A hollow core antiresonant optical fiber

Abstract

The present invention provides a hollow-core anti-resonant optical fiber, comprising an outer cladding, an inner cladding and a core arranged in sequence from the outside to the inside, characterized in that the inner cladding comprises semicircular glass nested tubes and circular glass nested tubes arranged alternately at intervals; the refractive index of the semicircular glass nested tubes and the circular glass nested tubes is lower than the refractive index of the outer cladding. The present invention adopts an alternating interval distribution design of circular and semicircular nested tubes, which suppresses high-order mode coupling, reduces crosstalk between modes, and improves single-mode transmission efficiency; the refractive index of the semicircular glass nested tubes and the circular glass nested tubes is lower than that of the outer cladding, which can significantly expand the bandwidth of the hollow-core anti-resonant optical fiber and improve mechanical stability while maintaining low-loss transmission, and has broad application prospects.

Description

Technical Field

[0001] The present invention relates to the field of optical fiber technology, and in particular to a hollow core anti-resonance optical fiber. Background Art

[0002] Existing hollow-core antiresonant optical fibers have been widely used in fields such as ultrafast laser transmission, high-precision sensors and broadband communications due to their low nonlinearity, low dispersion and resistance to high power loss.

[0003] In existing research, hollow-core antiresonant fibers often use negative curvature, node-free, nested tube structures, which usually have problems such as high mode coupling, limited transmission bandwidth, and insufficient mechanical stability. Therefore, optimizing the geometric structure of hollow-core antiresonant fibers to achieve both transmission performance and structural stability requirements over a wider wavelength range has become a research hotspot. Summary of the invention

[0004] The purpose of the present invention is to overcome the defects of the prior art and provide a hollow core antiresonant optical fiber, which can solve the problems existing in the prior art such as high mode coupling, limited transmission bandwidth and insufficient mechanical stability.

[0005] In order to achieve the above purpose and other purposes, the present invention is implemented by including the following technical solutions: The present invention proposes a hollow-core antiresonant optical fiber, including an outer cladding, an inner cladding and a core arranged in sequence from the outside to the inside, characterized in that the inner cladding includes semicircular glass nested tubes and circular glass nested tubes arranged alternately at intervals; the refractive index of the semicircular glass nested tubes and the circular glass nested tubes is lower than the refractive index of the outer cladding.

[0006] In one embodiment, the layers of the semicircular glass nested tubes are concentrically arranged; and the layers of the circular glass nested tubes are tangent to the inner wall of the outer cladding at the same point.

[0007] In one embodiment, the semicircular glass nested tubes and the circular glass nested tubes are arranged in an alternating manner with equal spacing.

[0008] In one embodiment, the semicircular glass nested tubes and the circular glass nested tubes are arranged in an alternating manner with non-equidistant spacing.

[0009] In one embodiment, the closest distance between the semicircular glass nested tubes and the circular glass nested tubes cannot exceed 2 μm.

[0010] In one embodiment, the semicircular glass nested tubes and the circular glass nested tubes both have 2 to 3 layers.

[0011] In one embodiment, the ratio of the diameters of the layers of the circular glass nested tubes from the inside to the outside is 0.4-0.6:0.6-0.8:1.

[0012] In one embodiment, the refractive index of the outer cladding is 1.44-1.45, and the thickness ranges from 22.5 μm to 37.5 μm; the refractive index of the semicircular glass nested tube and the circular glass nested tube is 1.42-1.43, and the thickness of each layer of the tube wall ranges from 270 nm to 273 nm.

[0013] In one embodiment, the semicircular glass nested tubes and the circular glass nested tubes are made of silicon dioxide material doped with a specific element, and the specific element is one or more of fluorine, germanium, and boron.

[0014] In one embodiment, the semicircular glass nested tubes and the circular glass nested tubes are made of fluorine- and boron-doped silicon dioxide material.

[0015] In one embodiment, the center of the fiber core is filled with rarefied gas or vacuum, and the diameter is 20 μm to 30 μm.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] 1. The present invention adopts an alternating interval distribution design of circular and semicircular nested tubes, which suppresses high-order mode coupling, reduces crosstalk between modes, and improves single-mode transmission efficiency; the refractive index of the semicircular glass nested tube and the circular glass nested tube is lower than that of the outer cladding, which can significantly expand the bandwidth of the hollow-core anti-resonant fiber and improve the mechanical stability while maintaining low-loss transmission. The hollow-core anti-resonant fiber has a low-loss bandwidth of more than 200nm in the C band, and the average loss is less than 0.2dB / km;

[0018] 2. The closest distance design of the circular and semicircular nested tubes of the present invention can avoid light leakage, further reduce transmission loss, inhibit high-order mode coupling, and reduce crosstalk between modes;

[0019] 3. The present invention can significantly expand the low-loss transmission bandwidth of hollow-core anti-resonant optical fiber by optimizing the geometric parameters of the nested tube wall, and is suitable for optical signal transmission in multiple wavelength ranges;

[0020] 4. The semicircular tube wall of the present invention provides additional mechanical support, effectively enhances the compression and bending resistance of the optical fiber, reduces the optical fiber loss caused by external forces, and is suitable for applications in complex environments;

[0021] 5. The design of the nested tube wall of the present invention is flexible, and the size and material can be adjusted according to the target application requirements to adapt to a variety of optical scenarios;

[0022] 6. The design of the fiber core of the present invention can further reduce material dispersion and nonlinear effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1Shown is a schematic structural diagram of a hollow-core anti-resonant optical fiber of the present invention.

[0024] In the figure: 1. Outer cladding; 2. Inner cladding; 3. Semicircular glass nested tubes; 3-1. Semicircular inner nested tubes; 3-2. Semicircular outer nested tubes; 4. Circular glass nested tubes; 4-1. Circular inner nested tubes; 4-2. Circular middle nested tubes; 4-3. Circular outer nested tubes; 5. Fiber core. DETAILED DESCRIPTION

[0025] See also Figure 1 The following describes the embodiments of the present invention through specific examples. Those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification.

[0026] It should be noted that the structures, proportions, sizes, etc. illustrated in the drawings in this specification are only used to match the contents disclosed in the specification for the technical personnel in this field to understand and read, and are not used to limit the conditions under which the present invention can be implemented. Therefore, they have no substantive technical significance. Any modification of the structure, change in the proportion relationship or adjustment of the size should still fall within the scope of the technical contents disclosed in the present invention without affecting the effects and purposes that can be achieved by the present invention.

[0027] Unless otherwise defined, the technical or scientific terms used herein shall have the common meanings understood by persons with ordinary skills in the field to which the present invention belongs. The words "include" or "comprise" and the like used in the present invention mean that the elements or objects preceding the words include the elements or objects listed after the words and their equivalents, but do not exclude other elements or objects. The "connection" mentioned in the present invention includes direct and indirect connection unless otherwise specified.

[0028] like Figure 1 As shown, the present invention provides a hollow-core antiresonant optical fiber, comprising an outer cladding 1, an inner cladding 2 and a core 5 which are sequentially arranged from the outside to the inside.

[0029] The outer cladding 1 is made of silicon dioxide material with a refractive index of 1.44 to 1.45. The thickness of the outer cladding 1 ranges from 22.5 μm to 37.5 μm to provide mechanical strength and support effective reflection of the inner cladding mode. When higher bending resistance is required, it can be achieved by increasing the thickness of the outer cladding 1.

[0030] The inner cladding 2 includes semicircular glass nested tubes 3 and circular glass nested tubes 4 that are alternately arranged. The refractive index of the semicircular glass nested tubes 3 and circular glass nested tubes 4 is similar to that of the outer cladding 1, and the refractive index is 1.42-1.43. Specifically, a silica material doped with a specific element can be used to make its refractive index slightly lower than that of the outer cladding 1, so as to optimize the anti-resonance mechanism and ensure low loss and high stability transmission of the hollow core anti-resonance optical fiber in a specific band. The specific element can be one or more of fluorine, germanium, and boron.

[0031] Specifically, in Figure 1 In the hollow core antiresonant optical fiber shown, the semicircular glass nested tubes 3 and the circular glass nested tubes 4 are arranged in an equidistant and alternating manner, which can evenly distribute the optical mode reflection points in space, reduce the excitation of high-order modes, reduce the crosstalk between modes, and improve the single-mode transmission performance. It should be noted that under certain specific design goals, such as the goal of optimizing a certain wavelength, the semicircular glass nested tubes 3 and the circular glass nested tubes 4 can also be arranged in an unequally spaced and alternating manner, but the thickness or refractive index of the nested tube wall needs to be redesigned to compensate for the problem of uneven distribution of optical modes caused by the change in spacing.

[0032] Furthermore, the closest distance between the semicircular glass nested tube 3 and the circular glass nested tube 4 cannot exceed 2 μm. The distance between the semicircular glass nested tube 3 and the circular glass nested tube 4 will directly affect the reflection and interference behavior of light waves between different nested tubes. If the distance between the nested tubes is too large (more than 2 μm), part of the light may "leak" from the gap and cannot be effectively reflected back to the inner cladding, resulting in higher transmission loss. Conversely, if the distance is too small, it may induce excessive mode coupling, resulting in inter-mode interference or excitation of high-order modes.

[0033] Furthermore, the semicircular glass nested tube 3 and the circular glass nested tube 4 both have 2 to 3 layers. Multilayer nested tubes can further optimize the antiresonance conditions and form a stronger multi-level reflection structure. Each layer of nested tubes can effectively reflect light at different propagation angles, reduce the probability of light propagating outward, and thus reduce losses. Compared with single-layer glass tubes, multilayer nested tubes can cover a wider wavelength range, and the wall thickness of different layers can be designed to adapt to different wavelengths, so that the optical fiber has a wider low-loss bandwidth to meet the needs of communication, multimode transmission or special optical fiber. In the present invention, the semicircular glass nested tube 3 and the circular glass nested tube 4 select a nested structure of 2 to 3 layers to achieve a good balance between performance and manufacturing difficulty, meeting the needs of most practical applications. As the number of layers increases, the reflection interference of different layers may become complicated, resulting in enhanced coupling between optical modes, thereby introducing additional losses, and reducing the performance of the optical fiber. Therefore, when the number of nested layers exceeds 3, the reflection between the multiple layers may cause nonlinear effects or mode crosstalk, thereby weakening the support for low-loss transmission. The increase in complexity and manufacturing costs reduces practicality.

[0034] Furthermore, the layers of the semicircular glass nested tubes 3 are concentrically arranged and may include a semicircular inner nested tube 3-1 and a semicircular outer nested tube 3-2, wherein the diameter of the semicircular inner nested tube 3-1 is 12 μm to 17 μm, and the diameter of the semicircular outer nested tube 3-2 is 18 μm to 22 μm.

[0035] Further, each layer of the circular glass nested tube 4 is tangent to the inner wall of the outer cladding 1 at the same point, that is, the center of each layer is on the same diameter. Specifically, the circular glass nested tube 4 may include a circular inner nested tube 4-1, a circular middle nested tube 4-2, and a circular outer nested tube 4-3, and the diameter ratio of the circular inner nested tube 4-1, the circular middle nested tube 4-2, and the circular outer nested tube 4-3 is: 0.4-0.6:0.6-0.8:1, for example: the diameters of the circular inner nested tube 4-1, the circular middle nested tube 4-2, and the circular outer nested tube 4-3 may be 7μm-10μm, 12μm-15μm, and 18μm-22μm, respectively. This design can make the morphological structure of the circular nested tube most effectively improve the single-mode transmission performance.

[0036] Furthermore, the wall thickness of the semicircular glass nested tube 3 and the circular glass nested tube 4 needs to meet the anti-resonance condition: Wherein λ is the target wavelength in nm, and n is the refractive index of the material of the semicircular glass nested tube 3 and the circular glass nested tube 4. For example, in the 1550nm band, the refractive index is 1.42-1.43, and the wall thickness of the semicircular glass nested tube 3 and the circular glass nested tube 4 is in the range of 270nm-273nm to achieve low loss and high mode field transmission.

[0037] The core 5 is a hollow core area filled with rarefied gas or vacuum, located at the center of the optical fiber, and used for the transmission of optical signals. The diameter of the core 5 is 20 μm to 30 μm. The design of the core 5 can further reduce material dispersion and nonlinear effects.

[0038] (Example 1)

[0039] This embodiment is in the above Figure 1 The dimensions are limited based on the structure. This embodiment is a hollow-core antiresonant optical fiber working at a wavelength of 1550nm. The refractive index of the outer cladding 1 is 1.444, the inner diameter is 65μm, and the thickness is 30μm; the refractive index of the semicircular glass nested tube 3 and the circular glass nested tube 4 are both 1.42; the diameters of the circular glass nested tube 4 are 20μm, 12.94μm, and 8μm from the outside to the inside, and the wall thickness of the nested tube is 272nm; the diameters of the semicircular glass nested tube 3 are 21.12μm and 16.14μm from the outside to the inside, and the wall thickness of the nested tube is also 272nm; the point of tangency between the inner wall of the circular glass nested tube 4 and the outer cladding 1 is 22.15μm from the center of the adjacent semicircular glass nested tube 3; the diameter of the core 5 is 25.42μm. The results of finite element simulation tests show that the hollow-core antiresonant optical fiber has a low-loss bandwidth of more than 200nm in the C-band and an average loss of less than 0.2dB / km.

[0040] Therefore, the present invention effectively overcomes various shortcomings in the prior art and has a high industrial utilization value. The above embodiments are only illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the technology can modify or change the above embodiments without violating the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical ideas disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A hollow core antiresonant optical fiber, comprising an outer cladding, an inner cladding and a core arranged in sequence from the outside to the inside, characterized in that: The inner cladding includes semicircular glass nested tubes and circular glass nested tubes that are alternately arranged; the refractive index of the semicircular glass nested tubes and circular glass nested tubes is lower than the refractive index of the outer cladding.

2. The hollow core antiresonant optical fiber according to claim 1, characterized in that: The layers of the semicircular glass nested tubes are concentrically arranged; and the layers of the circular glass nested tubes are tangent to the inner wall of the outer cladding at the same point.

3. The hollow core antiresonant optical fiber according to claim 2, characterized in that: The semicircular glass nested tubes and the circular glass nested tubes are arranged in an equidistant and alternate manner.

4. The hollow core antiresonant optical fiber according to claim 2, characterized in that: The semicircular glass nested tubes and the circular glass nested tubes are arranged in an alternating manner with non-equidistant spacing.

5. The hollow core antiresonant optical fiber according to claim 3 or 4, characterized in that: The closest distance between the semicircular glass nested tube and the circular glass nested tube cannot exceed 2 μm.

6. The hollow core antiresonant optical fiber according to claim 5, characterized in that: The semicircular glass nested tubes and the circular glass nested tubes both have 2 to 3 layers.

7. The hollow core antiresonant optical fiber according to claim 6, characterized in that: The ratio of the diameters of the layers of the circular glass nested tubes from the inside to the outside is 0.4-0.6:0.6-0.8:

1.

8. The hollow core antiresonant optical fiber according to claim 3, characterized in that: The refractive index of the outer cladding is 1.44-1.

45. The thickness ranges from 22.5 μm to 37.5 μm; the refractive index of the semicircular glass nested tubes and the circular glass nested tubes is 1.42 to 1.43, and the thickness of each layer of the tube wall ranges from 270 nm to 273 nm.

9. The hollow core antiresonant optical fiber according to claim 1, characterized in that: The semicircular glass nested tubes and the circular glass nested tubes are made of silicon dioxide material doped with specific elements, and the specific elements are one or more of fluorine, germanium, and boron.

10. The hollow core antiresonant optical fiber according to claim 1, characterized in that: The center of the fiber core is filled with rarefied gas or vacuum, and the diameter is 20 μm to 30 μm.

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