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

Abstract

A hollow-core microstructured fiber with subtractive mark units (2). 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; the plurality of anti-resonant microstructured units (1) are rotationally symmetrical; one or more subtractive 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; each subtractive mark unit (2) is a trench or a through hole; and the area of each subtractive mark unit (2) accounts for 0.002%-2% of the area of the cladding hollow-core sleeve (3). By means of each subtractive mark unit (2), each anti-resonant microstructured unit (1) can be marked and identified during drawing detection, and the geometric uniformity of the hollow-core microstructured fiber is determined.

Description

Hollow-core microstructured optical fiber with subtractive marking, preform and drawing inspection method 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 subtractive mark, 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 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 fiber in design and application, its transmission loss remains higher than that of traditional quartz fiber. 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 manufacture of hollow-core microstructured fibers.

[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 subtractive marking. Its subtractive 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 a subtractive marking 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] One or more subtractive marking units are provided on the outside of the fiber core, so that the end face structure of the hollow-core microstructured optical fiber has an asymmetric property;

[0009] The distance D between the subtractive marking unit and the center of the optical fiber structure is such that: D ≤0.5%

[0010] 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; R is the fiber radius;

[0011] The subtractive marking unit is a groove provided on the inner wall of the cladding hollow-core casing, and the groove is arranged parallel to the axial direction of the cladding hollow-core casing; or the subtractive marking unit is a through hole provided in the cladding hollow-core casing, and the through hole is arranged parallel to the axial direction of the cladding hollow-core casing;

[0012] In the cross section of the hollow-core microstructured optical fiber, the area enclosed by the outer contour of a single subtractive marking unit accounts for 0.002% to 2% of the cladding area.

[0013] Preferably, the outer contour of the cladding hollow-core casing is circular; the subtractive marking unit is a groove arranged on the inner wall of the cladding hollow-core casing, and its outer contour is a part of a rectangle, a U-shape, a V-shape or a semicircle; or the subtractive marking unit is a through hole arranged in the cladding hollow-core casing, and its outer contour is circular, elliptical, rectangular and / or polygonal.

[0014] Preferably, the distance D between the subtractive marking unit and the center of the optical fiber structure of the hollow-core microstructure optical fiber with subtractive marking is such that: D≤0.1%; the distance D between the subtractive 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.

[0015] Preferably, in the hollow-core microstructure optical fiber with subtractive marking, the subtractive marking unit is located in a region between the geometric centers of the outer contours of adjacent antiresonant microstructure units and the line connecting the geometric center of the optical fiber.

[0016] Preferably, in the hollow-core microstructure optical fiber with a subtractive mark, the subtractive mark unit is close to one of the adjacent antiresonant microstructure units.

[0017] Preferably, in the hollow-core microstructure optical fiber with a subtractive mark, the subtractive mark unit is a groove arranged on the inner wall of the cladding hollow-core sleeve, the arc between the position of the subtractive mark unit and the attachment point of the antiresonant microstructure unit close to the subtractive mark unit is R1, the arc between the attachment points of two adjacent antiresonant microstructure units is R2, and R1 / R2=1 / 6 to 1 / 3.

[0018] Preferably, the hollow-core microstructure optical fiber with subtractive marking has a plurality of subtractive marking units on the inner wall of the cladding hollow-core casing, and the plurality of subtractive marking units have different outer contour shapes, types and / or areas.

[0019] According to another aspect of the present invention, a preform rod of a hollow-core microstructured optical fiber with a subtractive marking is provided, comprising a glass component used for drawing to form the hollow-core microstructured optical fiber with a subtractive marking provided by the present invention.

[0020] According to another aspect of the present invention, a method for detecting drawing of a hollow-core microstructured optical fiber with a subtractive marker is provided, comprising the following steps:

[0021] (1) Cutting the hollow-core microstructured optical fiber with a subtractive mark provided by the present invention at a preset position;

[0022] (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;

[0023] (3) for the end face image obtained in step (2), performing anti-resonance microstructure identification according to its subtractive marking unit to obtain an image of each anti-resonance microstructure unit;

[0024] (4) Extracting geometric parameters from the image of the anti-resonance microstructure unit identified and obtained in step (3) to determine the geometric uniformity of the hollow-core microstructure optical fiber.

[0025] Preferably, in the drawing detection method for the hollow-core microstructured optical fiber preform, step (2) uses a microscope to image the end face.

[0026] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:

[0027] 1) The hollow-core microstructured optical fiber with subtractive 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 optical fiber.

[0028] 2) The hollow-core microstructured optical fiber with subtractive marking of the present invention can mark and identify each antiresonant microstructure unit during drawing detection through the subtractive 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 preform rods of hollow-core microstructured optical fibers, 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.

[0029] 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

[0030] FIG1 is a schematic diagram of an unmarked hollow-core microstructured optical fiber, for comparison with Example 1;

[0031] FIG2 is a schematic structural diagram of a hollow-core microstructured optical fiber preform with groove marks provided in Example 1 of the present invention;

[0032] FIG3 is a schematic diagram of pressure control during the drawing process of a hollow-core microstructure optical fiber preform with groove marks provided in Example 1 of the present invention;

[0033] 4 is a schematic diagram of pressure control during the drawing process of a hollow-core microstructured optical fiber preform with drilling marks provided in Example 2 of the present invention;

[0034] FIG5 is a schematic diagram of pressure control during the drawing process of a hollow-core optical microstructure fiber preform with drilling marks provided in Example 3 of the present invention.

[0035] In all drawings, the same reference numerals are used to denote the same elements or structures, where: 1 - anti-resonant microstructure unit, 2 - subtractive marking unit, 3 - cladding hollow core sleeve. DETAILED DESCRIPTION

[0036] 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.

[0037] According to one aspect of the present invention, a hollow-core microstructure optical fiber with a subtractive marking 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;

[0038] One or more subtractive marking units 2 are provided on the outside of the fiber core, so that the end face structure of the hollow-core microstructured optical fiber has an asymmetric property;

[0039] The distance D between the subtractive marking unit 2 and the center of the optical fiber structure is such that: D ≤0.5%

[0040] 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; R is the fiber radius;

[0041] The preferred solution is: E D ≤0.1%;

[0042] The subtractive marking unit 2 is a groove provided on the inner wall of the cladding hollow-core casing 3, and the groove is arranged parallel to the axial direction of the cladding hollow-core casing 3; or the subtractive marking unit is a through hole provided in the cladding hollow-core casing 3, and the through hole is arranged parallel to the axial direction of the cladding hollow-core casing 3;

[0043] On the cross section of the hollow core microstructured optical fiber, the area of ​​a single subtractive 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 the antiresonant microstructure unit.

[0044] Preferably, the outer contour of the cladding hollow-core sleeve 3 is circular; the subtractive marking unit 2 is a groove arranged on the inner wall of the cladding hollow-core sleeve 3, and its outer contour is a part of a rectangle, a U-shape, a V-shape or a semicircle; the subtractive marking unit 2 is a through hole arranged in the cladding hollow-core sleeve 3, and its outer contour is circular, elliptical, rectangular and / or polygonal.

[0045] Preferably, the distance D between the subtractive marking unit 2 and the center of the optical fiber structure satisfies: D≥d, where d is the core diameter of the hollow-core microstructure optical fiber.

[0046] Preferably, the subtractive marking unit 2 is located in the area between the geometric center of the adjacent antiresonant microstructure unit 1 and the line connecting the geometric center of the optical fiber, and the area is generally fan-shaped; the subtractive marking unit 2 is close to one of the adjacent antiresonant microstructure units 1, and the subtractive marking unit 2 falls within this area, so that the optical fiber end face is asymmetric, and the acquisition of an asymmetric optical fiber end face image can be achieved.

[0047] Preferably, the subtractive marking unit 2 is a groove arranged on the inner wall of the cladding hollow core sleeve 3, the arc between the position of the subtractive marking unit 2 and the attachment point of the anti-resonance microstructure unit 1 close to the subtractive marking unit is R1, the arc between the attachment points of two adjacent anti-resonance microstructure units 1 is R2, and R1 / R2=1 / 6 to 1 / 3.

[0048] Preferably, the inner wall of the cladding hollow core casing has a plurality of subtractive marking units 1, and the plurality of subtractive marking units 1 have different outer contour shapes, types and / or areas.

[0049] According to another aspect of the present invention, a preform rod of a hollow-core microstructured optical fiber with a subtractive marking is provided, comprising a glass component used for drawing to form the hollow-core microstructured optical fiber with a subtractive marking provided by the present invention.

[0050] 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.

[0051] While the aforementioned patents propose asymmetric hollow-core microstructured fiber designs, these primarily address polarization issues and post-processing issues for hollow-core fibers used in fiber-optic sensing. None of these patents address controlling geometric uniformity during the hollow-core microstructured fiber drawing process. Consequently, they fail to consider the difficulty of imaging the fiber end face and whether the asymmetry is sufficiently pronounced to distinguish antiresonant microstructure units in the end face image.

[0052] Considering asymmetric marking, a crucial question is whether it affects the performance and drawing difficulty of hollow-core microstructured fibers. Specifically, a sufficiently large subtractive mark is required, which is relatively more likely to affect the transmission performance and drawing difficulty of microstructured fibers.

[0053] Through clever design, the subtractive marking unit is set in an area where the energy distribution of the optical fiber outside the core is less than 0.5%, preferably in an area where the energy distribution of the optical fiber outside the core is less than 0.1%, so as to minimize the impact on the transmission performance of the hollow-core microstructure optical fiber.

[0054] The subtractive marking unit cannot be set on the outer surface of the circular sleeve. Since the outer surface of the sleeve has a relatively obvious drawing tension, the imperfect cladding will cause overall deformation of the optical fiber during the drawing process, increase transmission loss, and cause the outer contour of the subtractive mark to deform, making it difficult to identify and losing the meaning of the mark.

[0055] If the subtractive mark is a closed mark, that is, a through hole set in the hollow core sleeve of the cladding, it will hardly affect the drawing process of the antiresonant microstructure unit, and therefore will hardly affect the optical fiber transmission performance. From this perspective, the through hole as a subtractive marking unit has theoretically better transmission performance than the groove as a subtractive marking unit, but during drawing, it is necessary to increase the airflow to maintain the outer contour to avoid collapse, and the through hole processing is more difficult.

[0056] If the subtractive mark is an open mark, that is, a groove, it needs to be set on the inner wall of the cladding hollow core sleeve. At the same time, the groove will affect the airflow entering the sleeve during drawing to a certain extent, and its outer contour is also affected by the airflow and tension entering the sleeve during drawing. Therefore, the cross-sectional area of ​​the groove and its position have a crucial influence on the recognition of the subtractive mark unit of the hollow core optical fiber obtained by the final drawing. Considering the groove area parameter, the area surrounded by the outer contour of the subtractive mark unit accounts for 0.002% to 2% of the cladding area. Within this range, it generally has good recognizability, and its position selection can be easily seen to be close to one of the anti-resonance microstructure units, thereby reflecting more obvious asymmetry. If the area of ​​the groove is too large, the deformation will be more serious under the influence of the drawing tension. At the same time, the position difference between the two adjacent anti-resonance microstructure units on the inner wall is relatively insignificant, resulting in difficulties in identifying the anti-resonance microstructure unit using the end face image method.

[0057] In a preferred embodiment, the subtractive marking unit is a groove arranged on the inner wall of the cladding hollow core sleeve. The arc between the position of the subtractive marking unit and the attachment point of the anti-resonance microstructure unit close to the subtractive marking unit is R1, and the arc between the attachment points of two adjacent anti-resonance microstructure units is R2, R1 / R2=1 / 6 to 1 / 3.

[0058] According to another aspect of the present invention, a method for detecting the drawing of a preform rod of a hollow-core microstructured optical fiber is provided, comprising the following steps:

[0059] (1) cutting the hollow-core microstructured optical fiber with the subtractive mark at a preset position;

[0060] (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;

[0061] (3) For the end face image obtained in step (2), anti-resonance microstructure identification is performed based on its subtractive marking unit 2 to obtain an image of each anti-resonance microstructure unit 1;

[0062] (4) Extracting geometric parameters from the image of the anti-resonance microstructure unit identified and obtained in step (3) to determine the geometric uniformity of the hollow-core microstructure optical fiber.

[0063] Preferably, in step (2), a microscope is used to image the end face.

[0064] The above method can quickly identify the antiresonant microstructure unit 1 in the hollow-core microstructure fiber, facilitates online control of the size uniformity of the antiresonant microstructure unit 1, and is beneficial to reducing the transmission loss of the hollow-core microstructure fiber; at the same time, during the coupling process of the hollow-core microstructure fiber, it is easy to identify different antiresonant microstructure units 1, thereby reducing the coupling loss of the hollow core.

[0065] A typical hollow-core microstructured optical fiber preform with subtractive markings, as shown in Figure 2, includes an antiresonant microstructure unit 1 and a cladding hollow-core sleeve 3 with a subtractive marking unit 2 having a through hole formed by a groove or a drill hole. The hollow-core microstructured optical fiber preform comprises n antiresonant microstructure units 1, where n ≥ 3, and m grooves or drill holes are formed on the cladding hollow-core sleeve 3, where m ≥ 1.

[0066] Furthermore, the anti-resonance microstructure unit 1 is composed of single-layer or multi-layer negative curvature structure components.

[0067] Furthermore, the drilling mark is a closed shape, such as a circle, an ellipse, a square, etc., and the groove mark is a non-closed shape, such as a non-closed semicircle, a rectangle, etc.

[0068] The above-mentioned method for preparing a hollow-core microstructure optical fiber with grooves or drilling marks is characterized in that the preparation steps are as follows:

[0069] 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.

[0070] Step 2: Prepare grooves or drill hole marks on the cladding hollow-core casing 3: Prepare one or more grooves or drill hole marks on the cladding hollow-core casing 3 by drilling, grinding, etching, cutting, or other processes.

[0071] Step 3, preform stacking: the antiresonant microstructure unit 1 obtained in step 1 is stacked and assembled in the hollow core sleeve 3 with grooved or drilled marks obtained in step 2, thereby forming a hollow core microstructure optical fiber preform with grooved or drilled marks.

[0072] Step 4: Directly draw the hollow-core microstructured optical fiber preform with grooves or drilled holes from step 3 into a hollow-core microstructured optical fiber, or first draw it into an intermediate preform, which is then inserted into an intermediate sleeve and drawn into a hollow-core microstructured optical fiber. During the drawing process, the grooves or drilled holes can be used to 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.

[0073] Furthermore, the antiresonant microstructure unit 1, the subtractive marking unit 2 with grooves or holes, 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.

[0074] Furthermore, the hollow-core microstructured optical fiber has a cladding diameter greater than or equal to 100 μm.

[0075] 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.

[0076] 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.

[0077] The following are examples:

[0078] Example 1

[0079] As shown in Figure 2, capillaries are first prepared from a mother tube. The mother tube is then drawn into capillaries in a drawing furnace, forming an antiresonant microstructure unit 1 with an outer diameter of 10.3 mm and a wall thickness of 0.56 mm. A groove is then created on the inner wall of the cladding hollow-core sleeve 3 through etching and grinding, serving as the subtractive marking unit 2. The cladding hollow-core sleeve 3 has an outer diameter of 50 mm and an inner diameter of 35 mm. The grooved subtractive marking unit 2 is semicircular and has a diameter of 3.0 mm. Five capillaries are stacked within the cladding hollow-core sleeve 3 with the subtractive marking unit 2 to form the grooved hollow-core microstructure fiber preform shown in Figure 1. This grooved hollow-core microstructure fiber preform can be directly drawn into a hollow-core microstructure fiber in a drawing furnace. If no air pressure is applied during drawing, temperature fluctuations can cause the antiresonant microstructure unit 1 to vary in size. As shown in Figure 1, the maximum deviation in the outer diameter of the antiresonant microstructure unit 1 is 25%. To this end, it is necessary to introduce gases of different pressures into the antiresonant microstructure unit 1 to make the size of the antiresonant microstructure unit 1 uniform. As shown in Figure 3, the required gas pressure in the antiresonant microstructure unit 1 is identified by a grooved subtractive marking unit. P0 is normal pressure, and P1, P2, P3, P4, and P5 are the gas pressures in the antiresonant microstructure unit 1, with values ​​of 10.3mbar, 10.6mbar, 11.1mbar, 10.4mbar, and 10.7mbar, respectively. After being drawn into an optical fiber, the maximum deviation of the outer diameter of its antiresonant microstructure unit 1 is 4.1%, and its attenuation at 1550nm is 5.1dB / km. When this hollow-core microstructure optical fiber is fused, the capillary orientation can be identified by a grooved subtractive marking unit, thereby achieving more precise docking, and its minimum fusion loss is 0.48dB.

[0080] Example 2

[0081] As shown in Figure 4, two sizes of capillaries are first prepared through a mother tube. The large capillary has an outer diameter of 7.9 mm and a wall thickness of 0.42 mm, and the small capillary has an outer diameter of 4.5 mm and a wall thickness of 0.44 mm. Then, a drilling mark 4 is prepared inside the wall of the cladding hollow-core sleeve 3 by drilling. The dimensions of the cladding hollow-core sleeve 3 are 45 mm in outer diameter and 30 mm in inner diameter; the subtractive marking unit 2 formed by drilling is a circular through hole with a diameter of 2.5 mm. The large capillary and the small capillary are assembled into an anti-resonance microstructure unit 1 by welding. Five anti-resonance microstructure units 1 are stacked in the cladding hollow-core sleeve 3 with the subtractive marking unit 4 to form a hollow-core microstructure optical fiber preform with a subtractive mark as shown in Figure 4. The hollow-core microstructure optical fiber preform with a subtractive mark can be first drawn into an intermediate preform in a drawing furnace. The intermediate preform has an outer diameter of 10 mm, and then is inserted into an intermediate sleeve with an outer diameter of 18 mm and an inner diameter of 10.5 mm for drawing. As in the previous embodiment, the size of the antiresonant microstructure unit 1 is made uniform by introducing gases of different pressures into the antiresonant microstructure unit 1. P0 is normal pressure, and P1, P2, P3, P4, and P5 are the gas pressures in the large capillary of the antiresonant microstructure unit 1, respectively, and their values ​​are 22.1 mbar, 22.2 mbar, 22.1 mbar, 22.4 mbar, and 22.5 mbar, respectively. P6, P7, P8, P9, and P10 are the gas pressures in the small capillary of the antiresonant microstructure unit, respectively, and their values ​​are 93.1 mbar, 93.2 mbar, 93.2 mbar, 93.7 mbar, and 93.7 mbar, respectively. The maximum outer diameter deviation of the large capillary in the antiresonant microstructure unit 1 of the drawn hollow-core microstructured optical fiber is 3.3%, and the maximum outer diameter deviation of the small capillary in the antiresonant microstructure unit 1 is 4.2%. Its attenuation at 1550nm is 0.42dB / km. During fusion splicing, this hollow-core microstructured optical fiber uses a drilled subtractive marking unit to identify the capillary orientation, and the rotation function of the fusion splicer allows for more precise splicing. The minimum splicing loss is 0.36dB.

[0082] Example 3

[0083] As shown in Figure 5, two sizes of capillaries are first prepared through a mother tube. The large capillary has an outer diameter of 12.4mm and a wall thickness of 0.65mm, and the small capillary has an outer diameter of 7.2mm and a wall thickness of 0.55mm. Then, two through holes are prepared inside the wall of the cladding hollow core sleeve 3 by drilling to form two subtractive marking units 2. The dimensions of the cladding hollow core sleeve 3 are an outer diameter of 66mm and an inner diameter of 40mm; the drilled subtractive marking unit 2 is a circular through hole with a diameter of 3.0mm. The large capillary and the small capillary are assembled into an anti-resonance microstructure unit 1 by welding. Five anti-resonance microstructure units 1 are stacked in the cladding hollow core sleeve 3 to form a hollow core microstructure optical fiber preform with subtractive marking as shown in Figure 5. The hollow-core microstructure optical fiber preform with the subtractive marking unit 2 can be first drawn into an intermediate preform in a drawing furnace. The intermediate preform has an outer diameter of 12.8 mm, and then is inserted into an intermediate sleeve with an outer diameter of 20 mm and an inner diameter of 13.5 mm for drawing. As in the previous embodiment, the size of the antiresonant microstructure unit 1 is made uniform by introducing gases of different pressures into the antiresonant microstructure unit 1. P0 is normal pressure, and P1, P2, P3, P4, and P5 are the gas pressures in the large capillary of the antiresonant microstructure unit 1, respectively, and their values ​​are 25.2 mbar, 25.2 mbar, 25.5 mbar, 25.8 mbar, and 25.5 mbar, respectively. P6, P7, P8, P9, and P10 are the gas pressures in the small capillary of the antiresonant microstructure unit 1, respectively, and their values ​​are 66.5 mbar, 66.6 mbar, 66.8 mbar, 66.8 mbar, and 66.4 mbar, respectively. The maximum outer diameter deviation of the large capillary in the antiresonant microstructure unit 1 of the drawn hollow-core microstructured optical fiber is 2.5%, and the maximum outer diameter deviation of the small capillary in the antiresonant microstructure unit 1 is 2.7%. Its attenuation at 1550nm is 0.33dB / km. During fusion splicing, this hollow-core microstructured optical fiber uses a drilled subtractive marking unit to identify the capillary orientation, and the rotation function of the fusion splicer allows for more precise splicing, achieving a minimum splice loss of 0.32dB.

[0084] 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 microstructured optical fiber with a subtractive 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 subtractive marking units are provided on the outside of the fiber core, so that the end face structure of the hollow core microstructure optical fiber has asymmetry; The distance D between the subtractive 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; R is the fiber radius; Wherein, the subtractive marking unit is a groove arranged on the inner wall of the cladding hollow-core casing, and the groove is arranged parallel to the axial direction of the cladding hollow-core casing; or, the subtractive marking unit is a through hole arranged in the cladding hollow-core casing, and the through hole is arranged parallel to the axial direction of the cladding hollow-core casing; In the cross section of the hollow-core microstructured optical fiber, the area enclosed by the outer contour of a single subtractive marking unit accounts for 0.002% to 2% of the cladding area.

2. The hollow core microstructure optical fiber with subtractive marking according to claim 1, characterized in that: The outer contour of the cladding hollow-core casing is circular; the subtractive marking unit is a groove arranged on the inner wall of the cladding hollow-core casing, and its outer contour is a part of a rectangle, a U-shape, a V-shape or a semicircle; or the subtractive marking unit is a through hole arranged in the cladding hollow-core casing, and its outer contour is circular, elliptical, rectangular and / or polygonal.

3. The hollow core microstructure optical fiber with subtractive marking according to claim 1 or 2, characterized in that: The distance D between the subtractive marking unit and the center of the optical fiber structure is such that: D ≤0.1%; the distance D between the subtractive 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 subtractive marking according to claim 3, characterized in that: The subtractive marking unit is located in a region between a line connecting a geometric center of an outer contour of an adjacent anti-resonance microstructure unit and a geometric center of the optical fiber.

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

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

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

8. A preform of a hollow core microstructured optical fiber with a subtractive marking, characterized in that: The invention comprises a glass component used for drawing to form the hollow-core microstructure optical fiber with subtractive marking as claimed in any one of claims 1 to 7.

9. A method for detecting the drawing of a hollow-core microstructured optical fiber with a subtractive marker, characterized in that: The following steps are involved: (1) Cutting the hollow-core microstructured optical fiber with a subtractive mark according to 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 The end face image of the hollow core microstructure optical fiber at this position is obtained; (3) for the end face image obtained in step (2), anti-resonance microstructure identification is performed according to its subtractive 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.

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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