Air-core microstructured optical fiber preform, optical fiber and method of manufacturing same

Abstract

To provide an air core fine structure optical fiber preform capable of increasing the number of reflective surfaces of an air core fine structure optical fiber finally manufactured on the assumption without increasing a nest layer number, and a method for manufacturing the air core fine structure optical fiber preform, capable of reducing the manufacture difficulty of a multilayer nest type glass tube and providing the manufacturing precision and lot consistency of the multilayer nest type glass tube.SOLUTION: An air core fine structure optical fiber preform includes a clad air core sleeve and a plurality of nest structure units arranged on the inner wall of the clad air core sleeve. The nest structure unit used for forming an air core area having the inscribed circle size thereof includes a multilayer nest type glass tube; a support sheet is provided between the glass tubes of at least one set of adjacent nests in the multilayer nest type glass tube; and the support sheet firmly fixes the glass tubes of the adjacent nests so as to form at least 7 reflective surfaces by the glass tubes of the adjacent nests.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to the field of optical fiber communication technology, and more particularly to an air-core microstructured optical fiber preform, an optical fiber, and a method for manufacturing the same. [Background technology]

[0002] Air-core microstructured optical fiber has the characteristics of simple structure, air-core single-mode light guiding, wide transmission spectrum, and has important applications in the fields of light and filling material interaction, nonlinear optics, gas detection, gas laser generation, optofluidic technology and other fields. Large air-hole core light guiding has ultra-low Rayleigh scattering, low nonlinear coefficient, dispersion tunable characteristics, and can provide higher laser damage threshold, so that it has potential applications in the aspects of high-power laser transmission, ultraviolet / mid-infrared light transmission, pulse compression and optical soliton transmission, etc. The ultra-low loss, low dispersion, low nonlinearity and propagation speed close to the speed of light of air core can realize the development of air-core optical fiber communication transmission and communication devices, and lay the foundation for the construction and development of next-generation ultra-large capacity, low latency and high-speed optical communication systems.

[0003] Although air-core optical fiber has great advantages in design and application, its transmission loss is much higher than that of traditional silica optical fiber. In recent years, people have been surprised to discover that air-core optical fiber based on the anti-resonance principle can effectively reduce transmission loss under reasonable structural design, and has potential as ultra-long distance communication optical fiber. Further reducing the attenuation of air-core microstructured optical fiber remains an important challenge in the field of optical fiber manufacturing. Existing research has revealed that by increasing the number of layers of glass thin film through structural design and controlling the curvature of each layer of glass thin film, this optical fiber can provide lower loss than existing traditional optical fibers at any wavelength.

[0004] In the prior art, the attenuation of air-core fiber is often reduced by negative curvature cladding design and no-node structure. Document US10989866B2 proposes an air-core photonic crystal fiber consisting of an outer cladding region and seven air-core tubes around the outer cladding region, each air-core tube is fused to the outer cladding to form an annular ring, the air-core tubes do not contact each other and have a distance from the adjacent air-core tubes, each air-core tube has an average outer diameter d2 and an average inner diameter d1, and d1 / d2 is about 0.8 or more, thereby controlling the curvature of the glass thin film, and thus the attenuation of the air-core optical fiber can be up to 30dB / km. However, the attenuation is limited by further reducing the curvature of the reflecting surface, which limits its application scenario, and a technology has emerged to achieve lower optical fiber attenuation performance by increasing the number of anti-resonance layers in the cladding capillary.

[0005] Document US10527782B2 proposes that the number of anti-resonant layers can be increased by nesting tangent capillaries, which can reduce attenuation to a certain extent. However, the number of anti-resonant layers is only five, and the attenuation level is higher than that of traditional quartz optical fiber, which cannot meet the long-distance optical fiber transmission.

[0006] However, since the loss of the antiresonant optical fiber is reduced by increasing the number of structural unit layers at present, its manufacturing control is extremely difficult. Specifically, the difficulty of controlling the curvature of the reflective film also increases with the increase in the number of structural unit layers, and the tangent circular tube connection method is difficult to control in terms of manufacturing control, and the consistency between multiple structural units is not ideal. Overall, the current air-core microstructured antiresonant optical fiber with multi-layered reflective surface has low yield and poor lot consistency in the actual manufacturing process. The above problems have led to difficulties in mass production of the currently designed low-loss antiresonant optical fiber. Summary of the Invention [Problem to be solved by the invention]

[0007] In response to the above-mentioned deficiencies or needs for improvement in the prior art, the present invention provides an air-core microstructured optical fiber preform, an optical fiber and a manufacturing method thereof, and aims to solve the technical problems of the conventional anti-resonant optical fiber, such as the difficulty of controlling the curvature of the reflecting surface due to the increase in the number of layers of the nested microstructure unit, the low manufacturing accuracy, the large difference between the actual loss and the theoretical loss, or the poor lot consistency, by introducing a support sheet into the nested structure unit of the air-core microstructured optical fiber preform, not only increasing the reflecting surface without increasing the number of nested layers of the glass tube, but also making it easier to accurately position the support sheet than the tangent structure nested glass tube, and improving the manufacturing accuracy. [Means for solving the problem]

[0008] In order to achieve the above object, according to one aspect of the present invention, there is provided an air-core microstructured optical fiber preform, comprising: a clad air-core sleeve; and a plurality of nest structure units arranged on an inner wall of the clad air-core sleeve, the nest unit being used to form an air core region of an inscribed circle dimension thereof, the nest structure unit including a multi-layer nested glass tube, a support sheet being provided between at least one pair of glass tubes of adjacent nests among the multi-layer nested glass tubes, the support sheet being configured to firmly fix the glass tubes of the adjacent nests so that at least seven reflective surfaces are formed by the glass tubes of the adjacent nests.

[0009] Preferably, in the air-core microstructured optical fiber preform, the support sheet is distributed other than along the normal to the reflecting surface, and the normal to the reflecting surface passes through the geometric center of the cross section of the preform.

[0010] Preferably, in the air-core microstructured optical fiber preform, the support sheet is parallel to the tangent direction of the reflecting surface.

[0011] Preferably, in the air-core microstructured optical fiber preform, a pair of support sheets are included between the glass tubes of the adjacent nests, and the support sheets are arranged symmetrically with respect to the normal direction of the reflecting surface or symmetrically with respect to the geometric center of the nest structure unit.

[0012] Preferably, in the air-core microstructured optical fiber preform, at least one of the glass tubes of the adjacent nests has a circular cross-section, and preferably the outer glass tube of the glass tubes of the adjacent nests has a circular cross-section.

[0013] Preferably, in the air-core microstructured optical fiber preform, the nested structure unit includes a concentrically nested inner glass tube and an outer glass tube, the inner glass tube and the outer glass tube having a circular cross-section, and a pair of support sheets are included between the inner glass tube and the outer glass tube, and the support sheets are arranged symmetrically across the diameter of the inner glass tube with respect to the normal direction of the reflective surface.

[0014] Preferably, the air-core microstructured optical fiber preform comprises four or more nested structure units.

[0015] According to another aspect of the present invention, there is provided a method for manufacturing the air-core microstructured optical fiber preform, comprising the steps of: Assembly of nested structural unit: For a nested glass tube with an adjacent support sheet, fix the support sheet and the nested glass tube in a preset position and a preset direction from inside to outside. Assembly of the clad air-core sleeve: A preset number of nesting structural units and clad air-core sleeves are nested, positioned by a support sheet, and the nesting structural units and clad air-core sleeves are fixed at preset positions.

[0016] Preferably, in the method for producing the hollow-core microstructured optical fiber preform, the assembly of the nested structure units specifically includes: First, fix the inner glass tube and the support sheet, and use an auxiliary mold in the fixing process to maintain the relative position of the support sheet and the inner glass tube; Next, the inner glass tube with the support sheet fixed thereto and the outer glass tube are nested, and the support sheet and the outer glass tube are laterally arranged and fixed in a preset position.

[0017] Preferably, in the method for producing the air-core microstructured optical fiber preform, the positioning by the support sheet is mechanical visual positioning using cross-sectional imaging, or mechanical positioning using an end face sleeve.

[0018] According to another aspect of the present invention, there is provided an air-core microstructured optical fiber, comprising an outer cladding sleeve having a plurality of nested microstructures, the plurality of nested microstructures surrounding a core region, the nested microstructures being distributed on an inner wall of the outer cladding sleeve and tangentially fixed to the inner wall of the outer cladding sleeve, the nested structure including at least first and second anti-resonant rings nested from the outside to the inside, a connecting bridge between the first and second anti-resonant rings, and the nested microstructure having seven reflective surfaces formed by at least the first and second anti-resonant rings.

[0019] Preferably, in the air-core microstructured optical fiber, among the plurality of nested microstructures, the inscribed circles of the reflecting surfaces that are at the same distance from the axis of the air-core microstructured optical fiber divide the cladding into a plurality of regions, which are, from the inside to the outside, a core region with a diameter D0, a first anti-resonant ring with a diameter D1, a second anti-resonant ring with a diameter D2, and a connecting bridge with a thickness T0, respectively, and the diameter D0 of the core region is 10 to 50 μm, more preferably the diameter D0 of the core region is 10 to 20 μm, or more preferably the diameter D0 of the core region is 20 to 30 μm, or more preferably the diameter D0 of the core region is 30 to 40 μm, or more preferably the diameter D0 of the core region is 40 to 50 μm; The equivalent area S1 of the first anti-resonant ring is 20 to 1600 μm 2and the equivalent outer diameter S2 of the second anti-resonant ring is 3 to 500 μm 2 wherein the thickness T1 of the first anti-resonant ring is 0.1 to 2.0 μm, the thickness T2 of the second anti-resonant ring is 0.1 to 2.0 μm, and the thickness T0 of the connection bridge is 0.1 to 2.0 μm.

[0020] Preferably, in the hollow microstructure optical fiber, the reflective surface includes a positive curvature reflective surface and a negative curvature reflective surface, the radius of curvature range of the positive curvature reflective surface is 0.2 to 150 μm, and the radius of curvature range of the negative curvature reflective surface is -150 to -0.2 μm.

[0021] Preferably, in the hollow microstructure optical fiber, the first anti-resonant ring and / or the second anti-resonant ring are formed in a circular, elliptical or figure-eight shape.

[0022] Preferably, in the hollow microstructure optical fiber, the minimum distance g between the nested microstructures satisfies the relationship of 0 < g ≤ 15 μm, and the ratio g / T1 of the minimum distance g between the nested microstructures to the thickness T1 of the first anti-resonant ring is 5 to 20, or 1 to 6, or 15 to 25.

[0023] Preferably, in the hollow microstructure optical fiber, the refractive index of the nested microstructure material is < 2.0, and more preferably < 1.5.

[0024] Preferably, in the hollow microstructure optical fiber, the plurality of nested microstructures have different reflection performances. Preferably, the nested microstructures have different shapes, thicknesses, and / or dimensions, imparting asymmetry to the cross-section of the hollow microstructure fiber.

Advantages of the Invention

[0025] Overall, the above technical means devised by the present invention can obtain the following beneficial effects as compared with the prior art.

[0026] The air-core microstructured optical fiber preform provided by the present invention introduces a support sheet structure into the nested microstructure unit, and increases the number of reflective surfaces of the finally manufactured air-core microstructured optical fiber under the premise of not increasing the number of nested layers. At the same time, the structure of the support sheet is clear, and the tangent structure makes it easier to accurately position the air-core microstructured optical fiber preform when assembling it, thereby improving the manufacturing precision and batch consistency of the optical fiber preform. Therefore, by increasing the number of reflective surfaces, the loss of the air-core microstructured optical fiber is reduced, while the manufacturing precision of the optical fiber preform is improved, and the loss of the manufactured air-core microstructured optical fiber is closer to the theoretical value, and the loss of the manufactured air-core microstructured optical fiber is comprehensively reduced. A new method and concept are provided for the design and manufacturing of wideband low-loss air-core optical fiber.

[0027] The manufacturing method of the hollow-core optical fiber microstructure preform provided by the present invention reduces the manufacturing difficulty of the multi-layer nested glass tube by using the support sheet, and provides the manufacturing precision and lot consistency of the multi-layer nested glass tube. By positioning the support sheet in the nested glass tube, multiple nested structure units can be accurately fixed with the cladding hollow-core sleeve, which has high manufacturing precision and good lot consistency. [Brief description of the drawings]

[0028] [Figure 1] FIG. 2 is a structural schematic diagram of an air-core microstructured optical fiber provided by Example 1 of the present invention. [Diagram 2] FIG. 1 is a schematic diagram of the structure in which a support sheet and an inner glass tube are fixed in the fabrication of an air-core microstructured optical fiber preform according to Example 1 of the present invention. [Diagram 3] FIG. 2 is a schematic diagram of the structure in which the support sheet and the outer glass tube are fixed in the fabrication of the hollow-core microstructured optical fiber preform in accordance with the first embodiment of the present invention. [Figure 4] FIG. 2 is a schematic structural diagram of the air-core microstructured optical fiber provided by Examples 1-1 to 1-6 of the present invention. [Diagram 5] FIG. 2 is a structural schematic diagram of an air-core microstructured optical fiber provided by Example 2 of the present invention. [Figure 6] FIG. 2 is a structural schematic diagram of the air-core microstructured optical fiber provided by Examples 3 and 4 of the present invention. [Figure 7] FIG. 1 is a structural schematic diagram of an air-core microstructured optical fiber provided by Example 5 of the present invention. [Figure 8] FIG. 1 is a structural schematic diagram of an air-core microstructured optical fiber provided by Example 6 of the present invention. [Figure 9] FIG. 2 is a structural schematic diagram of the air-core microstructured optical fiber provided by Examples 7 and 8 of the present invention. [Figure 10] FIG. 1 is a structural schematic diagram of an air-core microstructured optical fiber provided by Examples 9 and 10 of the present invention. [Figure 11] FIG. 11 is a structural schematic diagram of an air-core microstructured optical fiber provided by Example 11 of the present invention. [Figure 12] FIG. 1 is a structural schematic diagram of an air-core microstructured optical fiber provided by Examples 12 and 13 of the present invention. [Figure 13] FIG. 14 is a structural schematic diagram of an air-core microstructured optical fiber provided by Example 14 of the present invention. [Figure 14] FIG. 2 is a structural schematic diagram of the air-core microstructured optical fiber provided by Examples 15 to 18 of the present invention. [Figure 15] FIG. 2 is a schematic diagram of the mode field distribution of the air-core microstructured optical fiber provided by Example 1 of the present invention. [Figure 16] FIG. 2 is an attenuation spectrum diagram of the air-core microstructured optical fibers provided by Examples 1, 1-1, 1-6 and 2 of the present invention. [Figure 17] FIG. 2 is an attenuation spectrum diagram of the air-core microstructured optical fibers provided by Examples 4, 5, 6 and 7 of the present invention. [Figure 18] 4 is an attenuation spectrum diagram of the air-core microstructured optical fibers provided by Examples 9, 11, 12, 14 and 17 of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] In order to clarify the purpose, technical means and advantages of the present invention, the present invention will be described in more detail in the following by combining examples. Note that the specific examples described herein are only used to explain the present invention, and are not used to limit the present invention. In addition, the technical features according to various embodiments of the present invention described below may be combined with each other as long as they are not in conflict with each other.

[0030] The air-core microstructured optical fiber preform provided by the present invention includes a cladding air-core sleeve and a plurality of nested structure units uniformly arranged on the inner wall of the cladding air-core sleeve. The nested structure units are used to form an air core region with an inscribed circle dimension. The nested structure units preferably include multi-layer nested glass tubes and include four or more nested structure units. The cladding air-core sleeve is used to form a cladding outer sleeve of the air-core microstructured optical fiber. The nested structure units are used to form a nested microstructure. The glass tubes are used to form an anti-resonant ring. A support sheet is provided between at least one pair of adjacent nested glass tubes of the multi-layer nested glass tubes. The support sheet firmly fixes the glass tubes of the adjacent nests so that at least seven reflecting surfaces are formed by the glass tubes of the adjacent nests. Preferably, the support sheet is distributed other than the normal to the reflecting surface. The support sheet is preferably parallel to the tangential direction of the reflecting surface. The normal to the reflecting surface passes through the geometric center of the cross section of the preform. Preferably, a pair of support sheets is included between the glass tubes of the adjacent nests, and the support sheets are arranged symmetrically with respect to the normal direction of the reflecting surface or symmetrically with respect to the geometric center of the nest structure unit.

[0031] At present, the support of the nested glass tube is generally supported by the tangent of the inner and outer glass tubes, in order to avoid the increase in glass thickness due to the connection of the use node or the unevenness of the thickness, which causes resonance and affects the performance of the optical fiber. However, although this support can avoid the effect on the thickness of the nested glass tube, it reduces at least two reflective surfaces. At the same time, the circular outer wall of the nested structure unit makes it difficult to accurately fix the tangent connection point to the inner wall of the cladding hollow-core sleeve during preform manufacturing, which makes the actual manufacturing of the microstructured optical fiber extremely difficult. The optical fiber structure actually manufactured is difficult to realize the design structure of the anti-resonant optical fiber, and the optical fiber attenuation is significantly different from the theoretical analysis value, making it difficult to mass-produce.

[0032] On the other hand, in the case of the support sheet, the walls of the glass tubes of the adjacent nests are not in contact with each other, and not only can more reflecting surfaces be formed, but also the support sheet can be positioned, and the nest structure unit and the inner wall of the clad hollow-core sleeve can be accurately fixed. The cross section is preferably of a straight line structure. Preferably, a pair of support sheets are provided symmetrically with respect to the normal direction of the reflecting surface and parallel to the tangential direction of the reflecting surface, so as to reduce the interference with the curvature and thickness control of the reflecting surface during the drawing process of the support sheet. The tangential support of the inner and outer glass tubes is generally at the reflective surface, and the thickness at the junction is determined by the sum of the thicknesses of the inner and outer glass tubes, and the thickness is obviously larger than other reflecting surfaces. In the present invention, the thickness of the anti-resonant ring formed by using the support sheet is uniform, and there are more reflecting surfaces. The adoption of the support sheet introduces more nodes, but the support sheet can be distributed on both sides of the normal direction of the reflecting surface of the anti-resonant ring, and the nodes can be distributed as much as possible to avoid the reflecting surface, so that the negative effect of the support sheet on the reduction of optical fiber attenuation can be effectively reduced. Overall, the optical fiber attenuation can be reduced, and the difference in attenuation between an actually manufactured optical fiber and an optical fiber simulated by a theoretical model can be reduced.

[0033] In a preferred embodiment, at least one of the adjacent nested glass tubes has a circular cross section, and preferably the outer glass tube of the adjacent nested glass tubes has a circular cross section. In the cross-sectional view, the circular glass tube and the linear support sheet significantly improve the symmetry of the nested structure unit, reduce the difficulty of the optical fiber preform manufacturing technology, and improve the structural precision of the low-loss optical fiber preform. In comparison, since the support sheet is installed inside the outer glass tube and is difficult to nest and fix, the circular cross section of the outer glass tube greatly contributes to improving the structural precision of the optical fiber preform.

[0034] The present invention provides an air-core microstructured optical fiber preform, the preferred manufacturing method of which includes the following steps.

[0035] Assembly of nested structure unit: For nested glass tubes with adjacent support sheets, fix the support sheet and nested glass tube from inside to outside in a preset position and in a preset direction. Specifically, first, fix the inner glass tube and the support sheet, preferably by melting and fixing, and use an auxiliary mold in the fixing process to maintain the relative position of the support sheet and the inner glass tube. Next, nest the inner glass tube with the fixed support sheet and the outer glass tube, arrange them horizontally so that the support sheet and the outer glass tube are in a preset position, and fix them, preferably by melting and fixing.

[0036] Assembling the clad air-core sleeve: nesting a preset number of nesting structural units and the clad air-core sleeve, positioning the nesting structural units and the clad air-core sleeve with a support sheet, and fixing the nesting structural units and the clad air-core sleeve at preset positions. Positioning with the support sheet can be performed by mechanical visual positioning using a cross-sectional image method, or mechanical positioning using an end face sleeve.

[0037] The air-core microstructured optical fiber preform provided by the present invention can control the curvature and thickness of the reflective surface of the microstructure of the cladding of the optical fiber finally formed by drawing by controlling the amount of air passing through each closed region during the drawing process. Even if the same optical fiber preform is used, air-core microstructured optical fibers having microstructures with different curvatures and thicknesses of the reflective surface can be formed by drawing.

[0038] The air-core microstructured optical fiber provided by the present invention includes an outer cladding sleeve having a nested microstructure. A core region is surrounded by the nested microstructure. The nested microstructure is uniformly distributed on the inner wall of the outer cladding sleeve and tangentially fixed to the inner wall of the outer cladding sleeve. The nested structure includes at least a first and a second anti-resonant ring nested from the outside to the inside. A connecting bridge is provided between the first and the second anti-resonant ring. The nested microstructure has at least seven reflective surfaces formed by the first and the second anti-resonant ring. The inscribed circles of the reflective surfaces of the plurality of nested microstructures, which are at the same distance from the axis of the air-core microstructured optical fiber, divide the cladding into a plurality of regions, which are respectively a core region with a diameter D0, a first anti-resonant ring with an area S1, a second anti-resonant ring with an area S2, and a support sheet with a thickness T0 from the inside to the outside. The diameter D0 of the core region is 10 to 50 μm, more preferably the diameter D0 of the core region is 10 to 20 μm, or more preferably the diameter D0 of the core region is 20 to 30 μm, or more preferably the diameter D0 of the core region is 30 to 40 μm, or more preferably the diameter D0 of the core region is 40 to 50 μm. The equivalent area S1 of the first anti-resonant ring is 20 to 1600 μm. 2 and the equivalent outer diameter S2 of the second anti-resonant ring is 3 to 500 μm. 2 The wall thickness T0 of the connecting bridge is 0.1 to 2.0 μm.

[0039] The reflecting surface includes two types: a positive-curvature reflecting surface and a negative-curvature reflecting surface. The curvature radius range of the positive-curvature reflecting surface is 0.2 to 150 μm, and the curvature radius range of the negative-curvature reflecting surface is -150 to -0.2 μm. The first anti-resonant ring and / or the second anti-resonant ring are formed in a circular, elliptical, or figure-eight shape.

[0040] The thickness T1 of the first anti-resonant ring is 0.1 to 2.0 μm, and the thickness T2 of the second anti-resonant ring is 0.1 to 2.0 μm.

[0041] The minimum distance g between the nested microstructures satisfies the relationship 0 < g ≤ 15 μm, and the ratio g / T1 of the minimum distance g between the nested microstructures to the thickness T1 of the first anti-resonant ring is 5 to 20, or 1 to 6, or 15 to 25.

[0042] The refractive index of the microstructure material is < 2.0, and more preferably < 1.5.

[0043] According to the hollow-core microstructure optical fiber designed as described above, its light guiding has low-loss performance from 0.25 μm to 3.5 μm, and its lowest optical propagation loss level is ≤ 50 dB / km, more preferably ≤ 1 dB / km, and even more preferably ≤ 0.1 dB / km.

[0044] The above-mentioned hollow-core microstructure optical fiber can be applied to scenes such as effective single-mode transmission, few-mode or multi-mode transmission, nonlinear optics, gas detection, gas laser generation, and polarization maintenance.

[0045] In particular, when used as a polarization-maintaining fiber, its multiple nested microstructures have different reflection performances. Preferably, the nested microstructures have different shapes, thicknesses, and / or dimensions, giving the cross-section of the hollow-core microstructure fiber an asymmetry, thereby realizing a large birefringence performance, and its birefringence is ≥ 10 -5 more preferably ≥ 10 -4 more preferably ≥ 10 -3 is.

[0046] An example is given below.

[0047] [Example 1] The air-core optical fiber preform provided in this embodiment includes a cladding air-core sleeve and six nest structure units uniformly arranged on the inner wall of the cladding air-core sleeve. The cladding air-core sleeve is used to form a cladding outer sleeve of an air-core microstructured optical fiber. The nest structure units are used to form a nest microstructure. The glass tube is used to form an anti-resonant ring. The nest unit is used to form an air core region with an inscribed circle dimension. In this embodiment, the nest unit includes two layers of concentrically nested circular glass tubes, and a support sheet is provided between the inner and outer glass tubes. The support sheet firmly fixes the glass tubes of the adjacent nests, so that the inner and outer glass tubes form seven reflective surfaces.

[0048] In this embodiment, the two support sheets are arranged perpendicular to the normal direction of the reflecting surface, connecting the first anti-resonant ring and the second anti-resonant ring. The normal direction of the reflecting surface is a radial direction passing through the geometric center of the optical fiber in this embodiment. The support sheets are symmetrically spaced apart with respect to the normal direction of this reflecting surface, and are parallel to the tangential direction of the reflecting surface. This moves the nodes of the support sheet away from the reflecting surface, reducing the influence on the reflecting surface, and the support sheet itself also plays the role of a reflecting surface to some extent, contributing to reducing attenuation.

[0049] The manufacturing method of the air-core microstructured optical fiber preform provided in this embodiment includes the following steps.

[0050] Assembly of nested structure unit: As shown in Figure 2, a prefabricated inner glass tube with an outer diameter of 3.2 mm and a wall thickness of 0.12 mm and a support sheet with a width of 1.5 mm and a thickness of 0.12 mm are fixed with a mold to the extension lines on both sides of the diameter of the inner glass tube, and both are fused and fixed by oxyhydrogen flame or laser welding. Next, as shown in Figure 3, they are inserted into a prefabricated outer glass tube with an outer diameter of 6.3 mm and a wall thickness of 0.13 mm to form a nest, fixed with an end mold, and the support sheet and the inner wall of the outer glass tube are fused and fixed by oxyhydrogen flame or laser welding.

[0051] Assembling the clad air-core sleeve: The six nest structure units are inserted into the clad air-core sleeve in sequence to form a nest, and mechanical visual positioning is performed each time a nest structure unit is inserted. That is, the camera side projects a partial or entire cross-sectional image of a predetermined air-core microstructure optical fiber preform in advance, and the inserted nest mechanism unit is positioned at the inner bottom of the side-mounted clad air-core sleeve, and the microstructure unit is rotated so that the support sheet and the support sheet in the projected cross-sectional image are aligned, and the nest structure unit is positioned at the position of the support sheet. After the adjustment is completed, the nest structure unit and the clad air-core sleeve are melted and fixed together by oxyhydrogen flame or laser welding. Next, the clad air-core sleeve is rotated so that the fixed nest structure unit is at the projection position of the other nest structure units in the projected cross-sectional image, and the next nest structure unit is inserted, and the above operations are repeated until all the nest microstructure units are fixed at the preset positions.

[0052] This embodiment uses cross-sectional imaging to perform mechanical visual positioning, is not limited by the machining accuracy of the end sleeve, and has good accuracy and lot-to-lot consistency.

[0053] The air-core optical fiber drawn by the air-core optical fiber preform provided in this embodiment includes an outer cladding sleeve 1 having a nested microstructure 5, as shown in FIG. 1, which is surrounded by the nested microstructure 5 to form a core region. The cladding region is composed of the outer cladding sleeve 1 and a number of nested microstructure units 5. The nested microstructure unit 5 is composed of a first anti-resonant ring 2 and a second anti-resonant ring 3 connected via a connecting bridge 4. The core region is surrounded by the nested microstructure 5. The core region is the maximum inscribed circle tangent to the nested microstructure unit 5, and has a diameter D0 of 34.5 μm. The equivalent area S1 of the first anti-resonant ring is 480 μm. 2 The thickness T1 of the first anti-resonant ring is 0.5 μm. The equivalent area S2 of the second anti-resonant ring is 122 μm. 2 and the thickness T2 of the second anti-resonant ring is 0.45 μm. The thickness T0 of the connecting bridge 4 is 0.45 μm. The spacing g between the nested microstructure units 5 is 4.4 μm. The number of anti-resonant layers is increased by adding a second anti-resonant ring inside the first anti-resonant ring, and the number of anti-resonant layers is increased to seven layers (5a to 5g) as shown in FIG. 1. The advantage of this is that more light can be reflected and transmitted from the cladding to the core layer, and the purpose of further reducing optical fiber attenuation is achieved. As shown in FIG. 15, the mode field distribution at 1550 nm of the modeled optical fiber of Example 1 shows that light is well confined and transmitted in the air-core core. As shown in FIG. 16, the wavelength change of loss corresponding to the modeled optical fiber shown in Example 1 can be made the minimum attenuation is 0.01 dB / km or less. Here, the attenuation in the document US10527782B2 is shown in FIG. 16 to FIG. 18 as Comparative Example 1. Simulations show that the anti-resonant fiber designed in this invention has significantly lower attenuation.

[0054] The air-core microstructured optical fiber preform provided by this embodiment can control the curvature and thickness of the reflective surface of the microstructure of the cladding of the optical fiber finally formed by drawing by controlling the amount of gas flowing into each closed region during drawing. The air-core optical fibers having the structures shown in Examples 1-1 to 1-6 shown in FIG. 4 are all structural deformations that occur when the air-core optical fiber preform shown in Example 1 is drawn, and the first anti-resonant ring and the second anti-resonant ring can be deformed into a circular, elliptical, runway, or "8" shape, but are not limited thereto, and have low-loss air-core optical transmission capabilities. The attenuation curves of Examples 1-1 and 1-6 are as shown in FIG. 16. The structural parameters of Examples 1 and 1-1 to 1-6 are as shown in Table 1. The curvature radii 1, 2, 3, and 4 correspond to the curvature radii in the normal direction of the reflecting surfaces 5a, 5c, 5e, and 5g, respectively.

[0055] [Table 1]

[0056] [Example 2] The air-core optical fiber provided in this embodiment has the same basic structure as that of the first embodiment, and is different only in that the connecting bridge of the nested structure unit has a different crossing angle with the normal direction of the reflecting surface. As shown in FIG. 5, the connecting bridge of the structure of the second embodiment forms a certain angle with the normal direction of the reflecting surface. The connecting bridges in the second embodiment are distributed at 60° with respect to the normal direction. The core region diameter D0 is 37.8 μm, and the equivalent area S1 of the first anti-resonant ring is 585 μm. 2 The thickness T1 of the first anti-resonant ring is 0.64 μm, and the equivalent area S2 of the second anti-resonant ring is 190 μm 2 The thickness T2 of the second anti-resonant ring is 0.76 μm, and the thickness T0 of the connecting bridge is 0.56 μm. The attenuation curve of the second embodiment is shown in FIG.

[0057] [Examples 3 and 4] The air-core optical fiber provided in this embodiment has the same basic structure as that of the first embodiment, and only the distribution of the connecting bridges of the nested structure units is different. In the structure of the third embodiment, as shown in FIG. 6, the connecting bridges formed by one connecting bridge are distributed in the normal direction, while the connecting bridges formed by the other connecting bridge are distributed perpendicular to the normal direction. The diameter D0 of the core region is 36.4 μm, and the equivalent area S1 of the first anti-resonant ring is 540 μm. 2 The thickness T1 of the first anti-resonant ring is 0.46 μm, and the equivalent area S2 of the second anti-resonant ring is 180 μm. 2 The thickness T2 of the second anti-resonant ring is 0.46 μm, the thickness T0 of the connecting bridge is 0.51 μm, the angle between the two connecting bridges and the normal direction in the fourth embodiment is 30°, the diameter D0 of the core region is 31.3 μm, and the equivalent area S1 of the first anti-resonant ring is 448 μm. 2 The thickness T1 of the first anti-resonant ring is 0.68 μm, and the equivalent area S2 of the second anti-resonant ring is 132 μm 2 The thickness T2 of the second anti-resonant ring is 0.46 μm, and the thickness T0 of the connecting bridge is 0.59 μm. The attenuation curve of Example 4 is shown in FIG.

[0058] [Example 5] The air-core optical fiber provided in this embodiment adopts a non-concentric nest microstructure. Its basic structure is the same as that of the first embodiment, but the lengths and azimuth angles of the connecting bridges on both sides are different. As shown in FIG. 7, the structure of the fifth embodiment has connecting bridges distributed at 90° along the normal direction, the length of the short connecting bridge is 1 / 4 of the length of the long connecting bridge, the diameter D0 of the core region is 33.2 μm, and the equivalent area S1 of the first anti-resonant ring is 515 μm. 2 The thickness T1 of the first anti-resonant ring is 0.77 μm, and the equivalent area S2 of the second anti-resonant ring is 155 μm. 2The thickness T2 of the second anti-resonant ring is 0.56 μm, and the thickness T0 of the connecting bridge is 0.43 μm. The attenuation curve of Example 5 is shown in FIG.

[0059] [Example 6] The air-core optical fiber provided in this embodiment has a nested microstructure in which the connecting bridges are located on the non-diameter chords of the outer circular glass tube, making the inner and outer circular glass tubes concentric or non-concentric nested. The structure is shown in Figure 8. The connecting bridges in the sixth embodiment are distributed at 90° along the normal direction, and the connecting bridges and the center of the first anti-resonant ring are offset by 1 / 6 of the diameter of the first anti-resonant ring. The core region diameter D0 is 38.5 μm, and the equivalent area S1 of the first anti-resonant ring is 590 μm. 2 The thickness T1 of the first anti-resonant ring is 0.87 μm, and the equivalent area S2 of the second anti-resonant ring is 187 μm. 2 The thickness T2 of the second anti-resonant ring is 0.69 μm, and the thickness T0 of the connecting bridge is 0.57 μm. Here, the concentric nested attenuation curve of Example 6 is shown in FIG.

[0060] [Examples 7 and 8] A single connecting bridge can realize seven layers of anti-resonance surfaces, and the structure of the air-core optical fiber can be seen in Fig. 9. The connecting bridges in the seventh embodiment are distributed at 90° in the normal direction, the length of the connecting bridge is half the diameter of the first anti-resonance ring, the diameter D0 of the core region is 31.6 μm, and the equivalent area S1 of the first anti-resonance ring is 488 μm. 2 The thickness T1 of the first anti-resonant ring is 0.42 μm, and the equivalent area S2 of the second anti-resonant ring is 122 μm. 2 The thickness T2 of the second anti-resonant ring is 0.52 μm, and the thickness T0 of the connecting bridge is 0.57 μm. The connecting bridges of Example 8 are distributed at 90° in the normal direction, the length of the connecting bridge is 1 / 6 of the diameter of the first anti-resonant ring, the diameter D0 of its core region is 25.8 μm, and the equivalent area S1 of the first anti-resonant ring is 443 μm. 2The thickness T1 of the first anti-resonant ring is 0.75 μm, and the equivalent area S2 of the second anti-resonant ring is 114 μm. 2 , the thickness T2 of the second anti-resonant ring is 0.63 μm, and the thickness T0 of the connecting bridge is 0.65 μm. The attenuation curve of Example 7 is shown in FIG.

[0061] [Examples 9 and 10] The diameter connecting bridge can more accurately determine the relative positions of the anti-resonant rings in the air-core microstructure, and can improve the conformity of the microstructure, as shown in Figure 10. The connecting bridge in Example 9 passes through the center of the first anti-resonant ring and distributes at 90° in the normal direction, and the second anti-resonant ring is fixed to the side closer to the core through the connecting bridge, and its core area diameter D0 is 28.9 μm, and the equivalent area S1 of the first anti-resonant ring is 457 μm. 2 The thickness T1 of the first anti-resonant ring is 0.52 μm, and the equivalent area S2 of the second anti-resonant ring is 83 μm. 2 The thickness T2 of the second anti-resonant ring is 0.48 μm, and the thickness T0 of the connecting bridge is 0.64 μm. The connecting bridge of Example 10 passes through the center of the first anti-resonant ring and is distributed at 90° in the normal direction, and the second anti-resonant ring is fixed to the side closer to the cladding via the connecting bridge, and its core region diameter D0 is 29.6 μm, and the equivalent area S1 of the first anti-resonant ring is 460 μm. 2 The thickness T1 of the first anti-resonant ring is 0.86 μm, and the equivalent area S2 of the second anti-resonant ring is 102 μm. 2 The thickness T2 of the second anti-resonant ring is 0.74 μm, and the thickness T0 of the connecting bridge is 0.79 μm. The attenuation curve of Example 9 is shown in FIG.

[0062] [Example 11] The purpose of supporting the second anti-resonant ring can also be achieved by using three or more connecting bridges. The number of connecting bridges in Example 11 of FIG. 11 is three. The connecting bridge is based on the structure of Example 1, and the third connecting bridge is added along the normal direction. The core area diameter D0 is 26.5 μm, and the equivalent area S1 of the first anti-resonant ring is 432 μm. 2 The thickness T1 of the first anti-resonant ring is 0.41 μm, and the equivalent area S2 of the second anti-resonant ring is 113 μm 2 , the thickness T2 of the second anti-resonant ring is 0.53 μm, and the thickness T0 of the connecting bridge is 0.55 μm. The attenuation curve is shown in FIG.

[0063] [Examples 12 and 13] More glass tubes and more anti-resonant rings can also be added to the nested glass tubes, as in Example 12 and Example 13 of FIG. 5, to achieve similar low-loss performance. Example 12 adds a third anti-resonant ring inside the second anti-resonant ring through a connecting bridge, and the connecting bridge between the first and second anti-resonant rings and the connecting bridge between the second and third anti-resonant rings are on the same diameter. Its core area diameter D0 is 33.8 μm, and the equivalent area S1 of the first anti-resonant ring is 447 μm. 2 The thickness T1 of the first anti-resonant ring is 0.44 μm, and the equivalent area S2 of the second anti-resonant ring is 143 μm 2 The thickness T2 of the second anti-resonant ring is 0.43 μm, and the equivalent area S3 of the third anti-resonant ring is 32 μm. 2 , the thickness T3 of the third anti-resonant ring is 0.48 μm, and the thickness T0 of the connecting bridge is 0.54 μm. Example 13 adds to Example 1 by directly nesting the third anti-resonant ring inside the second anti-resonant ring, and the third anti-resonant ring is mounted in the second anti-resonant ring in a tangential support manner, with the junction being the radial intersection of the outside of the second anti-resonant ring with the optical fiber. Its core region diameter D0 is 35.4 μm, and the equivalent area S1 of the first anti-resonant ring is 477 μm. 2The thickness T1 of the first anti-resonant ring is 0.45 μm, and the equivalent area S2 of the second anti-resonant ring is 157 μm 2 The thickness T2 of the second anti-resonant ring is 0.54 μm, and the equivalent area S3 of the third anti-resonant ring is 38 μm. 2 The thickness T3 of the third anti-resonant ring is 0.66 μm, and the thickness T0 of the connecting bridge is 0.57 μm. The attenuation curve of Example 12 is shown in FIG.

[0064] [Example 14] The multi-layer nested nested structure unit is more difficult to assemble, and the use of connecting bridges greatly improves the manufacturing accuracy and the stability of optical fiber drawing. At the same time, as shown in FIG. 13, the combination of ellipse and circle can realize an accurate multi-layer nested structure. The second anti-resonant ring of Example 14 is elliptical, and the third anti-resonant ring is nested inside the second anti-resonant ring, and the third anti-resonant ring is circular and nested tangent to the second anti-resonant ring. Its core area diameter D0 is 47.9 μm, and the equivalent area S1 of the first anti-resonant ring is 677 μm. 2 the thickness T1 of the first anti-resonant ring is 1.13 μm, the equivalent area S2 of the second anti-resonant ring is 159 μm, the thickness T2 of the second anti-resonant ring is 1.05 μm, and the equivalent area S2 of the third anti-resonant ring is 64 μm 2 , the thickness T3 of the third anti-resonant ring is 0.93 μm, and the thickness T0 of the connecting bridge is 0.89 μm. The attenuation curve of Example 14 is shown in FIG.

[0065] [Examples 15 to 18] In addition, the air-core microstructured optical fiber can reduce the symmetry of the structure and achieve large birefringence performance by introducing capillaries with different shapes, different thicknesses, different sizes, and different numbers of reflective layers, as shown in Figure 14. For example, Example 15 is based on the structure of Example 1, and changes the shape of the first resonant ring of the two symmetric distributions from circular to elliptical, and the long semi-axis of the ellipse is 16.4 μm and the short semi-axis is 12.4 μm long, and the remaining parameters are the same as those of Example 1, and its birefringence is 4.5 × 10 -4 The air-core microstructured optical fiber shown in Example 16 improves the birefringence performance of the air-core microstructured optical fiber by changing the thickness. Based on the structure of Example 1, the thickness of the first resonant ring with two symmetrical distributions is changed to 1.1 μm, and the remaining parameters are the same as those of Example 1, and its birefringence is 3.7 × 10 -5 The air-core microstructured optical fiber shown in Example 17 has an equivalent area of ​​the first resonant ring of two symmetrical distributions of 570 μm2 based on the structure of Example 1. 2 The remaining parameters were the same as in Example 1, and the birefringence was 5.3 × 10 -4 The air-core microstructured optical fiber shown in Example 18 can still achieve a large birefringence effect after removing the two symmetrically distributed second resonant rings and their connecting bridges based on the structure of Example 1, and its birefringence is 1.8 × 10 -5 In addition, the attenuation curve of Example 17, as shown in FIG. 18, also has the performance of low-loss transmission.

[0066] In the above-mentioned embodiments, the preform can be manufactured by using an end face sleeve type method, and the specific method is as follows.

[0067] The axial end faces of the glass tube and the connecting bridge are fixed to a mold, and assembled into a nested structure unit, and each part of the nested structure unit is fused and fixed.

[0068] In assembling the clad air-core sleeve, the cross section of the end sleeve has a positioning groove corresponding to the connecting bridge position of the designed air-core microstructured optical fiber preform, and multiple nest structure units are fixed by the positioning groove, and then inserted into the clad air-core sleeve, and the two are melted and fixed by oxyhydrogen flame or laser welding.

[0069] The end face sleeve type method is used to assemble the air-core microstructured optical fiber preform. Although the precision is limited by the machining process, it can position multiple nested structure units at the same time, which is highly efficient and suitable for mass production of large-sized air-core optical fiber preforms.

[0070] Those skilled in the art will easily understand that the above are only preferred embodiments of the present invention, and do not limit the present invention, and any modifications, equivalent replacements and improvements made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

[0071] (Additional Note) (Appendix 1) An air-core microstructured optical fiber preform, comprising: a cladding air-core sleeve; and a plurality of nested units arranged on an inner wall of the cladding air-core sleeve, the nested units being used to form an air-core region of an inscribed circle dimension thereof, the nested units comprising multi-layer nested glass tubes; The air-core microstructured optical fiber preform is characterized in that a support sheet is provided between the glass tubes of at least one pair of adjacent nests of the multi-layer nested glass tubes, and the support sheet firmly fixes the glass tubes of the adjacent nests so that the glass tubes of the adjacent nests form at least seven reflective surfaces.

[0072] (Appendix 2) 2. The air-core microstructured optical fiber preform of claim 1, wherein the support sheet is distributed other than along the normal to the reflecting surface, and the normal to the reflecting surface passes through the geometric center of the cross-section of the preform.

[0073] (Appendix 3) 3. The air-core microstructured optical fiber preform according to claim 1 or 2, wherein the support sheet is parallel to a tangent direction of the reflective surface.

[0074] (Appendix 4) The air-core microstructured optical fiber preform according to claim 1 or 2, characterized in that a pair of support sheets are included between the glass tubes of adjacent nests, and the support sheets are arranged symmetrically with respect to the normal direction of the reflective surface or symmetrically with respect to the geometric center of the nest structure unit.

[0075] (Appendix 5) 2. The air-core microstructured optical fiber preform of claim 1, wherein at least one of the glass tubes of the adjacent nest has a circular cross-section, and preferably an outer glass tube of the adjacent nest has a circular cross-section.

[0076] (Appendix 6) The hollow-core microstructured optical fiber preform described in any one of Appendices 1 to 5, characterized in that the nested structure unit includes an inner glass tube and an outer glass tube which are concentrically nested, the inner glass tube and the outer glass tube having a circular cross-section, and a pair of support sheets are included between the inner glass tube and the outer glass tube, and the support sheets are arranged symmetrically with respect to the diameter of the inner glass tube with respect to the normal direction of the reflective surface.

[0077] (Appendix 7) 2. The air-core microstructured optical fiber preform of claim 1, comprising four or more nested structure units.

[0078] (Appendix 8) A method for producing an air-core microstructured optical fiber preform according to any one of claims 1 to 7, comprising the steps of: Assembly of nested structural unit: For a nested glass tube with an adjacent support sheet, fix the support sheet and the nested glass tube in a preset position and a preset direction from inside to outside. Assembly of the clad air-core sleeve: A preset number of nesting structural units and clad air-core sleeves are nested, positioned by a support sheet, and the nesting structural units and clad air-core sleeves are fixed at preset positions.

[0079] (Appendix 9) The assembly of the nest structure unit is specifically performed as follows: First, fix the inner glass tube and the support sheet, and use an auxiliary mold in the fixing process to maintain the relative position of the support sheet and the inner glass tube; Next, the inner glass tube with the support sheet fixed thereto and the outer glass tube are nested, and the support sheet and the outer glass tube are arranged and fixed laterally so that they are in a preset position.

[0080] (Appendix 10) 9. The method for producing an air-core microstructured optical fiber preform according to claim 8, wherein the positioning by the support sheet is performed by mechanical visual positioning using a cross-sectional image method or mechanical positioning using an end face sleeve.

[0081] (Appendix 11) An air-core microstructured optical fiber, comprising an outer cladding sleeve having a plurality of nested microstructures surrounding a core region, the nested microstructures being distributed on an inner wall of the outer cladding sleeve and tangentially fixed to the inner wall of the outer cladding sleeve; 1. An air-core microstructured optical fiber, comprising: a nested structure including at least first and second anti-resonant rings nested from the outside to the inside, with a connecting bridge between the first and second anti-resonant rings, and the nested microstructure having seven reflective surfaces formed by at least the first and second anti-resonant rings.

[0082] (Appendix 12) Among the plurality of nested microstructures, the inscribed circle of the reflecting surface with the same distance from the axis of the hollow-core microstructure optical fiber divides the cladding into a plurality of regions, which are, from the inside out, a core region with a diameter D0, a first anti-resonant ring with a diameter D1, a second anti-resonant ring with a diameter D2, and a connection bridge with a thickness T0. The diameter D0 of the core region is 10 to 50 μm, and more preferably, the diameter D0 of the core region is 10 to 20 μm, or more preferably, the diameter D0 of the core region is 20 to 30 μm, or more preferably, the diameter D0 of the core region is 30 to 40 μm, or more preferably, the diameter D0 of the core region is 40 to 50 μm. The equivalent area S1 of the first anti-resonant ring is 20 to 1600 μm 2 and the equivalent outer diameter S2 of the second anti-resonant ring is 3 to 500 μm 2 The wall thickness T1 of the first anti-resonant ring is 0.1 to 2.0 μm, the wall thickness T2 of the second anti-resonant ring is 0.1 to 2.0 μm, and the wall thickness T0 of the connection bridge is 0.1 to 2.0 μm. The hollow-core microstructure optical fiber according to Supplementary Note 11 is characterized in this.

[0083] (Supplementary Note 13) The reflecting surface includes a positive-curvature reflecting surface and a negative-curvature reflecting surface. The range of the radius of curvature of the positive-curvature reflecting surface is 0.2 to 150 μm, and the range of the radius of curvature of the negative-curvature reflecting surface is -150 to -0.2 μm. The hollow-core microstructure optical fiber according to Supplementary Note 11 is characterized in this.

[0084] (Supplementary Note 14) The first anti-resonant ring and / or the second anti-resonant ring is formed in a circular, elliptical, or figure-eight shape. The hollow-core microstructure optical fiber according to Supplementary Note 11 is characterized in this.

[0085] (Supplementary Note 15) The minimum distance g between the nested microstructures satisfies the relationship of 0 < g ≤ 15 μm, and the ratio g / T1 of the minimum distance g between the nested microstructures to the wall thickness T1 of the first anti-resonant ring is 5 to 20, or 1 to 6, or 15 to 25. The hollow-core microstructure optical fiber according to Supplementary Note 11 is characterized in this.

[0086] (Appendix 16) 12. The air-core microstructured optical fiber of claim 11, wherein the refractive index of the nested microstructure material is <2.0, more preferably <1.5.

[0087] (Appendix 17) 12. The air-core microstructured optical fiber of claim 11, wherein the nested microstructures have different reflective properties, and preferably the nested microstructures have different shapes, thicknesses, and / or dimensions, providing asymmetry in the cross-section of the air-core microstructured fiber. Structure Fiber Optic.

Claims

1. An air-core microstructured optical fiber preform, comprising: a cladding air-core sleeve; and a plurality of nested units arranged on an inner wall of the cladding air-core sleeve, the nested units being used to form an air-core region of an inscribed circle dimension thereof, the nested units comprising multi-layer nested glass tubes; The air-core microstructured optical fiber preform is characterized in that a support sheet is provided between the glass tubes of at least one pair of adjacent nests of the multi-layer nested glass tubes, and the support sheet firmly fixes the glass tubes of the adjacent nests so that at least seven reflective surfaces are formed by the glass tubes of the adjacent nests.

2. 2. The air-core microstructured optical fiber preform of claim 1, wherein the support sheet is distributed other than along a normal to the reflective surface, and the normal to the reflective surface passes through a geometric center of a cross section of the preform.

3. 3. The air-core microstructured optical fiber preform according to claim 1, wherein the support sheet is parallel to the tangent direction of the reflective surface.

4. The air-core microstructured optical fiber preform according to claim 1 or 2, characterized in that a pair of support sheets are included between the glass tubes of the adjacent nests, and the support sheets are arranged symmetrically with respect to the normal direction of the reflective surface or symmetrically with respect to the geometric center of the nest structure unit.

5. 10. The air-core microstructured optical fiber preform of claim 1, wherein at least one of the glass tubes of the adjacent nests has a circular cross-section.

6. The hollow-core microstructured optical fiber preform according to claim 1 or 2, characterized in that the nested structure unit includes an inner glass tube and an outer glass tube which are concentrically nested, the inner glass tube and the outer glass tube having a circular cross-section, and a pair of support sheets are included between the inner glass tube and the outer glass tube, and the support sheets are arranged symmetrically with respect to the diameter of the inner glass tube with respect to the normal direction of the reflective surface.

7. 10. The air-core microstructured optical fiber preform of claim 1, comprising four or more nested units.

8. 3. The method for producing an air-core microstructured optical fiber preform according to claim 1, comprising the steps of: Assembly of nested structural unit: For a nested glass tube with an adjacent support sheet, fix the support sheet and the nested glass tube in a preset position and a preset direction from inside to outside. Assembly of the clad air-core sleeve: A preset number of nesting structural units and clad air-core sleeves are nested, and positioned by a support sheet, and the nesting structural units and clad air-core sleeves are fixed at preset positions.

9. The assembly of the nest structure unit is specifically performed as follows: First, fix the inner glass tube and the support sheet, and use an auxiliary mold in the fixing process to maintain the relative position of the support sheet and the inner glass tube; The method for manufacturing an air-core microstructured optical fiber preform according to claim 8, characterized in that the inner glass tube and the outer glass tube with the support sheet fixed thereto are nested, and then the support sheet and the outer glass tube are arranged and fixed laterally so that they are in a preset position.

10. 9. The method for manufacturing an air-core microstructured optical fiber preform according to claim 8, wherein the positioning by the support sheet is mechanical visual positioning using a cross-sectional image method or mechanical positioning using an end face sleeve.

11. An air-core microstructured optical fiber, comprising an outer cladding sleeve having a plurality of nested microstructures surrounding a core region, the nested microstructures being distributed on an inner wall of the outer cladding sleeve and tangentially fixed to the inner wall of the outer cladding sleeve; 1. An air-core microstructured optical fiber, comprising: a first anti-resonant ring having a first width and a second width; a nested microstructure having at least a first anti-resonant ring and a second anti-resonant ring; a connecting bridge between the first anti-resonant ring and the second anti-resonant ring; and a nested microstructure having seven reflective surfaces formed by the at least the first anti-resonant ring and the second anti-resonant ring.

12. Among the plurality of nested microstructures, the inscribed circles of the reflecting surfaces at the same distance from the axis of the air-core microstructured optical fiber divide the cladding into a plurality of regions, each of which has a diameter D from the inside to the outside. ０ Core area of ​​diameter D １ A first anti-resonant ring of diameter D ２ A second anti-resonant ring of thickness T ０ and the diameter of the core region D ０ is 10 to 50 μm, The equivalent area S of the first anti-resonant ring １ 20 to 1600 μm ２ and the equivalent outer diameter S of the second anti-resonant ring ２ 3 to 500 μm ２ and the thickness T of the first anti-resonant ring １ is 0.1 to 2.0 μm, and the thickness T of the second anti-resonant ring ２ is 0.1 to 2.0 μm, and the wall thickness T ０ The air-core microstructured optical fiber according to claim 11, characterized in that the thickness is 0.1-2.0 μm.

13. The air-core microstructured optical fiber according to claim 11, characterized in that the reflective surface includes a positive curvature reflective surface and a negative curvature reflective surface, the radius of curvature of the positive curvature reflective surface is in the range of 0.2 to 150 μm, and the radius of curvature of the negative curvature reflective surface is in the range of −150 to −0.2 μm.

14. The air-core microstructured optical fiber of claim 11, wherein the first anti-resonant ring and / or the second anti-resonant ring are shaped as a circle, an ellipse, or a figure-eight.

15. The minimum distance g between the nested microstructures satisfies the relationship 0<g≦15 μm, and the minimum distance g between the nested microstructures and the wall thickness T of the first anti-resonant ring １ Ratio of g / T １ is 5-20, or 1-6, or 15-25.

16. The air-core microstructured optical fiber of claim 11, wherein the refractive index of the nested microstructure material is <2.

0.

17. The air-core microstructured optical fiber of claim 11, wherein a plurality of said nested microstructures have different reflective properties, resulting in an asymmetry in the cross-section of said air-core microstructured optical fiber.

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