Azimuthally marked hollow core optical fiber and method for detecting an end face of a hollow core optical fiber

Abstract

The application discloses an azimuth angle marked hollow core optical fiber and a hollow core optical fiber end face detection method. The optical fiber comprises a cladding hollow core sleeve and a plurality of circumferentially uniformly arranged anti-resonant microstructure units arranged and attached to the inner wall of the cladding hollow core sleeve, and a hollow area surrounded by the anti-resonant microstructure units is a core; the azimuth angle of at least one anti-resonant microstructure unit is different from the azimuth angle of at least one other anti-resonant microstructure unit. The azimuth angle marked hollow core optical fiber and the hollow core optical fiber end face detection method provided by the application can quickly identify the anti-resonant microstructure units in the hollow core optical fiber under the premise that the complexity of the optical fiber preparation is not improved and the transmission performance of the optical fiber is almost not affected, and the geometric uniformity of the anti-resonant microstructure units can be conveniently controlled on line.

Description

Technical Field

[0001] This invention belongs to the field of optical communication, and more specifically, relates to a hollow optical fiber with azimuth marking and a method for detecting the end face of the hollow optical fiber. Background Technology

[0002] Hollow-core optical fiber is characterized by its simple structure, single-mode optical guidance, and wide transmission spectrum, making it important for applications in fields such as light-filled material interaction, nonlinear optics, gas detection, gas laser generation, and optofluidics. Large-aperture fiber cores exhibit ultra-low Rayleigh scattering, low nonlinearity, and tunable dispersion, providing a higher laser damage threshold and potential applications in high-power laser transmission, ultraviolet / mid-infrared light transmission, pulse compression, and optical soliton transmission. The ultra-low loss, low dispersion, low nonlinearity, and near-light-speed propagation of the air core enable hollow-core optical fiber communication transmission and the development of communication devices, laying the foundation for the construction and development of next-generation ultra-high-capacity, low-latency, and high-speed optical communication systems.

[0003] While hollow-core optical fiber offers significant advantages in design and application, its transmission loss has consistently exceeded that of traditional silica optical fiber. Recent discoveries have shown that hollow-core optical fiber based on the anti-resonance principle, with proper structural design, can effectively reduce transmission loss, demonstrating its potential as an ultra-long-distance communication fiber. Further reducing attenuation remains a crucial challenge in the field of hollow-core optical fiber manufacturing.

[0004] Although known hollow-core antiresonant fibers, especially those with nested structural elements, can significantly reduce fiber attenuation, the manufacturing process of hollow-core antiresonant fibers differs fundamentally from that of conventional solid-core fibers. The microscopic three-dimensional structure of hollow-core fibers is the basis for their light guiding. To form or maintain a specific microstructure, gas needs to be continuously introduced during the fiber drawing process. Due to factors such as the inhomogeneity of raw materials, deviations during the stacking of nested structural elements, and uneven thermal field distribution during drawing, the antiresonant structural elements in the drawn hollow-core antiresonant fibers may exhibit inconsistent sizes. Figure 1 As shown, this geometric inhomogeneity will significantly affect the transmission loss of hollow anti-resonant optical fibers. Because this manufacturing method is revolutionary compared to existing solid optical fibers, it is impossible to improve the geometric inhomogeneity using the methods typically employed for solid optical fibers, such as increasing the size of the fiber preform. Summary of the Invention

[0005] To address the aforementioned deficiencies or improvement needs of existing technologies, this invention provides an azimuth-marked hollow optical fiber and a method for detecting the end face of the hollow optical fiber. The purpose is to mark the end face of the optical fiber by adjusting the azimuth of the anti-resonant microstructure unit with multiple negative curvature layers, while ensuring the optical fiber transmission performance. This method identifies each anti-resonant microstructure unit and can be used to detect the geometric uniformity of the optical fiber, thereby solving the technical problem that existing hollow optical fibers have difficulty distinguishing their anti-resonant units and detecting geometric uniformity.

[0006] To achieve the above objectives, according to one aspect of the present invention, an azimuth-marked hollow optical fiber is provided, comprising a cladding hollow sleeve and a plurality of circumferentially uniformly distributed anti-resonant microstructure units arranged and attached to the inner wall of the cladding hollow sleeve, wherein the hollow region surrounded by the anti-resonant microstructure units is the fiber core.

[0007] The anti-resonant microstructure unit has multiple negative curvature layers, with the layer furthest from the fiber core as the inner side and the layer closest to the fiber core as the outer side. The azimuth angle is the angle formed by connecting the curvature center of the outermost negative curvature layer to the geometric center of the optical fiber and then to the curvature center of the innermost negative curvature layer.

[0008] There exists an anti-resonant microstructure unit whose azimuth angle differs from that of at least one other anti-resonant microstructure unit.

[0009] Preferably, the azimuth difference between the hollow optical fibers marked with azimuth angles is ≥1.5°.

[0010] Preferably, the azimuth-marked hollow fiber has an azimuth angle that differs from all other anti-resonant microstructure units.

[0011] Preferably, the azimuth-marked hollow fiber has the same azimuth angle as all other anti-resonant microstructure units.

[0012] Preferably, the azimuth-marked hollow fiber has an azimuth angle of 0° for all other anti-resonant microstructure units.

[0013] Preferably, in the hollow optical fiber with azimuth marking, the azimuth angle of the marked anti-resonant microstructure unit is θ, where 1.5°≤θ≤45°.

[0014] Preferably, the azimuth-marked hollow optical fiber has an anti-resonant microstructure unit comprising two tangentially nested capillaries, wherein the included angle formed by connecting the center of the inner capillary to the geometric center of the optical fiber and then to the center of the outer capillary is the azimuth angle of the anti-resonant microstructure unit.

[0015] Preferably, in the hollow optical fiber with azimuth marking, the capillary tangent of the other anti-resonant microstructure units is attached to the inner wall of the cladding hollow sleeve.

[0016] Preferably, the hollow fiber with azimuth marking has a circular cladding hollow tube, and the outer contours of the plurality of anti-resonant microstructure units are the same.

[0017] According to another aspect of the present invention, a method for detecting the end face of a hollow optical fiber is provided, comprising the following steps:

[0018] (1) Cut the hollow fiber marked with the azimuth angle at the preset position;

[0019] (2) Image the cut end face obtained in step (1) using transmitted light or reflected light to obtain an image of the end face of the hollow fiber at that location.

[0020] (3) For the end face image obtained in step (2), the anti-resonance microstructure unit is identified according to its azimuth angle, and the image of each anti-resonance microstructure unit is obtained.

[0021] (4) Extract geometric parameters from the image of the anti-resonant microstructure unit obtained in step (3) to determine the geometric uniformity of the hollow fiber.

[0022] In summary, compared with the prior art, the above-described technical solutions conceived by this invention can achieve the following beneficial effects:

[0023] This invention provides an azimuth-marked hollow optical fiber and a method for detecting the end face of the hollow optical fiber. By using azimuth marking, the anti-resonant microstructure units in the hollow optical fiber can be quickly identified without increasing the complexity of fiber fabrication or affecting the fiber transmission performance. This facilitates online control of the geometric uniformity of the anti-resonant microstructure units, which helps reduce the transmission loss of the hollow optical fiber. At the same time, during the coupling process of the hollow optical fiber, it is easy to identify different anti-resonant microstructure units, thereby reducing the coupling loss of the hollow optical fiber. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the hollow optical fiber preform with azimuth marking provided in Embodiment 1 of the present invention;

[0025] Figure 2 This is a schematic diagram of an unmarked hollow optical fiber, used for comparison with Example 1;

[0026] Figure 3 This is a schematic diagram of pressure control during the drawing process of the hollow optical fiber preform with azimuth marking provided in Embodiment 1 of the present invention;

[0027] Figure 4This is a schematic diagram of pressure control during the drawing process of a hollow optical fiber preform with two azimuth angle marks provided in Embodiment 2 of the present invention;

[0028] Figure 5 This is a schematic diagram of pressure control during the drawing process of a hollow optical fiber preform with azimuth markings provided in Embodiment 3 of the present invention.

[0029] In all the figures, the same reference numerals are used to denote the same elements or structures, wherein: 1 is an anti-resonant microstructure unit, 2 is a cladding hollow sleeve, 3 is the only marked anti-resonant microstructure unit used in Embodiment 1, 4 and 5 are two adjacent marked anti-resonant microstructure units used in Embodiment 2, and 6, 7, and 8 are three adjacent marked anti-resonant microstructure units used in Embodiment 3. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0031] The azimuth-marked hollow optical fiber provided by the present invention includes a cladding hollow sleeve and a plurality of circumferentially uniformly arranged anti-resonant microstructure units arranged and attached to the inner wall of the cladding hollow sleeve. The hollow region surrounded by the anti-resonant microstructure units is the fiber core. The cladding hollow sleeve is circular, and the outer contours of the plurality of anti-resonant microstructure units are the same.

[0032] The number of anti-resonant microstructure units n≥3.

[0033] The anti-resonant microstructure unit has multiple negative curvature layers, with the layer furthest from the fiber core as the inner side and the layer closest to the fiber core as the outer side. The azimuth angle is the distance from the curvature center of the outermost negative curvature layer to the geometric center of the optical fiber and then to the curvature center of the innermost negative curvature layer.

[0034] At least one anti-resonant microstructure unit has an azimuth angle that differs from at least one other anti-resonant microstructure unit. All anti-resonant microstructure units can be identified by recognizing this azimuth angle difference: first, the anti-resonant microstructure unit with the difference is identified; then, the other anti-resonant microstructure units are identified by their relative positions to the aforementioned unit with the difference. For easy identification of anti-resonant microstructure units, the azimuth angle difference needs to be greater than 1.5° to clearly distinguish it from assembly errors. That is, the azimuth angle offset of the anti-resonant microstructure unit is used as the indicator of the hollow fiber's azimuth, and the number of anti-resonant microstructure units with azimuth angle offsets is m, where m ≥ 1.

[0035] Anti-resonant microstructures that differ in azimuth angle from all other anti-resonant microstructures are easily identifiable and are called marked anti-resonant microstructures.

[0036] The azimuth angle of the anti-resonant microstructure unit affects the transmission performance of the hollow-core optical fiber to some extent, and is preferably ≤45°. When the azimuth angle of the anti-resonant microstructure unit is 0°, the multilayer negative curvature layer is maximally aligned with the fiber core direction, typically with both negative curvature layers aligned with the fiber core direction, theoretically possessing better transmission performance. Therefore, in the preferred scheme, except for the marked anti-resonant microstructure unit, the azimuth angle of all other anti-resonant microstructure units is 0°.

[0037] In a relatively easy-to-implement manner, a uniquely marked anti-resonant microstructure unit is used, making its azimuth angle different from that of all other anti-resonant microstructure units, while the azimuth angles of all other anti-resonant microstructure units are the same. This makes the marked anti-resonant microstructure unit easier to identify, while the other anti-resonant microstructure units are identified by their relative positions to the marked anti-resonant microstructure unit.

[0038] However, the azimuth angle difference of the marked anti-resonant microstructure unit also affects the transmission performance of the optical fiber. Excessive azimuth angle difference leads to increased transmission loss and, due to the significant asymmetry of the fiber cross-section, may distort the light propagation mode. Therefore, the azimuth angle of the marked anti-resonant microstructure unit is θ, with 1.5°≤θ≤45°, preferably 1.5°≤θ≤15°, to maintain good transmission performance of the hollow-core optical fiber.

[0039] Preferably, the anti-resonant microstructure unit includes two layers of tangentially nested capillaries, with the azimuth angle of the anti-resonant microstructure unit being the distance from the center of the inner capillary to the geometric center of the optical fiber and then to the center of the outer capillary. Except for the marked anti-resonant microstructure unit, the tangential points of the capillaries of other anti-resonant microstructure units are attached to the inner wall of the cladding hollow sleeve, with an azimuth angle of 0°.

[0040] The method for preparing hollow-core optical fiber with azimuth marking provided by the present invention includes the following steps:

[0041] Step 1: Prepare nested anti-resonant microstructure units: The required capillary tube is drawn from the mother tube in a high-temperature wire drawing furnace; the capillary tube can be further processed according to design requirements, such as cutting, grinding, welding, etc., to form nested anti-resonant microstructure units.

[0042] Step 2, Preform Stacking: The nested anti-resonant microstructure units obtained in Step 1 are stacked and assembled in the sleeve. When stacking, m nested anti-resonant microstructure units are selected to generate an azimuth angle offset, which is used as an indicator of the azimuth of the hollow fiber, thus forming a hollow fiber preform with azimuth marking.

[0043] Step 3: Directly draw the hollow fiber preform marked with azimuth angles from Step 2 into a hollow fiber, or first draw it into an intermediate preform and then insert it into a sleeve to draw it into a hollow fiber. During the drawing process, the correspondence between the anti-resonant microstructure units in the fiber and the anti-resonant microstructure units in the preform is quickly identified by the azimuth angle markings. This allows for the adjustment of the size of the anti-resonant microstructure units in the fiber by controlling the air pressure within the anti-resonant microstructure units in the preform.

[0044] Furthermore, the anti-resonance microstructure unit, sleeve, and azimuth marker can be made of high-purity silicon dioxide, doped quartz (doped with one or more elements such as germanium, fluorine, chlorine, boron, and aluminum), multi-component glass, or plastic.

[0045] Furthermore, the hollow optical fiber has a cladding diameter of 100 μm or more.

[0046] The method for detecting the end face of hollow optical fiber provided by this invention includes the following steps:

[0047] (1) Cut the hollow fiber marked with the azimuth angle at the preset position;

[0048] (2) Image the cut end face obtained in step (1) using transmitted light or reflected light to obtain an image of the end face of the hollow fiber at that location.

[0049] (3) For the end face image obtained in step (2), the anti-resonance microstructure unit is identified according to its azimuth angle, and the image of each anti-resonance microstructure unit is obtained.

[0050] (4) Extract geometric parameters from the image of the anti-resonant microstructure unit obtained in step (3) to determine the geometric uniformity of the hollow fiber.

[0051] Based on its geometric uniformity, the pressure of the gas introduced into each region of each anti-resonant microstructure unit and the sleeve during the drawing of the hollow fiber can be adjusted, thereby controlling the fiber drawing process, improving the geometric uniformity of the fiber, and enabling the hollow fiber to have lower transmission loss and splice loss.

[0052] The hollow-core optical fiber provided by this invention has low transmission loss, with the lowest transmission loss being ≤30dB / km and more preferably ≤1dB / km; and it also has low fusion splicing loss, with the self-fusion splicing loss of the hollow-core optical fiber being ≤0.5dB.

[0053] The following is an example:

[0054] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0055] Example 1

[0056] The hollow fiber structure provided in this embodiment is as follows: Figure 1 As shown, it includes a cladding hollow sleeve and five circumferentially uniformly arranged anti-resonance microstructure units arranged and attached to the inner wall of the cladding hollow sleeve. The hollow region surrounded by the anti-resonance microstructure units is the fiber core. The cladding hollow sleeve is circular, and the outer contours of the multiple anti-resonance microstructure units are the same.

[0057] The anti-resonant microstructure unit comprises two nested, tangential capillaries. The angle formed by connecting the center of the inner capillary to the geometric center of the optical fiber and then to the center of the outer capillary is the azimuth angle of the anti-resonant microstructure unit. A uniquely marked anti-resonant microstructure unit is used, with an azimuth angle of θ = 7.8°, while the azimuth angles of all other anti-resonant microstructure units are 0°, and the tangential points of the capillaries are attached to the inner wall of the cladding hollow sleeve. Its fabrication method is as follows:

[0058] First, two sizes of capillaries are prepared using a mother tube: a large capillary with an outer diameter of 10.4 mm and a wall thickness of 0.32 mm, and a small capillary with an outer diameter of 6.2 mm and a wall thickness of 0.34 mm. The small capillary is then inserted into the large capillary and fixed using laser heating, thus forming the anti-resonant microstructure unit 1. Next, a pure silica sleeve is prepared, with an outer diameter of 65 mm and an inner diameter of 55 mm. Five anti-resonant microstructure units 1 are stacked in the sleeve 2 as shown in the diagram. Figure 1 The hollow fiber preform shown has one anti-resonant microstructure unit 3 whose azimuth angle is shifted during the stacking process, resulting in an θ of 7.8°. The remaining azimuth angles maintain an assembly error ≤1.5°, thus obtaining a hollow fiber preform with azimuth markings. This azimuth-marked preform can be directly drawn into hollow fiber in a drawing furnace. However, during drawing, temperature fluctuations can cause variations in the size of the anti-resonant microstructure units, which can affect imaging detection. Figure 2 As shown, the maximum deviation of the outer diameter of its anti-resonant microstructure unit is 25%. Therefore, it is necessary to introduce gases at different pressures into the anti-resonant microstructure unit to ensure uniformity of its dimensions. Figure 3As shown, the required gas pressure in the anti-resonant microstructure unit is identified by azimuth markings. P1, P2, P3, P4, and P5 represent the gas pressure in the large capillary of the anti-resonant microstructure unit, with values ​​of 15.3 mbar, 15.5 mbar, 15.5 mbar, 15.8 mbar, and 15.2 mbar, respectively. P6, P7, P8, P9, and P10 represent the gas pressure in the small capillary of the anti-resonant microstructure unit, with values ​​of 64.3 mbar, 64.4 mbar, 64.9 mbar, 64.7 mbar, and 64.5 mbar, respectively. After being drawn into an optical fiber, the maximum deviation of the outer diameter of the large capillary in the anti-resonant microstructure unit is 2.9%, and the maximum deviation of the outer diameter of the small capillary in the anti-resonant microstructure unit is 3.3%. Its attenuation at 1550 nm is 0.58 dB / km. When splicing this hollow fiber, the orientation of the capillary can be identified by the azimuth marker unit, thereby achieving more accurate splicing. Its minimum splice loss is 0.36dB.

[0059] Example 2

[0060] The hollow fiber structure provided in this embodiment is as follows: Figure 4 As shown, it includes a cladding hollow sleeve and five circumferentially uniformly arranged anti-resonance microstructure units arranged and attached to the inner wall of the cladding hollow sleeve. The hollow region surrounded by the anti-resonance microstructure units is the fiber core. The cladding hollow sleeve is circular, and the outer contours of the multiple anti-resonance microstructure units are the same.

[0061] The anti-resonant microstructure unit comprises two nested, tangential capillaries. The azimuth angle of the anti-resonant microstructure unit is the distance from the center of the inner capillary to the geometric center of the optical fiber and then to the center of the outer capillary. Two adjacent anti-resonant microstructure units, 4 and 5, are used, with azimuth angles θ of 11.2° and 9.4° respectively. All other anti-resonant microstructure units have an azimuth angle of 0°, and the tangential points of the capillaries are attached to the inner wall of the cladding hollow sleeve. The fabrication method is as follows:

[0062] First, two sizes of capillaries are prepared using a mother tube: a large capillary with an outer diameter of 8.2 mm and a wall thickness of 0.62 mm, and a small capillary with an outer diameter of 4.15 mm and a wall thickness of 0.44 mm. The small capillary is then inserted into the large capillary and fixed using laser heating, thus forming the anti-resonant microstructure unit 1. Next, a pure silica sleeve is prepared, with an outer diameter of 55 mm and an inner diameter of 45 mm. Five anti-resonant microstructure units 1 are stacked in the sleeve 2 as shown in the diagram. Figure 4The hollow fiber preform shown has two anti-resonant microstructure units (4 and 5) whose azimuth angles are shifted during the stacking process. The azimuth angle θ of anti-resonant microstructure unit 4 is 11.2°, and the azimuth angle θ of anti-resonant microstructure unit 5 is 9.4°. The remaining azimuth angles remain ≤1.5°, thus obtaining a hollow fiber preform with azimuth angle markings. The azimuth-marked hollow fiber preform can be first drawn into an intermediate preform with an outer diameter of 7.5 mm in a drawing furnace, and then inserted into a sleeve with an outer diameter of 14.2 mm and an inner diameter of 8.1 mm for drawing. Similar to the previous embodiment, the dimensions of the anti-resonant microstructure units are made uniform by introducing gases at different pressures into the anti-resonant microstructure units. Figure 4 As shown, the required gas pressure in the anti-resonant microstructure unit is identified by azimuth marker units. P1, P2, P3, P4, and P5 represent the gas pressure in the large capillary of the anti-resonant microstructure unit, with values ​​of 29.9 mbar, 29.8 mbar, 30.2 mbar, 30.3 mbar, and 30.4 mbar, respectively. P6, P7, P8, P9, and P10 represent the gas pressure in the small capillary of the anti-resonant microstructure unit, with values ​​of 112.5 mbar, 112.1 mbar, 113.2 mbar, 112.7 mbar, and 113.2 mbar, respectively. After being drawn into an optical fiber, the maximum deviation of the outer diameter of the large capillary in the anti-resonant microstructure unit is 2.7%, and the maximum deviation of the outer diameter of the small capillary in the anti-resonant microstructure unit is 2.8%. Its attenuation at 1550 nm is 0.46 dB / km. When splicing this hollow fiber, the orientation of the capillary can be identified by the azimuth marker unit, thereby achieving more accurate splicing. Its minimum splice loss is 0.25dB.

[0063] Example 3

[0064] The hollow fiber structure provided in this embodiment is as follows: Figure 5 As shown, it includes a cladding hollow sleeve and five circumferentially uniformly arranged anti-resonance microstructure units arranged and attached to the inner wall of the cladding hollow sleeve. The hollow region surrounded by the anti-resonance microstructure units is the fiber core. The cladding hollow sleeve is circular, and the outer contours of the multiple anti-resonance microstructure units are the same.

[0065] The anti-resonant microstructure unit comprises two nested, tangential capillaries. The included angle formed by connecting the center of the inner capillary to the geometric center of the optical fiber and then to the center of the outer capillary is the azimuth angle of the anti-resonant microstructure unit. Three adjacent anti-resonant microstructure units 6, 7, and 8 are used, with azimuth angles θ of 6.4°, 7.2°, and 7.8°, respectively. The azimuth angles of all other anti-resonant microstructure units are 0°, and the tangential points of the capillaries are attached to the inner wall of the cladding hollow sleeve. The fabrication method is as follows:

[0066] like Figure 5 As shown, two sizes of capillaries are first prepared using a mother tube: a large capillary with an outer diameter of 6.6 mm and a wall thickness of 0.37 mm, and a small capillary with an outer diameter of 2.8 mm and a wall thickness of 0.24 mm. The small capillary is then inserted into the large capillary and fixed using laser heating, thus forming the anti-resonant microstructure unit 1. Next, a pure silica sleeve is prepared, with an outer diameter of 27 mm and an inner diameter of 21 mm. Five anti-resonant microstructure units 1 are stacked in the sleeve 2 as shown in the diagram. Figure 5 The hollow fiber preform shown has its azimuth angles shifted during the stacking process of three anti-resonant microstructure units (6, 7, and 8). The azimuth angle θ of anti-resonant microstructure unit 6 is 6.4°, that of anti-resonant microstructure unit 7 is 7.2°, and that of anti-resonant microstructure unit 8 is 7.8°. The remaining azimuth angles remain ≤1.5°, thus obtaining a hollow fiber preform with azimuth angle markings. The azimuth-marked hollow fiber preform can be first drawn into an intermediate preform in a drawing furnace. The outer diameter of the intermediate preform is 10.5 mm, and then it is inserted into a sleeve with an outer diameter of 18.2 mm and an inner diameter of 11.0 mm for drawing. Similar to the previous embodiment, the dimensions of the anti-resonant microstructure units are made uniform by introducing gases at different pressures into the anti-resonant microstructure units. Figure 5 As shown, the required gas pressure in the anti-resonant microstructure unit is identified by azimuth marker units. P1, P2, P3, P4, and P5 represent the gas pressure in the large capillary of the anti-resonant microstructure unit, with values ​​of 46.2 mbar, 46.9 mbar, 47.6 mbar, 46.3 mbar, and 46.5 mbar, respectively. P6, P7, P8, P9, and P10 represent the gas pressure in the small capillary of the anti-resonant microstructure unit, with values ​​of 156.3 mbar, 157.4 mbar, 159.4 mbar, 158.5 mbar, and 157.9 mbar, respectively. After being drawn into an optical fiber, the maximum deviation of the outer diameter of the large capillary in the anti-resonant microstructure unit is 3.1%, and the maximum deviation of the outer diameter of the small capillary in the anti-resonant microstructure unit is 3.4%. Its attenuation at 1550 nm is 0.43 dB / km. When splicing this hollow fiber, the orientation of the capillary can be identified by the azimuth marker unit, thereby achieving more accurate splicing. Its minimum splice loss is 0.27dB.

[0067] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A hollow optical fiber with azimuth marking, characterized in that, It includes a clad hollow sleeve and multiple circumferentially uniformly distributed anti-resonance microstructure units arranged and attached to the inner wall of the clad hollow sleeve, wherein the hollow region surrounded by the anti-resonance microstructure units is the fiber core. The anti-resonant microstructure unit has multiple negative curvature layers, with the layer furthest from the fiber core as the inner side and the layer closest to the fiber core as the outer side. The azimuth angle is the angle formed by connecting the curvature center of the outermost negative curvature layer to the geometric center of the optical fiber and then to the curvature center of the innermost negative curvature layer. There exists an anti-resonant microstructure unit whose azimuth angle differs from that of at least one other anti-resonant microstructure unit.

2. The hollow-core optical fiber with azimuth marking as described in claim 1, characterized in that, The difference between azimuth angles is ≥1.5°.

3. The hollow-core optical fiber with azimuth marking as described in claim 1 or 2, characterized in that, The azimuth angle of the marked anti-resonant microstructure unit differs from that of all other anti-resonant microstructure units.

4. The hollow-core optical fiber with azimuth marking as described in claim 3, characterized in that, The azimuth angles of all other anti-resonant microstructure units are the same.

5. The hollow-core optical fiber with azimuth marking as described in claim 4, characterized in that, The azimuth angle of all other anti-resonant microstructure units is 0°.

6. The hollow-core optical fiber with azimuth marking as described in claim 3, characterized in that, The azimuth angle of the marked anti-resonant microstructure unit is θ, and 1.5°≤θ≤45°.

7. The hollow-core optical fiber with azimuth marking as described in claim 3, characterized in that, The anti-resonant microstructure unit includes two tangentially nested capillaries. The included angle formed by connecting the center of the inner capillary to the geometric center of the optical fiber and then to the center of the outer capillary is the azimuth angle of the anti-resonant microstructure unit.

8. The hollow-core optical fiber with azimuth marking as described in claim 7, characterized in that, The capillary tangents of the other anti-resonance microstructure units are attached to the inner wall of the cladding hollow sleeve.

9. The hollow-core optical fiber with azimuth marking as described in claim 1, characterized in that, The cladding hollow sleeve is circular, and the outer contours of the multiple anti-resonance microstructure units are the same.

10. The method for detecting the end face of hollow optical fiber as described in any one of claims 1 to 9, characterized in that, Includes the following steps: (1) Cut the hollow fiber marked with the azimuth angle at the preset position; (2) Image the cut end face obtained in step (1) using transmitted light or reflected light to obtain an image of the end face of the hollow fiber at that location. (3) For the end face image obtained in step (2), the anti-resonance microstructure unit is identified according to its azimuth angle, and the image of each anti-resonance microstructure unit is obtained. (4) Extract geometric parameters from the image of the anti-resonant microstructure unit obtained in step (3) to determine the geometric uniformity of the hollow fiber.

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