Low-loss hollow-core optical fiber and application

Abstract

The invention relates to a low-loss hollow-core optical fiber and application, the low-loss hollow-core optical fiber comprises an outer cladding and an inner cladding, the inner cladding is composed of anti-resonance structure units, the anti-resonance structure units are arranged in the circumferential direction of the inner wall of the outer cladding and are connected with the inner wall of the outer cladding, a fiber core is formed by a central cavity wrapped by the inner cladding, and the fiber core is connected with the inner cladding. The filter is characterized in that each anti-resonance structure unit comprises four or more than four layers of circular anti-resonance tubes with different radiuses, and an outer anti-resonance tube of each anti-resonance structure unit is tangent to the inner wall of the outer cladding; every two adjacent circular anti-resonance tubes are tangent in sequence, and the positions of all tangent points are alternately switched from outside to inside on the side away from the geometric center of the fiber core and on the side close to the geometric center of the fiber core. In the structure of the optical fiber, transmitted light is effectively limited in the fiber core for low-loss transmission by the multi-layer anti-resonance glass layer and the air area contained in the inner cladding; the number of reflecting surfaces in the inner cladding layer is increased by arranging the four layers of glass nested tubes, and the loss of the hollow-core optical fiber is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of hollow-core optical fibers, and in particular to a low-loss hollow-core optical fiber and its application. Background Art

[0002] Since the advent of the first solid optical fiber, fiber optic technology has undergone over half a century of development and has been widely used in various fields including communications, sensing, and healthcare. With the rapid development of society and the improvement of people's living standards, there is an urgent need for optical fibers with longer transmission distances, higher power, and greater capacity. However, the performance of traditional quartz optical fibers has reached its theoretical limits, prompting people to explore more advanced optical fiber technologies to meet the growing demand for data transmission.

[0003] As a new type of optical fiber, hollow-core fiber confines light waves within an air core, offering inherent advantages such as low Rayleigh scattering, low nonlinearity, and tunable dispersion. This allows for theoretically extremely low loss and a higher laser damage threshold, leading to potential applications in high-power laser transmission, ultraviolet / mid-infrared light transmission, pulse compression, and soliton transmission. Furthermore, the air core's large mode area, single-mode operation, low nonlinearity, low dispersion, and low latency make it promising for breaking the nonlinear Shannon limit of traditional optical fiber and providing a novel transmission medium for next-generation high-capacity, long-distance optical communication systems.

[0004] A common structure of hollow-core optical fiber is a multi-layer nested nodeless hollow-core optical fiber. Relevant patents are mostly concentrated on double-layer nested structures and triple-layer nested structures, such as patents CN111474627B, CN117388980A, and CN118688896A. However, there is little research on hollow-core optical fibers with four or more nested structures in the currently disclosed technologies. At the same time, lower optical fiber attenuation can also be achieved by adding a glass anti-resonance layer in the inner cladding. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to propose a low-loss hollow-core optical fiber and its application that can reduce the transmission loss of the hollow-core optical fiber in response to the deficiencies in the above-mentioned prior art.

[0006] The technical solution adopted by the present invention to solve the above-mentioned problems is: A low-loss hollow-core optical fiber comprises an outer cladding and an inner cladding, wherein the inner cladding is composed of antiresonance structural units, which are arranged circumferentially along the inner wall of the outer cladding and connected to the inner wall of the outer cladding. The central cavity covered by the inner cladding forms a fiber core. The invention is characterized in that: the antiresonance structural units include four or more layers of circular antiresonance tubes of different radii, the outer antiresonance tubes of the antiresonance structural units are tangent to the inner wall of the outer cladding; two adjacent circular antiresonance tubes are tangent to each other in sequence, and the positions of the tangent points alternate from the outside to the inside, away from the geometric center of the fiber core and close to the geometric center of the fiber core.

[0007] According to the above technical solution, the anti-resonance structure unit includes four layers of anti-resonance tubes with different radii, including an outer anti-resonance tube, a first inner anti-resonance tube, a second inner anti-resonance tube and a third inner anti-resonance tube from the outside to the inside. The outer anti-resonance tube is tangent to the inner wall of the outer cladding; the first inner anti-resonance tube is tangent to the inner wall of the outer anti-resonance tube, and the tangent point is on the side away from the geometric center of the fiber core; the second inner anti-resonance tube is tangent to the inner wall of the first inner anti-resonance tube, and the tangent point is on the side close to the geometric center of the fiber core; the third inner anti-resonance tube is tangent to the inner wall of the second inner anti-resonance tube, and the tangent point is on the side away from the geometric center of the fiber core.

[0008] According to the above technical solution, the line connecting the centers of curvature of each anti-resonance tube coincides with the extended line connecting the center of curvature of the outer anti-resonance tube and the geometric center of the fiber core.

[0009] According to the above technical solution, a line connecting the centers of curvature of at least one adjacent and tangent antiresonance tube and a line connecting the geometric center of the fiber core and the center of curvature of the outer antiresonance tube form a deflection angle.

[0010] According to the above technical solution, the deflection angle is greater than 0° and less than or equal to 90°.

[0011] According to the above technical solution, the ratios of the outer diameters of the outer anti-resonance tube, the first inner anti-resonance tube, the second inner anti-resonance tube and the third inner anti-resonance tube are 1:0.75-0.9:0.55-0.75:0.3-0.55 respectively.

[0012] According to the above technical solution, the wall thickness of each internal anti-resonance tube is the same, which is 0.3~1.5μm.

[0013] According to the above technical solution, the wall thickness of each inner anti-resonance tube is different, and the thickness of each anti-resonance tube increases from the outside to the inside. The wall thickness of the outer anti-resonance tube is 0.8-1.22 μm, the wall thickness of the first inner anti-resonance tube is 0.8-1.5 μm, the wall thickness of the second inner anti-resonance tube is 0.8-1.5 μm, and the wall thickness of the third inner anti-resonance tube is 1.22-1.5 μm.

[0014] According to the above technical solution, the inner cladding has 4 to 6 anti-resonance structural units.

[0015] According to the above technical solution, the outer cladding and the inner wall are both circular.

[0016] According to the above technical solution, the outer cladding layer and the substrate material of the anti-resonance structure unit are both pure quartz glass.

[0017] According to the above technical solution, the core region and other hollow regions within the inner cladding are filled with gas.

[0018] According to the above technical solution, the gas is argon, nitrogen, helium, air or a mixture of multiple gases.

[0019] According to the above technical solution, the LP01 mode loss of the optical fiber is lower than 1 dB / km.

[0020] An application of the low-loss hollow-core optical fiber as described above is characterized in that the low-loss hollow-core optical fiber is used in the fields of communication, laser or sensing.

[0021] The beneficial effects of the present invention are: 1. In the structure of the present invention, the multiple layers of antiresonant nested glass layers and air regions contained in the inner cladding effectively confine the transmitted light to the fiber core for low-loss transmission. By providing four or more layers of nested glass tubes, the number of reflective surfaces in the inner cladding is increased, thereby reducing the loss of the hollow-core optical fiber.

[0022] 2. This structure increases the number of glass tubes and the number of glass reflective layers to at least 9, so that light can be reflected back to the fiber core multiple times, thus achieving low-loss transmission. The tangent points between the glass tubes are separated from each other to minimize the geometric deformation caused by adhesion. Excessive geometric deformation will significantly increase the loss of the optical fiber.

[0023] 3. Since the glass tube wall of the hollow-core optical fiber itself acts as a Fabry-Perot resonant cavity, different wall thicknesses can cause it to be in an antiresonant state at the corresponding wavelength, and light is reflected back to the fiber core. When the antiresonance tube is thin, it can reflect light corresponding to shorter wavelengths, and when the antiresonance tube is thicker, it can reflect light corresponding to longer wavelengths. The present invention can achieve complementary antiresonance effects for light of different wavelengths by arranging antiresonance tubes with increasing thickness from the outside to the inside, thereby achieving a good low-attenuation bandwidth. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0025] Figure 1 This is a radial cross-sectional structure diagram of a low-loss hollow-core optical fiber provided in Example 1 of the present invention.

[0026] Figure 2 This is a partially enlarged view of an anti-resonance tube in Example 1 of the present invention. Figure 3 This is a graph showing how the LP01 mode loss varies with wavelength in the first embodiment of the present invention.

[0027] Figure 4 This is a radial cross-sectional structure diagram of a low-loss hollow-core optical fiber provided in Example 2 of the present invention.

[0028] Figure 5 This is a radial cross-sectional structure diagram of a low-loss hollow-core optical fiber provided in Example 3 of the present invention.

[0029] Figure 6 This is a radial cross-sectional structure diagram of a low-loss hollow-core optical fiber provided in Example 4 of the present invention. DETAILED DESCRIPTION

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Generally, the components of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations.

[0031] Example 1: The first embodiment of the present invention is Figure 1 、 2As shown, it includes an outer cladding 1 and an inner cladding, the inner cladding is composed of four anti-resonance structural units, the anti-resonance structural units are arranged along the circumference of the inner wall of the outer cladding and connected to the inner wall of the outer cladding, and the central cavity covered by the inner cladding forms a fiber core 10. The anti-resonance structural unit includes four layers of circular anti-resonance tubes with different radii, including an outer anti-resonance tube 2, a first inner anti-resonance tube 3, a second inner anti-resonance tube 4 and a third inner anti-resonance tube 5, which constitute an anti-resonance unit. The circular anti-resonance tubes include four circular anti-resonance tubes with different radii, wherein the diameter of the outer anti-resonance tube is d1, the diameter of the first inner anti-resonance tube is d2, the diameter of the second inner anti-resonance tube is d3, and the diameter of the third inner anti-resonance tube is d4, wherein the wall thickness of the outer anti-resonance tube is h1, the wall thickness of the first inner anti-resonance tube is h2, the wall thickness of the second inner anti-resonance tube is h3, and the wall thickness of the third inner anti-resonance tube is h4. The line connecting the centers of curvature of the first, second, third, and fourth inner antiresonance tubes completely coincides with the extension of the line connecting the center of curvature of the outer antiresonance tube and the geometric center of the fiber core. The outer wall of the outer antiresonance tube is tangent to the inner wall of the outer cladding; the outer wall of the first inner antiresonance tube is tangent to the inner wall of the outer antiresonance tube, with the tangent point located on the side away from the geometric center of the fiber core; the outer wall of the second inner antiresonance tube is tangent to the inner wall of the second nested tube, with the tangent point located on the side close to the geometric center of the fiber core; and the third inner antiresonance tube is tangent to the inner wall of the second inner antiresonance tube, with the tangent point located on the side away from the geometric center of the fiber core. The core region and other internal spaces, including the outer antiresonance tube cavity 6, the first inner antiresonance tube cavity 7, the third nested tube glass cavity 8, and the fourth nested glass cavity 9, are filled with gas. The gas is argon, nitrogen, helium, air, or a mixture of multiple gases.

[0032] Specifically, the relevant parameters of this embodiment are: the core diameter D is 31 μm, the outer diameter d1 of the outer antiresonance tube is 54 μm, the outer diameter d2 of the first inner antiresonance tube is 46 μm, the outer diameter d3 of the second inner antiresonance tube is 38 μm, and the outer diameter d4 of the third inner antiresonance tube is 28 μm; the inner diameter of the outer cladding (the outer cladding cavity diameter) is 139 μm, and the wall thickness h1 of the outer antiresonance tube, the wall thickness h2 of the first inner antiresonance tube, the wall thickness h3 of the second inner antiresonance tube, and the wall thickness h4 of the third inner antiresonance tube are all 1.22 μm. This embodiment also provides an application of a low-loss hollow-core optical fiber, which is applied to the fields of communication, laser, or sensing.

[0033] The present invention has both a reasonable and feasible nested structure and an optimized anti-resonance tube structure, which comprehensively produces the following technical effects: the nine glass reflection layers brought by the four-layer anti-resonance tube can significantly reduce the attenuation of the hollow-core optical fiber, such as Figure 3 As shown, the minimum loss of the LP01 mode of the present invention is 0.027dB / km.

[0034] Example 2: The second embodiment of the present invention is Figure 4 As shown, it differs from the first embodiment in that the third inner antiresonance tube is tangent to the inner wall of the second inner antiresonance tube and is deflected to one side, that is, the line L1 connecting the center of curvature of the third inner antiresonance tube and the center of curvature of the second inner antiresonance tube forms a deflection angle with the line L2 connecting the geometric center of the fiber core and the center of curvature of the outer antiresonance tube, and the deflection angle is 50°.

[0035] Example 3: The third embodiment of the present invention is Figure 5 As shown, the difference from the second embodiment is that the second inner anti-resonance tube is tangent to the inner wall of the first inner anti-resonance tube and deflected to one side, that is, the line L3 connecting the center of curvature of the second inner anti-resonance tube and the center of curvature of the first inner anti-resonance tube and the line L4 connecting the geometric center of the fiber core and the center of curvature of the outer anti-resonance tube form a deflection angle of 45°.

[0036] Example 4: The fourth embodiment of the present invention is Figure 6 As shown, it differs from the third embodiment in that the first inner anti-resonance tube is tangent to the inner wall of the outer anti-resonance tube and deflected to one side, that is, the line L5 connecting the center of curvature of the first inner anti-resonance tube and the center of curvature of the outer anti-resonance tube and the line L6 connecting the geometric center of the fiber core and the center of curvature of the outer anti-resonance tube form a deflection angle of 60°.

[0037] Among them, the wall thickness h1 of the outer anti-resonance tube, the wall thickness h2 of the first inner anti-resonance tube, the wall thickness h3 of the second inner anti-resonance tube, and the wall thickness h4 of the second inner anti-resonance tube are different, and increase in thickness from the outside to the inside, which are 0.8μm, 1μm, 1.22μm, and 1.35μm respectively.

[0038] The embodiments described above are part of the embodiments of the present application, rather than all of the embodiments. The detailed description of the embodiments of the present application is not intended to limit the scope of the present application for protection, but merely represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

Claims

1. A low-loss hollow-core optical fiber comprising an outer cladding and an inner cladding, wherein the inner cladding is composed of antiresonant structural units arranged circumferentially along and in contact with the inner wall of the outer cladding, and a central cavity enclosed by the inner cladding forms a fiber core, characterized in that: The anti-resonance structure unit includes four or more layers of circular anti-resonance tubes with different radii. The outer anti-resonance tube of the anti-resonance structure unit is tangent to the inner wall of the outer cladding. Two adjacent circular anti-resonance tubes are tangent to each other in sequence, and the positions of the tangent points are alternately switched from the outside to the inside on the side away from the geometric center of the fiber core and the side close to the geometric center of the fiber core.

2. The low-loss hollow-core optical fiber according to claim 1, wherein: The anti-resonance structure unit includes four layers of anti-resonance tubes with different radii, including an outer anti-resonance tube, a first inner anti-resonance tube, a second inner anti-resonance tube and a third inner anti-resonance tube from the outside to the inside. The outer anti-resonance tube is tangent to the inner wall of the outer cladding; the first inner anti-resonance tube is tangent to the inner wall of the outer anti-resonance tube, and the tangent point is on the side away from the geometric center of the fiber core; the second inner anti-resonance tube is tangent to the inner wall of the first inner anti-resonance tube, and the tangent point is on the side close to the geometric center of the fiber core; the third inner anti-resonance tube is tangent to the inner wall of the second inner anti-resonance tube, and the tangent point is on the side away from the geometric center of the fiber core.

3. The low-loss hollow-core optical fiber according to claim 1 or 2, characterized in that: The line connecting the centers of curvature of each anti-resonance tube coincides with the extended line connecting the center of curvature of the outer anti-resonance tube and the geometric center of the fiber core.

4. The low-loss hollow-core optical fiber according to claim 1 or 2, characterized in that: A line connecting the centers of curvature of at least two adjacent and tangent antiresonance tubes and a line connecting the geometric center of the fiber core and the center of curvature of the outer antiresonance tube form a deflection angle.

5. The low-loss hollow-core optical fiber according to claim 4, characterized in that: The deflection angle is greater than 0° and less than or equal to 90°.

6. The low-loss hollow-core optical fiber according to claim 2, wherein: The ratios of the outer diameters of the outer anti-resonance tube, the first inner anti-resonance tube, the second inner anti-resonance tube and the third inner anti-resonance tube are 1:0.75-0.9:0.55-0.75:0.3-0.55 respectively.

7. The low-loss hollow-core optical fiber according to claim 1 or 2, characterized in that: The wall thickness of each internal anti-resonance tube is the same, ranging from 0.3 to 1.5 μm.

8. The low-loss hollow-core optical fiber according to claim 6, wherein: The wall thickness of each inner anti-resonance tube is different. The thickness of each anti-resonance tube increases from the outside to the inside. The wall thickness of the outer anti-resonance tube is 0.8-1.22 μm, the wall thickness of the first inner anti-resonance tube is 0.8-1.5 μm, the wall thickness of the second inner anti-resonance tube is 0.8-1.5 μm, and the wall thickness of the third inner anti-resonance tube is 1.22-1.5 μm.

9. The low-loss hollow-core optical fiber according to claim 1 or 2, characterized in that: The inner cladding has 4 to 6 anti-resonance structural units.

10. The low-loss hollow-core optical fiber according to claim 1 or 2, characterized in that: The outer cladding and the inner wall are both circular.

11. The low-loss hollow-core optical fiber according to claim 1 or 2, characterized in that: The outer cladding layer and the substrate material of the anti-resonance structure unit are both made of pure quartz glass.

12. The low-loss hollow-core optical fiber according to claim 1 or 2, characterized in that: The core region and other hollow regions within the inner cladding are filled with gas.

13. The low-loss hollow-core optical fiber according to claim 12, wherein: The gas is argon, nitrogen, helium, air or a mixture of multiple gases.

14. The low-loss hollow-core optical fiber according to claim 1 or 2, characterized in that: The LP01 mode loss of the optical fiber is lower than 1 dB / km.

15. Use of the low-loss hollow-core optical fiber according to any one of claims 1 to 14, characterized in that: The low-loss hollow-core optical fiber is used in the fields of communication, laser or sensing.

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