High-precision hollow optical fiber preform preparation method and optical fiber preform

Abstract

The application discloses a high-precision hollow optical fiber preform preparation method and an optical fiber preform, and relates to the technical field of optical fiber preform preparation. The application discloses a high-precision hollow optical fiber preform preparation method and an optical fiber preform, and relates to the technical field of optical fiber preform preparation. The method controls the precision and cleanliness of the pipe material from the source through pretreatment, solves the eccentric misplacement problem through pre-assembly, improves the roundness and wall thickness uniformity, realizes reliable combination of the pipe material through gradient welding, releases residual stress through annealing, and corrects the slight deviation of the forming through shaping correction. The application has the advantages of coherent process, good repeatability, improved preform precision and yield, guaranteed batch consistency, low loss and good stability of the obtained hollow optical fiber through drawing, and suitability for the large-scale high-precision preparation of microstructure hollow optical fibers such as anti-harmonic and photonic crystal.

Description

Technical Field

[0001] This invention relates to the field of optical fiber processing technology, and in particular to a method for preparing a high-precision hollow optical fiber preform and the optical fiber preform itself. Background Technology

[0002] Hollow optical fiber, with its hollow core transmission, low optical nonlinearity, high laser power tolerance, and excellent electromagnetic interference resistance, has irreplaceable application value in high-power laser transmission, high-precision fiber optic sensing, quantum communication, infrared light transmission, and other high-end optoelectronic technologies. The transmission loss, structural stability, service life, and batch performance consistency of hollow optical fiber depend primarily on the preparation precision and forming quality of the hollow optical fiber preform. The coaxiality, inner diameter roundness, wall thickness uniformity, internal cleanliness, and residual stress state of the preform directly determine the core optical and mechanical properties of the hollow optical fiber after drawing.

[0003] Currently, the mainstream hollow optical fiber preform manufacturing process in the industry mostly adopts traditional simple nested assembly combined with one-time high-temperature fusion splicing. The overall manufacturing process has a low degree of refinement, lacks a full-process precision control system, and has many inherent technical defects, making it difficult to meet the needs of large-scale manufacturing of high-precision, low-loss hollow optical fibers. In the raw material processing stage, the existing manufacturing process lacks a rigorous tube precision screening and micro-defect detection mechanism, and cannot effectively remove quartz tubes with dimensional deviations, rough inner walls, air bubbles, and elliptical deformation. This results in insufficient inherent structural precision of the preform, creating potential risks for scattering loss in subsequent optical fiber transmission.

[0004] Meanwhile, the pipe ends are mostly processed using ordinary cutting and grinding methods, which cannot guarantee the flatness of the end face and the perpendicularity of the axis. This easily leaves burrs, chipped edges, and micro-uneven structures, resulting in uneven gaps in the assembly and bonding of multi-layer pipes. This can easily lead to problems such as interlayer misalignment and assembly eccentricity, significantly reducing the overall structural regularity of the precast rod. Furthermore, the lack of dedicated precision coaxial tooling and accurate leveling and correction mechanisms in the assembly and molding process, along with the absence of standardized benchmarks to control the nesting accuracy of multi-layer pipes, results in large deviations in the overall coaxiality and inner diameter roundness of the precast rod, poor wall thickness uniformity, high parameter dispersion between different batches of products, and extremely poor repeatability and consistency.

[0005] In the post-processing stage of high-temperature molding, the one-time high-temperature welding process can easily generate a large amount of uneven residual thermal stress inside the preform. Moreover, the existing process does not have a professional and standardized stress relief procedure. As a result, the preform is prone to problems such as slight deformation and micro-cracking during storage, secondary processing and wire drawing, which seriously damages the structural stability.

[0006] Furthermore, traditional manufacturing processes lack systematic shaping and correction procedures and comprehensive non-destructive testing processes, making it impossible to accurately identify micro-defects and dimensional deviations within the preform. Defective and substandard products flowing into the fiber drawing process directly cause problems such as high transmission loss, insufficient structural stability, and low yield in the finished hollow optical fiber. This greatly limits the industrialization, large-scale, and high-precision production of high-end microstructure hollow optical fibers such as anti-resonant hollow optical fibers and photonic crystal hollow optical fibers. Therefore, developing a high-precision hollow optical fiber preform manufacturing method with precise control over the entire process, controllable accuracy, strong stability, and excellent batch consistency has become an urgent need for the current technological development in this field. Summary of the Invention

[0007] Therefore, the technical problem to be solved by the present invention is to overcome the defects of low processing accuracy and uniformity, many internal micro-defects and difficulty in eliminating residual stress in the preparation of hollow optical fiber preforms in the prior art, and to provide a high-precision hollow optical fiber preform preparation method and optical fiber preform.

[0008] To solve the above-mentioned technical problems, the present invention provides a method for preparing a high-precision hollow optical fiber preform, comprising: step S1, pre-treating the tubing; step S2, pre-assembling multiple pre-treated tubings in a layered nested manner, correcting coaxiality and controlling uniform interlayer gaps during the pre-assembly process to obtain a pre-assembled blank; step S3, performing gradient heating fusion sealing on the pre-assembled blank, followed by isothermal annealing to eliminate residual stress, to obtain a shaped preform blank; and step S4, shaping and correcting the preform blank to obtain the target high-precision hollow optical fiber preform.

[0009] In one embodiment of the present invention, in step S1, the pretreatment includes sequentially performing precision screening, end face precision treatment, and dust-free cleaning treatment on the high-purity quartz tube.

[0010] In one embodiment of the present invention, in step S1, the precision screening is as follows: high-purity quartz tubing with a purity ≥ 99.999% is selected, the outer diameter deviation of the tubing is ≤ ±0.02mm, the wall thickness deviation is ≤ ±0.01mm, and the inner wall roughness is ≤ 0.8μm, and tubing with defects such as scratches, bubbles, impurities, and elliptical deformation is rejected; the end face precision treatment adopts diamond cutting combined with mirror polishing until the flatness of the end face of the tubing is ≤ 0.01mm and the perpendicularity deviation between the end face and the tube axis is ≤ 0.02°, and the end face burrs, chipped edges, and micro-uneven structures are removed; the dust-free cleaning treatment is as follows: in a Class 100 constant temperature and humidity environment, the tubing is ultrasonically cleaned sequentially with anhydrous ethanol and high-purity deionized water, the cleaning temperature is 40-50℃, the cleaning time for each cleaning is 5-8min, and after being dried with nitrogen, it is placed in a constant temperature drying oven at 100-120℃ for 30-60min to remove moisture, oil stains, and dust impurities.

[0011] In one embodiment of the present invention, step S2 specifically involves: using the central axis of the preform as a reference for layered nesting, correcting the alignment error in real time through a leveling mechanism, controlling the overall assembly coaxiality deviation to be ≤0.015mm, and uniformly controlling the gap between each layer of pipe to be 0.03~0.05mm.

[0012] In one embodiment of the present invention, in step S3, the gradient heating welding is specifically carried out as follows: under a high-purity inert protective gas atmosphere, the temperature is first raised to 600°C at a rate of 5~8°C / min and held for 20~30min, and then raised to 1100~1200°C at a rate of 3~5°C / min and held for 40~60min to achieve welding and sealing of the end faces of each layer of pipe; the isothermal annealing is carried out by cooling the furnace to 800~850°C and isothermal annealing for 60~90min to release the residual stress inside the preform.

[0013] In one embodiment of the present invention, the second stage heating rate in the gradient heating welding process is less than the first stage heating rate.

[0014] In one embodiment of the present invention, the ratio of the first heating rate to the second heating rate in the gradient heating welding process is 1.5 to 2.0.

[0015] In one embodiment of the present invention, the shaping and correction includes fine grinding of the outer circle and secondary polishing of the end face.

[0016] In one embodiment of the present invention, in step S4, the preform blank after shaping and correction is subjected to non-destructive testing to screen target high-precision hollow optical fiber preforms. Specifically, the non-destructive testing involves using a laser interferometer and an ultrasonic non-destructive testing instrument to detect dimensions and internal defects. The qualified preforms have an inner diameter roundness error ≤0.02mm, a wall thickness uniformity error ≤0.015mm, and a coaxiality error ≤0.01mm.

[0017] The present invention also provides a high-precision hollow optical fiber preform, which is processed by the above-mentioned high-precision hollow optical fiber preform preparation method.

[0018] The technical solution of the present invention has the following advantages over the prior art: The high-precision hollow optical fiber preform preparation method and optical fiber preform of this invention, through pretreatment of the tube, can control the dimensional accuracy and cleanliness of the tube from the source, reducing the contamination of defects and impurities inherent in the raw materials. Then, through the coaxiality correction and uniform control of the interlayer gap during the layered nesting pre-assembly process, the problems of eccentricity and misalignment between layers in the assembly of multi-layer tubes are effectively improved, and the roundness and wall thickness uniformity of the preform after molding are enhanced. Combined with gradient heating fusion sealing, reliable integrated bonding of multi-layer tubes is achieved, avoiding the risk of tube deformation caused by direct high-temperature sintering. Subsequent isothermal annealing treatment can fully release the residual stress inside the preform blank, reduce the probability of deformation and micro-cracking of the preform, and ensure the long-term stability of the preform structure dimensions. Finally, the slight dimensional deviations caused by molding are further corrected through shaping and correction.

[0019] The present invention has strong overall process continuity and good repeatability, which can improve the finished product accuracy and preparation yield of hollow optical fiber preforms, ensure the parameter consistency of batch products, and the hollow optical fiber obtained by drawing from the preform has lower transmission loss and better structural stability, which can better meet the high-precision large-scale preparation requirements of microstructure hollow optical fibers such as anti-resonant hollow optical fibers and photonic crystal hollow optical fibers. Attached Figure Description

[0020] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0021] Figure 1 This is a flowchart of a high-precision hollow optical fiber preform preparation method according to a preferred embodiment of the present invention; Figure 2 This is a cross-sectional view of a high-precision hollow optical fiber preform according to another embodiment of the present invention.

[0022] Explanation of reference numerals in the accompanying drawings: 100, hollow core layer; 200, protective layer; 300, structural layer. Detailed Implementation

[0023] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0024] Example 1: Refer to Figure 1 As shown, the present invention provides a method for preparing a high-precision hollow optical fiber preform, which includes: Step S1: Pre-treatment of the pipes; This step mainly involves precision screening, end-face precision treatment, and dust-free cleaning of the pipes. Pipes with defects such as out-of-tolerance dimensions, scratches, and bubbles are removed from the source of raw materials. The flatness and perpendicularity of the pipe end faces are adjusted, and dust, oil, moisture, and other impurities are removed from the inner and outer walls of the pipes. This not only eliminates the inherent structural defects of the pipes themselves, but also prevents impurities from being introduced into the preform and forming a scattering source. This lays the foundation for the high-precision nesting assembly of multi-layer pipes in the future, and prevents the performance of the preform from deteriorating due to pipe defects, poor end-face fit, and impurity contamination.

[0025] Specifically, in step S1 of this embodiment, the pretreatment includes sequentially performing precision screening, end-face precision treatment, and dust-free cleaning on the high-purity quartz tubes. Precision screening eliminates quartz tubes with dimensional defects, air bubbles, scratches, or other inherent flaws, preventing the transfer of tube defects to downstream processes. End-face precision treatment ensures the flatness and perpendicularity of the tube mating surfaces, eliminating the risk of uneven assembly gaps caused by burrs and chipped edges. Dust-free cleaning removes dust, oil, and moisture impurities from the inner and outer walls of the tubes, preventing impurities from remaining inside the preform and causing optical scattering defects. These three processes work together to provide a tube substrate with qualified dimensions, reliable end-face fit, and adequate cleanliness for subsequent layered nested pre-assembly, reducing preform forming defects from the source and laying the foundation for high-precision preform assembly.

[0026] Specifically, the precision screening involves selecting high-purity quartz tubing with a purity ≥ 99.999%, with an outer diameter deviation ≤ ±0.02mm, a wall thickness deviation ≤ ±0.01mm, and an inner wall roughness ≤ 0.8μm. Tubes with scratches, bubbles, impurities, or elliptical deformation are removed. The end-face precision treatment employs diamond cutting combined with mirror polishing until the flatness of the end-face is ≤ 0.01mm and the perpendicularity deviation between the end-face and the tube axis is ≤ 0.02°. Burrs, chipped edges, and microscopic uneven structures are removed from the end-face. The dust-free cleanroom treatment involves sequentially ultrasonic cleaning with anhydrous ethanol and high-purity deionized water in a Class 100 constant temperature and humidity environment. The cleaning temperature is 40–50℃, and the cleaning time for each cycle is 5–8 minutes. After nitrogen drying, the tube is placed in a constant temperature drying oven at 100–120℃ for 30–60 minutes to remove moisture, oil, and dust impurities. This process involves selecting high-purity quartz tubing with a purity ≥99.999% and strictly controlling the outer diameter, wall thickness, and inner wall roughness. Tubes with scratches, bubbles, impurities, and elliptical deformation are also eliminated. This ensures control over the purity of the base material and the accuracy of basic dimensions from the source, preventing inherent defects in the tubing from being introduced into the preform. Diamond cutting combined with mirror polishing is used to process the tubing end faces, strictly limiting the flatness of the end faces and the perpendicularity deviation between the end faces and the tube axis. Burrs, chipped edges, and microscopic uneven structures are removed, ensuring a tight fit of the tubing end faces during subsequent nesting assembly and reducing uneven assembly gaps and interlayer misalignment. The process involves ultrasonic cleaning and constant temperature drying under Class 100 constant temperature and humidity conditions. Under specified temperature and duration conditions, the tubes are cleaned sequentially with anhydrous ethanol and high-purity deionized water, followed by nitrogen blowing and high-temperature drying to thoroughly remove moisture, oil, and dust impurities. This effectively prevents impurities from remaining inside the preform and causing scattering defects. This multi-indicator synergistic pretreatment method provides high-purity, dimensionally qualified, high-precision end face, and cleanliness tubes for subsequent coaxial nesting pre-assembly processes. It reduces preform forming defects from the substrate end, laying a solid foundation for the pre-process of preparing high-precision hollow optical fiber preforms.

[0027] Step S2: Multiple pre-treated pipes are layered and nested for pre-assembly. During the pre-assembly process, coaxiality is corrected and the interlayer gaps are controlled to be uniform, resulting in a pre-assembled blank. This step relies on a coaxial reference to complete the nested arrangement of multiple layers of pipes. Real-time coaxiality correction prevents eccentric misalignment of each layer of pipes, while controlling the gaps between layers within a uniform range. Figure 2 As shown in the precast rod structure, it ensures that each layer of the structure is coaxial around the central reference line without misalignment or displacement. This effectively avoids the problems of interlayer offset and inconsistent gap size caused by traditional manual nesting, ensuring the roundness and wall thickness uniformity of the precast rod. It provides a regular pre-assembled blank for subsequent welding and forming, and prevents assembly defects from being solidified into the final precast rod product.

[0028] Further, step S2 specifically involves: layered nesting based on the central axis of the preform, real-time correction of alignment errors using a leveling mechanism, controlling the overall assembly coaxiality deviation to ≤0.015mm, and uniformly controlling the gap between each layer of tubing within 0.03~0.05mm. This step, using the central axis of the preform as the assembly reference for layered nesting, and using a leveling mechanism to correct alignment errors in real time, limits the overall assembly coaxiality deviation and the gap between each layer of tubing within the corresponding numerical range. This ensures that multiple layers of tubing are strictly arranged around the same central axis, effectively suppressing problems such as eccentricity, misalignment, and inconsistent gap sizes that easily occur during assembly. It also prevents structural deviations generated during the assembly stage from being solidified into the preform blank by subsequent fusion processes, ensuring the roundness and wall thickness uniformity of the preform blank. This provides a pre-assembled blank with precise alignment and consistent gap status for subsequent gradient heating fusion sealing, reducing the increase in optical fiber transmission loss caused by assembly defects. It is a key assembly guarantee for achieving high-precision forming of hollow optical fiber preforms.

[0029] Step S3: The pre-assembled billet is subjected to gradient heating and welding sealing, followed by isothermal annealing to eliminate residual stress, resulting in a shaped preform billet. Gradient heating and welding sealing can avoid local thermal collapse and deformation of the pipe caused by excessive heating rate, achieve stable welding of the end faces of multi-layer pipes, eliminate interlayer gaps, and combine multi-layer pipes into a complete preform billet. The isothermal annealing process after welding can release the residual thermal stress accumulated inside the billet during the high-temperature welding process, alleviate the risk of deformation and micro-cracking during subsequent storage and processing of the preform, stabilize the overall structural dimensions of the preform, and ensure the structural reliability of the preform billet after molding.

[0030] Further, in step S3, the gradient heating welding is specifically carried out in a high-purity inert protective gas atmosphere, first heating to 600℃ at a rate of 5~8℃ / min and holding for 20~30min, then heating to 1100~1200℃ at a rate of 3~5℃ / min and holding for 40~60min to achieve welding and sealing of the end faces of each layer of pipe; the isothermal annealing is carried out by cooling to 800~850℃ in the furnace and isothermal annealing for 60~90min to release the residual stress inside the preform. The process involves first heating the billet to 600℃ at a rate of 5-8℃ / min and holding it for 20-30 minutes to fully expel residual gas and prevent internal bubble defects. Then, heating it to 1100-1200℃ at a lower rate of 3-5℃ / min and holding it for 40-60 minutes slows down the heating rate of the pipe, preventing local collapse and twisting deformation caused by rapid heating. This ensures a smooth weld seal at the ends of each layer of pipe, integrating the pre-assembled billet into a single structure. The inert gas atmosphere also prevents oxidation, crystallization, and surface contamination of the quartz pipe. After welding, the billet is cooled to 800-850℃ and annealed at a constant temperature for 60-90 minutes. This fully releases the residual thermal stress accumulated in the billet during the high-temperature welding process, reducing the risk of deformation and micro-cracking during later storage, processing, and wire drawing of the preform. It also stabilizes the overall structural dimensions of the preform, providing a preform billet with a complete structure and good stress state for subsequent shaping and correction processes.

[0031] Furthermore, in this embodiment, the second stage heating rate in the gradient heating welding process is lower than the first stage heating rate. The higher heating rate in the first stage can quickly reach 600°C to complete the pre-treatment of the billet degassing, efficiently removing the gas remaining between the layers of the pre-assembled billet. The second stage uses a lower heating rate to heat up to the welding temperature range, which can slow down the heating rate of the quartz tube, making the heating of the multi-layer tube more uniform. This avoids the tube from being rapidly heated in a short time, resulting in local overheating, collapse, or twisting deformation. It ensures that the end faces of each layer of tube can be smoothly and fully welded and sealed, reducing structural distortion and internal defects generated during the welding stage. This helps maintain the coaxiality and gap distribution already formed in the pre-assembly stage, preventing the assembled precision structure from being damaged in the high-temperature welding process, and ensuring the structural accuracy of the preformed billet after molding.

[0032] Specifically, the ratio of the first heating rate to the second heating rate in the gradient heating welding process is 1.5 to 2.0. This provides a reasonable matching constraint between the two heating rates, ensuring that the first stage reaches 600°C at a relatively faster heating efficiency to complete the degassing of the billet and efficiently remove interlayer gas. At the same time, the second stage heating rate can be appropriately reduced to avoid a large rate difference causing abrupt changes in the process. This achieves a smooth transition in the heating process of the pipe, making the heating of the multi-layer quartz pipe uniform and controllable. It prevents sudden changes in heating rate from causing local overheating, collapse, and distortion, ensuring a smooth and sufficient fusion and sealing of the end faces of each layer of pipe. It effectively preserves the coaxial accuracy obtained in the pre-assembly process, avoids distortion of the precision assembly structure during the high-temperature welding stage, reduces the generation of internal defects in the preform, and improves the structural integrity and dimensional stability of the billet after welding.

[0033] Step S4: Shape and correct the preform blank to obtain the target high-precision hollow optical fiber preform. The preform blank after fusion splicing and annealing may have slight shape deformation and end face deviation. The shaping and correction can adjust the outer circle and end face of the blank, compensate for the small dimensional errors generated during the forming process, correct the dimensional deviations caused by forming, and further ensure the key indicators such as the outer diameter and roundness of the preform. Finally, a target high-precision hollow optical fiber preform with regular structure and qualified precision is obtained, ensuring that the hollow optical fiber obtained by subsequent drawing has low loss and stable structural performance.

[0034] Furthermore, the shaping and correction includes fine grinding of the outer circle and secondary polishing of the end face, which enables fine finishing of the outer circle contour and end face of the preform blank after welding and annealing. This eliminates minor shape deformation, roundness deviation and minor unevenness defects remaining on the end face generated during high-temperature welding and annealing, corrects dimensional errors caused by the blank forming stage, optimizes the coaxiality of the outer circle and the flatness of the end face of the preform, removes local burr defects on the surface, avoids stress concentration caused by preform shape defects during subsequent wire drawing, ensures the overall geometric accuracy of the preform, and provides a preform substrate with regular shape and good end face quality for subsequent wire drawing processes.

[0035] Specifically, in step S4, the preform blank after shaping and correction is subjected to non-destructive testing to screen for target high-precision hollow optical fiber preforms. The non-destructive testing specifically involves using a laser interferometer and an ultrasonic non-destructive testing instrument to detect dimensions and internal defects. Qualified preforms have an inner diameter roundness error ≤0.02mm, a wall thickness uniformity error ≤0.015mm, and a coaxiality error ≤0.01mm. This allows for accurate identification of geometric dimensional deviations and internal defects such as microcracks and bubbles in the preform without damaging the preform itself. Blanks that do not meet the precision indicators are screened out in advance, preventing unqualified preforms from flowing into the fiber drawing process and causing problems such as high fiber loss and structural failure. This ensures that all key geometric parameters of the produced hollow optical fiber preforms meet high-precision requirements, guarantees the consistency of batch products, controls the quality of preforms from the finished product end, and provides a reliable preform foundation for the preparation of low-loss, high-stability hollow optical fibers.

[0036] Example 2: See Figure 2 As shown, this embodiment provides a high-precision hollow optical fiber preform, which is processed using the high-precision hollow optical fiber preform preparation method described in Embodiment 1. It includes three main tubular layers to be assembled, namely a hollow core layer 100, a protective layer 200, and a structural layer 300.

[0037] In summary, the high-precision hollow optical fiber preform preparation method and optical fiber preform described in this invention, through pretreatment of the tubing, can control the dimensional accuracy and cleanliness of the tubing from the source, reducing defects and impurities inherent in the raw materials. Furthermore, through coaxiality correction and uniform control of interlayer gaps during the layered nesting pre-assembly process, the problems of eccentricity and misalignment in multi-layer tubing assembly are effectively improved, enhancing the roundness and wall thickness uniformity of the preform after molding. Combined with gradient heating fusion sealing, reliable integrated bonding of multi-layer tubing is achieved, avoiding the risk of tubing deformation caused by direct high-temperature sintering. Subsequent isothermal annealing treatment can fully release the residual stress inside the preform blank, reducing the probability of deformation and micro-cracking of the preform, ensuring the long-term stability of the preform's structural dimensions. Finally, shaping and correction further correct the minor dimensional deviations caused by molding.

[0038] The present invention has strong overall process continuity and good repeatability, which can improve the finished product accuracy and preparation yield of hollow optical fiber preforms, ensure the parameter consistency of batch products, and the hollow optical fiber obtained by drawing from the preform has lower transmission loss and better structural stability, which can better meet the high-precision large-scale preparation requirements of microstructure hollow optical fibers such as anti-resonant hollow optical fibers and photonic crystal hollow optical fibers.

[0039] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing a high-precision hollow optical fiber preform, characterized in that: include: Step S1: Pre-treat the pipes; Step S2: Multiple pre-treated pipes are pre-assembled by nesting them in layers. During the pre-assembly process, the coaxiality is corrected and the interlayer gap is controlled to be uniform, so as to obtain a pre-assembled blank. Step S3: The pre-assembled billet is subjected to gradient heating and welding sealing, and then constant temperature annealing is performed to eliminate residual stress, resulting in a shaped preformed rod billet. Step S4: Shape and correct the preform blank to obtain the target high-precision hollow optical fiber preform.

2. The method for preparing high-precision hollow optical fiber preforms according to claim 1, characterized in that: In step S1, the pretreatment includes sequentially performing precision screening, end face precision treatment, and dust-free cleaning treatment on the high-purity quartz tube.

3. The method for preparing high-precision hollow optical fiber preforms according to claim 2, characterized in that: In step S1, the precision screening is as follows: high-purity quartz tubing with a purity ≥ 99.999% is selected, with an outer diameter deviation ≤ ±0.02mm, a wall thickness deviation ≤ ±0.01mm, and an inner wall roughness ≤ 0.8μm. Tubing with defects such as scratches, bubbles, impurities, and elliptical deformation is removed. The end face precision treatment uses diamond cutting combined with mirror polishing until the flatness of the end face is ≤ 0.01mm and the perpendicularity deviation between the end face and the tube axis is ≤ 0.02°. Burrs, chipped edges, and micro-uneven structures on the end face are removed. The dust-free cleaning treatment is as follows: ultrasonic cleaning is performed sequentially with anhydrous ethanol and high-purity deionized water in a Class 100 constant temperature and humidity environment. The cleaning temperature is 40-50℃ and the cleaning time is 5-8min per cycle. After nitrogen drying, the tube is placed in a constant temperature drying oven at 100-120℃ for 30-60min to remove moisture, oil, and dust impurities.

4. The method for preparing a high-precision hollow optical fiber preform according to claim 1, characterized in that: Step S2 specifically involves: using the central axis of the precast rod as a reference for layered nesting, correcting the alignment error in real time through a leveling mechanism, controlling the overall assembly coaxiality deviation to be ≤0.015mm, and uniformly controlling the gap between each layer of pipes to be 0.03~0.05mm.

5. The method for preparing a high-precision hollow optical fiber preform according to claim 1, characterized in that: In step S3, the gradient heating fusion welding is specifically carried out in a high-purity inert protective gas atmosphere. First, the temperature is raised to 600℃ at a rate of 5~8℃ / min and held for 20~30min. Then, the temperature is raised to 1100~1200℃ at a rate of 3~5℃ / min and held for 40~60min to achieve fusion sealing of the end faces of each layer of pipe. The isothermal annealing involves cooling the furnace to 800~850℃ and annealing at that temperature for 60~90 minutes to release the residual stress inside the preform.

6. The method for preparing a high-precision hollow optical fiber preform according to claim 5, characterized in that: The second stage of the gradient heating welding process has a lower heating rate than the first stage.

7. The method for preparing a high-precision hollow optical fiber preform according to claim 6, characterized in that: The ratio of the first heating rate to the second heating rate in the gradient heating welding process is 1.5 to 2.

0.

8. The method for preparing a high-precision hollow optical fiber preform according to claim 1, characterized in that: The shaping and correction includes fine grinding of the outer circle and secondary polishing of the end face.

9. The method for preparing a high-precision hollow optical fiber preform according to claim 8, characterized in that: In step S4, the preform blank after shaping and correction is subjected to non-destructive testing to screen the target high-precision hollow optical fiber preform. Specifically, the non-destructive testing is carried out by using a laser interferometer and an ultrasonic non-destructive testing instrument to detect dimensions and internal defects. The qualified preform has an inner diameter roundness error ≤0.02mm, a wall thickness uniformity error ≤0.015mm, and a coaxiality error ≤0.01mm.

10. A high-precision hollow optical fiber preform, characterized in that: It is prepared by the high-precision hollow optical fiber preform preparation method according to any one of claims 1 to 9.

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