fourth and third refractive indices is 0.001; and the fifth refractive index difference between the fifth and third refractive indices is -0.0015. Specifically, the first filling circular hole at the center of the core region is given the largest positive offset, aiming to form a sufficiently significant positive refractive index difference interface between it and the adjacent first annular core. The strong optical potential trap generated by this interface can efficiently confine the fundamental mode energy to the core center, providing a basis for single-mode operation. At the same time, the negative refractive index difference interface between the core body and the outer first groove ring drives the lateral expansion of the mode field to achieve a large mode field area. The inner cladding background is given a very small positive offset, which forms a weak gradient interface and a clear negative refractive index difference interface between it and the inner groove ring and the second filling circular hole embedded inside itself, respectively. The former serves as a light field buffer zone, while the latter becomes a periodically distributed scattering center. Together, they endow the inner cladding with the ability to adaptively control the curved offset light field. Similarly, the mode filtering unit in the outer cladding utilizes the adjacent combination of the positive offset guiding layer and the negative offset leakage ring to achieve effective filtering of higher-order modes.

[0069] In this embodiment, the refractive index parameter is set based on the third refractive index. By precisely and hierarchically designing the relative offsets of each refractive index, multiple optical functions such as strong confinement, weak guidance, controllable leakage, and efficient filtering are simultaneously achieved within the optical fiber. Each functional region takes effect through a comparison with the specific refractive index formed by its directly adjacent medium. These local interfaces work together to ultimately achieve the technical effects of large-mode-field single-mode transmission and omnidirectional bending resistance.

[0070] In a preferred embodiment, the first filling circular hole, the first annular fiber core, the second annular fiber core, and the third annular fiber core are made of yttrium aluminum garnet crystal. Simultaneously, the inner cladding, the petal-shaped inner cladding, the first trench ring, the second trench ring, the outer cladding, the first annular outer cladding, the third trench ring, the second filling circular hole, and the third filling circular hole are made of yttrium aluminum garnet crystal doped with non-rare earth elements. By employing a fully solid-state, lattice-matched rare earth / non-rare earth doped YAG material system, perfect physical bonding can be achieved between the various regions, avoiding the weak mechanical strength, encapsulation difficulties, and contamination problems caused by air-hole structures, thus ensuring the overall mechanical strength and environmental reliability of the optical fiber.

[0071] In some preferred embodiments, based on combinations of the structures described in the foregoing embodiments, please refer to... Figure 4The fiber core structure includes: a first filling circular hole 1 is disposed at the center of the fiber core region, and a first annular fiber core 2 is surrounded by the first annular fiber core 2; a first grooved ring 5 is surrounded by the first annular fiber core 2; a second annular fiber core 3 is surrounded by the first grooved ring 5; a second grooved ring 6 is surrounded by the second annular fiber core 3; and a third annular fiber core 4 is surrounded by the second grooved ring 6; with the ring widths of the first annular fiber core 2, the second annular fiber core 3, and the third annular fiber core 4 decreasing in that order. Based on this structure, combined with the structure with a second filling circular hole 9 and a third filling circular hole 10 in the aforementioned embodiment, the annular region of the inner cladding layer is further distributed with a plurality of third filling circular holes 10, and the positions of the plurality of third filling circular holes 10 correspond to the positions of the plurality of spoke regions. At this time, the second filling circular holes 9 are also distributed in the annular region of the inner cladding layer 7, and at least one second filling circular hole 9 is located between every two adjacent third filling circular holes 10. The center of the third filling circular hole 10 and the center of the second filling circular hole 9 are both equidistant from the center of the first filling circular hole 1. The third filling circular hole 10 has a fifth diameter and a fifth refractive index, and the second filling circular hole 9 has a fourth diameter, with the fifth diameter being larger than the fourth diameter. A single first annular outer cladding layer 11 and the third grooved ring 12 form a set of outer cladding units; two sets of outer cladding units are wrapped between the inner cladding layer 7 and the outer cladding layer 13.

[0072] In some preferred embodiments, based on combinations of the structures described in the foregoing embodiments, please refer further. Figure 4 and combined Figure 5 and Figure 6 In this embodiment, the preferred parameters of the optical fiber structure are set as follows: the first diameter D1 of the first filling circular hole 1 is 3.2 μm; the first ring width d1 of the first annular core 2 is 14.2 μm; the second ring width d2 of the second annular core 3 is 4.6 μm; the third ring width d3 of the third annular core 4 is 2.6 μm; and the fourth ring width d4 of the first groove ring 5 and the second groove ring 6 is 1.7 μm. The third diameter D3 of the annular region of the inner cladding 7 is 96 μm, and the second diameter D2 of the junction between its spoke region and the annular region is 114 μm. The fourth diameter D4 of the second filling circular hole 9 is 5.2 μm, and the fifth diameter D5 of the third filling circular hole 10 is 9.2 μm. The first distance between the center of the second filling hole 9 and the center of the third filling hole 10 and the center point of the optical fiber is L, where L is 42 μm. Except for the first filling hole 1, the included angle θ between adjacent holes is 15°. The width w1 of a single spoke region is 14 μm. The sixth diameter D6 of the cladding 13 is 162 μm, the fifth ring width d5 ​​of its first annular cladding 11 is 1.5 μm, and the sixth ring width of its third groove ring 12 is 5.5 μm. The first refractive index difference Δn1 = 0.004, the second refractive index difference Δn2 = 0.002, the third refractive index difference Δn3 = 0.001, and the fourth refractive index difference Δn4 = -0.0015. The test conditions for this embodiment are: working wavelength 1.064 μm and bending radius 5 cm.

[0073] Based on the above parameter settings, such as Figure 6 As shown, both the fundamental mode leakage loss and the minimum leakage loss of higher-order modes exhibit a trend of first increasing and then decreasing with the bending direction from 0° to approximately 30°, eventually stabilizing. A significant peak appears at approximately 3°, indicating a temporary weakening of the fiber's confinement capability at this point. When the bending direction exceeds approximately 9°, both losses remain at a low level, demonstrating stable bending resistance. Simultaneously, the mode field area of ​​the fundamental mode generally increases with the bending direction, and its fluctuations are correlated with the loss changes. Particularly at the loss peak, the mode field area also changes significantly, confirming the close relationship between optical field distribution and energy confinement. Therefore, under these optimized parameters, the fiber in this embodiment can achieve low-loss fundamental mode transmission and large mode field characteristics in most bending directions, with performance-sensitive regions existing only at a very few angles, exhibiting excellent overall omnidirectional bending resistance.

[0074] In some preferred embodiments, based on combinations of some structures described in the foregoing embodiments, please refer further. Figure 4 and combined Figure 5 , Figure 7 and Figure 8 .in Figure 7 and Figure 8 This demonstrates the impact of the first diameter D1 of the first filling circular hole 1 at the center of the fiber core region on fiber performance. In this embodiment, a set of preferred parameters are set as follows: the first ring width d1 of the first annular fiber core 2 is 14.2 μm; the second ring width d2 of the second annular fiber core 3 is 4.6 μm; the third ring width d3 of the third annular fiber core 4 is 2.6 μm; the fourth ring width d4 of the first trench ring 5 and the second trench ring 6 is 1.7 μm; the second diameter D2 of the inner cladding 7 is 114 μm, and the third diameter D3 of its annular region is 96 μm; the fourth diameter D4 of the second filling circular hole 9 is 5.2 μm; the fifth diameter D5 of the third filling circular hole 10 is 9.2 μm; and the second filling circular hole 9 and the third filling circular hole 10... The first distance L between the center of the circular hole and the center point of the optical fiber is 42 μm, and the included angle θ between two adjacent circular holes, except for the first filling circular hole 1, is 15°; the width w1 of a single spoke region is 14 μm; the sixth diameter D6 of the cladding 13 is 162 μm, the fifth ring width d5 ​​of its first annular cladding 11 is 1.5 μm, and the sixth ring width d6 of its third groove ring 12 is 5.5 μm; and the first refractive index difference Δn1 is 0.004, the second refractive index difference Δn2 is 0.002, the third refractive index difference Δn3 is 0.001, and the fourth refractive index difference Δn4 is -0.0015. The test conditions of this embodiment are: working wavelength 1.064 μm, bending radius 5 cm. While keeping the preferred parameters and test conditions unchanged, the transmission characteristics of the optical fiber are compared when the first diameter D1 of the first filling circular hole 1 is 0 μm, 3.2 μm, and 4.0 μm.

[0075] like Figure 7 As shown, the larger the first diameter D1, the higher the overall leakage loss ratio between higher-order modes and the fundamental mode across the entire bending direction. In particular, when the first diameter D1 = 4.0 μm, its loss ratio curve is significantly higher than that when the first diameter D1 = 3.2 μm and when there is no central hole (first diameter D1 = 0 μm). This proves that increasing the diameter of the first filling circular hole 1 can effectively enhance the suppression capability of higher-order modes and help ensure the purity of single-mode transmission.

[0076] Figure 8 This shows the variation of the mode field area of ​​the fundamental mode under different first diameters D1 of the first filling circular hole 1. It can be observed that as the first diameter D1 increases, the mode field area of ​​the fundamental mode decreases accordingly. When the first diameter D1 = 4.0 μm, the mode field area stabilizes at a relatively small level, about 450 μm², which indicates that the fundamental mode energy is more tightly confined near the central high refractive index region.

[0077] comprehensive Figure 7 and Figure 8 It is evident that the design of the first diameter D1 of the first filling circular hole 1 requires a balance between two key performance indicators: increasing the first diameter D1 can improve the suppression ratio of higher-order modes, i.e., optimize single-mode characteristics, but may also lead to shrinkage of the mode field area. Therefore, in practical design, an appropriate first diameter D1 can be selected based on the specific requirements for tolerance to nonlinear effects and single-mode stability.

[0078] In some preferred embodiments, based on combinations of some of the structures described in the foregoing embodiments, please refer further. Figure 4 and combined Figure 5 and Figure 9This embodiment analyzes the influence of the fourth diameter D4 of the second filling circular hole 9 in the inner cladding 7 on the single-mode properties of the optical fiber. This embodiment sets a set of preferred parameters including: the first diameter D1 of the first filling circular hole 1 is 3.2 μm; the first ring width d1 of the first annular core 2 is 14.2 μm; the second ring width d2 of the second annular core 3 is 4.6 μm; the third ring width d3 of the third annular core 4 is 2.6 μm; and the fourth ring width d4 of the first groove ring 5 and the second groove ring 6 is 1.7 μm; the second diameter D2 of the inner cladding 7 is 114 μm, and the third diameter D3 of its annular region is 96 μm; the fourth diameter D4 of the second filling circular hole 9 is 5.2 μm; the fifth diameter D5 of the third filling circular hole 10 is 9.2 μm; and the second filling circular hole 9... The first distance L between the center of the filling hole 9 and the third filling hole 10 and the center point of the optical fiber is 42 μm, and the included angle θ between two adjacent holes, except for the first filling hole 1, is 15°; the width w1 of a single spoke region is 14 μm; the sixth diameter D6 of the cladding 13 is 162 μm, the fifth ring width d5 ​​of its first annular cladding 11 is 1.5 μm, and the sixth ring width d6 of its third groove ring 12 is 5.5 μm; and the first refractive index difference Δn1 is 0.004, the second refractive index difference Δn2 is 0.002, the third refractive index difference Δn3 is 0.001, and the fourth refractive index difference Δn4 is -0.0015. The test conditions of this embodiment are: working wavelength 1.064 μm, bending radius 5 cm. While keeping the preferred parameters and test conditions unchanged, the variation of the leakage loss ratio of the higher-order mode to the fundamental mode with the bending direction was analyzed when the fourth diameter D4 of the second filling circular hole 9 was 4.0 μm, 5.2 μm and 5.8 μm respectively.

[0079] like Figure 9 As shown, when the fourth diameter D4 is small, for example, 4.0 μm, the leakage loss ratio between higher-order modes and the fundamental mode is less than 10 in multiple bending directions. Therefore, higher-order modes cannot be effectively suppressed, and the single-mode transmission condition cannot be strictly met. As the fourth diameter D4 increases to 5.2 μm and 5.8 μm, the loss ratio curve shifts significantly upward overall, especially when the fourth diameter D4 = 5.8 μm, its peak value exceeds 250. This indicates that increasing the fourth diameter D4 can greatly enhance the leakage effect of the low-refractive-index scattering center of the inner cladding 7 on higher-order modes. Although the loss ratio still fluctuates with the bending direction, increasing the fourth diameter D4 effectively increases the minimum value in all directions, enhancing the adaptability to changes in the bending direction. Therefore, choosing a sufficiently large fourth diameter D4, such as 5.2 μm, can ensure that the fiber can maintain higher-order mode suppression under any bending orientation, thereby achieving stable single-mode transmission in conjunction with other structures.

[0080] In some preferred embodiments, based on combinations of some of the structures described in the foregoing embodiments, please refer further. Figure 4 and combined Figure 5 and Figure 10This embodiment analyzes the impact of different values ​​of the fifth diameter D5 of the third filling circular hole 10 in the inner cladding 7 on the fiber performance. The preferred parameters set in this embodiment include: the first diameter D1 of the first filling circular hole 1 is 3.2 μm; the first ring width d1 of the first annular core 2 is 14.2 μm; the second ring width d2 of the second annular core 3 is 4.6 μm; the third ring width d3 of the third annular core 4 is 2.6 μm; and the fourth ring width d4 of the first groove ring 5 and the second groove ring 6 is 1.7 μm. The second diameter D2 of the inner cladding 7 is 114 μm, and the third diameter D3 of its annular region is 96 μm. The fourth diameter D4 of the second filling circular hole 9 is 5.2 μm. The first distance L between the center of hole 10 and the center point of the optical fiber is 42 μm, and the included angle θ between two adjacent holes, except for the first filling hole, is 15°; the width w1 of a single spoke region is 14 μm; the sixth diameter D6 of the cladding 13 is 162 μm, the fifth ring width d5 ​​of its first annular cladding 11 is 1.5 μm, and the sixth ring width d6 of its third groove ring 12 is 5.5 μm; and the first refractive index difference Δn1 is 0.004, the second refractive index difference Δn2 is 0.002, the third refractive index difference Δn3 is 0.001, and the fourth refractive index difference Δn4 is -0.0015. The test conditions of this embodiment are: working wavelength 1.064 μm, bending radius 5 cm. While keeping the preferred parameters and test conditions unchanged, the leakage loss ratio of the higher-order mode to the fundamental mode was compared for three cases where the fifth diameter D5 of the third filling circular hole 10 was 7.6 μm, 9.2 μm, and 10.0 μm.

[0081] like Figure 10 As shown, when the fifth diameter D5 is 7.6 μm, the leakage loss ratio of higher-order modes to the fundamental mode is less than 10 in most bending directions, which cannot meet the single-mode transmission requirements. When the fifth diameter D5 is increased to 10.0 μm, although the overall loss ratio improves, it still drops below 10 in some bending directions, such as around 18°, indicating insufficient single-mode stability. When the fifth diameter D5 is set to 9.2 μm, the leakage loss ratio of higher-order modes to the fundamental mode is consistently higher than 10 in all bending directions from 0° to 30°, which meets the single-mode transmission requirements. Therefore, the value of the fifth diameter D5 is not necessarily better the larger or smaller it is, but rather needs to be precisely coordinated with the overall structure and refractive index distribution of the inner cladding 7. Furthermore, when the fifth diameter D5 is close to or set to 9.2 μm, it ensures that the alternating lattice formed by the third filling circular hole 10 and the second filling circular hole 9 produces a balanced and effective leakage effect on various higher-order modes excited by bending at all angles.

[0082] In some preferred embodiments, based on combinations of some of the structures described in the foregoing embodiments, please refer further. Figure 4 and combined Figure 5 and Figure 11This embodiment specifically analyzes the influence of the ratio of the fifth ring width d5 ​​of the first annular outer cladding 11 to the sixth ring width d6 of the third trench ring 12 on the optical fiber performance. Preferred parameters in this embodiment include: the first diameter D1 of the first filling circular hole 1 is 3.2 μm; the first ring width d1 of the first annular core 2 is 14.2 μm; the second ring width d2 of the second annular core 3 is 4.6 μm; the third ring width d3 of the third annular core 4 is 2.6 μm; the fourth ring width d4 of the first trench ring 5 and the second trench ring 6 is 1.7 μm; the second diameter D2 of the inner cladding 7 is 114 μm, and the third diameter D3 of its annular region is 96 μm; the fourth diameter D4 of the second filling circular hole 9 is 5.2 μm; the third filling circular hole 12... The fifth diameter D5 of the filling hole 10 is 9.2 μm; the first distance L between the center of the second filling hole 9 and the third filling hole 10 and the center point of the optical fiber is 42 μm; and the included angle θ between two adjacent holes, except for the first filling hole 1, is 15°; the width w1 of a single spoke region is 14 μm; the sixth diameter D6 of the cladding 13 is 162 μm; and the first refractive index difference Δn1 is 0.004, the second refractive index difference Δn2 is 0.002, the third refractive index difference Δn3 is 0.001, and the fourth refractive index difference Δn4 is -0.0015. The test conditions in this embodiment are: working wavelength 1.064 μm and bending radius 5 cm. While keeping the preferred parameters and test conditions unchanged, the ratios of d5 to d6 are compared for three cases: 0 (i.e., no periodic trench structure), 1.5:5.5, and 2.0:5.0.

[0083] like Figure 11 As shown, this ratio is crucial in determining the filtering performance of the cladding. When the ratio is 0 (i.e., lacking a trench structure) or 2.0:5.0, the leakage loss ratio between higher-order modes and the fundamental mode is below 10 in multiple bending directions, failing to guarantee single-mode transmission. However, when the ratio is close to or set at 1.5:5.5, the loss ratio curve remains high in all tested bending directions, with peak values ​​exceeding 160, far exceeding the threshold required for single-mode transmission. The fiber structure at this ratio ensures that the high-refractive-index annular layer and the low-refractive-index trench ring in the cladding form an optimal width match, thus creating a periodic structure on the periphery that maintains efficient and stable filtering across all bending angles. Deviating from this optimal ratio, such as eliminating the trench or changing the relative width ratio, will weaken the filtering capability to some extent.

[0084] In some preferred embodiments, based on combinations of some of the structures described in the foregoing embodiments, please refer further. Figure 4 and combined Figure 5 and Figure 12This embodiment provides a set of preferred parameters and analyzes the mode field distribution of the fiber structure using these preferred parameters at four representative bending directions: 0°, 6°, 12°, and 22.5°. The preferred parameters of this embodiment include: the first diameter D1 of the first filling circular hole 1 is 3.2 μm; the first ring width d1 of the first annular core 2 is 14.2 μm; the second ring width d2 of the second annular core 3 is 4.6 μm; the third ring width d3 of the third annular core 4 is 2.6 μm; and the fourth ring width d4 of the first groove ring 5 and the second groove ring 6 is 1.7 μm. The second diameter D2 of the inner cladding 7 is 114 μm, and the third diameter D3 of its annular region is 96 μm. The fourth diameter D4 of the second filling circular hole 9 is 5.2 μm, and the fifth diameter D5 of the third filling circular hole 10 is 9.2 μm. The first distance L between the center of the second filling circular hole 9 and the center of the third filling circular hole 10 and the center point of the optical fiber is 42 μm, and the included angle θ between two adjacent circular holes is 15°; the width w1 of a single spoke region is 14 μm; the sixth diameter D6 of the outer cladding 13 is 162 μm, the fifth ring width d5 ​​of its first annular outer cladding 11 is 1.5 μm, and the sixth ring width d6 of its third groove ring 12 is 5.5 μm; the first refractive index difference Δn1 is 0.004, the second refractive index difference Δn2 is 0.002, the third refractive index difference Δn3 is 0.001, and the fourth refractive index difference Δn4 is -0.0015. The test conditions of this embodiment are: working wavelength 1.064 μm, bending radius 5 cm.

[0085] like Figure 12 As shown in the figure, the mode field distribution of the fundamental mode in the upper row indicates that, under different bending directions, the fundamental mode energy is always tightly and stably confined to the central region of the fiber core, with minimal changes in its optical field morphology and range. This directly verifies that, when the aforementioned preferred parameters are selected, the fiber structure of this embodiment has a strong confinement capability and bend insensitivity for the fundamental mode. In contrast, the mode field distribution of the lowest-loss higher-order modes in the lower row shows a significant change: as the bending direction changes from 0° to 22.5°, the optical field of the higher-order modes gradually diffuses significantly from a relatively concentrated state to the periphery and edges, becoming increasingly diffuse. It can be seen that the fundamental mode remains stable due to the strong confinement design of the overall waveguide structure; while the higher-order modes, due to their own field distribution characteristics, are more likely to couple to low-refractive-index scattering and leakage structures in the cladding, such as filling holes and trenches, under bending stress, resulting in higher leakage loss. The mode field evolution diagram intuitively confirms the fundamental reason why the leakage loss ratio of higher-order modes to the fundamental mode changes with the bending direction in the aforementioned embodiments. It also demonstrates that under the above-mentioned preferred parameters and test conditions, the optical fiber of this embodiment can achieve stable large mode field transmission of the fundamental mode in complex bending environments, while effectively filtering out higher-order modes, thus meeting the stringent requirements of all-round single-mode bending resistance.

[0086] It should be understood that the specific embodiments described herein are merely illustrative of the application and not intended to limit it. All other embodiments derived by those skilled in the art based on the embodiments provided in this application without inventive effort are within the scope of protection of this application.

[0087] Obviously, the accompanying drawings are merely some examples or embodiments of this application. Those skilled in the art can apply this application to other similar situations based on these drawings without any creative effort. Furthermore, it is understood that although the work done in this development process may be complex and lengthy, for those skilled in the art, certain design, manufacturing, or production modifications made based on the technical content disclosed in this application are merely conventional technical means and should not be considered as insufficient disclosure of this application.

[0088] The term "embodiment" in this application refers to a specific feature, structure, or characteristic described in connection with an embodiment that may be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily imply the same embodiment, nor does it imply that it is mutually exclusive with or independent of other embodiments. It will be clearly or implicitly understood by those skilled in the art that the embodiments described in this application may be combined with other embodiments without conflict.

[0089] The above embodiments merely illustrate several implementation methods of this application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of patent protection. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the scope of protection of this application.

Claims

1. A bend-resistant all-solid-state microstructure optical fiber, characterized in that, Including the core region and the inner cladding; The fiber core region includes a first filling circular hole, a first annular fiber core, and a first grooved ring; the first filling circular hole is located at the center of the fiber core region and has a first refractive index; the first annular fiber core surrounds the first filling circular hole and has a second refractive index; the first grooved ring surrounds the first annular fiber core and has a third refractive index. The inner cladding layer surrounds the fiber core region and has a fourth refractive index; The inner cladding layer has a plurality of second filling circular holes distributed thereon, and the second filling circular holes have a fifth refractive index; The first refractive index is higher than the second refractive index; the second refractive index is higher than the fourth refractive index; the fourth refractive index is higher than the third refractive index; and the third refractive index is higher than the fifth refractive index.

2. The bend-resistant all-solid-state microstructure optical fiber according to claim 1, characterized in that, The fiber core region also includes a second annular fiber core and a second grooved ring; The second annular fiber core surrounds the first grooved ring and has the second refractive index and the second ring width; the first annular fiber core has a first ring width, which is greater than the second ring width. The second grooved ring surrounds the second annular fiber core and has the third refractive index.

3. The bend-resistant all-solid-state microstructure optical fiber according to claim 2, characterized in that, The fiber core region also includes a third annular fiber core; The third annular fiber core surrounds the second grooved ring and has the second refractive index and the third ring width; the second ring width is greater than the third ring width. Both the first grooved ring and the second grooved ring have a fourth ring width; the third ring width is greater than the fourth ring width.

4. The bend-resistant all-solid-state microstructure optical fiber according to claim 1, characterized in that, The inner cladding includes an annular region and several spoke regions; Several spoke areas extend outward along the annular area and are evenly distributed along the circumference of the annular area; Each pair of adjacent spoke regions is filled with a petal-shaped inner cladding; The petal-shaped inner cladding has the third refractive index, and the radial width of the petal-shaped inner cladding is equal to the annular width of the spoke region.

5. The bend-resistant all-solid-state microstructure optical fiber according to claim 4, characterized in that, The second filling circular holes are uniformly distributed circumferentially along the annular region of the inner cladding.

6. The bend-resistant all-solid-state microstructure optical fiber according to claim 4, characterized in that, The annular region is also distributed with several third filling circular holes; The positions of the third filling holes correspond to the positions of the spoke areas; the second filling holes are distributed in the annular area of ​​the inner cladding, and at least one second filling hole is located between every two adjacent third filling holes; The center of the third filling hole and the center of the second filling hole are both at a first distance from the center of the first filling hole; The third filling hole has a fifth diameter and a fifth refractive index; the second filling hole has a fourth diameter; the fifth diameter is larger than the fourth diameter.

7. The bend-resistant all-solid-state microstructure optical fiber according to claim 1, characterized in that, It also includes a first annular outer cladding, a third grooved ring, and an outer cladding; The first annular outer cladding surrounds the inner cladding and has the second refractive index and the fifth annular width; The third groove ring surrounds the first annular outer cladding layer and has the fifth refractive index and the sixth ring width; The width of the sixth ring is greater than the width of the fifth ring; The outer cladding layer is located outside the third groove ring and has the third refractive index.

8. The bend-resistant all-solid-state microstructure optical fiber according to claim 7, characterized in that, The ratio of the width of the fifth ring to the width of the sixth ring is 1.5:5.

5.

9. The bend-resistant all-solid-state microstructure optical fiber according to claim 7, characterized in that, A single first annular outer cladding layer and the third grooved ring form a set of outer cladding layer units; At least one set of outer cladding units is also wrapped between the third groove ring and the outer cladding.

10. The bend-resistant all-solid-state microstructure optical fiber according to claim 1, characterized in that, The range of the third refractive index is 1.80 to 1.86; The first refractive index difference between the first refractive index and the third refractive index is 0.004; the second refractive index difference between the second refractive index and the third refractive index is 0.002; the fourth refractive index difference between the fourth refractive index and the third refractive index is 0.001; and the fifth refractive index difference between the fifth refractive index and the third refractive index is -0.0015.

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