Hollow-core microstructured fiber with additive marks, and preform and drawing detection method

Abstract

A hollow-core microstructured fiber with additive marks, and a preform and a drawing detection method. The fiber comprises a cladding hollow-core sleeve (3) and a plurality of anti-resonant microstructured units (1) arranged on and attached to an inner wall of the cladding hollow-core sleeve (3), wherein each anti-resonant microstructured unit (1) is used for forming an air fiber core region having the size of an inscribed circle of the anti-resonance microstructured unit (1); the plurality of anti-resonant microstructured units (1) are rotationally symmetrical; one or more additive mark units (2) are provided on an outer side of a fiber core, such that an end-face structure of the hollow-core microstructured fiber has asymmetry; and the area of each additive mark unit (2) accounts for 0.002%-2% of the area of the cladding hollow-core sleeve (3). By means of each additive mark unit (2), each anti-resonant microstructured unit (1) is marked and identified during drawing detection, and the geometric uniformity of the hollow-core microstructured fiber is determined.

Description

Hollow-core microstructured optical fiber, preform, and drawing inspection method with additive marking 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 an additive marker, a preform rod, and a drawing detection method. 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 a specific microstructure, gas must be maintained during the drawing process. Due to factors such as the inhomogeneity of the raw materials, 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 1. 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 usual method of increasing the size of the fiber preform used for solid fibers cannot be used to improve geometric inhomogeneity.

[0005] Summary of the Invention

[0006] In response to the above-mentioned defects or improvement needs of the prior art, the present invention provides a hollow-core microstructure optical fiber, a preform rod and a drawing detection method with additive marking. Its additive marking unit can mark and identify each antiresonant microstructure unit during drawing detection, which has guiding significance for the production and operation of hollow-core microstructure optical fibers.

[0007] According to one aspect of the present invention, a hollow-core microstructure optical fiber with an additive marker is provided, comprising a cladding hollow-core sleeve and a plurality of antiresonant microstructure units arranged and attached to the inner wall of the cladding hollow-core sleeve, wherein the antiresonant microstructure units are used to form an air core region of the same size as the inscribed circle thereof; the plurality of antiresonant microstructure units are rotationally symmetric;

[0008] The distance D between the additive marking unit and the center of the optical fiber structure is such that: E D ≤0.5%

[0009] Among them, E D is the energy distribution ratio of the area on the fiber cross section that is greater than D from the center of the fiber structure; for a point in the polar coordinate system with the center of the fiber structure as the pole in the fiber cross section, its polar diameter is r, its polar angle is θ, and f(r,θ) is the normalized light field distribution function of the fiber cross section;

[0010] In the cross section of the hollow-core microstructured optical fiber, the outer edge area of ​​a single additive marking unit accounts for 0.002% to 2% of the cladding area.

[0011] Preferably, the outer contour of the cladding hollow sleeve is circular; the additive marking unit is a solid glass strip or a hollow glass tube, and the outer contour of the additive marking unit is circular, elliptical, rectangular and / or polygonal.

[0012] Preferably, the distance D between the additive marking unit and the center of the optical fiber structure is such that: D ≤0.1%; the distance D between the additive marking unit and the center of the optical fiber structure satisfies: D≥d, where d is the core diameter of the hollow-core microstructure optical fiber.

[0013] Preferably, the additive marking unit is attached to the inner wall of the hollow sleeve, preferably outside the anti-resonance microstructure unit.

[0014] Preferably, the additive marking unit is attached between adjacent anti-resonance microstructure units, close to one of the anti-resonance microstructure units.

[0015] Preferably, on the inner wall of the hollow sleeve, the arc between the attachment point of the additive marking unit and the attachment point of the anti-resonance microstructure unit close to the additive marking unit is R1, the arc between the attachment points of two adjacent anti-resonance microstructure units is R2, and R1 / R2=1 / 6 to 1 / 3.

[0016] Preferably, the inner wall of the cladding hollow core sleeve has a plurality of additive marking units, and the plurality of additive marking units have different outer contour shapes, types and / or areas.

[0017] According to another aspect of the present invention, a preform rod of a hollow-core microstructured optical fiber with an additive marker is provided, comprising a glass member for drawing to form the hollow-core microstructured optical fiber with an additive marker.

[0018] 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:

[0019] (1) cutting the hollow-core microstructured optical fiber with the additive marking at a preset position;

[0020] (2) imaging the truncated end face obtained in step (1) using transmitted light or reflected light to obtain an end face image of the hollow-core microstructured optical fiber at that position;

[0021] (3) For the end face image obtained in step (2), anti-resonance microstructure identification is performed based on its additive marking unit to obtain an image of each anti-resonance microstructure unit;

[0022] (4) Extracting geometric parameters from the image of the anti-structure microstructure unit identified in step (3) to determine the geometric uniformity of the hollow-core microstructure optical fiber.

[0023] Preferably, in step (2), a microscope is used to image the end face.

[0024] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:

[0025] 1) The hollow-core microstructured optical fiber with additive marking of the present invention can quickly identify the antiresonant microstructure units in the hollow-core microstructured optical fiber, facilitate online control of the size uniformity of the antiresonant microstructure units, and help reduce the transmission loss of the hollow-core microstructured optical fiber.

[0026] 2) The hollow-core microstructured optical fiber with additive marking of the present invention can mark and identify each antiresonant microstructure unit during drawing detection through the additive marking unit, judge and analyze the geometric uniformity of the hollow-core microstructured optical fiber, thereby providing reference and guidance for the subsequent production of hollow-core microstructured preform rods, and timely making process adjustments and improvements to control the geometric uniformity, which can ensure the geometric uniformity of the hollow-core microstructured optical fiber in the subsequent manufacturing process of the hollow-core microstructured optical fiber from the preform rod.

[0027] 3) During the coupling process of the hollow-core microstructured optical fiber, it is easy to identify different anti-resonant microstructure units, thereby reducing the coupling loss of the hollow-core microstructured optical fiber. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] FIG1 is a schematic diagram of an unmarked hollow-core microstructured optical fiber;

[0029] FIG2 is a schematic structural diagram of a hollow-core microstructured optical fiber preform with an additive marking provided in Example 1 of the present invention;

[0030] FIG3 is a schematic diagram of pressure control during the drawing process of a hollow-core microstructure optical fiber preform with an additive marking provided in Example 1 of the present invention;

[0031] FIG4 is a schematic diagram of pressure control during the drawing process of a hollow-core microstructure optical fiber preform with an additive marking provided in Example 2 of the present invention;

[0032] FIG5 is a schematic diagram of pressure control during the drawing process of a hollow-core microstructure optical fiber preform with an additive mark provided in Example 3 of the present invention.

[0033] In all drawings, the same reference numerals are used to denote the same elements or structures, where: 1 - anti-resonance microstructure unit, 2 - marking unit, 3 - cladding hollow core sleeve. DETAILED DESCRIPTION

[0034] 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.

[0035] According to one aspect of the present invention, a hollow-core microstructure optical fiber with an additive marker is provided, comprising a cladding hollow-core sleeve 3 and a plurality of antiresonant microstructure units 1 arranged and attached to the inner wall of the cladding hollow-core sleeve 3, wherein the antiresonant microstructure units 1 have an air core region inscribed in the inner wall of the cladding hollow-core sleeve 3; the plurality of antiresonant microstructure units 1 are rotationally symmetric;

[0036] In the area where the optical fiber energy distribution outside the core is less than 0.5%, one or more additive marking units 2 are provided, so that the end face structure of the hollow core microstructure optical fiber has an asymmetric structure;

[0037] A hollow-core microstructure optical fiber with an additive marking comprises a cladding hollow-core sleeve 3 and a plurality of antiresonant microstructure units 1 arranged and attached to the inner wall of the cladding hollow-core sleeve 3, wherein the antiresonant microstructure units 1 have an air core region inscribed in the inner wall of the cladding hollow-core sleeve 3; the plurality of antiresonant microstructure units 1 are rotationally symmetric;

[0038] In the area where the energy distribution of the optical fiber outside the core is less than 0.5%, one or more additive marking units 2 are provided, so that the end face structure of the hollow core microstructure optical fiber has an asymmetric structure;

[0039] On the cross section of the hollow-core microstructured optical fiber, the area of ​​a single additive marking unit 2 accounts for 0.002% to 2% of the cladding area; the cladding includes an outer cladding formed by a hollow sleeve and an antiresonant cladding formed by an antiresonant microstructure unit.

[0040] Preferably, the outer contour of the cladding hollow sleeve 3 is circular; the additive marking unit 2 is a solid glass strip or a hollow glass tube, and the outer contour of the additive marking unit 2 is circular, elliptical, rectangular and / or polygonal.

[0041] Preferably, the additive marking unit 2 is arranged in an area outside the fiber core where the optical fiber energy distribution is less than 0.1%; the additive marking unit 2 is arranged in a corresponding area of ​​the optical fiber preform rod used to form an area where the distance between the fiber core and the center of the optical fiber structure exceeds the core diameter.

[0042] Preferably, the additive marking unit 2 is attached to the inner wall of the hollow core sleeve 3 of the hollow cladding, and is preferably located outside the anti-resonance microstructure unit 1 .

[0043] Preferably, the additive marking unit 2 is attached between adjacent anti-resonance microstructure units 1 , close to one of the anti-resonance microstructure units 1 .

[0044] Preferably, on the inner wall of the hollow core sleeve 3 of the hollow cladding, the arc between the attachment point of the additive marking unit 2 and the attachment point of the anti-resonance microstructure unit 1 close to the additive marking unit 2 is R1, and the arc between the attachment points of two adjacent anti-resonance microstructure units 1 is R2, and R1 / R2=1 / 6 to 1 / 3.

[0045] Preferably, the inner wall of the cladding hollow core sleeve 3 has a plurality of additive marking units 2, and the plurality of additive marking units 2 have different outer contour shapes, types and / or areas; the type of the additive marking unit is a solid or hollow additive marking unit.

[0046] According to another aspect of the present invention, a preform rod of a hollow-core microstructured optical fiber with an additive marker is provided, comprising a glass member, wherein the glass member is used for drawing to form the hollow-core microstructured optical fiber with an additive marker.

[0047] There is currently no mature and feasible technical solution for the detection of geometric uniformity of antiresonant microstructured optical fibers. This patent conceives the use of an image method to perform end face detection and extract geometric features to solve the problem of geometric uniformity detection. The difficulty of image detection lies in the fact that the end faces of antiresonant microstructured optical fibers theoretically have perfect symmetry and are difficult to distinguish from each other. At present, some antiresonant microstructured optical fibers have asymmetric end faces, such as CN115185034A, which has a circular nested structure in one capillary and a U-shaped nested structure in the other capillaries, thereby forming a single-mode, low-loss, simple-structured single-polarization hollow-core antiresonant optical fiber, which is suitable for long-distance scenarios and easy to prepare. Patent CN113885120A proposes a hollow-core microstructured optical fiber with a two-layer outer cladding structure. The first outer cladding defines the outer surface of the inner unclosed cladding; the second outer cladding is unclosed and has a microchannel running through the optical fiber; the second outer cladding is tightly connected to the first outer cladding and defines the inner surface of the inner unclosed cladding; the capillary layer is attached to the inner surface of the second outer cladding as an antiresonance layer and together with the second outer cladding defines a fiber core with an effective radius; the capillaries in the capillary layer are arranged at intervals, and there are intervals between adjacent capillaries; the first outer cladding can effectively ensure the mechanical reliability of the optical fiber, and the second outer cladding has an unclosed structure, which can greatly reduce the complexity of optical fiber post-processing and improve the performance of the optical fiber, solving the problems of loss characteristics and processing complexity of existing antiresonant hollow-core microstructure optical fibers.

[0048] Although the above patents propose an asymmetric hollow-core microstructure fiber structure design, it is mainly for solving polarization problems and post-processing problems of hollow-core microstructure fibers in fiber optic sensing. None of them proposes a solution to the geometric uniformity control during the drawing process of hollow-core microstructure fibers. Therefore, the difficulty of imaging the end face of the optical fiber and whether the asymmetry is obvious enough to distinguish the anti-resonant microstructure units on the end face image have not been considered. Compared with other types of markers, the additive marking unit does not require fine machining, does not affect the existing preform rod assembly process, and has the advantage of simple setting. However, based on the consideration of asymmetric marking, a problem that must be solved is whether the asymmetric marking will affect the performance and drawing difficulty of the hollow-core microstructure fiber. Specifically, a sufficiently obvious additive marking unit needs to have a large enough area, which is relatively more likely to affect the transmission performance and drawing preparation difficulty of the microstructure fiber.

[0049] Through clever design, the additive marking unit is placed in an area where the energy distribution of the optical fiber outside the core is less than 0.5%, preferably less than 0.1%, to minimize the impact on the transmission performance of the hollow-core microstructure optical fiber. That is:

[0050] The distance D between the additive marking unit and the center of the optical fiber structure is such that: E D ≤0.5%

[0051] Among them, E D is the energy distribution ratio of the area on the fiber cross section that is greater than D from the center of the fiber structure; for a point in the polar coordinate system with the center of the fiber structure as the pole in the fiber cross section, its polar diameter is r, its polar angle is θ, and f(r,θ) is the normalized light field distribution function of the fiber cross section;

[0052] Preferred solution, E D ≤0.1%.

[0053] Preferably, the distance D between the additive marking unit and the center of the optical fiber structure satisfies: D≥d, where d is the core diameter of the hollow-core microstructure optical fiber.

[0054] The preferred solution is to set it on the inner wall of the hollow sleeve and the outside of the antiresonant microstructure unit, that is, between adjacent antiresonant microstructure sleeves. It not only has little effect on the transmission performance, but also has little effect on the airflow in the sleeve during the drawing process, reducing sleeve deformation or structural impact on the sleeve. More preferably, it is set on the side close to the adjacent microstructure unit, which can not only effectively destroy the symmetry of the optical fiber end face and improve the recognizability of the antiresonant microstructure unit, but also reduce the impact on the airflow in the sleeve during drawing. The drawing process requires the introduction of a large amount of gas, which is the technical key that distinguishes antiresonant microstructure optical fiber from solid optical fiber and other optical fibers such as photonic crystal fiber. Reducing the impact on the airflow during drawing is one of the key considerations for the setting of the additive marking unit. At the same time, since gas needs to be introduced into the antiresonant microstructure unit during drawing, and its gas pressure even exceeds the gas pressure at the center of the sleeve, it is necessary to avoid unexpected changes in the thickness and shape of the antiresonant microstructure unit due to the setting of the additive marking unit, such as adhesion to the additive marking unit, excessive thickness deviation, etc., which ultimately lead to deterioration of optical fiber performance. Preferably, the additive marking unit is set so that the arc between the attachment points of the antiresonant microstructure unit close to the additive marking unit is R1, and the arc between the attachment points of two adjacent antiresonant microstructure units is R2, R1 / R2=1 / 6 to 1 / 3, thereby ensuring that the additive marking unit with an easily observable area is set at an appropriate position, forming a clear asymmetric mark while having little impact on the antiresonant microstructure unit in the preparation process, avoiding adhesion between the additive marking unit and the antiresonant microstructure unit during drawing, or abnormal shape of the antiresonant microstructure units that are close to each other.

[0055] 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:

[0056] (1) cutting the hollow-core microstructured optical fiber with the additive marking at a preset position;

[0057] (2) imaging the truncated end face obtained in step (1) using transmitted light or reflected light to obtain an end face image of the hollow-core microstructured optical fiber at that position;

[0058] (3) For the end face image obtained in step (2), anti-resonance microstructure identification is performed based on its additive marking unit 2 to obtain an image of each anti-resonance microstructure unit 1;

[0059] (4) Extracting geometric parameters from the image of the anti-structure microstructure unit identified in step (3) to determine the geometric uniformity of the hollow-core microstructure optical fiber.

[0060] Preferably, in step (2), a microscope is used to image the end face.

[0061] A typical hollow-core microstructured optical fiber with additive marking includes an antiresonant microstructure unit 1, an additive marking unit 2, and a cladding hollow-core sleeve 3. The number of antiresonant microstructure units 1, n ≥ 3, and m additive marking units 2 are inserted between the antiresonant microstructure units 1, where m ≥ 1.

[0062] Furthermore, the anti-resonance microstructure unit 1 is composed of single-layer or multi-layer negative curvature structure components.

[0063] Furthermore, the additive marking unit 2 may be composed of a rod, a tube, a plate or a combination thereof, and may be circular, elliptical, rectangular, polygonal or the like.

[0064] The preparation method of the hollow-core microstructure optical fiber with additive markings mentioned above comprises the following steps:

[0065] Step 1: Prepare the anti-resonance microstructure unit 1: 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.

[0066] Step 2: Prepare the additive marking unit 2: Use a mother tube or mother rod to draw the required capillary or capillary rod in a high-temperature wire drawing furnace; the capillary or capillary rod can be used directly as the additive marking unit 2, or it can be processed secondary, such as cutting, grinding, and welding, and then used as the additive marking unit 2.

[0067] Step 3, preform stacking: The antiresonant microstructure unit 1 obtained in step 1 and the additive marking unit 2 obtained in step 2 are stacked and assembled in the cladding hollow core sleeve 3 to form a hollow core microstructure optical fiber preform with additive marking.

[0068] Step 4: Directly draw the hollow-core microstructured optical fiber preform with the additive marking from Step 3 into a hollow-core microstructured optical fiber, or first draw it into an intermediate preform, which is then sheathed into an intermediate sleeve to form a hollow-core microstructured optical fiber. During the drawing process, the additive marking unit 2 can quickly distinguish the corresponding relationship between the antiresonant microstructure unit 1 in the optical fiber and the antiresonant microstructure unit 1 in the preform, thereby adjusting the size of the antiresonant microstructure unit 1 in the optical fiber by controlling the air pressure within the antiresonant microstructure unit 1 in the preform.

[0069] Furthermore, the antiresonant microstructure unit 1, the additive marking unit 2, and the cladding hollow core sleeve 3 can be made of high-purity silica material, doped quartz material (doped with one or more elements such as germanium, fluorine, chlorine, boron, aluminum, etc.), multi-component glass material, plastic material, etc.

[0070] Furthermore, the hollow-core microstructured optical fiber has a cladding diameter greater than or equal to 100 μm.

[0071] 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.

[0072] 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.

[0073] The following are examples:

[0074] Example 1

[0075] As shown in Figure 2, a capillary tube is first formed from a mother tube to serve as an antiresonant microstructure unit 1. The antiresonant microstructure unit 1 has an outer diameter of 6.7 mm and a wall thickness of 0.4 mm. Another capillary tube is then drawn from another line tube to serve as an additive marking unit 2. The additive marking unit 2 is a hollow capillary tube with an outer diameter of 1.5 mm and a wall thickness of 0.35 mm. Five antiresonant microstructure units 1 and one additive marking unit 2 are stacked in a cladding hollow core sleeve 3 to form a hollow-core microstructure optical fiber preform with additive markings, as shown in Figure 2. The hollow-core microstructure optical fiber preform with additive markings can be directly drawn into a hollow-core microstructure optical fiber in a drawing furnace. However, due to temperature fluctuations during drawing, if no pressure is applied, the dimensions of the antiresonant microstructure units can vary. As shown in Figure 1, the maximum deviation in the outer diameter of the antiresonant microstructure unit 1 is 13%. To achieve this, it is necessary to introduce gases of different pressures into the antiresonant microstructure units to make the dimensions of the antiresonant microstructure units uniform. As shown in Figure 3, the additive marking unit 2 is used to identify the required air pressure in the anti-resonant microstructure unit 1. P1, P2, P3, P4, and P5 are the air pressures in the anti-resonant microstructure unit 1, and their values ​​are 24.2mbar, 26.6mbar, 22.5mbar, 26.7mbar, and 24.5mbar, respectively. The maximum deviation of the outer diameter of the anti-resonant microstructure unit 1 is 3.5%, and its attenuation at 1550nm is 4.2dB / km. When this hollow-core microstructure fiber is fused, the additive marking unit 2 can be used to identify the orientation of the anti-resonant microstructure unit 1, thereby achieving more precise docking, and its minimum fusion loss is 0.44dB.

[0076] Example 2

[0077] As shown in Figure 4, two capillary sizes are first prepared from a mother tube: the large capillary has an outer diameter of 8.2 mm and a wall thickness of 0.33 mm, and the small capillary has an outer diameter of 3.9 mm and a wall thickness of 0.36 mm. The mother rod is then used to draw an additive marking unit 2, which is a solid round rod with a diameter of 1.36 mm. The large and small capillaries are assembled into an antiresonant microstructure unit 1 by welding. Five antiresonant microstructure units 1 and one additive marking unit 2 are stacked in a cladding hollow core sleeve 3 to form a hollow-core microstructure optical fiber preform with additive markings, as shown in Figure 4. The hollow-core microstructure optical fiber preform with additive markings can be drawn into an intermediate preform in a drawing furnace. The intermediate preform has an outer diameter of 8 mm, which is then inserted into an intermediate sleeve with an outer diameter of 17 mm and an inner diameter of 8.5 mm for drawing. As in the previous embodiment, the antiresonant microstructure units 1 are uniformly sized by introducing gases of different pressures into the antiresonant microstructure units 1. P1, P2, P3, P4, and P5 represent the air pressure inside the large capillary of the antiresonant microstructure unit, with values ​​of 18.4 mbar, 19.6 mbar, 20.6 mbar, 20.8 mbar, and 19.5 mbar, respectively. P6, P7, P8, P9, and P10 represent the air pressure inside the small capillary of the antiresonant microstructure unit, with values ​​of 82.4 mbar, 84.8 mbar, 85.2 mbar, 85.8 mbar, and 84.5 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 4.5%, and the maximum deviation of the outer diameter of the small capillary in the antiresonant microstructure unit is 2.7%. Its attenuation at 1550 nm is 0.5 dB / km. When this hollow-core microstructured optical fiber is fused, the capillary position can be identified by the marking unit, and more precise docking can be achieved through the rotation function of the fusion splicer, with a minimum fusion loss of 0.32dB.

[0078] Example 3

[0079] As shown in Figure 5, two capillary sizes are first prepared from a mother tube: the large capillary has an outer diameter of 6.4 mm and a wall thickness of 0.25 mm, and the small capillary has an outer diameter of 3.2 mm and a wall thickness of 0.28 mm. Then, the additive marking unit 2 is drawn from a square mother rod. The additive marking unit 2 is a solid square rod with a side length of 0.95 mm. The large and small capillaries are assembled into an antiresonant microstructure unit 1 by welding. Five antiresonant microstructure units 1 and two additive marking units 2 are stacked in a cladding hollow-core sleeve 3 to form a hollow-core microstructure fiber preform with additive marking, as shown in Figure 5. The hollow-core microstructure fiber preform with additive marking can be drawn into an intermediate preform in a drawing furnace. The intermediate preform has an outer diameter of 6.2 mm, which is then inserted into an intermediate sleeve with an outer diameter of 13 mm and an inner diameter of 6.8 mm for drawing. As in the previous embodiment, the dimensions of the antiresonant microstructure unit 1 are made uniform by introducing gases of different pressures into the antiresonant microstructure unit. P1, P2, P3, P4, and P5 represent the gas pressures within the large capillary tube of the antiresonant microstructure unit 1, with values ​​of 33.6 mbar, 33.9 mbar, 34.5 mbar, 34.8 mbar, and 34.5 mbar, respectively. P6, P7, P8, P9, and P10 represent the gas pressures within the small capillary tube of the antiresonant microstructure unit 1, with values ​​of 112.2 mbar, 112.8 mbar, 113.2 mbar, 113.8 mbar, and 112.4 mbar, respectively. The drawn hollow-core microstructured fiber has a maximum outer diameter deviation of 2.9% for the large capillary in its antiresonant microstructure unit, and 2.5% for the small capillary. Its attenuation at 1550nm is 0.4dB / km. During fusion splicing, this hollow-core microstructured fiber uses a marking unit to identify the capillary orientation, allowing for more precise splicing using the splicer's rotation function. The fiber achieves a minimum splice loss of 0.28dB.

[0080] It will be easily understood by those skilled in the art 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 in the scope of protection of the present invention.

Claims

1. A hollow core microstructure optical fiber with an additive marking, characterized in that: It comprises a cladding hollow core sleeve and a plurality of anti-resonance microstructure units arranged and attached to the inner wall of the cladding hollow core sleeve, wherein the anti-resonance microstructure units are used to form an air core region of the size of its inscribed circle; the plurality of anti-resonance microstructure units are rotationally symmetric; One or more additive marking units are arranged outside the fiber core, so that the end face structure of the hollow core microstructure optical fiber has asymmetry; The distance D between the additive marking unit and the center of the optical fiber structure is such that: E D ≤0.5％ Among them, E D is the energy distribution ratio of the area on the fiber cross section that is greater than D from the center of the fiber structure; for a point in the polar coordinate system with the center of the fiber structure as the pole in the fiber cross section, its polar diameter is r, its polar angle is θ, and f(r,θ) is the normalized light field distribution function of the fiber cross section; In the cross section of the hollow-core microstructure optical fiber, the outer edge area of ​​a single additive marking unit accounts for 0.002% to 2% of the cladding area.

2. The hollow-core microstructured optical fiber with additive marking according to claim 1, characterized in that: The outer contour of the cladding hollow sleeve is circular; the additive marking unit is a solid glass strip or a hollow glass tube, and the outer contour of the additive marking unit is circular, elliptical, rectangular and / or polygonal.

3. The hollow-core microstructured optical fiber with additive marking according to claim 1 or 2, characterized in that: The distance D between the additive marking unit and the center of the optical fiber structure is such that: D ≤0.1%; the distance D between the additive marking unit and the center of the optical fiber structure satisfies: D≥d, where d is the core diameter of the hollow-core microstructure optical fiber.

4. The hollow core microstructure optical fiber with additive marking according to claim 3, characterized in that: The additive marking unit is attached to the inner wall of the hollow sleeve, preferably outside the anti-resonance microstructure unit.

5. The hollow core microstructure optical fiber with additive marking according to claim 4, characterized in that: The additive marking unit is attached between adjacent anti-resonance microstructure units and is close to one of the anti-resonance microstructure units.

6. The hollow-core microstructure optical fiber with additive marking according to claim 5, characterized in that: On the inner wall of the hollow sleeve, the arc between the attachment point of the additive marking unit and the attachment point of the anti-resonance microstructure unit close to the additive marking unit is R1, and the arc between the attachment points of two adjacent anti-resonance microstructure units is R2, and R1 / R2=1 / 6 to 1 / 3.

7. The hollow-core microstructured optical fiber with additive marking according to claim 1, characterized in that: The inner wall of the cladding hollow core sleeve has a plurality of additive marking units, and the plurality of additive marking units have different outer contour shapes, types and / or areas.

8. A preform of a hollow core microstructure optical fiber with an additive marking, characterized in that: The invention comprises a hollow-core microstructured optical fiber glass member with additive markings for forming the hollow-core microstructure optical fiber glass member according to any one of claims 1 to 7.

9. 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 an additive marking as described in any one of claims 1 to 7 at a preset position; (2) imaging the truncated end face obtained in step (1) using transmitted light or reflected light to obtain an end face image of the hollow-core microstructured optical fiber at that position; (3) for the end face image obtained in step (2), anti-resonance microstructure identification is performed according to its additive marking unit to obtain an image of each anti-resonance microstructure unit; (4) Extracting geometric parameters from the image of the anti-structure microstructure unit identified in step (3) to determine the geometric uniformity of the hollow-core microstructure optical fiber.

10. The drawing detection method of hollow core microstructure optical fiber preform according to claim 9, characterized in that: Step (2) uses a microscope to image the end face.

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