Hollow core optical fiber preform, optical fiber and method for manufacturing the same

Abstract

The application belongs to the technical field of optical fiber communication, and discloses a hollow optical fiber preform, an optical fiber and a preparation method thereof. The hollow optical fiber preform provided by the application comprises a sleeve and anti-resonance units. The sleeve is in a tubular structure, and the anti-resonance units are fixedly arranged on the inner wall of the sleeve at equal intervals. The area surrounded by the anti-resonance units constitutes a central hole of the hollow optical fiber preform. The anti-resonance units are composed of one or more capillary tubes, and at least one capillary tube in the anti-resonance units has a non-circular structure. The application can realize accurate positioning of the anti-resonance units in the hollow optical fiber.

Description

Technical Field

[0001] This invention belongs to the field of optical fiber communication technology, and more specifically, relates to a hollow optical fiber preform, an optical fiber, and a method for preparing the same. Background Technology

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

[0003] Hollow-core optical fibers offer significant advantages in design and application; however, their transmission loss has consistently exceeded that of traditional silica optical fibers. Recent discoveries have shown that hollow-core optical fibers based on the anti-resonance principle, with proper structural design, can effectively reduce transmission loss and possess the potential to serve as ultra-long-distance communication fibers. While known anti-resonant hollow-core fibers, particularly those with nested structural elements, can significantly reduce fiber attenuation, their complex internal geometry and the fact that even minute geometric deviations can alter the anti-resonance conditions make precise and repeatable production difficult. Achieving precise positioning of the anti-resonant units within hollow-core optical fibers and ensuring axial uniformity remains a crucial challenge in this field. Summary of the Invention

[0004] This invention provides a hollow fiber preform, an optical fiber, and a method for preparing the same, thereby solving the problem of accurately positioning the anti-resonant unit of hollow fiber in the prior art.

[0005] In a first aspect, the present invention provides a hollow optical fiber preform, comprising: a sleeve and anti-resonance units; the sleeve is a tubular structure, and a plurality of anti-resonance units are fixedly disposed at equal intervals on the inner wall of the sleeve, the area enclosed by the plurality of anti-resonance units constitutes the central hole of the hollow optical fiber preform; the anti-resonance units are composed of one or more capillaries, and at least one of the capillaries in the anti-resonance units has a missing circle structure.

[0006] Preferably, the anti-resonance unit is composed of multiple capillaries of different sizes nested together, and at least one of the multiple capillaries has a missing circle structure.

[0007] Preferably, the anti-resonance unit is composed of a capillary with a missing circle structure, the notch of the capillary facing the inner wall of the sleeve.

[0008] Preferably, the number of anti-resonant units is greater than or equal to 4.

[0009] Preferably, the various capillaries constituting the anti-resonance unit have different diameters but the same missing circle chord length. The various capillaries are numbered from 1 to n in descending order of diameter, and the various capillaries satisfy the following formula:

[0010] sinθ i ·(D i -T i )=sinθ i+1 ·D i+1

[0011] In the formula, θ i Let D be the missing circle angle of the i-th type of capillary. i Let T be the outer diameter of the i-th type of capillary. i Let θ be the wall thickness of the i-th type of capillary. i+1 Let D be the missing circle angle of the (i+1)th type of capillary. i+1 Let be the outer diameter of the (i+1)th type of capillary, where i ranges from 1 to n-1;

[0012] Multiple capillaries are nested together and fixed together after the notches of each capillaries are aligned, to obtain the anti-resonance unit, wherein the notch of the anti-resonance unit faces the inner wall of the sleeve.

[0013] Preferably, the wall thickness T of the i-th type of capillary i With the outer diameter D of the i-th type of capillary i The ratio is greater than or equal to 20%.

[0014] Preferably, the anti-resonance unit is composed of two capillaries with different sizes. The anti-resonance unit is a double-layer anti-resonance unit with an outer missing circle and an inner positive circle. In the double-layer anti-resonance unit, the notch of the outer missing circle faces the inner wall of the sleeve.

[0015] Preferably, the anti-resonance unit is composed of two capillaries with different sizes, and the anti-resonance unit is a double-layer anti-resonance unit with an outer circle and an inner missing circle.

[0016] Preferably, the capillary is processed by mechanical grinding, wire cutting, or laser cutting to form a notch, thus obtaining the notched structure.

[0017] Secondly, the present invention provides a method for preparing hollow-core optical fiber, comprising the following steps:

[0018] Using the aforementioned hollow optical fiber preform as a primary preform, the primary preform is subjected to high-temperature drawing to obtain an intermediate.

[0019] Several intermediates are fitted into an outer sleeve and assembled to obtain a secondary preform;

[0020] Hollow optical fiber is obtained by drawing the secondary preform.

[0021] Thirdly, the present invention provides a hollow optical fiber, which is prepared by the above-described method for preparing hollow optical fibers.

[0022] Preferably, the cladding diameter of the hollow optical fiber is greater than or equal to 100 μm.

[0023] Preferably, the transmission loss of the hollow optical fiber is ≤30dB / km.

[0024] One or more technical solutions provided in this invention have at least the following technical effects or advantages:

[0025] The hollow-core optical fiber preform provided by this invention includes a sleeve and several anti-resonant units. Each anti-resonant unit is composed of one or more capillaries, and at least one capillary in the anti-resonant unit has a missing-circle structure. This missing-circle structure design facilitates a stable connection between various capillaries and / or a stable connection between the anti-resonant unit and the sleeve, helping to avoid azimuth shift of the anti-resonant unit during the preform stacking process. This allows for precise positioning of the anti-resonant unit and ensures axial uniformity. Furthermore, when the anti-resonant unit is composed of multiple capillaries, i.e., when the hollow-core optical fiber preform is a multi-layer nested structure, this invention increases the number of anti-resonant layers while maintaining the azimuth angle, further reducing fiber attenuation. This is particularly suitable for the fabrication of long-distance, highly uniform hollow-core optical fibers. Due to the above advantages of the preform, azimuth shift of the anti-resonant unit can also be avoided during the drawing process of hollow-core optical fibers using the preform, ensuring precise positioning of the anti-resonant unit in the hollow-core optical fiber and ensuring axial uniformity, making precise and repeatable production of hollow-core optical fibers easier. Furthermore, compared to existing technologies, this invention does not introduce other materials to position the anti-resonant unit (e.g., by inserting additional positioning templates made of other materials), thereby reducing impurity contamination and improving the attenuation and strength performance of the optical fiber. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the structure of a hollow optical fiber preform provided in Embodiment 1 of the present invention;

[0027] Figure 2 This is a schematic diagram of the structure of a hollow optical fiber preform before and after processing of the first capillary and the second capillary, as provided in Embodiment 1 of the present invention.

[0028] Figure 3 This is a schematic diagram of the anti-resonant unit in a hollow optical fiber preform provided in Embodiment 1 of the present invention;

[0029] Figure 4 This is a schematic diagram of the structure of a hollow optical fiber preform provided in Embodiment 2 of the present invention;

[0030] Figure 5 This is a schematic diagram of the structure of a hollow optical fiber preform provided in Embodiment 3 of the present invention;

[0031] Figure 6 This is a schematic diagram of the structure of a hollow optical fiber preform provided in Embodiment 4 of the present invention;

[0032] Figure 7 This is a schematic diagram of the structure of a hollow optical fiber preform provided in Embodiment 5 of the present invention. Detailed Implementation

[0033] To better understand the above technical solutions, the following will provide a detailed explanation of the technical solutions in conjunction with the accompanying drawings and specific implementation methods.

[0034] The present invention provides a hollow optical fiber preform, comprising: a sleeve and anti-resonance units; the sleeve is a tubular structure, and a plurality of anti-resonance units are fixedly disposed at equal intervals on the inner wall of the sleeve, the area enclosed by the plurality of anti-resonance units constitutes the central hole of the hollow optical fiber preform; the anti-resonance units are composed of one or more capillaries, and at least one of the capillaries in the anti-resonance units has a missing circle structure.

[0035] The number of anti-resonance units is greater than or equal to 4, and in a preferred embodiment, the number of anti-resonance units is 5 or 6.

[0036] The notch of the anti-resonance unit is adjacent to the inner wall of the sleeve.

[0037] The anti-resonance unit is preferably composed of two or three capillaries, each with a notched circular structure. Specifically, the notched structure is obtained by processing the capillaries through methods such as mechanical grinding, wire cutting, or laser cutting.

[0038] The capillary tube and the sleeve can be made of high-purity silicon dioxide, doped quartz (e.g., doped with one or more elements such as germanium, fluorine, chlorine, boron, and aluminum), multi-component glass, plastic, etc.

[0039] The following section describes various design methods for anti-resonance units.

[0040] (1) The anti-resonance unit is composed of multiple capillaries of different sizes nested together, and at least one of the multiple capillaries has a missing circle structure.

[0041] The following provides examples of three structures.

[0042] (1a) The various capillaries constituting the anti-resonant unit have different diameters but the same missing circle chord length. The various capillaries are numbered from 1 to n in descending order of diameter, and the following formula for equal chord lengths is satisfied among the various capillaries:

[0043] sinθ i ·(D i -T i )=sinθ i+1 ·D i+1

[0044] In the formula, θ i Let D be the missing circle angle of the i-th type of capillary. i Let T be the outer diameter of the i-th type of capillary. i Let θ be the wall thickness of the i-th type of capillary. i+1 Let D be the missing circle angle of the (i+1)th type of capillary. i+1 Let be the outer diameter of the (i+1)th type of capillary, where i ranges from 1 to n-1.

[0045] Multiple capillaries are nested together and fixed together after the notches of each capillaries are aligned, to obtain the anti-resonance unit, wherein the notch of the anti-resonance unit faces the inner wall of the sleeve.

[0046] Among them, the wall thickness T of the i-th type of capillary i With the outer diameter D of the i-th type of capillary i The ratio is greater than or equal to 20%, and in the preferred scheme, this ratio can be between 5% and 10%.

[0047] The above structure can ensure a stable connection between various capillaries and a stable connection between the anti-resonance unit and the sleeve, thereby ensuring that the anti-resonance unit will not shift its azimuth angle during the stacking process, achieving precise positioning of the anti-resonance unit and ensuring axial uniformity.

[0048] (1b) The anti-resonance unit is composed of two capillaries with different sizes. The anti-resonance unit is a double-layer anti-resonance unit with an outer missing circle and an inner positive circle. The notch of the outer missing circle in the double-layer anti-resonance unit faces the inner wall of the sleeve.

[0049] The above structure can ensure a stable connection between the anti-resonance unit and the sleeve, which helps to avoid the azimuth angle shift of the anti-resonance unit during the stacking process, thereby enabling the precise positioning of the anti-resonance unit and ensuring axial uniformity.

[0050] (1c) The anti-resonance unit is composed of two capillaries with different sizes. The anti-resonance unit is a double-layer anti-resonance unit with an outer circle and an inner missing circle.

[0051] The above structure can ensure a stable connection between various capillaries, thereby ensuring that the anti-resonant unit will not shift in azimuth during the stacking process, achieving precise positioning of the anti-resonant unit and ensuring axial uniformity.

[0052] Taking the anti-resonance unit comprising two types of capillaries as an example, the azimuth angle α in the above explanation of the advantages of the scheme refers to the angle between the line connecting the center of the capillary with the first size to the center of the sleeve and the line connecting the center of the capillary with the second size to the center of the sleeve. See [link to relevant documentation]. Figure 1 .

[0053] (2) The anti-resonance unit is composed of a capillary with a missing circle structure, the notch of the capillary facing the inner wall of the sleeve.

[0054] When the anti-resonance unit is composed of a capillary tube, a stable connection can be formed between the anti-resonance unit and the sleeve, thereby enabling precise positioning of the anti-resonance unit and ensuring axial uniformity.

[0055] Based on the above-described hollow fiber preform scheme, this invention also provides a method for preparing hollow fiber and a corresponding hollow fiber. Hollow fiber can be obtained by "stacking and drawing" the aforementioned hollow fiber preform.

[0056] Specifically, the present invention provides a method for preparing hollow optical fiber, comprising the following steps:

[0057] Using the aforementioned hollow optical fiber preform as a primary preform, the primary preform is subjected to high-temperature drawing to obtain an intermediate.

[0058] Several intermediates are fitted into an outer sleeve and assembled to obtain a secondary preform;

[0059] Hollow optical fiber is obtained by drawing the secondary preform.

[0060] The present invention provides a hollow optical fiber, which is prepared by the above-described method for preparing hollow optical fibers.

[0061] The cladding diameter of the hollow-core optical fiber is greater than or equal to 100 μm. The transmission loss of the hollow-core optical fiber is ≤30 dB / km, and in the preferred embodiment, the transmission loss is ≤1 dB / km.

[0062] The following examples illustrate this with reference to parameters.

[0063] Example 1:

[0064] See Figures 1 to 3 First, five capillaries of each of two sizes were selected. The larger diameter capillary, designated as capillary 110, has an outer diameter of 6.7 mm and a wall thickness of 0.4 mm. The smaller diameter capillary, designated as capillary 120, has an outer diameter of 4.3 mm and a wall thickness of 0.32 mm. A portion of both capillary 110 and capillary 120 was ground away axially to create notches. The notch angle θ1 of the processed capillary 111 is 55°, and the notch angle θ2 of the processed capillary 121 is 90°. The processed capillary 111 and capillary 121 were nested together, aligning their notches, and then fused together using an oxyhydrogen flame to form a double-layered anti-resonant unit 130. Five anti-resonance units 130 are arranged at equal intervals in a sleeve 140, which has an outer diameter of 34 mm and a wall thickness of 3.5 mm, thereby forming a hollow fiber preform.

[0065] When fabricating hollow optical fibers based on the aforementioned hollow optical fiber preform, the preform is first drawn into an intermediate body with an outer diameter of 5.6 mm in a high-temperature drawing furnace. Then, several of these intermediate bodies are fitted into an outer sheath with an outer diameter of 15 mm to assemble the final preform (i.e., the secondary preform). Finally, a hollow optical fiber with an outer diameter of 239 μm is obtained through drawing. This hollow optical fiber exhibits an attenuation of 3.7 dB / km at 1550 nm.

[0066] Example 2:

[0067] See Figure 4 First, a capillary tube of a specific size is selected, with an outer diameter of 8.8 mm and a wall thickness of 0.45 mm. This capillary tube is designated as the first capillary tube. A portion of the first capillary tube is cut off axially using laser cutting to create a notch. The notch angle of the first capillary tube is 47°. The processed first capillary tube constitutes an anti-resonance unit 210. Multiple anti-resonance units 210 are arranged at equal intervals in a sleeve 220. The sleeve 220 has an outer diameter of 45 mm and a wall thickness of 7 mm, thereby forming a hollow optical fiber preform.

[0068] When fabricating hollow optical fibers based on the aforementioned hollow optical fiber preform, the preform is drawn into an intermediate body with an outer diameter of 7.8 mm in a high-temperature drawing furnace. Several of these intermediate bodies are then assembled into a 23 mm outer diameter outer sheath to form the final preform, which is ultimately drawn into a hollow optical fiber with an outer diameter of 189 μm. This hollow optical fiber exhibits an attenuation of 14.7 dB / km at 1550 nm.

[0069] Example 3:

[0070] See Figure 5First, five capillaries of each of three sizes were selected. One type was a large-diameter capillary with an outer diameter of 7.5 mm and a wall thickness of 0.55 mm, designated as the first capillary; another type was a medium-diameter capillary with an outer diameter of 4.15 mm and a wall thickness of 0.3 mm, designated as the second capillary; and the third type was a small-diameter capillary with an outer diameter of 2.6 mm and a wall thickness of 0.23 mm, designated as the third capillary. A portion of each capillary was cut axially using laser cutting to create notches. The notch angle of the processed first capillary 310 was 38°, the notch angle of the processed second capillary 320 was 66°, and the notch angle of the processed third capillary 330 was 107°. The processed first capillary 310, the processed second capillary 320, and the processed third capillary 330 are nested together, with their notches aligned, and then fused together by laser welding to form a three-layer anti-resonance unit 340. Five of these anti-resonance units 340 are arranged at equal intervals in a sleeve 350, which has an outer diameter of 48 mm and a wall thickness of 10 mm, to form a hollow fiber preform.

[0071] When fabricating hollow optical fibers based on the aforementioned hollow optical fiber preform, the preform is drawn into an intermediate body with an outer diameter of 12.5 mm in a high-temperature drawing furnace. Several of these intermediate bodies are then assembled into a final preform by fitting them into an outer sheath with an outer diameter of 34 mm. Finally, the preform is drawn into a hollow optical fiber with an outer diameter of 156 μm. This hollow optical fiber exhibits an attenuation of 0.32 dB / km at 1550 nm.

[0072] Example 4:

[0073] See Figure 6 First, five capillaries of each of two sizes are selected. One type is a large-diameter capillary with an outer diameter of 12.3 mm and a wall thickness of 0.6 mm, designated as the first capillary; the other type is a small-diameter capillary with an outer diameter of 4.3 mm and a wall thickness of 0.5 mm, designated as the second capillary 420. A portion of the first capillary 410 is ground off axially to create a notch, resulting in a notch angle of 66°. The second capillary 420 is not ground. The processed first capillary 410s are then arranged at equal intervals in a sleeve 440, which has an outer diameter of 54 mm and a wall thickness of 7.9 mm. The second capillary 420s are then inserted into their corresponding processed first capillary 410s and fixed using an oxyhydrogen flame to form a double-layered anti-resonant unit 430 with an outer notch and an inner circle, thus obtaining a hollow fiber preform.

[0074] When fabricating hollow optical fibers based on the aforementioned hollow optical fiber preform, the preform is drawn into an intermediate body with an outer diameter of 9.5 mm in a high-temperature drawing furnace. Several of these intermediate bodies are then assembled into a final preform by fitting them into an outer sheath with an outer diameter of 28 mm. Finally, the preform is drawn into a hollow optical fiber with an outer diameter of 145 μm. This hollow optical fiber exhibits an attenuation of 0.71 dB / km at 1550 nm.

[0075] Example 5:

[0076] See Figure 7 First, six capillaries of each of two sizes are selected. One type is a large-diameter capillary with an outer diameter of 4.3 mm and a wall thickness of 0.34 mm, designated as the first capillary 510; the other type is a small-diameter capillary with an outer diameter of 2.1 mm and a wall thickness of 0.26 mm, designated as the second capillary. A portion of the second capillary is ground away axially to create a notch, resulting in a notch angle of 45° for the processed second capillary 520. The first capillary 510 is not ground. The first capillary 510 is then arranged at equal intervals in a sleeve 540, which has an outer diameter of 32 mm and a wall thickness of 4 mm. The processed second capillary 520 is then inserted into the corresponding first capillary 510, and both ends are fixed using an oxyhydrogen flame to form a double-layered anti-resonant unit 530 with an outer circle and an inner missing circle, thus obtaining a hollow fiber preform.

[0077] When fabricating hollow optical fibers based on the aforementioned hollow optical fiber preform, the preform is drawn into an intermediate body with an outer diameter of 7.6 mm in a high-temperature drawing furnace. Several of these intermediate bodies are then assembled into a final preform by fitting them into an outer sheath with an outer diameter of 32 mm. Finally, the preform is drawn into a hollow optical fiber with an outer diameter of 233 μm. This hollow optical fiber exhibits an attenuation of 0.46 dB / km at 1550 nm.

[0078] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A hollow optical fiber preform, characterized in that, include: A sleeve and anti-resonance units; the sleeve is a tubular structure, and a plurality of anti-resonance units are fixedly arranged at equal intervals on the inner wall of the sleeve, the area enclosed by the plurality of anti-resonance units constitutes the central hole of the hollow fiber preform; the anti-resonance unit is composed of one or more capillaries, and at least one of the capillaries in the anti-resonance unit has a missing circle structure; the capillaries are processed by mechanical grinding, wire cutting or laser cutting to form a notch, thus obtaining the missing circle structure; the missing circle structure is used to make a stable connection between multiple capillaries and / or to make a stable connection between the anti-resonance unit and the sleeve.

2. The hollow optical fiber preform according to claim 1, characterized in that, The anti-resonance unit is composed of multiple capillaries of different sizes nested together, and at least one of the capillaries has a missing circle structure.

3. The hollow optical fiber preform according to claim 1, characterized in that, The anti-resonance unit is composed of a capillary with a missing circle structure, the notch of which faces the inner wall of the sleeve.

4. The hollow optical fiber preform according to claim 1, characterized in that, The number of anti-resonance units is greater than or equal to 4.

5. The hollow optical fiber preform according to claim 2, characterized in that, The various capillaries constituting the anti-resonant unit have different diameters but the same missing circle chord length. These capillaries are numbered 1 to n sequentially from largest to smallest diameter, and the following formula applies to the various capillaries: sinθ i (D i -T i )=sinθ i+1 D i+1 In the formula, θ i Let D be the missing circle angle of the i-th type of capillary. i Let T be the outer diameter of the i-th type of capillary. i Let θ be the wall thickness of the i-th type of capillary. i+1 Let D be the missing circle angle of the (i+1)th type of capillary. i+1 Let be the outer diameter of the (i+1)th type of capillary, where i ranges from 1 to n-1; Multiple capillaries are nested together and fixed together after the notches of each capillaries are aligned, to obtain the anti-resonance unit, wherein the notch of the anti-resonance unit faces the inner wall of the sleeve.

6. The hollow optical fiber preform according to claim 5, characterized in that, The wall thickness T of the i-th type of capillary i With the outer diameter D of the i-th type of capillary i The ratio is greater than or equal to 20%.

7. The hollow optical fiber preform according to claim 2, characterized in that, The anti-resonance unit is composed of two capillaries with different sizes. The anti-resonance unit is a double-layer anti-resonance unit with an outer missing circle and an inner positive circle. In the double-layer anti-resonance unit, the notch of the outer missing circle faces the inner wall of the sleeve.

8. The hollow optical fiber preform according to claim 2, characterized in that, The anti-resonance unit is composed of two capillaries with different sizes. The anti-resonance unit is a double-layer anti-resonance unit with an outer circle and an inner missing circle.

9. A method for preparing hollow-core optical fiber, characterized in that, Includes the following steps: Using the hollow optical fiber preform as described in any one of claims 1-8 as a primary preform, the primary preform is subjected to high-temperature drawing to obtain an intermediate. Several intermediates are fitted into an outer tube and assembled to obtain a secondary preform; Hollow optical fiber is obtained by drawing the secondary preform.

10. A hollow-core optical fiber, characterized in that, The hollow-core optical fiber was prepared using the method described in claim 9.

11. The hollow-core optical fiber according to claim 10, characterized in that, The cladding diameter of the hollow optical fiber is greater than or equal to 100 μm.

12. The hollow-core optical fiber according to claim 10, characterized in that, The transmission loss of the hollow optical fiber is ≤30dB / km.

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