Fluoride hollow-core anti-resonant optical fiber and method of making same

Abstract

This invention relates to the field of hollow-core optical fiber technology, and more particularly to a fluoride hollow-core antiresonant optical fiber and its fabrication method. The optical fiber comprises, from the inside out, an air core, an inner cladding, an outer cladding, and a protective coating; both the inner and outer cladding are made of fluoride glass free of monovalent alkali metal fluorides, and the refractive index of the fluoride glass is greater than that of the air core; the inner cladding is an array structure formed by multiple inner capillaries arranged in a ring-shaped periodic pattern around the air core; the outer cladding is a solid fluoride glass layer wrapped around the inner cladding; the inner and outer claddings are fixed together with epoxy resin; the fluoride glass includes ZrF4, ZnF2, BaF2, SrF2, CaF2, AlF3, and YF3. The advantages are: the use of deliquescent fluoride glass free of monovalent alkali metal fluorides solves the problems of easy moisture absorption and crystallization of traditional fluoride fibers, achieving low-loss transmission in the mid-infrared region at wavelengths of 2-5 μm and above.

Description

Technical Field

[0001] This invention relates to the field of hollow optical fiber technology, and in particular to a fluoride hollow anti-resonant optical fiber and its preparation method. Background Technology

[0002] Mid-infrared lasers have significant applications in gas detection, medical surgery, infrared countermeasures, and high-harmonic generation. Optical fiber, as the core medium for laser transmission and generation, plays a crucial role in this process. Fluoride glass, a special type of glass-fiber material, possesses a wide transmission window from the ultraviolet to the mid-infrared band, low phonon energy, and a high concentration of rare-earth ion doping, making it an ideal material for mid-infrared laser generation and transmission, and thus possessing significant research and application value.

[0003] Currently, mid-infrared optical fibers are mainly divided into two categories: solid-core optical fibers and hollow-core optical fibers, specifically including: 1. Solid Fluoride Fibers: Solid fluoride glass fibers, represented by ZBLAN (fluorozirconate), InF3 (fluoroindium), and AlF3 (fluoroaluminate), are currently the most mature mid-infrared fibers. They possess extremely low phonon energy and wide transmission windows, and rare-earth-doped solid fluoride fibers have been widely used in mid-infrared lasers. However, solid fibers suffer from high nonlinear coefficients, low damage thresholds (prone to end-face and thermal damage), and difficulties in flexibly controlling material dispersion, which limit their application in high-power ultrashort pulse laser transmission.

[0004] 2. Quartz Hollow-Core Antiresonant Fiber: Hollow-core antiresonant fiber utilizes the principle of antiresonant reflection waveguides to confine light within an air core, exhibiting extremely low nonlinearity, extremely high damage threshold, and low transmission loss. However, the absorption loss of the quartz matrix material increases sharply beyond 2.4 μm, meaning that the loss of quartz-based hollow-core fiber above 4 μm is mainly limited by matrix absorption, failing to meet the transmission requirements of the longer mid-infrared band.

[0005] 3. Chalcogenide glass hollow antiresonant fiber: Chalcogenide glass has a wider mid-infrared transmission range and lower phonon energy, but chalcogenide glass materials are highly toxic, have low glass transition temperature and laser damage threshold, and the sulfur-hydrogen bond (SH) in chalcogenide glass has strong absorption near 4μm, which limits the application of this material in the mid-infrared band.

[0006] Although there is theoretical research on fluoride microstructure optical fibers, fluoride glasses have characteristics such as steep viscosity-temperature change curves and easy crystallization during the drawing process; at the same time, traditional fluoride glasses (such as ZBLAN) have weak chemical stability and are prone to moisture absorption and deliquescence, leading to performance degradation. It is difficult to maintain the complex microstructure morphology in the fluoride glass system using conventional stacking-drawing processes, resulting in a long-term technical bottleneck in the preparation and application of fluoride glass hollow anti-resonant optical fibers. Specifically, the existing technology has the following shortcomings: (1) Quartz-based hollow anti-resonant optical fibers are limited by the absorption of the matrix material in the long-wave mid-infrared band. Even if the optical field overlap is reduced by the hollow structure, the transmission loss is still difficult to further reduce when the wavelength is greater than 4μm; (2) Chalcogenide glass materials are highly toxic and have poor physical and chemical stability, and are not ideal matrix materials for mid-infrared hollow anti-resonant optical fibers; (3) Fluoride glasses are prone to deliquescence and have poor environmental stability. Existing fluoride optical fibers are prone to performance degradation during long-term use, which limits their engineering applications.

[0007] Therefore, how to fabricate a hollow anti-resonant optical fiber that combines wide mid-infrared transmission and low material absorption to meet the low-loss laser transmission requirements in the long-wave mid-infrared band has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0008] To address the aforementioned problems, this invention provides a fluoride hollow anti-resonant optical fiber and its preparation method.

[0009] The primary objective of this invention is to provide a fluoride hollow anti-resonant optical fiber, comprising an air core, an inner cladding, an outer cladding, and a protective coating arranged sequentially from the inside out. Both the inner and outer cladding layers are made of fluoride glass that does not contain monovalent alkali metal fluorides. The refractive index of the fluoride glass is greater than that of the air core. The inner cladding is an array structure formed by multiple inner capillaries arranged in a ring-shaped periodic pattern around the air core; The outer cladding is a solid fluoride glass layer that wraps around the inner cladding; The inner and outer cladding layers are fixed together with high-temperature resistant epoxy resin adhesive.

[0010] Preferably, the fluoride glass includes ZrF4, ZnF2, BaF2, SrF2, CaF2, AlF3, and YF3.

[0011] Preferably, the composition of the fluoride glass is ZrF4-ZnF2-BaF2-SrF2-CaF2-AlF3-YF3, wherein the molar percentage of each component is ZrF4 10~30 mol%, ZnF 25~40 mol%, BaF 25~30 mol%, SrF 25~20 mol%, CaF2 10~20 mol%, AlF3 10~20 mol%, and YF 35~10 mol.

[0012] Preferably, the inner cladding layer includes 6 to 10 inner capillaries, each inner capillary having an outer diameter of 10 to 30 μm and a wall thickness of 0.3 to 1.5 μm; The diameter of the air core is 50~150μm.

[0013] Preferably, the protective coating is a polymer coating with a thickness of 10~50μm, and the material is selected from UV-curable acrylate.

[0014] Preferably, the outer cladding layer has a diameter of 200~400μm and a thickness of 50~150μm.

[0015] The second objective of this invention is to provide a method for preparing fluoride hollow antiresonant optical fiber, which specifically includes the following steps: S1. Fluoride raw materials are mixed in a closed environment with a water vapor content of less than 10 ppm and an oxygen content of less than 1 ppm, and melted at 850~900℃ for 1~2 hours. The mixture is then rotated to form a pre-formed tube with an outer glass cladding. S2. Fluoride raw materials are mixed in a closed environment with a water vapor content of less than 10 ppm and an oxygen content of less than 1 ppm, and melted at 850~900℃ for 1~2 hours. The mixture is then extruded to obtain an inner-clad capillary preform. S3. The outer cladding glass preform and the inner cladding capillary preform are ultrasonically cleaned and nitrogen-dried; the inner cladding capillary preform is evenly arranged on the inner wall of the outer cladding glass preform and fixed to form an optical fiber preform. S4. The optical fiber preform is heated to 310~340℃ in a protective gas atmosphere for drawing, while the protective gas is introduced into the air core and inner cladding capillary to maintain the hollow structure, thus producing hollow optical fiber. S5. A protective coating is applied to the surface of the hollow optical fiber and cured to obtain a fluoride hollow anti-resonant optical fiber.

[0016] Preferably, the specific method for rotational molding in step S1 is as follows: pour the molten fluoride glass liquid into a high-speed rotating copper mold and rotate for 1 minute, then anneal the copper mold at 310~340℃ for 3~5 hours.

[0017] Preferably, in step S4, a protective gas, namely nitrogen or argon, is introduced into the air core and inner cladding capillary at a pressure of 0.5~5 kPa and a flow rate of 2~10 L / min; the drawing speed is 2~10 m / min.

[0018] Preferably, the curing method is ultraviolet curing.

[0019] Compared with the prior art, the present invention can achieve the following beneficial effects: (1) In this invention, fluoride glass with good stability is used to replace quartz glass and chalcogenide glass. By utilizing its wide infrared transmission window characteristics, the working band of hollow anti-resonant optical fiber is extended from near-infrared to 2~5μm or even longer wavelength. (2) In view of the fact that fluoride glass is prone to moisture absorption, multi-layer protection measures are adopted: the environmental atmosphere is strictly controlled during the preparation process, and glass preparation and fiber drawing are carried out in a dry nitrogen or argon atmosphere. A dense polymer protective coating is applied to the surface of the optical fiber to prevent moisture intrusion, thus solving the problem of the difficulty in preparing fluoride glass hollow anti-resonant optical fiber.

[0020] (3) The total transmission loss of the fluoride hollow anti-resonant fiber prepared by the present invention is significantly reduced compared with that of the quartz hollow anti-resonant fiber. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the cross-section of a fluoride hollow anti-resonant optical fiber provided according to an embodiment of the present invention.

[0022] Figure 2 This is a flowchart of the fabrication process of fluoride hollow antiresonant optical fiber according to an embodiment of the present invention.

[0023] Figure 3 This is a schematic diagram showing the calculation results comparing the total transmission loss of the fluoride glass hollow anti-resonant optical fiber and the quartz optical fiber of the present invention.

[0024] Figure label: 1. Air core; 2. Inner cladding; 3. Outer cladding; 4. Protective coating. Detailed Implementation

[0025] In the following description, embodiments of the invention will be described with reference to the accompanying drawings. In the description below, the same modules are denoted by the same reference numerals. Where the same reference numerals are used, their names and functions are also the same. Therefore, their detailed description will not be repeated.

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not constitute a limitation thereof.

[0027] This invention provides a fluoride hollow anti-resonant optical fiber. The optical fiber uses fluoride glass as the matrix material and achieves low-loss transmission of light in the air core by designing a periodically arranged nested capillary anti-resonant structure in the cladding. The working band is extended from near-infrared to 2~5μm or even longer wavelengths. Optical fiber comprises, from the inside out, an air core, an inner cladding, an outer cladding, and a protective coating; Both the inner and outer cladding layers are made of fluoride glass that does not contain monovalent alkali metal fluorides (NaF, LiF, KF). The fluoride glasses include ZrF4, ZnF2, BaF2, SrF2, CaF2, AlF3, and YF3; the content range of each component is shown in Table 1 below: Table 1. Fluoride Glass Formulation Table

[0028] In some embodiments, the fluoride glass composition is ZrF4-ZnF2-BaF2-SrF2-CaF2-AlF3-YF3; The fluoride glass has good thermal properties and deliquescence resistance, and has the following characteristics: (1) Infrared transmission range: 0.25~7μm; (2) Glass transition temperature: 310~340℃; (3) Crystallization temperature: 420~450℃; (4) Weight loss of glass after immersion in water for 24 hours is <0.1%.

[0029] Traditional fluoride glasses (such as ZBLAN) contain a high proportion of monovalent alkali metal fluorides such as NaF. Due to the small radius and high polarizability of monovalent alkali metal ions, they readily undergo hydration reactions with water molecules in the environment, leading to damage to the glass network structure and macroscopic deliquescence. This invention completely eliminates monovalent alkali metal fluorides and uses divalent alkaline earth metals and trivalent metals to construct a more compact and stable glass network structure, fundamentally blocking the intrusion channels of water molecules, thereby endowing optical fibers with excellent deliquescence resistance.

[0030] The air core is the central hollow region of the optical fiber, with a diameter D1 of 50~150μm, preferably 80~120μm. The air core is the main region for light transmission. The refractive index of air is about 1.0, which is much lower than that of fluoride glass (about 1.5), resulting in a large refractive index difference.

[0031] The inner cladding is an array structure formed by multiple inner capillaries arranged in a ring around the air core, including 6 to 10 (preferably 8) inner capillaries; each inner capillary is a hollow tubular structure with a circular cross-section, an outer diameter of D2 (10 to 30 μm, preferably 15 to 25 μm), and a wall thickness of t1 (0.3 to 1.5 μm, preferably 0.5 to 1 μm); the inner capillaries are evenly distributed on the circumference centered on the air core.

[0032] The outer cladding is a solid fluoride glass layer wrapped around the inner cladding, with a diameter D3 of 200~400μm and a thickness of 50~150μm, used to provide mechanical strength and structural support.

[0033] The protective coating is a polymer protective coating applied to the surface of the outer cladding layer, with a thickness of 10~50μm. The material is UV-cured acrylate, which is used to protect the optical fiber from environmental moisture corrosion and improve its mechanical strength.

[0034] The method for preparing the above-mentioned fluoride hollow anti-resonant optical fiber is also provided, specifically including: S1. Preparation of the outer cladding glass preform: Weigh the fluoride raw materials according to the formula ratio, mix them thoroughly and evenly in a closed environment with a water vapor content of less than 10 ppm and an oxygen content of less than 1 ppm, and put them into a platinum crucible; melt them at 850~900℃, then pour the molten fluoride glass liquid into a high-speed rotating mold to form it, cool it to room temperature, and obtain a high coaxiality outer cladding glass preform. Polish the preform to optical quality for later use. Specifically, the rotational molding method is as follows: molten fluoride glass is poured into a high-speed rotating copper mold and rotated for 1 minute. The copper mold is then annealed at 310~340℃ for 3~5 hours. The outer diameter of the high coaxiality (coaxial inner and outer walls, uniform wall thickness) outer cladding glass preform is 10~20mm and the wall thickness is 2~4mm. This step also includes grinding and polishing the glass tube to optical quality before use.

[0035] S2. Preparation of inner-clad capillary preform: Weigh the fluoride raw materials according to the formula ratio, mix them thoroughly and evenly in a closed environment with water vapor content of less than 10 ppm and oxygen content of less than 1 ppm, and put them into a platinum crucible; melt them at 850~900℃, and then pour the molten fluoride glass liquid into a mold to extrude and shape it to obtain the inner-clad capillary preform. Specifically, the outer diameter of the inner cladding capillary preform is 1~3mm and the wall thickness is 0.1~0.3mm; In steps S1 and S2, the fluoride raw material is 99.99% high-purity fluoride; it is thoroughly mixed in a dry glove box and then placed into a platinum crucible; the melting is carried out in a resistance furnace, heated to 850~900℃ and held for 1~2 hours, during which it is stirred once every 20 minutes to remove bubbles and promote homogenization.

[0036] S3. Fiber preform stacking and assembly: The prepared outer cladding glass preform and inner cladding capillary preform are ultrasonically cleaned and nitrogen dried respectively; the inner cladding capillary preform is evenly arranged on the inner wall of the outer cladding glass preform; to prevent the inner cladding capillary from shifting during the fiber drawing process, high-temperature resistant epoxy resin is used to fix the inner cladding capillary preform and the outer cladding glass preform to form a complete fiber preform; Specifically, the ultrasonic cleaning medium is anhydrous ethanol, and the cleaning time is 5-10 minutes; nitrogen drying is performed by nitrogen purging, and the drying time is 3-5 minutes.

[0037] S4. Hollow-core fiber drawing: The assembled fiber preform is drawn in a protective gas atmosphere at 310~340℃ to obtain hollow-core anti-resonant fiber; Specifically, the protective gas is nitrogen or argon, with a flow rate of 2~10 L / min; the wire drawing speed is 2~10 m / min; The specific operation is as follows: The assembled optical fiber preform is placed in a special optical fiber drawing tower, which is equipped with a precise temperature control system (drawing furnace), a pressure control system, and a diameter monitoring system; dry nitrogen or argon is introduced into the drawing furnace to establish a protective atmosphere at a flow rate of 2~10 L / min; the preform is heated to a softening temperature of 310~340℃ and drawn at a speed of 2~10 m / min; at the same time, dry nitrogen or argon is introduced into the air core region or capillary of the optical fiber at a pressure of 0.5~5 kPa to maintain the hollow structure of the air core and capillary; the outer diameter of the optical fiber is monitored in real time through the diameter monitoring system and the drawing speed and heating power are controlled in a closed loop to ensure dimensional uniformity and obtain hollow optical fibers with a diameter of 200~400 μm.

[0038] S5. Protective coating: After the drawn hollow optical fiber is cooled, a protective coating is immediately applied. After the coating is completed, it is cured and shaped to obtain the finished fluoride hollow anti-resonant optical fiber. Specifically, a coating device is used to coat the fiber surface with a polymer using a mold coating method. The thickness of the protective coating is 10~50μm. The polymer is selected from UV-curable acrylate. The curing method is UV curing, and the specific parameters for UV curing are as follows: the wavelength of the UV curing light source is 365nm, and the light intensity is 5.0 W / cm². 2 The curing time is 0.1 to 5 seconds.

[0039] Example 1 See Figures 1-2 This embodiment of a fluoride hollow anti-resonant optical fiber includes an air core 1, an inner cladding 2, an outer cladding 3, and a protective coating 4 arranged sequentially from the inside out. Both the inner cladding layer 2 and the outer cladding layer 3 are made of fluoride glass. The composition of the fluoride glass is ZrF4-ZnF2-BaF2-SrF2-CaF2-AlF3-YF3, and the content of each component is shown in Table 2 below. Table 2 Fluoride Glass Formulation Table

[0040] The diameter D1 of the air core 1 is 100 μm; The inner cladding 2 is an array structure formed by 8 inner capillaries arranged in a ring around the air core. Each inner capillary is a hollow tubular structure with a circular cross-section, an outer diameter D2 of 20 μm, and a wall thickness t1 of 0.8 μm. The inner capillaries are evenly distributed on the circumference centered on the air core 1. The outer cladding 3 is a solid fluoride glass layer wrapped around the inner cladding 2, with a diameter D3 of 300 μm and a thickness of 100 μm; The thickness of protective coating 4 is 30 μm.

[0041] The preparation methods specifically include: S1. Preparation of the outer cladding glass preform: Weigh 99.99% high-purity fluoride raw material according to the formula ratio, mix it thoroughly in a dry glove box, and put it into a platinum crucible; heat it to 900℃ in a resistance furnace and keep it at that temperature for 2 hours, stirring it every 20 minutes to remove air bubbles and promote homogenization; pour the molten fluoride glass liquid into a high-speed rotating copper mold, rotate it for 1 minute, and then anneal the copper mold at 320℃ for 3 hours, and then slowly cool it to room temperature to obtain a high coaxiality outer cladding glass preform. Polish the preform to optical quality for later use.

[0042] S2. Preparation of inner cladding capillary preform: Weigh 99.99% high-purity fluoride raw material according to the same formula ratio, mix it evenly in a dry glove box, and put it into a platinum crucible; heat it to 900℃ in a resistance furnace and keep it at that temperature for 2 hours, stirring once every 20 minutes during the process to remove air bubbles and promote homogenization; pour the molten glass liquid into a special copper mold and prepare the inner cladding capillary preform by extrusion.

[0043] S3. Fiber preform stacking assembly: The prepared outer cladding glass preform and inner cladding capillary preform are ultrasonically cleaned and nitrogen dried respectively. The capillary preform is evenly arranged on the inner wall of the outer cladding glass preform. The capillary preform and the outer cladding glass preform are fixed with high-temperature resistant epoxy resin to form a complete fiber preform.

[0044] S4. Hollow-core fiber drawing: The assembled fiber preform is placed in a special fiber drawing tower. Dry nitrogen or argon is introduced into the drawing furnace to establish a protective atmosphere at a flow rate of 5 L / min. The preform is heated to the softening temperature of 340℃ and drawn at a speed of 5 m / min. At the same time, dry nitrogen or argon is introduced into the air core region or inside the capillary at a pressure of 1 kPa to maintain the hollow structure of the air core and capillary. The outer diameter of the fiber is monitored in real time through a diameter monitoring system, and the drawing speed and heating power are controlled in a closed loop to ensure dimensional uniformity and obtain hollow-core fiber.

[0045] S5. Protective Coating Application: Immediately after cooling, the drawn optical fiber is coated with a UV-curable acrylate protective coating using a mold coating method. After coating, the coating is fixed by UV curing. The UV curing light source wavelength is 365nm, and the light intensity is 5.0W / cm². 2 The curing time is 1 second. The resulting fluoride hollow antiresonant optical fiber is then obtained.

[0046] To verify the transmission performance of the fluoride hollow antiresonant fiber of this invention, the transmission loss of the fiber sample prepared in the example was tested in the mid-infrared band, and compared with that of a traditional quartz hollow antiresonant fiber. The test results are as follows: Figure 3 As shown in the figure, the transmission loss of the fluoride optical fiber of this invention is consistently significantly lower than that of silica optical fiber. In the long-wavelength mid-infrared band above 4μm, the loss of silica optical fiber rapidly increases to over 1dB / m due to the sharp increase in intrinsic absorption of the matrix. However, the fluoride optical fiber of this invention, thanks to the wide mid-infrared transmission window of the fluoride glass, maintains a low loss level in the 4~5.5μm band, fully verifying the significant performance advantage of the optical fiber of this invention in long-wavelength mid-infrared laser transmission scenarios.

[0047] It should be understood that the various forms of processes shown above can be used to reorder, add, or delete steps. For example, the steps described in this invention disclosure can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution disclosed in this invention can be achieved, and this is not limited herein.

[0048] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A fluoride hollow antiresonant optical fiber, characterized in that: It includes an air core, an inner cladding, an outer cladding, and a protective coating arranged sequentially from the inside out; Both the inner and outer cladding layers are made of fluoride glass that does not contain monovalent alkali metal fluorides. The refractive index of the fluoride glass is greater than that of the air core. The inner cladding is an array structure formed by multiple inner capillaries arranged in a ring-shaped periodic pattern around the air core; The outer cladding is a solid fluoride glass layer that wraps around the inner cladding; The inner and outer cladding layers are fixed together with high-temperature resistant epoxy resin adhesive.

2. The fluoride hollow anti-resonant optical fiber according to claim 1, characterized in that: The fluoride glass includes ZrF4, ZnF2, BaF2, SrF2, CaF2, AlF3, and YF3.

3. The fluoride hollow anti-resonant optical fiber according to claim 2, characterized in that: The composition of the fluoride glass is ZrF4-ZnF2-BaF2-SrF2-CaF2-AlF3-YF3, wherein the molar percentage of each component is ZrF4 10~30mol%, ZnF 25~40mol%, BaF 25~30mol%, SrF 25~20mol%, CaF2 10~20mol%, AlF3 10~20mol%, and YF 3 5~10mol.

4. The fluoride hollow anti-resonant optical fiber according to claim 1, characterized in that: The inner cladding layer includes 6 to 10 inner capillaries, each with an outer diameter of 10 to 30 μm and a wall thickness of 0.3 to 1.5 μm. The diameter of the air core is 50~150μm.

5. The fluoride hollow anti-resonant optical fiber according to claim 1, characterized in that: The protective coating is a polymer coating with a thickness of 10~50μm, and the material is selected from UV-curable acrylate.

6. The fluoride hollow anti-resonant optical fiber according to claim 1, characterized in that: The outer cladding layer has a diameter of 200~400μm and a thickness of 50~150μm.

7. A method for preparing a fluoride hollow anti-resonant optical fiber, used to prepare the fluoride hollow anti-resonant optical fiber according to claim 1, characterized in that: Specifically, the steps include the following: S1. Fluoride raw materials are mixed in a closed environment with a water vapor content of less than 10 ppm and an oxygen content of less than 1 ppm, and melted at 850~900℃ for 1~2 hours. The mixture is then rotated to form a pre-formed tube with an outer glass cladding. S2. Fluoride raw materials are mixed in a closed environment with a water vapor content of less than 10 ppm and an oxygen content of less than 1 ppm, and melted at 850~900℃ for 1~2 hours. The mixture is then extruded to obtain an inner-clad capillary preform. S3. The outer cladding glass preform and the inner cladding capillary preform are ultrasonically cleaned and nitrogen-dried; the inner cladding capillary preform is evenly arranged on the inner wall of the outer cladding glass preform and fixed to form an optical fiber preform. S4. The optical fiber preform is heated to 310~340℃ in a protective gas atmosphere for drawing, while the protective gas is introduced into the air core and inner cladding capillary to maintain the hollow structure, thus producing hollow optical fiber. S5. A protective coating is applied to the surface of the hollow optical fiber and cured to obtain a fluoride hollow anti-resonant optical fiber.

8. The method for preparing a fluoride hollow antiresonant optical fiber according to claim 7, characterized in that: The specific method for rotational molding in step S1 is as follows: pour the molten fluoride glass liquid into a high-speed rotating copper mold and rotate for 1 minute, then anneal the copper mold at 310~340℃ for 3~5 hours.

9. The method for preparing a fluoride hollow antiresonant optical fiber according to claim 7, characterized in that: In step S4, a protective gas, either nitrogen or argon, is introduced into the air core and inner cladding capillary at a pressure of 0.5-5 kPa and a flow rate of 2-10 L / min; the wire drawing speed is 2-10 m / min.

10. The method for preparing a fluoride hollow antiresonant optical fiber according to claim 7, characterized in that: The curing method is ultraviolet curing.

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