Hollow-core microstructured fiber with refractive index marks, preparation method therefor and detection method

Abstract

A hollow-core microstructured fiber with refractive index marks (2), and a preparation method therefor and a detection method. The fiber comprises a cladding hollow-core sleeve (3) and a plurality of anti-resonant microstructured units (1) arranged on an inner wall of the cladding hollow-core sleeve (3), wherein the plurality of anti-resonant microstructured units (1) are rotationally symmetric; the cladding hollow-core sleeve (3) is provided with one or more refractive index mark units (2); there is the refractive index difference between the refractive index of each refractive index mark unit (2) and the refractive index of the cladding hollow-core sleeve (3); and an end-face structure of the hollow-core microstructured fiber has asymmetry.

Description

Hollow-core microstructured optical fiber with refractive index marker, preparation method and detection method thereof Technical Field

[0001] The present invention belongs to the field of optical communications, and more specifically, relates to a hollow-core microstructure optical fiber with a refractive index marker, and a preparation and detection method thereof. Background Art

[0002] Hollow-core microstructured optical fiber has the characteristics of simple structure, hollow-core single-mode light guidance, and wide transmission spectrum. It has important applications in the fields of interaction between light and filling materials, nonlinear optics, gas detection, gas laser generation, optofluidic technology, etc.; large air hole core light guidance has ultra-low Rayleigh scattering, low nonlinear coefficient, and adjustable dispersion characteristics, which can provide a higher laser damage threshold, making it potentially applicable 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 propagation speed close to the speed of light of the air core can realize the development of hollow-core microstructured optical fiber communication transmission and communication devices, laying the foundation for the construction and development of the next generation of ultra-large capacity, low latency, and high-speed optical communication systems.

[0003] Despite the significant advantages of hollow-core microstructured fibers in design and application, their transmission loss remains higher than that of traditional quartz fibers. Recent discoveries have shown that hollow-core microstructured fibers, based on the principle of antiresonance, can effectively reduce transmission loss with appropriate structural design, demonstrating their potential as ultra-long-haul communication fibers. Further reducing attenuation is a key issue in the field of hollow-core microstructured fiber manufacturing.

[0004] Although known hollow-core antiresonant fibers, especially those with nested structural elements, can significantly reduce optical fiber attenuation, the manufacturing process of hollow-core antiresonant fibers is fundamentally different from that of existing solid-core fibers. The microscopic three-dimensional structure of hollow-core microstructured fibers is the basis of their light guidance. In order to maintain or form this specific microstructure, gas must be maintained during the drawing process. Due to factors such as raw material inhomogeneity, deviations during the stacking of nested structural elements, and uneven thermal field distribution during the drawing process, the antiresonant structural elements of the drawn hollow-core antiresonant fibers will have different sizes, as shown in Figure 2. This geometric structural inhomogeneity will greatly affect the transmission loss of the hollow-core antiresonant fibers. Precisely because this manufacturing method is subversive compared to existing solid-core fibers, the conventional method of increasing the fiber size, which is used for solid-core fibers, cannot be used to improve geometric inhomogeneity. Summary of the Invention

[0005] In response to the above-mentioned defects or improvement needs of the prior art, the present invention provides a hollow-core microstructure optical fiber with a refractive index marker, and a preparation and detection method thereof. Its purpose is to form an asymmetric end face structure by using a distinguishable refractive index marker unit on the hollow sleeve forming the outer cladding, thereby achieving marking of multiple rotationally symmetric antiresonant microstructure units, evaluating their geometric uniformity, and better controlling the hollow-core microstructure optical fiber drawing process, thereby solving the technical problem that the transmission performance of the existing hollow-core microstructure optical fiber is greatly different from the theoretical design due to the poor geometric uniformity of the end face.

[0006] To achieve the above objectives, according to one aspect of the present invention, a hollow-core microstructure optical fiber with a refractive index marker is provided, comprising a cladding hollow sleeve, and a plurality of antiresonant microstructure units arranged on the inner wall of the cladding hollow sleeve, wherein the plurality of antiresonant microstructure units are rotationally symmetric;

[0007] The cladding hollow sleeve is provided with one or more refractive index marking units, and there is a refractive index difference between the refractive index marking unit and the refractive index of the sleeve; the end face structure of the hollow core microstructure optical fiber is asymmetric.

[0008] Preferably, the outer wall contour and inner wall contour of the hollow-core sleeve of the cladding of the hollow-core microstructure optical fiber with a refractive index marker are circular.

[0009] Preferably, for the hollow-core microstructured optical fiber with a refractive index marker, the maximum refractive index difference between the refractive index marker unit and the cladding hollow sleeve is ≥0.05%.

[0010] Preferably, the refractive index marking unit of the hollow-core microstructured optical fiber with a refractive index marker is made of high-purity silica material, doped quartz material, multi-component glass material, or plastic material.

[0011] Preferably, in the hollow-core microstructure optical fiber with a refractive index marker, the area of ​​a single refractive index marker unit accounts for 0.002% to 2% of the area of ​​the optical fiber cladding; the optical fiber cladding includes an outer cladding formed by the cladding hollow sleeve and an antiresonant cladding formed by the antiresonant microstructure unit.

[0012] Preferably, in the hollow-core microstructure optical fiber with refractive index marking, at least one of the refractive index marking units is located in the area between the geometric center of the adjacent antiresonant microstructure unit and the line connecting the geometric center of the optical fiber and is close to one of the adjacent antiresonant microstructure units.

[0013] Preferably, the hollow core microstructure optical fiber with refractive index marking has the cladding hollow sleeve provided with a plurality of refractive index marking units, and the plurality of refractive index marking units have identifiable differences, and the differences are differences in outline shape and / or area.

[0014] Preferably, in the hollow-core microstructured optical fiber with a refractive index marker, the outer contour of the refractive index marker unit is circular, rectangular, or regular polygonal.

[0015] According to another aspect of the present invention, a method for manufacturing the hollow-core microstructured optical fiber with a refractive index marker is provided, comprising the following steps: drilling a hole in a region of a hollow-core microstructured optical fiber preform rod used to form a cladding hollow sleeve, embedding a core rod having a maximum refractive index difference of ≥0.05% with the cladding hollow sleeve, and assembling the preform rod for forming the hollow-core microstructured optical fiber with a refractive index marker; and drawing the preform rod to obtain the hollow-core microstructured optical fiber with a refractive index marker.

[0016] According to another aspect of the present invention, a method for detecting wire drawing of a preform rod with a hollow microstructure is provided, comprising the following steps:

[0017] (1) Cutting the hollow-core microstructured optical fiber with a refractive index marker provided by the present invention at a preset position;

[0018] (2) imaging the truncated end face obtained in step (1) using transmitted light to obtain an end face image of the hollow-core microstructured optical fiber at that position;

[0019] (3) For the end face image obtained in step (2), antiresonance microstructure identification is performed based on its refractive index marking unit to obtain an image of each antiresonance microstructure unit;

[0020] (4) Extracting geometric parameters from the image of the anti-resonance microstructure unit identified in step (3) to determine the geometric uniformity of the hollow-core microstructure optical fiber.

[0021] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:

[0022] The hollow-core microstructured optical fiber with a refractive index marker provided by the present invention forms an asymmetric end face structure by using a distinguishable refractive index marker unit on a hollow cladding sleeve forming an outer cladding, thereby marking multiple rotationally symmetric antiresonant microstructure units and realizing the evaluation and detection of geometric uniformity without destroying the uniformity of the geometric profile of the optical fiber end face and without affecting the airflow of the optical fiber during the drawing process, so that the antiresonant microstructure units are identifiable and as close as possible to the theoretical design shape.

[0023] The present invention provides a hollow-core microstructured optical fiber with a refractive index marker and a preparation method thereof. The hollow-core microstructured optical fiber can quickly identify antiresonant microstructure units in the hollow-core microstructured optical fiber, facilitates online control of the size uniformity of the antiresonant microstructure units, and is beneficial to reducing the transmission loss of the hollow-core microstructured optical fiber. At the same time, during the coupling process of the hollow-core microstructured optical fiber, different antiresonant microstructure units are easily identified, thereby reducing the coupling loss of the hollow-core microstructured optical fiber. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] FIG1 is a schematic structural diagram of a hollow-core microstructured optical fiber preform with a refractive index marking unit provided in Example 1 of the present invention;

[0025] FIG2 is a schematic diagram of an unmarked hollow-core microstructured optical fiber, i.e., a schematic diagram of a hollow-core microstructured optical fiber for comparison with Example 1;

[0026] FIG3 is a schematic diagram of a perforated casing provided in Example 1 of the present invention;

[0027] FIG4 is a schematic diagram of the end face structure of a hollow core microstructured optical fiber provided in Example 1 of the present invention;

[0028] FIG5 is a schematic diagram of the end face structure of a hollow core microstructured optical fiber provided in Example 2 of the present invention;

[0029] FIG6 is a schematic diagram of the end face structure of a hollow-core microstructured optical fiber provided in Example 3 of the present invention.

[0030] In all drawings, the same reference numerals are used to denote the same elements or structures, wherein: 1 is an anti-resonance microstructure unit, 2 is a refractive index marking unit, 3 is a cladding hollow sleeve, and 4 is a hole on the sleeve. DETAILED DESCRIPTION

[0031] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely for the purpose of explaining the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0032] The hollow-core microstructure optical fiber with a refractive index marker provided by the present invention comprises a cladding hollow sleeve and a plurality of anti-resonance microstructure units arranged on the inner wall of the cladding hollow sleeve, wherein the plurality of anti-resonance microstructure units are rotationally symmetric.

[0033] The cladding hollow sleeve is made of glass; the outer wall contour and the inner wall contour of the cladding hollow sleeve are circular.

[0034] The hollow cladding tube is provided with one or more refractive index marking units. There is a refractive index difference between the refractive index marking units and the cladding tube, and the maximum refractive index difference between the refractive index marking units and the hollow cladding tube is ≥0.05%. The refractive index marking units are made of high-purity silica, doped quartz, multi-component glass, or plastic. The outer contour of the refractive index marking units is circular, rectangular, or regular polygonal.

[0035] The area of ​​a single refractive index marking unit accounts for 0.002% to 2% of the area of ​​the optical fiber cladding; the optical fiber cladding includes an outer cladding formed by the cladding hollow sleeve and an antiresonance cladding formed by the antiresonance microstructure unit.

[0036] At least one of the refractive index marking units is located in the region between the geometric centers of adjacent antiresonant microstructure units and the lines connecting the geometric centers of the optical fiber and is close to one of the adjacent antiresonant microstructure units. The region between the geometric centers of adjacent antiresonant microstructure units and the lines connecting the geometric centers of the optical fiber is generally fan-shaped, and the cladding hollow sleeve is generally fan-shaped in this region. For a hollow-core microstructure optical fiber having a rotationally symmetric antiresonant microstructure unit, the refractive index marking unit falls within this region, causing the optical fiber end face to be asymmetric, thereby achieving an asymmetric optical fiber end face diagram.

[0037] To improve the recognizability, a plurality of refractive index marking units may be used. Preferably, the plurality of refractive index marking units have identifiable differences, wherein the differences are differences in contour shape and / or area.

[0038] There is currently no mature and feasible technical solution for detecting the geometric uniformity of antiresonant microstructured optical fibers. This patent proposes to use an imaging method to detect the end face and extract geometric features to solve the problem of geometric uniformity detection. The difficulty of imaging detection lies in the fact that the end face of an antiresonant microstructured optical fiber theoretically has relatively perfect symmetry and is difficult to distinguish from each other. If shape marking is used, such as adding a structure inside the sleeve or groove processing the sleeve, the regular end face structure of the optical fiber will be destroyed, which may cause the transmission performance to deteriorate or change.

[0039] Whether the light-guiding principle of hollow-core antiresonant optical fibers is explained based on antiresonant waveguide theory or suppressed coupling theory, a more perfect and designed optical fiber end face structure means better and more controllable transmission performance.

[0040] In order to minimize the impact on the transmission performance of hollow-core microstructured optical fibers, the present invention adopts a refractive index marking unit set in the outer cladding formed by the sleeve. Under the premise of maintaining the geometric structure of the end face of the hollow-core microstructured optical fiber unchanged, when the end face is detected by the imaging method, a mark that destroys the end face symmetry of the hollow-core microstructured optical fiber is formed, so that multiple anti-resonant microstructure units can be identified, the geometric parameters can be extracted, and the geometric uniformity can be judged.

[0041] The present invention provides a method for fabricating a hollow-core microstructured optical fiber with refractive index markings. The main steps are: drilling a hole in the region of a hollow-core microstructured optical fiber preform used to form a cladding hollow sleeve, embedding a core rod having a maximum refractive index difference of ≥0.05% with the cladding hollow sleeve, assembling the preform for forming the hollow-core microstructured optical fiber with refractive index markings; and drawing the preform to obtain the hollow-core microstructured optical fiber with refractive index markings. The core rod can be made of high-purity silica, doped quartz, multi-component glass, or plastic, and can also have a non-uniform refractive index profile, such as an optical waveguide structure. Such a core rod can be prepared using an in-tube deposition method.

[0042] The present invention provides a method for detecting wire drawing of a preform rod having a hollow microstructure, characterized by comprising the following steps:

[0043] (1) Cutting the hollow-core microstructured optical fiber with a refractive index marker provided by the present invention at a preset position;

[0044] (2) The truncated end face obtained in step (1) is imaged using transmitted light to obtain an end face image of the hollow-core microstructured optical fiber at that position; since the refractive index difference interface appears as a distinct outline under the action of transmitted light, the refractive index mark is recognizable on the end face image.

[0045] (3) For the end face image obtained in step (2), antiresonance microstructure identification is performed based on its refractive index marking unit to obtain an image of each antiresonance microstructure unit;

[0046] (4) Extracting geometric parameters from the image of the anti-resonance microstructure unit identified in step (3) to determine the geometric uniformity of the hollow-core microstructure optical fiber.

[0047] The following are examples:

[0048] The end face structure of a typical hollow-core anti-microstructured fiber is shown in Figure 1. The outer cladding is formed by a hollow sleeve, whose inner wall is arranged with multiple antiresonant microstructure units. These units are rotationally symmetrical, forming an antiresonant cladding. The number of antiresonant microstructure units, n, is generally n ≥ 3, and in this embodiment, n is 5. The antiresonant microstructure units are composed of single-layer or multi-layer negative curvature structure components. An example of a single-layer negative curvature structure component is shown in Figure 1, and examples of a multi-layer negative curvature structure component are shown in Figures 4 to 6.

[0049] The cladding hollow sleeve is provided with one or more refractive index marking units, and there is a refractive index difference between the refractive index marking unit and the refractive index of the sleeve, and the maximum refractive index difference between the refractive index marking unit and the cladding hollow sleeve is ≥0.05%; the refractive index marking unit is made of high-purity silica, doped quartz, multi-component glass, or plastic. In this embodiment, doped quartz glass is used.

[0050] The hollow-core microstructured optical fiber with a refractive index marker is prepared in the following steps:

[0051] Step 1: Prepare the anti-resonance microstructure unit: draw the required capillary tube through the mother tube in a high-temperature drawing furnace; the capillary tube can be subjected to secondary processing such as cutting, grinding, welding, etc. according to design requirements.

[0052] Step 2: Prepare a casing with holes: Prepare a casing with one or more holes by drilling holes in the casing.

[0053] Step 3: Prepare the marking core rod: Using the preform doping process, a doped core rod is prepared. Its refractive index differs from that of the sleeve, with a maximum refractive index difference of ≥0.05%. The doped core rod is then drawn into a capillary rod, which is the desired marking core rod.

[0054] Step 4, preform stacking: insert the marked core rod obtained in step 3 into the hole of the perforated sleeve prepared in step 3, and stack and assemble the antiresonant microstructure units obtained in step 1 in the sleeve to form a hollow-core microstructure optical fiber preform with a refractive index mark.

[0055] Step 5: The hollow-core microstructured optical fiber preform with the refractive index mark from step 4 is directly drawn into a hollow-core microstructured optical fiber, or first drawn into an intermediate preform, which is then sheathed into a sleeve to form the hollow-core microstructured optical fiber. By marking the core rod during the drawing process, the corresponding relationship between the antiresonant microstructure units in the optical fiber and the antiresonant microstructure units in the preform can be quickly determined. The size of the antiresonant microstructure units in the optical fiber can be adjusted by controlling the air pressure within the antiresonant microstructure units in the preform.

[0056] Furthermore, the antiresonant microstructure unit, sleeve, and marking core rod can be made of high-purity silica, doped quartz (doped with one or more elements such as germanium, fluorine, chlorine, boron, and aluminum), multi-component glass, plastic, etc., as long as there is a refractive index difference between the sleeve and the marking core rod. The embodiments of this patent use doped adaptive materials.

[0057] Furthermore, the hollow-core microstructured optical fiber has a cladding diameter greater than or equal to 100 μm.

[0058] Furthermore, the hollow-core microstructured optical fiber prepared by the method of the present invention has a low transmission loss, with the lowest transmission loss being ≤30 dB / km, and even better being ≤1 dB / km.

[0059] Furthermore, the hollow-core microstructure optical fiber prepared by the method of the present invention has a low fusion loss, and the self-fusion loss of the hollow-core microstructure optical fiber is ≤0.5dB. Example 1

[0060] This embodiment uses a component with a single-layer negative curvature structure as an antiresonant microstructure unit, as shown in Figure 1. The manufacturing method is as follows: first, a capillary is prepared through a mother tube to form an antiresonant microstructure unit 1. The mother tube is drawn into a capillary through a drawing furnace with an outer diameter of 5.4 mm and a wall thickness of 0.32 mm. Then, a hole parallel to the axis of the sleeve is drilled on a pure silica sleeve through a drilling process, as shown in Figure 3. The glass tube used to form the cladding hollow sleeve 3 has an outer diameter of 30 mm and an inner diameter of 26 mm. The drilled hole has a diameter of 3.0 mm and is used to set the refractive index marking unit. The hole is located between the two antiresonant microstructure units, close to one of them. A core rod with a refractive index difference of 0.20% is manufactured through a plasma vapor deposition process. The core rod is drawn into a capillary rod with an outer diameter of 2.8 mm on a drawing tower to form a refractive index marking unit. A capillary rod is inserted into the hole drilled on the sleeve, and then five capillaries are stacked in the sleeve to form a hollow-core microstructured optical fiber preform with a refractive index mark as shown in Figure 1. The hollow-core microstructured optical fiber preform with a refractive index mark can be directly drawn into a hollow-core microstructured optical fiber in a drawing furnace. However, during drawing, due to temperature fluctuations, the size of the antiresonant microstructure unit will be different. As shown in Figure 2, the maximum deviation of the outer diameter of the antiresonant microstructure unit is 33%. Transmission imaging of the optical fiber end face can observe the difference in the end face image, mark the antiresonant microstructure unit, and adjust the drawing process accordingly to ensure the geometric uniformity of the optical fiber. To achieve this, it is necessary to introduce gases of different pressures into the antiresonant microstructure unit to make the size of the antiresonant microstructure unit uniform. As shown in Figure 4, the refractive index markers are used to identify the required air pressure in the antiresonant microstructure unit. P0 represents normal pressure, while P1, P2, P3, P4, and P5 represent the air pressures in the antiresonant microstructure unit, with values ​​of 33.6 mbar, 33.7 mbar, 34.1 mbar, 34.0 mbar, and 33.9 mbar, respectively. After being drawn into optical fiber, the maximum deviation in the outer diameter of the antiresonant microstructure unit is 3.9%, and its attenuation at 1550 nm is 4.8 dB / km. When splicing this hollow-core microstructure fiber, the refractive index markers can be used to identify the capillary orientation, enabling more precise splicing. The minimum splicing loss is 0.44 dB. Example 2

[0061] This embodiment uses a multi-layer negative curvature structure as an antiresonant microstructure unit. The antiresonant microstructure unit is formed by nesting tangential capillary glass tubes, which contact the inner wall of the glass tube used to form the cladding hollow sleeve 3. As shown in Figure 5, the production method is as follows: First, two sizes of capillaries are prepared from a mother tube: the large capillary has an outer diameter of 13.6 mm and a wall thickness of 0.49 mm, and the small capillary has an outer diameter of 6.8 mm and a wall thickness of 0.54 mm. Then, two holes parallel to the sleeve axis are drilled into a pure silica sleeve to accommodate refractive index markers. The relative position of the two holes ensures that the angle between them and the center line of the structure is less than 72°. Because the antiresonant microstructure units are uniformly distributed around the circumference, the refractive index markers placed in this manner do not need to consider the relative position of the antiresonant microstructure units and will not necessarily destroy the rotational symmetry of the end-face image. The sleeve dimensions are 55 mm outer diameter and 43 mm inner diameter, and the drilled holes have a diameter of 2.5 mm. A core rod with a refractive index difference of 0.60% is manufactured through a plasma vapor deposition process. The core rod is then drawn into a capillary rod with an outer diameter of 2.3 mm on a drawing tower. Two capillary rods are inserted into holes drilled in a sleeve, and then five antiresonant microstructure units are stacked in the sleeve to form a hollow-core microstructure optical fiber preform with a refractive index mark as shown in Figure 5. The hollow-core microstructure optical fiber preform with a refractive index mark can be first drawn into an intermediate preform in a drawing furnace. The intermediate preform has an outer diameter of 6.9 mm, and then inserted into a sleeve with an outer diameter of 16 mm and an inner diameter of 7.5 mm for drawing. As in the previous embodiment, the size of the antiresonant microstructure units is made uniform by introducing gases of different pressures into the antiresonant microstructure units. Transmission imaging of the optical fiber end face can observe the difference in the end face image, mark the antiresonant microstructure units, and adjust the drawing process accordingly to ensure the geometric uniformity of the optical fiber. P0 represents normal pressure, while P1, P2, P3, P4, and P5 represent the air pressure in the large capillary of the antiresonant microstructure unit, with values ​​of 44.4 mbar, 44.7 mbar, 44.5 mbar, 44.6 mbar, and 44.8 mbar, respectively. P6, P7, P8, P9, and P10 represent the air pressure in the small capillary of the antiresonant microstructure unit, with values ​​of 113.3 mbar, 113.2 mbar, 113.7 mbar, 113.7 mbar, and 113.9 mbar, respectively. The maximum deviation of the outer diameter of the large capillary in the antiresonant microstructure unit of the drawn hollow-core microstructured fiber is 3.9%, and the maximum deviation of the outer diameter of the small capillary in the antiresonant microstructure unit is 4.0%. Its attenuation at 1550 nm is 0.32 dB / km. When this hollow-core microstructured optical fiber is fused, the refractive index marking unit can be used to identify the capillary position, and the rotation function of the fusion splicer can be used to achieve more precise docking, with the lowest fusion loss of 0.32dB. Example 3

[0062] This embodiment uses a multi-layer negative curvature structure component as an antiresonant microstructure unit, and nested tangential capillary glass tubes are used to form the antiresonant microstructure unit. The tangent part contacts the inner wall of the glass tube used to form the cladding hollow sleeve 3. As shown in Figure 6, two sizes of capillaries are first prepared through a mother tube. The large capillary has an outer diameter of 10.35mm and a wall thickness of 0.32mm, and the small capillary has an outer diameter of 6.8mm and a wall thickness of 0.44mm. Then, a square hole parallel to the axis of the sleeve is drilled on the pure silica sleeve through a drilling process. The sleeve size is 80mm outer diameter and 40mm inner diameter, and the side length of the drilled hole is 3.0mm. A core rod with a refractive index difference of 0.73% is manufactured by a plasma vapor deposition process. The core rod is first polished into a square shape, and then the square core rod is drawn into a capillary rod with a side length of 2.8mm on a drawing tower. A square capillary rod is inserted into the hole drilled on the sleeve, and then five antiresonant microstructure units are stacked in the sleeve to form a hollow-core microstructure optical fiber preform with a refractive index mark as shown in Figure 6. The hollow-core microstructure optical fiber preform with a refractive index mark can be first drawn into an intermediate preform in a drawing furnace. The intermediate preform has an outer diameter of 5.5 mm, and then is inserted into a sleeve with an outer diameter of 10 mm and an inner diameter of 6.0 mm for drawing. As in the previous embodiment, the size of the antiresonant microstructure unit is made uniform by introducing gases of different pressures into the antiresonant microstructure unit. Transmission imaging of the optical fiber end face can observe the difference in the end face image, mark the antiresonant microstructure unit, and adjust the drawing process accordingly to ensure the geometric uniformity of the optical fiber. P0 represents normal pressure, while P1, P2, P3, P4, and P5 represent the air pressure in the large capillary of the antiresonant microstructure unit, with values ​​of 57.2 mbar, 57.5 mbar, 57.7 mbar, 57.5 mbar, and 57.2 mbar, respectively. P6, P7, P8, P9, and P10 represent the air pressure in the small capillary of the antiresonant microstructure unit, with values ​​of 148.5 mbar, 148.2 mbar, 148.9 mbar, 149.4 mbar, and 149.6 mbar, respectively. The maximum deviation of the outer diameter of the large capillary in the antiresonant microstructure unit of the drawn hollow-core microstructured optical fiber is 2.5%, and the maximum deviation of the outer diameter of the small capillary in the antiresonant microstructure unit is 2.6%. Its attenuation at 1550 nm is 0.33 dB / km. When this hollow-core microstructured optical fiber is fused, the refractive index marking unit can be used to identify the capillary orientation, and the rotation function of the fusion splicer can be used to achieve more precise docking, with the lowest fusion loss being 0.37dB.

[0063] It will be easily understood by those skilled in the art that the above description is only 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 in the scope of protection of the present invention.

Claims

1. A hollow core microstructure optical fiber with a refractive index marker, characterized in that: It comprises a cladding hollow sleeve and a plurality of anti-resonance microstructure units arranged on the inner wall of the cladding hollow sleeve, wherein the plurality of anti-resonance microstructure units are rotationally symmetric; The cladding hollow sleeve is provided with one or more refractive index marking units, and there is a refractive index difference between the refractive index marking unit and the refractive index of the sleeve; the end face structure of the hollow core microstructure optical fiber is asymmetric.

2. The hollow-core microstructured optical fiber with a refractive index marker according to claim 1, characterized in that: The outer wall contour and the inner wall contour of the cladding hollow casing are circular.

3. The hollow-core microstructured optical fiber with a refractive index marker according to claim 1, characterized in that: The maximum refractive index difference between the refractive index marking unit and the cladding hollow sleeve is ≥0.05%.

4. The hollow-core microstructured optical fiber with a refractive index marker according to claim 3, characterized in that: The refractive index marking unit is made of high-purity silicon dioxide, doped quartz, multi-component glass, or plastic.

5. The hollow-core microstructured optical fiber with a refractive index marker according to claim 1, characterized in that: The area of ​​a single refractive index marking unit accounts for 0.002% to 2% of the area of ​​the optical fiber cladding; the optical fiber cladding includes an outer cladding formed by the cladding hollow sleeve and an anti-resonance cladding formed by the anti-resonance microstructure unit.

6. The hollow-core microstructured optical fiber with a refractive index marker according to claim 1, characterized in that: At least one of the refractive index marking units is located in a region between a line connecting a geometric center of an adjacent anti-resonance microstructure unit and a geometric center of the optical fiber and is close to one of the adjacent anti-resonance microstructure units.

7. The hollow-core microstructured optical fiber with a refractive index marker according to claim 1, characterized in that: The cladding hollow sleeve is provided with a plurality of refractive index marking units, and the plurality of refractive index marking units have identifiable differences, wherein the differences are contour shape and / or area differences.

8. The hollow-core microstructured optical fiber with a refractive index marker according to claim 1, characterized in that: The outer contour of the refractive index marking unit is a circle, a rectangle, or a regular polygon.

9. The method for manufacturing a hollow-core microstructure optical fiber with a refractive index mark according to any one of claims 1 to 8, characterized in that: The following steps are involved: A hole is drilled in the area of ​​the hollow-core microstructured optical fiber preform rod used to form a cladding hollow sleeve, a core rod having a maximum refractive index difference of ≥0.05% with the cladding hollow sleeve is embedded therein, and a preform rod for forming the hollow-core microstructured optical fiber with a refractive index mark is assembled; and the preform rod is drawn to obtain the hollow-core microstructured optical fiber with a refractive index mark.

10. A wire drawing detection method for a preform rod with a hollow microstructure, characterized in that: The following steps are involved: (1) Cutting the hollow-core microstructured optical fiber with a refractive index mark according to any one of claims 1 to 8 at a preset position; (2) imaging the truncated end face obtained in step (1) using transmitted light to obtain an end face image of the hollow-core microstructure optical fiber at that position; (3) For the end face image obtained in step (2), anti-resonance microstructure identification is performed according to its refractive index marking unit to obtain an image of each anti-resonance microstructure unit; (4) Extracting geometric parameters from the image of the anti-resonance microstructure unit identified in step (3) to determine the geometric uniformity of the hollow-core microstructure optical fiber.

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