Hollow core microstructured optical fiber with subtractive index markings, preform, and draw detection method

Abstract

The application discloses a hollow microstructure optical fiber with subtractive marks, comprising a cladding hollow sleeve and a plurality of anti-resonant microstructure units arranged and attached to the inner wall of the cladding hollow sleeve, the anti-resonant microstructure units are used for forming an air core area with an inscribed circle size; the plurality of anti-resonant microstructure units are rotationally symmetrical; one or more subtractive mark units are arranged outside the core, so that the end face structure of the hollow microstructure optical fiber has asymmetry; the subtractive mark unit is a groove or a through hole, and the area of the subtractive mark unit accounts for 0.002% to 2% of the area of the cladding hollow sleeve. The hollow microstructure optical fiber with subtractive marks can mark and identify each anti-resonant microstructure unit in the drawing detection, judge the geometric uniformity of the hollow microstructure optical fiber, provide reference and guidance for the production of the hollow microstructure optical fiber, and timely process adjustment and improvement.

Description

Technical Field

[0001] This invention belongs to the field of optical communication, and more specifically, relates to hollow microstructure optical fibers with subtractive material markings, preforms, and fiber drawing detection methods. Background Technology

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

[0003] Even though hollow-core microstructured optical fibers have significant advantages in design and application, their transmission loss has consistently been higher than that of traditional silica optical fibers. Recent discoveries have shown that hollow-core microstructured optical fibers based on the anti-resonance principle, with proper structural design, can effectively reduce transmission loss and possess the potential to serve as ultra-long-distance communication optical fibers. Further reducing attenuation is a crucial issue in the manufacturing of hollow-core microstructured optical fibers.

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

[0005] To address the aforementioned deficiencies or improvement needs of existing technologies, this invention provides hollow microstructure optical fibers with subtractive material marking, preforms, and a fiber drawing inspection method. The subtractive material marking unit can mark and identify each anti-resonant microstructure unit during fiber drawing inspection, providing guidance for the production and operation of hollow microstructure optical fibers.

[0006] According to one aspect of the present invention, a hollow microstructure optical fiber with a subtractive material marking is provided, comprising a cladding hollow sleeve and a plurality of anti-resonant microstructure units arranged and attached to the inner wall of the cladding hollow sleeve, the anti-resonant microstructure units being used to form an air core region of the size of their inscribed circle; the plurality of anti-resonant microstructure units are rotationally symmetrical.

[0007] One or more subtractive marking units are provided on the outer side of the fiber core, which makes the end face structure of the hollow microstructure optical fiber asymmetrical;

[0008] The distance D between the subtractive material marking unit and the center of the optical fiber structure is such that:

[0009] E D ≤0.5%

[0010]

[0011] Among them, E D Let f(r,θ) be the energy distribution percentage of the region on the cross-section of the optical fiber that is more than D away from the center of the optical fiber structure; for a point in the polar coordinate system with the center of the optical fiber structure as the pole within the cross-section of the optical fiber, its polar radius is r, its polar angle is θ, and f(r,θ) is the normalized optical field distribution function of the cross-section of the optical fiber; R is the radius of the optical fiber.

[0012] Wherein, the subtractive material marking unit is a groove provided on the inner wall of the cladding hollow sleeve, the groove being arranged parallel to the axial direction of the cladding hollow sleeve; or, the subtractive material marking unit is a through hole provided in the cladding hollow sleeve, and the through hole being arranged parallel to the axial direction of the cladding hollow sleeve.

[0013] On the cross-section of the hollow 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.

[0014] Preferably, the outer contour of the cladding hollow sleeve is circular; the subtractive marking unit is a groove provided on the inner wall of the cladding hollow sleeve, and its outer contour is a part of a rectangle, a U-shape, a V-shape or a semi-circle; or the subtractive marking unit is a through hole provided in the cladding hollow sleeve, and its outer contour is circular, elliptical, rectangular and / or polygonal.

[0015] Preferably, in the hollow microstructure optical fiber with subtractive material markings, the distance D between the subtractive material marking unit and the center of the optical fiber structure is such that: E D ≤0.1%; The distance D between the subtractive material marking unit and the center of the optical fiber structure satisfies: D≥d, where d is the core diameter of the hollow microstructure optical fiber.

[0016] Preferably, in the hollow microstructure optical fiber with subtractive material markings, the subtractive material marking unit is located in the region between the geometric center of the outer contour of the adjacent anti-resonant microstructure unit and the geometric center of the optical fiber.

[0017] Preferably, in the hollow microstructure optical fiber with subtractive material markings, the subtractive material marking unit is located close to one of the adjacent anti-resonant microstructure units.

[0018] Preferably, in the hollow microstructure optical fiber with subtractive marking, the subtractive marking unit is a groove disposed on the inner wall of the cladding hollow sleeve, the arc between the position of the subtractive marking unit and the attachment point of the anti-resonant microstructure unit close to the subtractive marking unit is R1, the arc between the attachment points of two adjacent anti-resonant microstructure units is R2, and R1 / R2 = 1 / 6 to 1 / 3.

[0019] Preferably, the hollow microstructure optical fiber with subtractive markings has multiple subtractive marking units on the inner wall of its cladding hollow sleeve, and the multiple subtractive marking units have different outer contour shapes, types and / or areas.

[0020] According to another aspect of the invention, a preform of a hollow microstructured optical fiber with subtractive material markings is provided, comprising a glass component for drawing into the hollow microstructured optical fiber with subtractive material markings provided by the present invention.

[0021] According to another aspect of the present invention, a method for detecting the drawing of hollow microstructure optical fibers with subtractive material markings is provided, comprising the following steps:

[0022] (1) Cut the hollow microstructure optical fiber with subtractive material marking provided by the present invention at a preset position;

[0023] (2) Image the cut end face obtained in step (1) using transmitted light or reflected light to obtain an image of the end face of the hollow microstructure fiber at that location.

[0024] (3) For the end face image obtained in step (2), the anti-resonance microstructure is identified based on its subtractive material marking unit to obtain the image of each anti-resonance microstructure unit;

[0025] (4) Extract geometric parameters from the image of the anti-resonant microstructure unit obtained in step (3) to determine the geometric uniformity of the hollow microstructure fiber.

[0026] Preferably, in the method for detecting the drawing of the hollow microstructure optical fiber preform, step (2) involves imaging the end face using a microscope.

[0027] In summary, compared with the prior art, the above-described technical solutions conceived by this invention can achieve the following beneficial effects:

[0028] 1) The hollow microstructure optical fiber with subtractive material marking of the present invention can quickly identify the anti-resonant microstructure unit in the hollow microstructure optical fiber, which facilitates online control of the size uniformity of the anti-resonant microstructure unit and helps to reduce the transmission loss of the hollow microstructure optical fiber.

[0029] 2) The hollow microstructure optical fiber with subtractive material marking of the present invention can mark and identify each anti-resonant microstructure unit in the drawing inspection through the subtractive material marking unit, judge and analyze the geometric uniformity of the hollow microstructure optical fiber, thereby providing reference and guidance for the subsequent production of hollow microstructure optical fiber, and timely process adjustment and improvement to control geometric uniformity. It can ensure the geometric uniformity of hollow microstructure optical fiber in the subsequent manufacturing process of hollow microstructure optical fiber from preform.

[0030] 3) During the coupling process of hollow microstructured optical fiber, it is easier to identify different anti-resonant microstructure units, thereby reducing the coupling loss of hollow microstructured optical fiber. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of an unmarked hollow microstructure optical fiber, used for comparison with Example 1;

[0032] Figure 2 This is a schematic diagram of the hollow microstructure optical fiber preform with groove markings provided in Embodiment 1 of the present invention;

[0033] Figure 3 This is a schematic diagram of pressure control during the drawing process of a hollow microstructure optical fiber preform with groove markings provided in Embodiment 1 of the present invention;

[0034] Figure 4 This is a schematic diagram of pressure control during the drawing process of a hollow microstructure optical fiber preform with drill hole markings provided in Embodiment 2 of the present invention;

[0035] Figure 5 This is a schematic diagram of pressure control during the drawing process of a hollow microstructure optical fiber preform with drill hole markings provided in Embodiment 3 of the present invention.

[0036] In all the accompanying drawings, the same reference numerals are used to denote the same elements or structures, wherein: 1-anti-resonant microstructure unit, 2-subtractive material marking unit, 3-clad hollow sleeve. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0038] According to one aspect of the present invention, a hollow microstructure optical fiber with a subtractive material marking is provided, comprising a cladding hollow sleeve 3 and a plurality of anti-resonant microstructure units 1 arranged and attached to the inner wall of the cladding hollow sleeve 3, wherein the anti-resonant microstructure units 1 have an air core region tangent to the inner wall of the cladding hollow sleeve 3; the plurality of anti-resonant microstructure units 1 are rotationally symmetrical.

[0039] One or more subtractive marking units 2 are provided on the outer side of the fiber core, so that the end face structure of the hollow microstructure optical fiber has asymmetry;

[0040] The distance D between the subtractive material marking unit 2 and the center of the optical fiber structure is such that:

[0041] E D ≤0.5%

[0042]

[0043] Among them, E D Let f(r,θ) be the energy distribution percentage of the region on the cross-section of the optical fiber that is more than D away from the center of the optical fiber structure; for a point in the polar coordinate system with the center of the optical fiber structure as the pole within the cross-section of the optical fiber, its polar radius is r, its polar angle is θ, and f(r,θ) is the normalized optical field distribution function of the cross-section of the optical fiber; R is the radius of the optical fiber.

[0044] The preferred solution is that: E D ≤0.1%;

[0045] Wherein, the subtractive material marking unit 2 is a groove provided on the inner wall of the cladding hollow sleeve 3, the groove being arranged parallel to the axial direction of the cladding hollow sleeve 3; or, the subtractive material marking unit is a through hole provided in the cladding hollow sleeve 3, and the through hole being arranged parallel to the axial direction of the cladding hollow sleeve 3.

[0046] On the cross-section of the hollow microstructure 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 anti-resonant cladding formed by anti-resonant microstructure units.

[0047] Preferably, the outer contour of the cladding hollow sleeve 3 is circular; the subtractive material marking unit 2 is a groove provided on the inner wall of the cladding hollow sleeve 3, and its outer contour is a part of a rectangle, U-shaped, V-shaped or semi-circular; the subtractive material marking unit 2 is a through hole provided in the cladding hollow sleeve 3, and its outer contour is circular, elliptical, rectangular and / or polygonal.

[0048] Preferably, the distance D between the subtractive material marking unit 2 and the center of the optical fiber structure satisfies: D≥d, where d is the core diameter of the hollow microstructure optical fiber.

[0049] Preferably, the subtractive marking unit 2 is located in the region between the geometric center of the adjacent anti-resonant microstructure unit 1 and the geometric center of the optical fiber, and this region is generally fan-shaped; the subtractive marking unit 2 is close to one of the adjacent anti-resonant microstructure units 1, and the subtractive marking unit 2 falls in this region, so that the optical fiber end face presents asymmetry, and the acquisition of an image of the optical fiber end face with asymmetry can be realized.

[0050] Preferably, the subtractive marking unit 2 is a groove provided on the inner wall of the cladding hollow sleeve 3. The arc between the position of the subtractive marking unit 2 and the attachment point of the anti-resonant microstructure unit 1 that is close to the subtractive marking unit is R1, and the arc between the attachment points of two adjacent anti-resonant microstructure units 1 is R2, where R1 / R2 = 1 / 6 to 1 / 3.

[0051] Preferably, the inner wall of the cladding hollow sleeve has a plurality of subtractive material marking units 1, and the plurality of subtractive material marking units 1 have different outer contour shapes, types and / or areas.

[0052] According to another aspect of the invention, a preform of a hollow microstructured optical fiber with subtractive material markings is provided, comprising a glass component for drawing into the hollow microstructured optical fiber with subtractive material markings provided by the present invention.

[0053] Currently, there is no mature and feasible technical solution for detecting the geometric uniformity of antiresonant microstructured optical fibers. This patent concept uses an image-based method for end-face detection to extract geometric features and solve the problem of geometric uniformity detection. The difficulty of image-based detection lies in the end faces of antiresonant microstructured optical fibers, which theoretically possess perfect symmetry and are difficult to distinguish from each other. Some antiresonant microstructured optical fibers already have asymmetrical end faces, such as CN115185034A, which uses a circular nested structure within one capillary and U-shaped nested structures within the remaining capillaries to form a single-mode, low-loss, structurally simple, single-polarization hollow-core antiresonant optical fiber suitable for long-distance applications and easy to fabricate. Patent CN113885120A proposes a hollow-core microstructured optical fiber with a two-layer cladding structure. The first cladding layer defines the outer surface of the inner unsealed cladding; the second cladding layer is unsealed and has a microchannel running through the optical fiber; the second cladding layer is tightly connected to the first cladding layer and defines the inner surface of the inner unsealed cladding; the capillary layer, as an anti-resonant layer, is attached to the inner surface of the second cladding layer and, together with the second cladding layer, defines the fiber core with an effective radius; the capillaries in the capillary layer are spaced apart, and there is a gap between adjacent capillaries; the first cladding layer can effectively ensure the mechanical reliability of the optical fiber, and the second cladding layer, with its unsealed structure, can greatly reduce the complexity of post-processing of the optical fiber and improve its performance, solving the problems of loss characteristics and processing complexity of existing anti-resonant hollow-core microstructure optical fibers.

[0054] While the above patents propose asymmetric hollow microstructure fiber designs, they primarily address polarization issues and post-processing problems in fiber optic sensing. None of them offer solutions for controlling the geometric uniformity during the fiber drawing process. Therefore, they do not consider the difficulty of imaging the fiber end face or whether the asymmetry is sufficiently pronounced to distinguish anti-resonant microstructure units in the end face image.

[0055] Given the consideration of asymmetric marking, a crucial issue to address is whether the asymmetric marking affects the performance and drawing difficulty of hollow-core microstructured optical fibers. Specifically, sufficiently obvious subtractive markings require a sufficiently large area, which makes them more likely to impact the transmission performance and drawing difficulty of microstructured optical fibers.

[0056] Through ingenious design, the subtractive marking unit is placed in the region where the optical fiber energy distribution on the outer side of the fiber core is less than 0.5%, preferably in the region where the optical fiber energy distribution on the outer side of the fiber core is less than 0.1%, so as to minimize the impact on the transmission performance of the hollow microstructure optical fiber.

[0057] Subtractive fiber marking units cannot be placed on the outer surface of the circular sleeve. Because the outer surface of the sleeve has obvious drawing tension, imperfect cladding will cause overall deformation and increased transmission loss during the fiber drawing process, and will also cause deformation of the outer contour of the subtractive fiber marking, making it difficult to identify and losing the marking meaning.

[0058] If the subtractive material marking is a closed marking, that is, a through hole set in the cladding hollow sleeve, it hardly affects the wire drawing process of the anti-resonance mechanism unit, and therefore hardly affects the optical fiber transmission performance. From this perspective, through holes as subtractive material marking units have theoretically better transmission performance than grooves as subtractive material marking units. However, during wire drawing, it is necessary to increase the airflow to maintain the outer contour and avoid collapse, and the processing of through holes is more complicated.

[0059] If the subtractive fiber marking is an open marking, i.e., a groove, it needs to be placed on the inner wall of the cladding hollow fiber. Simultaneously, the groove will affect the airflow into the cladding during fiber drawing to some extent, and its outer contour is also affected by the airflow and tension within the cladding during drawing. Therefore, the cross-sectional area of ​​the groove and its location have a crucial impact on the recognizability of the subtractive fiber marking unit in the final drawn hollow fiber. Considering the groove area parameter, the area enclosed by the outer contour of the subtractive fiber marking unit accounts for 0.002% to 2% of the cladding area. Within this range, it generally has good recognizability, and its position selection easily shows its proximity to one of the anti-resonant microstructure units, thus exhibiting a more obvious asymmetry. If the groove area is too large, the deformation is more severe under the influence of drawing tension, and the positional difference between the marking unit and the two adjacent anti-resonant microstructure units on the inner wall is relatively insignificant, making it difficult to identify the anti-resonant microstructure unit using the end-face image method.

[0060] In a preferred embodiment, the subtractive marking unit is a groove set on the inner wall of the cladding hollow sleeve. The arc between the position of the subtractive marking unit and the attachment point of the anti-resonant microstructure unit close to the subtractive marking unit is R1, and the arc between the attachment points of two adjacent anti-resonant microstructure units is R2, where R1 / R2 = 1 / 6 to 1 / 3.

[0061] According to another aspect of the present invention, a method for detecting the drawing of a preform of a hollow microstructure optical fiber is also provided, comprising the following steps:

[0062] (1) Cut the hollow microstructure optical fiber with the material reduction mark at a preset position;

[0063] (2) Image the cut end face obtained in step (1) using transmitted light or reflected light to obtain an image of the end face of the hollow microstructure fiber at that location.

[0064] (3) For the end face image obtained in step (2), the anti-resonance microstructure is identified according to its subtractive marking unit 2, and the image of each anti-resonance microstructure unit 1 is obtained.

[0065] (4) Extract geometric parameters from the image of the anti-resonant microstructure unit obtained in step (3) to determine the geometric uniformity of the hollow microstructure fiber.

[0066] Preferably, step (2) involves using a microscope to image the end face.

[0067] The above method can quickly identify the anti-resonant microstructure unit 1 in the hollow microstructure fiber, which facilitates online control of the size uniformity of the anti-resonant microstructure unit 1 and helps to reduce the transmission loss of the hollow microstructure fiber. At the same time, during the coupling process of the hollow microstructure fiber, it is easy to identify different anti-resonant microstructure units 1, thereby reducing the coupling loss of the hollow core.

[0068] Typical hollow microstructure optical fiber preforms with subtractive material markings, such as Figure 2 As shown, the hollow cladding tube 3 includes anti-resonant microstructure units 1 and subtractive marking units 2 with grooves or drilled holes. The hollow microstructure optical fiber preform consists of n anti-resonant microstructure units 1, where n≥3, and the hollow cladding tube 3 has m grooves or drilled holes, where m≥1.

[0069] Furthermore, the anti-resonant microstructure unit 1 is composed of components with single-layer or multi-layer negative curvature structures.

[0070] Furthermore, drill hole markings are closed shapes, such as circles, ovals, and squares, while groove markings are open shapes, such as open semicircles and rectangles.

[0071] The above-mentioned method for fabricating hollow microstructure optical fibers with grooves or drill holes is characterized by the following fabrication steps:

[0072] Step 1: Preparation of anti-resonance microstructure unit 1: The required capillary tube is drawn into the mother tube in a high-temperature wire drawing furnace; the capillary tube can be further processed according to design requirements, such as cutting, grinding, welding, etc.

[0073] Step 2: Prepare the grooved or drilled marking cladding hollow sleeve 3: Prepare one or more grooved or drilled markings on the cladding hollow sleeve 3 through processes such as drilling, grinding, etching, and cutting.

[0074] Step 3, Preform Stacking: The anti-resonant microstructure unit 1 obtained in Step 1 is stacked and assembled into the cladding hollow sleeve 3 with grooves or drilled marks obtained in Step 2, thereby forming a hollow microstructure optical fiber preform with grooves or drilled marks.

[0075] Step 4: Directly draw the hollow microstructure fiber preform with grooves or drilled holes from Step 3 into a hollow microstructure fiber, or first draw it into an intermediate preform and then insert it into an intermediate sleeve to draw it into a hollow microstructure fiber. During the drawing process, the correspondence between the anti-resonant microstructure unit 1 in the fiber and the anti-resonant microstructure unit 1 in the preform can be quickly identified through grooves or drilled holes. Therefore, by controlling the air pressure within the anti-resonant microstructure unit 1 in the preform, the size of the anti-resonant microstructure unit 1 in the fiber can be adjusted.

[0076] Furthermore, the anti-resonance microstructure unit 1, the subtractive marking unit 2 with grooves or holes, and the cladding hollow sleeve 3 can be made of high-purity silicon dioxide, doped quartz (doped with one or more elements such as germanium, fluorine, chlorine, boron, and aluminum), multi-component glass, plastic, etc.

[0077] Furthermore, the hollow microstructure optical fiber has a cladding diameter of 100 μm or greater.

[0078] Furthermore, the hollow microstructure optical fiber prepared by the method of the present invention has low transmission loss, with the lowest transmission loss being ≤30dB / km and even better being ≤1dB / km.

[0079] Furthermore, the hollow microstructure optical fiber prepared by the method of the present invention has a low fusion splicing loss, with a self-fusion splicing loss of ≤0.5dB.

[0080] The following is an example:

[0081] Example 1

[0082] like Figure 2 As shown, capillary tubes are first prepared using a mother tube. The mother tube is then drawn into capillary tubes using a wire drawing furnace, forming an anti-resonance microstructure unit 1 with an outer diameter of 10.3 mm and a wall thickness of 0.56 mm. Next, a groove is created on the inner wall of the cladding hollow sleeve 3 using etching and grinding processes to serve as a subtractive material marking unit 2. The cladding hollow sleeve 3 has an outer diameter of 50 mm and an inner diameter of 35 mm; the subtractive material marking unit 2 with the groove is semi-circular with a diameter of 3.0 mm. Five capillary tubes are stacked within the cladding hollow sleeve 3 with the subtractive material marking unit 2 to form... Figure 1 The image shows a hollow microstructured fiber preform with grooved markings. This preform can be directly drawn into hollow microstructured fibers in a drawing furnace. Without applied air pressure, temperature fluctuations during drawing will cause variations in the dimensions of the anti-resonant microstructure unit 1, such as... Figure 1 As shown, the maximum deviation of the outer diameter of its anti-resonant microstructure unit 1 is 25%. Therefore, it is necessary to introduce gases at different pressures into the anti-resonant microstructure unit 1 to ensure uniformity of its dimensions. Figure 3As shown, the required air pressure in the anti-resonant microstructure unit 1 is identified by the grooved subtractive material marking unit. P0 is atmospheric pressure, and P1, P2, P3, P4, and P5 are the air pressure values ​​in the anti-resonant microstructure unit 1, which are 10.3 mbar, 10.6 mbar, 11.1 mbar, 10.4 mbar, and 10.7 mbar, respectively. After being drawn into an optical fiber, the maximum deviation of the outer diameter of the anti-resonant microstructure unit 1 is 4.1%, and its attenuation at 1550 nm is 5.1 dB / km. During the fusion splicing of this hollow microstructure optical fiber, the orientation of the capillary can be identified by the grooved subtractive material marking unit, thereby achieving more precise splicing, with a minimum splice loss of 0.48 dB.

[0083] Example 2

[0084] like Figure 4 As shown, two sizes of capillaries are first prepared using a mother tube: a large capillary with an outer diameter of 7.9 mm and a wall thickness of 0.42 mm, and a small capillary with an outer diameter of 4.5 mm and a wall thickness of 0.44 mm. Then, a drilling mark 4 is created inside the wall of the cladding hollow sleeve 3 using a drilling process. The cladding hollow sleeve 3 has an outer diameter of 45 mm and an inner diameter of 30 mm; the subtractive marking unit 2 formed by drilling is a circular through hole with a diameter of 2.5 mm. The large and small capillaries are assembled into an anti-resonance microstructure unit 1 by welding. Five anti-resonance microstructure units 1 are stacked in the cladding hollow sleeve 3 with the subtractive marking unit 4 as shown. Figure 4The hollow microstructure optical fiber preform shown is marked with a subtractive material designation. This preform can be drawn into an intermediate preform with an outer diameter of 10 mm in a drawing furnace, and then inserted into an intermediate sleeve with an outer diameter of 18 mm and an inner diameter of 10.5 mm for fiber drawing. Similar to the previous embodiment, different gas pressures are introduced into the anti-resonant microstructure unit 1 to ensure uniform dimensions. P0 represents atmospheric pressure, and P1, P2, P3, P4, and P5 represent the gas pressures in the large capillary tube of the anti-resonant microstructure unit 1, with values ​​of 22.1 mbar, 22.2 mbar, 22.1 mbar, 22.4 mbar, and 22.5 mbar, respectively. P6, P7, P8, P9, and P10 represent the air pressures in the small capillaries of the anti-resonant microstructure unit, with values ​​of 93.1 mbar, 93.2 mbar, 93.2 mbar, 93.7 mbar, and 93.7 mbar, respectively. The drawn hollow-core microstructure fiber exhibits a maximum outer diameter deviation of 3.3% for the large capillary in anti-resonant microstructure unit 1 and a maximum outer diameter deviation of 4.2% for the small capillary in anti-resonant microstructure unit 1. Its attenuation at 1550 nm is 0.42 dB / km. During fusion splicing of this hollow-core microstructure fiber, the capillary orientation can be identified through drilling subtractive material marking units, and more precise splicing can be achieved through the rotation function of the fusion splicer, with a minimum splice loss of 0.36 dB.

[0085] Example 3

[0086] like Figure 5 As shown, two sizes of capillaries are first prepared using a mother tube: a large capillary with an outer diameter of 12.4 mm and a wall thickness of 0.65 mm, and a small capillary with an outer diameter of 7.2 mm and a wall thickness of 0.55 mm. Then, two through holes are drilled inside the wall of the cladding hollow sleeve 3 to form two subtractive marking units 2. The cladding hollow sleeve 3 has an outer diameter of 66 mm and an inner diameter of 40 mm; the drilled subtractive marking units 2 are circular through holes with a diameter of 3.0 mm. The large and small capillaries are assembled by welding to form an anti-resonance microstructure unit 1. Five anti-resonance microstructure units 1 are stacked in the cladding hollow sleeve 3 as shown. Figure 5The hollow microstructure optical fiber preform shown is marked with a subtractive material mark. The hollow microstructure optical fiber preform with the subtractive material mark unit 2 can be first drawn into an intermediate preform in a drawing furnace. The outer diameter of the intermediate preform is 12.8 mm, and then it is inserted into an intermediate sleeve with an outer diameter of 20 mm and an inner diameter of 13.5 mm for drawing. Similar to the previous embodiment, the dimensions of the anti-resonant microstructure unit 1 are made uniform by introducing gases at different pressures into the anti-resonant microstructure unit 1. P0 is atmospheric pressure, and P1, P2, P3, P4, and P5 are the gas pressures in the large capillary tube of the anti-resonant microstructure unit 1, with values ​​of 25.2 mbar, 25.2 mbar, 25.5 mbar, 25.8 mbar, and 25.5 mbar, respectively. P6, P7, P8, P9, and P10 represent the air pressures in the small capillaries of the anti-resonant microstructure unit 1, with values ​​of 66.5 mbar, 66.6 mbar, 66.8 mbar, 66.8 mbar, and 66.4 mbar, respectively. The maximum deviation of the outer diameter of the large capillary in the drawn hollow-core microstructure fiber of anti-resonant microstructure unit 1 is 2.5%, and the maximum deviation of the outer diameter of the small capillary in anti-resonant microstructure unit 1 is 2.7%. Its attenuation at 1550 nm is 0.33 dB / km. During fusion splicing of this hollow-core microstructure fiber, the capillary orientation can be identified through the drilling subtractive material marking unit, and more precise splicing can be achieved through the rotation function of the fusion splicer. Its minimum splice loss is 0.32 dB.

[0087] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A hollow microstructure optical fiber with subtractive material markings, characterized in that, It includes a clad hollow sleeve and a plurality of anti-resonance microstructure units arranged and attached to the inner wall of the clad hollow sleeve, wherein the anti-resonance microstructure units are used to form an air core region with an inscribed circle size; the plurality of anti-resonance microstructure units are rotationally symmetrical. One or more subtractive marking units are provided on the outer side of the fiber core, which makes the end face structure of the hollow microstructure optical fiber asymmetrical; The distance D between the subtractive material marking unit and the center of the optical fiber structure is such that: E D ≤0.5％ IN D =∫0 2π ∫ D R f(r,θ)rdrdθ Among them, E D Let f(r,θ) be the energy distribution percentage of the region on the cross-section of the optical fiber that is more than D away from the center of the optical fiber structure; for a point in the polar coordinate system with the center of the optical fiber structure as the pole within the cross-section of the optical fiber, its polar radius is r, its polar angle is θ, and f(r,θ) is the normalized optical field distribution function of the cross-section of the optical fiber; R is the radius of the optical fiber. Wherein, the subtractive material marking unit is a groove provided on the inner wall of the cladding hollow sleeve, the groove being arranged parallel to the axial direction of the cladding hollow sleeve; or, the subtractive material marking unit is a through hole provided in the cladding hollow sleeve, and the through hole being arranged parallel to the axial direction of the cladding hollow sleeve. On the cross-section of the hollow 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 microstructure optical fiber with subtractive material markings as described in claim 1, characterized in that, The outer contour of the cladding hollow sleeve is circular; the subtractive material marking unit is a groove provided on the inner wall of the cladding hollow sleeve, and its outer contour is a part of a rectangle, U-shaped, V-shaped or semi-circular; or the subtractive material marking unit is a through hole provided in the cladding hollow sleeve, and its outer contour is circular, elliptical, rectangular and / or polygonal.

3. The hollow microstructure optical fiber with subtractive material markings as described in claim 1 or 2, characterized in that, The distance D between the subtractive material marking unit and the center of the optical fiber structure is such that: E D ≤0.1%; The distance D between the subtractive material marking unit and the center of the optical fiber structure satisfies: D≥d, where d is the core diameter of the hollow microstructure optical fiber.

4. The hollow microstructure optical fiber with subtractive material markings as described in claim 3, characterized in that, The subtractive marking unit is located in the region between the geometric center of the outer contour of the adjacent anti-resonant microstructure unit and the line connecting the geometric center of the optical fiber.

5. The hollow microstructure optical fiber with subtractive material markings as described in claim 4, characterized in that, The subtractive material marking unit is located near one of the adjacent anti-resonant microstructure units.

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

7. The hollow microstructure optical fiber with subtractive material markings as described in claim 1, characterized in that, The inner wall of the cladding hollow sleeve has multiple subtractive material marking units, and the multiple subtractive material marking units have different outer contour shapes, types and / or areas.

8. A preform of a hollow microstructure optical fiber with subtractive material markings, characterized in that, Includes a glass component for drawing the hollow microstructure optical fiber with subtractive material markings as described in any one of claims 1 to 7.

9. A method for detecting the drawing of hollow microstructure optical fibers with subtractive material markings, characterized in that, Includes the following steps: (1) Cut the hollow microstructure optical fiber with subtractive material marking as described in any one of claims 1 to 7 at a preset position; (2) Image the cut end face obtained in step (1) using transmitted light or reflected light to obtain an image of the end face of the hollow microstructure fiber at that location. (3) For the end face image obtained in step (2), the anti-resonance microstructure is identified based on its subtractive material marking unit to obtain the image of each anti-resonance microstructure unit; (4) Extract geometric parameters from the image of the anti-resonant microstructure unit obtained in step (3) to determine the geometric uniformity of the hollow microstructure fiber.

10. The method for detecting the drawing of hollow microstructure optical fiber preforms as described in claim 9, characterized in that, Step (2) Use a microscope to image the end face.

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