Integrated hollow core optical fiber preform, optical fiber, and method for manufacturing the same

Abstract

An integrated hollow-core optical fiber preform, an optical fiber, and a method for manufacturing the same. An initial preform is obtained by using a drilling method, and an optical fiber with an anti-resonant ring structure is manufactured by passing gas into the hole during the drawing process under pressure control. This method realizes accurate positioning of the azimuth angle of the anti-resonant unit by mechanically drilling holes, and ensures axial uniformity to avoid azimuth deviation during the drawing process. At the same time, the anti-resonant unit is positioned without introducing other materials, thereby reducing impurity contamination and improving the attenuation and strength performance of the optical fiber. Furthermore, the anti-resonant unit is expanded by air pressure control during the drawing process, which further reduces the wall thickness of the anti-resonant unit and reduces the attenuation of the optical fiber.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical fiber communication, and more specifically relates to an integrated hollow-core optical fiber preform and an optical fiber manufacturing method, which can be used for manufacturing hollow-core microstructured optical fibers.

Background Art

[0002] Hollow-core microstructured optical fibers have the features of simple structure, single-mode light guidance in the hollow core, and wide transmission spectrum, and have important applications in fields such as interaction between light and filled substances, nonlinear optics, gas detection, gas laser generation, and optofluidic technology. Large air-hole fiber core light guidance has ultra-low Rayleigh scattering, low nonlinear coefficient, and tunable dispersion characteristics, and by providing a higher laser damage threshold, it has potential applications in aspects such as high-power laser transmission, ultraviolet / mid-infrared light transmission, pulse compression and optical soliton transmission. The ultra-low loss, low dispersion, low nonlinearity, and propagation velocity close to the speed of light of the air core enable the development of hollow-core optical fiber communication transmission and communication devices, laying the foundation for the construction and development of next-generation ultra-large-capacity, low-latency, high-speed optical communication systems.

[0003] Even though hollow-core optical fibers have great advantages in terms of design and application, their transmission loss is much higher than that of conventional silica optical fibers. In recent years, it has been found that hollow-core optical fibers based on the anti-resonance principle can effectively reduce transmission loss under reasonable structural design, and have the potential to be used as ultra-long-distance communication optical fibers. Further reducing attenuation is an important issue in the field of hollow-core microstructured optical fiber manufacturing.

[0004] Known anti-resonant hollow-core optical fibers, especially optical fibers with nested structural elements, can significantly reduce the attenuation of the optical fiber, but their internal geometric shape is complex, and tiny geometric deviations may change the anti-resonance condition, making accurate and repetitive production difficult. At the same time, since a thinner-walled anti-resonant layer helps to achieve lower loss and wider bandwidth, manufacturing a thinner-walled anti-resonant layer is also a problem to be solved. [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] To address the shortcomings or improvement needs of the prior art, the present invention provides a hollow core microstructure optical fiber preform, an optical fiber, and a method for manufacturing the same. The objective is to provide a method for manufacturing an anti-resonant hollow core optical fiber with higher precision positioning. This method avoids the limitations of conventional manufacturing methods. [Means for solving the problem]

[0006] To achieve the above objective, the present invention employs the following technical means. An integrated hollow core optical fiber preform, comprising a sleeve, wherein a plurality of circumferentially distributed axial holes are formed within the tube wall of the sleeve, the minimum distance t1 between the inner wall of the axial holes and the inner wall of the sleeve is located towards the center of the sleeve, and the ratio of t1 to the diameter of the axial holes is 0.35 or less.

[0007] Furthermore, the axial holes are uniformly distributed along the same annular line, and their number is four or more.

[0008] Furthermore, the ratio of the inner diameter to the outer diameter of the sleeve is 0.2 to 0.8.

[0009] Furthermore, a capillary tube is inserted into the axial hole to form a nested optical fiber preform.

[0010] Furthermore, quartz pieces are inserted into the axial holes to form an optical fiber preform with a connecting piece structure. The quartz pieces are positioned perpendicular to the axial line of the sleeve.

[0011] A method for manufacturing a hollow core microstructure optical fiber includes the following steps: Step 1: Select one sleeve, drill holes from the end of the sleeve, and manufacture the above-mentioned integrated hollow core optical fiber preform. Step 2: The integrated hollow core optical fiber preform obtained in Step 1 is drawn at a high temperature. During the drawing process, gas is passed through the axial holes to make the air pressure in the axial holes higher than the air pressure in the sleeve center hole. Due to the differential pressure between the axial holes and the sleeve center hole and the action of surface tension, the drawn axial holes are made to protrude in the direction of the sleeve center hole, forming anti-resonant rings with negative curvature. All the anti-resonant rings together form an annular anti-resonant layer, and the region surrounded by the anti-resonant layer forms a hollow fiber core, thereby forming a hollow core microstructure optical fiber having anti-resonant rings with negative curvature.

[0012] Furthermore, in step 1, after drilling, the axial hole is corroded by passing an acid solution through it, so that the ratio of the minimum distance t1 between the inner wall of the axial hole and the inner wall of the sleeve to the diameter of the axial hole is 0.1 or less.

[0013] The acid solution is preferably hydrofluoric acid.

[0014] Furthermore, in step 1, if a capillary tube is fitted into the axial hole, gas is also passed through the capillary tube to control the decrease in the pressure gradient between the capillary tube, the axial hole, and the sleeve center hole.

[0015] Furthermore, in step 1, the gas passed through the axial hole or capillary tube is one or more of compressed air, nitrogen, helium, and argon.

[0016] Furthermore, in step 2, a cladding layer is formed by the anti-resonance layer and the drawn-out sleeve, the outer diameter of the cladding layer being 100 to 300 μm, and the diameter of the fiber core being 10 to 50 μm.

[0017] Furthermore, in step 2, the minimum wall thickness of the anti-resonance ring is 2 μm or less, and more preferably 1 μm or less.

[0018] The hollow-core microstructure optical fiber manufactured using the method of the present invention has a relatively low transmission loss, with a minimum transmission loss of 30 dB / km or less, and more preferably 1 dB / km or less.

Effects of the Invention

[0019] Compared with the prior art, the present invention can obtain the following beneficial effects through the above technical means. 1) Different from the traditional "stack-and-draw" method, the hollow core microstructured optical fiber preform according to the present invention uses a drilling method to obtain an initial preform, and further performs pressure control into the holes during the drawing process to realize an anti-resonant ring structure optical fiber. One of the beneficial effects of this method is that holes can be mechanically drilled, thereby achieving precise positioning of the anti-resonant units, ensuring axial uniformity, and avoiding the azimuthal deviation of the anti-resonant units during the drawing process. 2) The present invention positions the anti-resonant units without introducing other materials, thereby reducing impurity contamination and improving the attenuation and strength performance of the optical fiber. 3) In the drawing process, the present invention uses air pressure control to expand the anti-resonant units, thereby further reducing the wall thickness of the anti-resonant units and lowering the attenuation of the optical fiber.

Brief Description of the Drawings

[0020] [Figure 1] Figure 1 is a schematic structural view of an optical fiber preform having a hollow core microstructure according to Embodiment 1 of the present invention. [Figure 2] Figure 2 is a schematic structural view of a hollow core microstructured optical fiber according to Embodiment 1 of the present invention. [Figure 3] Figure 3 is a schematic structural view of an optical fiber preform having a hollow core microstructure according to Embodiment 2 of the present invention. [Figure 4] Figure 4 is a schematic structural view of a hollow core microstructured optical fiber according to Embodiment 2 of the present invention. [Figure 5] Figure 5 is a schematic structural view of a nested structure optical fiber preform according to Embodiment 3 of the present invention. [Figure 6] Figure 6 is a schematic structural view of a hollow core microstructured optical fiber according to Embodiment 3 of the present invention. [Figure 7]Figure 7 is a schematic structural diagram of an optical fiber preform with a connecting piece structure according to Embodiment 4 of the present invention. [Figure 8] Figure 8 is a schematic structural diagram of a hollow core microstructured optical fiber according to Embodiment 4 of the present invention. DETAILED DESCRIPTION OF EMBODIMENTS FOR IMPLEMENTING THE INVENTION

[0021] To make the objectives, technical means and advantages of the present invention clearer, the present invention is described in further detail below with reference to the embodiments. It should be noted that the specific embodiments described in the present specification are only used to explain the present invention, and are not used to limit the present invention. In addition, the technical features related to various embodiments of the present invention described below may be combined with each other as long as no contradiction arises therebetween.

[0022] The present invention provides a method for manufacturing a hollow core microstructured optical fiber, comprising the following steps. Step 1: Select one sleeve, and perform drilling from the end of the sleeve to manufacture an integrated hollow core optical fiber preform. The integrated hollow core optical fiber preform includes a sleeve, a plurality of axially extending holes distributed in the circumferential direction are formed in the tube wall of the sleeve, the minimum distance t1 between the inner wall of the axial hole and the inner wall of the sleeve is located on the center side of the sleeve, and the ratio of t1 to the diameter of the axial hole is 0.35 or less. Step 2: Draw the integrated hollow core optical fiber preform obtained in Step 1 at high temperature. During the drawing process, gas is passed into the axial holes to make the air pressure in the axial holes higher than the air pressure in the central hole of the sleeve. Under the action of the differential pressure and surface tension between the axial holes and the central hole of the sleeve, the drawn axial holes are protruded toward the central hole of the sleeve to form anti-resonant rings with negative curvature. All the anti-resonant rings jointly form an annular anti-resonant layer, and the region surrounded by the anti-resonant layer forms a hollow fiber core, thereby forming a hollow core microstructured optical fiber having anti-resonant rings with negative curvature.

[0023] (Embodiment 1) Manufacturing of optical fiber preform: As shown in Figure 1, first, one sleeve 2 is selected. The sleeve material is pure silica, the inner diameter d0 of the sleeve is 30 mm, the outer diameter D0 is 50 mm, and the length is 1000 mm. Using a drilling method, five axial holes 3 are drilled into the sleeve. The axial holes are arranged at equiazimuth angles (azimuth angle is 72°), the diameter d1 of the axial holes 3 is 6.5 mm, and the ratio of the minimum distance t1 between the inner wall of the axial hole 3 and the inner wall 17 of the sleeve to the diameter d1 of the axial hole is 0.08. In this way, the fabrication of the optical fiber preform 1 having a hollow core microstructure is completed.

[0024] Manufacturing of hollow core microstructure optical fibers: A fiber optic preform 1 having a hollow core microstructure is placed in a high-temperature drawing furnace and drawn. The furnace temperature is 1710°C, and the hollow core portion in the middle of the preform maintains a pressure equal to atmospheric pressure. An equal-pressure gas is passed through five axial holes, and the pressure is 2.9 kPa. Due to the pressure difference between the inside and outside of the axial holes, the axial holes expand after drawing, forming an anti-resonance ring 6, and finally, as shown in Figure 2 A hollow-core microstructure optical fiber 4 is formed as shown. The outer diameter of the optical fiber cladding layer 5 is 124.7 μm, the diameter of the hollow optical fiber core 7 is 27.4 μm, and the thinnest wall thickness of the anti-resonance ring is 637 nm. The attenuation of this optical fiber at 1550 nm is 12.7 dB / km.

[0025] (Example 2) Manufacturing of fiber optic preforms: As shown in Figure 3, first, one sleeve is selected, the sleeve material is pure silica, the inner diameter of the sleeve is 40 mm, the outer diameter is 80 mm, and the length is 900 mm. Six axial holes 3 are drilled into the sleeve using a drilling method. The axial holes 3 are arranged at equiazimuth angles (azimuth angle is 60°), the diameter of the axial holes 3 is 8.2 mm, and the ratio of the minimum distance 8 between the inner wall of the axial hole 3 and the inner wall 17 of the sleeve to the diameter of the axial hole 3 is 0.21. The drilled sleeve is then immersed in an acid solution to corrode it, and the ratio of the minimum distance 9 between the inner wall of the axial hole 16 and the inner wall 17 of the sleeve to the diameter of the axial hole 16 after corrosion is 0.06. In this way, the fabrication of the optical fiber preform 1 having a hollow core microstructure is completed.

[0026] Manufacturing of hollow core microstructure optical fibers: A preform 1 optical fiber having a hollow core microstructure is placed in a high-temperature drawing furnace and drawn. The furnace temperature is 1760°C, and gas is passed through the hollow core portion in the middle of the preform to maintain a pressure of approximately 0.56 kPa. Gas of equal pressure is passed through six axial holes 16, and the pressure is 1.9 kPa. Due to the pressure difference between the inside and outside of the axial holes 16, the axial holes expand after drawing, forming an anti-resonance ring 6, and finally a hollow core microstructure optical fiber 4 as shown in Figure 4 is formed. The outer diameter of the optical fiber cladding layer 5 is 243 μm, the diameter of the hollow optical fiber core 7 is 42.7 μm, and the thinnest wall thickness of the anti-resonance ring 6 is 336 nm. The attenuation of this optical fiber at 1550 nm is 1.45 dB / km.

[0027] (Example 3) Manufacturing of fiber optic preforms: As shown in Figure 5, first, one sleeve 2 is selected. The sleeve material is pure silica, the inner diameter of sleeve 2 is 13 mm, the outer diameter is 28 mm, and the length is 700 mm. Six axial holes 3 are drilled into the sleeve using a drilling method. The axial holes 3 are arranged at equiazimuth angles (azimuth angle is 60°), the diameter of the axial holes is 2.4 mm, and the ratio of the minimum distance between the inner wall of the axial hole and the inner wall 17 of the sleeve to the diameter of the axial hole is 0.13. After drilling, the sleeve is placed in an acid solution to corrode it, and after corrosion, the ratio of the minimum distance between the inner wall of the axial hole 3 and the inner wall 17 of the sleeve to the diameter of the axial hole is 0.06. Next, capillary tubes 10 with an outer diameter of 1.1 mm and a wall thickness of 0.12 mm are inserted into the axial holes to complete the manufacturing of the nested optical fiber preform 1.

[0028] Manufacturing of hollow core microstructure optical fibers: A nested optical fiber preform 1 is placed in a high-temperature drawing furnace and drawn. The furnace temperature is 1770°C, and the hollow core portion in the middle of the preform maintains a pressure equal to atmospheric pressure. Equivalent pressure gas is passed through six axial holes 3, and the pressure is 3.7 kPa. Equivalent pressure gas is passed through six nested capillaries, and the pressure is 4.6 kPa. Due to the pressure difference inside and outside the axial holes and the pressure difference inside and outside the nested capillaries, a nested anti-resonance ring is formed, and finally, the nested hollow core microstructure optical fiber 4 shown in Figure 6 is formed. The outer diameter of the optical fiber cladding layer 5 is 153 μm, the diameter of the optical fiber hollow core is 33.2 μm, the thinnest wall thickness of the first layer anti-resonance ring 11 is 217 nm, and the thinnest wall thickness of the second layer anti-resonance ring 12 is 265 nm. The attenuation of this optical fiber at 1550 nm is 0.78 dB / km.

[0029] (Example 4) Manufacturing of fiber optic preforms: As shown in Figure 7, first, one solid core rod is selected, the material is pure silica, the outer diameter of the core rod is 63 mm, and the length is 1000 mm. Using the drilling method, six small circular holes are drilled into the core rod as axial holes 3. The axial holes 3 are arranged at equiazimuth angles (azimuth angle is 60°), and the diameter of the axial holes is 7.4 mm. Furthermore, a large circular hole 18 is drilled in the center of the core rod as a sleeve center hole, and the ratio of the minimum distance between the inner wall of axial holes 3 and the inner wall of the sleeve center hole (large circular hole 18) to the diameter of the axial holes is 0.16. The drilled sleeve is then etched in an acid solution, and the ratio of the minimum distance between the inner wall of the axial holes and the inner wall of the sleeve center hole after etching to the diameter of the axial holes is 0.07. Next, a quartz piece 13 with a thickness of 0.19 mm is inserted into the axial hole, and the central perpendicular of the quartz piece 13 is passed through the center of the core rod, completing the manufacturing of the optical fiber preform rod 1 with a connecting piece structure.

[0030] Manufacturing of hollow core microstructure optical fibers: A fiber optic preform 1 having a connecting piece structure is placed in a high-temperature drawing furnace and drawn. The furnace temperature is 1735°C, and the hollow core portion in the middle of the preform maintains a pressure equal to atmospheric pressure. Gas of equal pressure is passed through six axial holes, and the pressure is 2.6 kPa. Due to the pressure difference inside and outside the axial holes, the axial holes expand after drawing, forming an anti-resonance ring 14. Quartz pieces 13 inserted into the axial holes 3 form anti-resonance pieces 15, and all the anti-resonance pieces 15 jointly constitute a second anti-resonance layer, finally forming a hollow core microstructure optical fiber 4 as shown in Figure 8. The outer diameter of the optical fiber cladding layer 5 is 201 μm, the diameter of the optical fiber hollow fiber core 7 is 53.2 μm, the thinnest wall thickness of the anti-resonance ring 14 is 616 nm, and the thinnest wall thickness of the anti-resonance pieces 15 is 543 nm. The attenuation of this optical fiber at 1550 nm is 1.54 dB / km.

[0031] To those skilled in the art, the above are merely preferred embodiments of the present invention and do not limit it. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0032] (Note) (Note 1) A sleeve is included, wherein a plurality of circumferentially distributed axial holes are formed within the tube wall of the sleeve, the minimum distance t1 between the inner wall of the axial holes and the inner wall of the sleeve is located towards the center of the sleeve, and the ratio of t1 to the diameter of the axial holes is 0.35 or less. Integrated hollow core optical fiber preform.

[0033] (Note 2) The axial holes are characterized by being uniformly distributed along the same annular line and having four or more holes. The integrated hollow core optical fiber preform described in Appendix 1.

[0034] (Note 3) The sleeve is characterized in that the ratio of its inner diameter to its outer diameter is 0.2 to 0.8. The integrated hollow core optical fiber preform described in Appendix 1.

[0035] (Note 4) A capillary tube is inserted into the axial hole to form a nested optical fiber preform, characterized in that The integrated hollow core optical fiber preform described in Appendix 1.

[0036] (Note 5) A quartz piece is inserted into the axial hole to form an optical fiber preform with a connecting piece structure, characterized in that The integrated hollow core optical fiber preform described in Appendix 1.

[0037] (Note 6) Step 1 involves selecting one sleeve, perforating from the end of the sleeve, and manufacturing an integrated hollow core optical fiber preform as described in one of the appendices 1 to 5. Step 2 involves drawing the integrated hollow core optical fiber preform obtained in Step 1 at a high temperature, passing gas through the axial holes during the drawing process to raise the air pressure in the axial holes higher than the air pressure in the sleeve center hole, and, due to the differential pressure between the axial holes and the sleeve center hole and the action of surface tension, causing the drawn axial holes to protrude in the direction of the sleeve center hole, thereby forming a negative curvature anti-resonance ring, and all the anti-resonance rings together to form an annular anti-resonance layer, and the region surrounded by the anti-resonance layer to form a hollow fiber core, thereby forming a hollow core microstructure optical fiber having a negative curvature anti-resonance ring. Features including, A method for manufacturing a hollow core microstructure optical fiber.

[0038] (Note 7) In step 1, the axial hole is corroded by passing an acid solution through it after drilling, so that the ratio of the minimum distance t1 between the inner wall of the axial hole and the inner wall of the sleeve to the diameter of the axial hole is 0.1 or less. A method for manufacturing a hollow-core microstructure optical fiber as described in Appendix 6.

[0039] (Note 8) In step 1, the acid solution is characterized by being hydrofluoric acid. A method for manufacturing a hollow-core microstructure optical fiber as described in Appendix 7.

[0040] (Note 9) In step 1, if a capillary tube is fitted into the axial hole, gas is also passed through the capillary tube to control the decrease in the pressure gradient between the capillary tube, the axial hole, and the sleeve center hole. A method for manufacturing a hollow-core microstructure optical fiber as described in Appendix 6.

[0041] (Note 10) In step 1, the gas passed through the axial hole or capillary tube is characterized by being one or more of compressed air, nitrogen, helium, and argon. A method for manufacturing a hollow-core microstructure optical fiber as described in Appendix 9.

[0042] (Note 11) In step 2, a cladding layer is formed by the anti-resonance layer and the drawn-out sleeve, the outer diameter of the cladding layer is 100 to 300 μm, and the diameter of the fiber core is 10 to 50 μm. A method for manufacturing a hollow-core microstructure optical fiber as described in Appendix 6.

[0043] (Note 12) In step 2, the minimum wall thickness of the anti-resonance ring is 2 μm or less, A method for manufacturing a hollow-core microstructure optical fiber as described in Appendix 6.

[0044] (Note 13) It is characterized by being manufactured using the manufacturing method described in any one of the appendices 6 to 12. Hollow core microstructure optical fiber. [Explanation of Symbols]

[0045] 1: Optical fiber preform, 2: Sleeve, 3: Axial hole, 4: Hollow core microstructure optical fiber, 5: Optical fiber cladding layer, 6: Anti-resonance ring, 7: Hollow fiber core, 10: Capillary tube, 11: First layer anti-resonance ring, 12: Second layer anti-resonance ring, 13: Quartz piece, 14: Anti-resonance ring, 15: Anti-resonance piece, 16: Axial hole, 17: Sleeve inner wall, 18: Large circular hole.

Claims

1. The device includes a sleeve, in which a plurality of circumferentially distributed axial holes are formed within the wall of the sleeve, and the minimum distance t between the inner wall of the axial holes and the inner wall of the sleeve is １ It is located on the sleeve center side, and t １ The ratio of the diameter of the axial hole to the diameter of the axial hole is 0.35 or less. Integrated hollow core optical fiber preform.

2. The axial holes are characterized by being uniformly distributed along the same annular line and having four or more holes. The integrated hollow core optical fiber preform according to claim 1.

3. The sleeve is characterized in that the ratio of the inner diameter to the outer diameter is 0.2 to 0.

8. The integrated hollow core optical fiber preform according to claim 1.

4. A capillary tube is inserted into the axial hole to form a nested optical fiber preform, characterized in that The integrated hollow core optical fiber preform according to claim 1.

5. A quartz piece is inserted into the axial hole to form an optical fiber preform with a connecting piece structure, characterized in that The integrated hollow core optical fiber preform according to claim 1.

6. Step 1 involves selecting a sleeve, perforating from the end of the sleeve, and manufacturing an integrated hollow core optical fiber preform according to any one of claims 1 to 5. Step 2 involves drawing the integrated hollow core optical fiber preform obtained in Step 1 at a high temperature, passing gas through the axial holes during the drawing process to raise the air pressure in the axial holes higher than the air pressure in the sleeve center hole, causing the drawn axial holes to protrude towards the sleeve center hole due to the differential pressure between the axial holes and the sleeve center hole and the action of surface tension, forming a negative curvature anti-resonance ring, and all the anti-resonance rings together to form an annular anti-resonance layer, and the region surrounded by the anti-resonance layer to form a hollow fiber core, thereby forming a hollow core microstructure optical fiber having a negative curvature anti-resonance ring. Features including, A method for manufacturing a hollow core microstructure optical fiber.

7. In step 1, after drilling, the axial hole is corroded by passing an acid solution through it, and the minimum distance t between the inner wall of the axial hole and the inner wall of the sleeve is measured. １ The ratio of the diameter of the axial hole to the diameter of the axial hole is 0.1 or less. A method for manufacturing a hollow core microstructure optical fiber according to claim 6.

8. In step 1, the acid solution is characterized by being hydrofluoric acid. A method for manufacturing a hollow core microstructure optical fiber according to claim 7.

9. In step 1, if a capillary tube is fitted into the axial hole, gas is also passed through the capillary tube to control the decrease in the pressure gradient between the capillary tube, the axial hole, and the sleeve center hole. A method for manufacturing a hollow core microstructure optical fiber according to claim 6.

10. In step 1, the gas passed through the axial hole or capillary tube is characterized by being one or more of compressed air, nitrogen, helium, and argon. A method for manufacturing a hollow core microstructure optical fiber according to claim 9.

11. In step 2, a cladding layer is formed by the anti-resonance layer and the drawn-out sleeve, the outer diameter of the cladding layer is 100 to 300 μm, and the diameter of the fiber core is 10 to 50 μm. A method for manufacturing a hollow core microstructure optical fiber according to claim 6.

12. In step 2, the minimum wall thickness of the anti-resonance ring is 2 μm or less. A method for manufacturing a hollow core microstructure optical fiber according to claim 6.

13. comprising a cladding layer and a hollow fiber core, The hollow fiber core is surrounded by an anti-resonance layer. The aforementioned hollow fiber core has a gear shape, The tooth profile of the gear is an arc-shaped tooth groove. The anti-resonance layer consists of four or more anti-resonance rings arranged at intervals around the hollow fiber core. The anti-resonance ring is aligned with the arc-shaped tooth groove of the hollow fiber core. The anti-resonance ring consists of a thin arc-shaped wall formed between the arc-shaped tooth groove and the expanded convex hole. The aforementioned expanded convex hole protrudes toward the center of the hollow fiber core, The thin wall of the formed arc is an anti-resonant ring with negative curvature. The aforementioned expanded convex hole is a circular hole formed by differential pressure and surface tension when the axial hole and sleeve center hole of the optical fiber preform are drawn, with a smaller radius at one end and a larger radius at the other end, and after drawing, the axial hole protrudes in the direction of the sleeve center hole. Characterized by, A hollow-core microstructure optical fiber having an anti-resonant ring with negative curvature.

14. The anti-resonance ring with negative curvature formed by the large end of the circular hole and the arc-shaped tooth groove in the hollow fiber core is the first layer anti-resonance ring. A second anti-resonance ring is positioned near the small end of the circular hole in the cladding layer. The preceding second layer anti-resonance ring is a cylindrical anti-resonance ring, The aforementioned cylindrical anti-resonance ring is formed by drawing out nested capillaries in the axial holes of the optical fiber preform. Characterized by, A hollow core microstructure optical fiber according to claim 13.

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