A hollow core anti-resonant optical fiber transmitting a single dark hollow mode

Abstract

This invention discloses a hollow-core anti-resonant optical fiber for transmitting a single-mode dark hollow beam, belonging to the field of optical fiber technology. The fiber structure, from the outside in, consists of an outer cladding tube, circular nested cladding tubes, and an air core. Two circular cladding tubes on the x-axis contain a small circular cladding resonator to suppress the fundamental mode; the remaining circular cladding tubes contain a support plate to suppress other higher-order modes. Through the combined effect of the two types of nested cladding tubes, the fundamental mode and the LP (lower-order) beam are transmitted. 11 The loss ratio of the mode is 5770; other higher-order modes LP 21 LP 02 It was also suppressed, achieving stable transmission of a single-mode dark hollow beam.

Description

Technical Field

[0001] This invention relates to the field of optical fiber technology, specifically to a hollow anti-resonant optical fiber capable of single-mode dark hollow beam transmission. Background Technology

[0002] Optical fiber technology plays a vital role in modern information and communication. Traditional silica-based optical fibers have a low-loss transmission wavelength range of approximately 1000–2000 nm. Hollow-core optical fibers, which use air as the transmission medium, offer a wider wavelength range and lower Rayleigh scattering loss, and are expected to solve current bottlenecks in optical fiber technology, thus attracting widespread attention.

[0003] Hollow-core optical fibers come in many varieties. In recent years, hollow-core anti-resonant optical fibers have attracted much attention due to their simple structure, low loss, and large transmission bandwidth. Hollow-core optical fibers can not only guide light but also be used to transmit neutral atoms. In 1993, Ol'Shanni et al. from Russia proposed using a Gaussian optical field to guide atoms in hollow-core optical fibers (MAOl'Shanii, Yu.B.Ovchinnikov, VSLetokhov, Laser guiding of atoms in a hollow optical fiber[J]. Optics Communications, 1993, 98(1-3):77-79). In 1994, Marksteiner et al. from Australia proposed the idea of ​​using a dark hollow optical field to guide atoms (S.Marksteiner, CMSavage, P.Zoller, et al, Coherent atomic waveguides from hollow optical fibers: Quantized atomic motion[J], Physics Review A, 1994, 50(3):2680-2690). Subsequently, scientists proposed different schemes for generating dark hollow beams in hollow optical fibers.

[0004] However, it is difficult for fibers with uniform cladding structures to suppress Gaussian mode fields and achieve high-purity dark hollow beam transmission. Fibers with complex cladding structures, such as hollow-core photonic bandgap fibers and Kagome hollow fibers, can suppress the fundamental mode through cladding design, enabling single-mode dark hollow beam transmission, but the fiber fabrication process is quite complex. Although hollow-core antiresonant fibers only have a single-turn cladding tube, they also offer high design flexibility. Therefore, through fiber structure design, the fundamental mode and other higher-order modes can be filtered out to achieve single-mode dark hollow beam transmission. However, existing hollow-core antiresonant fibers are not yet ideal, which remains a pressing technical problem to be solved. Summary of the Invention

[0005] To address the problems of existing technologies, the present invention aims to overcome the shortcomings of existing technologies and provide a hollow-core anti-resonant optical fiber for transmitting a single dark hollow mode. Through the combined effect of two types of nested cladding tubes, the fundamental mode and higher-order modes are suppressed, thereby achieving stable transmission of a single-mode dark hollow beam.

[0006] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0007] A hollow antiresonant optical fiber for transmitting a single dark hollow mode comprises, from the outside to the inside, an optical fiber jacket, a circular nested cladding tube, and an air fiber core.

[0008] The fiber optic sheath is the outermost layer of the hollow anti-resonant fiber, enclosing the cladding tube and the air core inside it. The circular nested cladding tube consists of a series of circular glass tubes disposed in an annular cavity between the fiber optic sheath and the air core. Adjacent circular glass tubes in the circular nested cladding tube are arranged without contacting each other, and the thickness of the glass tubes is t. AR The radius is R tube One side of the glass tube is fixed to the inner wall of the optical fiber outer tube, thus forming an integrated optical fiber stabilization structure that connects the optical fiber outer tube and the circular nested cladding tube.

[0009] The air core is a central region surrounded by multiple circular nested cladding tubes, and the radius of the air core surrounded by it is R;

[0010] The circular nested cladding tube comprises two nesting structures: a circular nested cladding tube along the x-axis; and a small nested circular resonant tube inside, the thickness of which is t. R The radius is R res The resonant tube has one side wall fixed to the inner wall of a circular nested cladding tube, forming a small circular resonant tube fiber optic stabilization structure and a transmission structure that suppresses the fundamental mode; the remaining circular nested cladding tubes have nested structures with a thickness of t inside. AR The support plate has its two ends fixedly connected to the inner walls of the circular nested cladding tubes in various directions, thus forming another fiber optic stabilization structure for small circular resonant tubes. The distance between the support plate and the bottom of the inner cavity of the circular nested cladding tube is z. The circular glass tubes with air-separated fiber cores with support plates are symmetrical in pairs. A group is formed by two adjacent pairs of symmetrical air-separated fiber cores with support plates, forming a structure that realizes the suppression of higher-order modes and transmits a single-mode dark hollow beam.

[0011] Preferably, the thickness t of the support plate AR Following the principle of anti-resonant reflective waveguides (ARROW), the following conditions are met:

[0012]

[0013] The thickness t of the small circular resonant tube R It also follows the principle of anti-resonant reflective waveguide (ARROW), that is, it satisfies the following:

[0014]

[0015] Where λ is the designed operating wavelength, n1 represents the refractive index of the glass cladding tube material, n0 represents the refractive index of air, and m is a positive integer, with a value range of 1, 2, ...

[0016] Preferably, for the resonant tube with a small circular resonant tube nested in the x-axis direction, the wall thickness of the small circular resonant tube is t. R One side wall of the small circular resonator is fixed to the circular cladding tube, and the fixing position coincides with the connection position of the outer glass tube and the fiber optic jacket tube, forming a stable fiber optic structure; the radius R of the small circular resonator is... res and the wall thickness t of the small circular resonant tube R This ensures that the fundamental mode of the fiber core is coupled with the resonant tube wall mode, thereby forming a structure that increases the limiting loss of the fundamental mode.

[0017] Preferably, for a circular glass tube with a support plate, the distance z between the support plate and the bottom of the inner cavity of the circular nested cladding tube is the intersection of the line connecting the center of the circular glass tube and the air fiber core with the inner side of the tube wall of the circular glass tube; the intensity of the suppression effect of higher-order modes can be adjusted by changing the distance z between the support plate and the glass tube.

[0018] Preferably, for transmitting LP 11 The mode, wherein the hollow-core antiresonant fiber transmitting a single dark hollow mode suppresses the fundamental mode and includes LP 21 LP 02 Other higher-order mode transmission modes.

[0019] Preferably, the small circular resonant tube and the support plate are made of silicon dioxide.

[0020] Compared with the prior art, the present invention has the following obvious and prominent substantive features and significant advantages:

[0021] 1. The support plate nested with a circular cladding tube of the present invention can effectively suppress higher-order modes. The suppression of a certain higher-order mode is achieved by changing the distance z between the support plate and the glass tube.

[0022] 2. The resonant tube nested with a circular cladding in the x-axis direction of this invention can effectively suppress the transmission of the fundamental mode;

[0023] 3. This invention combines a support plate with a circular cladding tube nested within a resonant tube, which can simultaneously suppress the fundamental mode and other higher-order modes, achieving the goal of transmitting a single-mode dark hollow beam; for transmitting LP... 11 Taking the fundamental mode as an example, it can suppress the interaction between the fundamental mode and other higher-order modes such as LP. 21 LP 02 Transmission in various modes. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the cross-sectional structure of a hollow anti-resonant optical fiber for transmitting a single-mode dark hollow beam according to a preferred embodiment of the present invention.

[0025] Figure 2 This is a curve showing the confinement loss of each mode in a hollow anti-resonant optical fiber with a support plate structure according to a preferred embodiment of the present invention, as a function of the distance z between the support plate and the cladding tube.

[0026] Figure 3 In the preferred embodiment of the present invention, the fundamental mode and a single LP 11 The curve showing the ratio of the dark to the hollow beam in the mode as a function of wavelength. Detailed Implementation

[0027] The specific embodiments of the present invention will now be described with reference to the accompanying drawings to enable those skilled in the art to better understand the invention. It should be particularly noted that in the following description, detailed descriptions of known functions and designs that might obscure the main content of the invention will be omitted.

[0028] The above solution will be further described below with reference to specific embodiments. The preferred embodiments of the present invention are described in detail below:

[0029] Example 1:

[0030] In this embodiment, as Figure 1 As shown, a hollow-core anti-resonant optical fiber for transmitting a single dark hollow mode includes, from the outside to the inside, an optical fiber jacket tube 1, a circular nested cladding tube 2, and an air fiber core 5.

[0031] The fiber optic outer sheath 1 is the outermost layer of the hollow anti-resonant fiber, enclosing the cladding tube 2 and the air core 5 inside it. The circular nested cladding tube 2 consists of a series of circular glass tubes disposed in an annular cavity between the fiber optic outer sheath 1 and the air core 5. Adjacent circular glass tubes in the circular nested cladding tube 2 are not in contact with each other, and the thickness of the glass tubes is t. AR The radius is R tube One side of the glass tube is fixed to the inner wall of the optical fiber outer tube 1, thus forming an integrated optical fiber stabilization structure that connects the optical fiber outer tube 1 and the circular nested cladding tube 2.

[0032] The air fiber core 5 is a central region surrounded by multiple circular nested cladding tubes, and the radius of the air fiber core surrounded by it is R;

[0033] The circular nested cladding tube 2 comprises two nested structures, wherein the circular nested cladding tube 2 in the x-axis direction contains nested small circular resonant tubes 3, the thickness of which is t. R The radius is R res The resonant tube 3 has one side wall fixed to the inner wall of the circular nested cladding tube 2, thus forming a fiber optic stabilization structure for the small circular resonant tube 3 and creating a transmission structure that suppresses the fundamental mode; the remaining circular nested cladding tubes 2 have nested structures with a thickness of t inside. AR The support plate 4 has its two ends fixedly connected to the inner wall of the circular nested cladding tube 2 in each direction, thus forming another small circular resonator tube 3 fiber optic stabilization structure. The distance between the support plate 4 and the bottom of the inner cavity of the circular nested cladding tube 2 is z. The circular glass tubes with the support plate 4 and the air-separated fiber core 5 are symmetrical in pairs. The adjacent pairs of symmetrical air-separated fiber cores 5 with the support plate 4 form a group, forming a structure that realizes the suppression of higher-order modes and transmits a single-mode dark hollow beam.

[0034] This embodiment uses a hollow anti-resonant optical fiber for transmitting a single-mode, dark, hollow beam. The outer layer of the circular nested cladding tube is a non-contact circular glass tube, with one side of its wall fixed to the outer sheath of the optical fiber, thus ensuring structural stability. The inner layer of the circular nested cladding tube includes two forms: one is a resonant tube at the x-axis position; the other is a support plate at other positions. The air core is a central region surrounded by multiple circular cladding tubes, and the radius of the hollow core enclosed by this region is R. The wall thickness of the resonant tube nested in the x-axis direction is t. R One side of its tube wall is fixed to a circular cladding tube to maintain the stability of the optical fiber structure; the radius R of the resonant tube res The wall thickness t of the small circular resonant tube R This ensures that the fundamental mode of the fiber core couples with the resonant tube wall mode, thereby increasing the confinement loss of the fundamental mode; the thickness of the nested support plate in the remaining directions is t. AR Each of these components is connected to a circular cladding tube in each direction to maintain the stability of the fiber structure. The nested support plate and the circular cladding tubes are symmetrical in pairs. The distance between the support plate and the bottom of the cladding tube (the intersection of the line connecting the center of the circular cladding tube and the fiber core with the inner side of the cladding tube wall) can be adjusted to enhance the suppression effect on specific higher-order modes.

[0035] Example 2:

[0036] This embodiment is basically the same as Embodiment 1, except that:

[0037] In this embodiment, Figure 1This is a schematic diagram of an embodiment of the present invention. Its structure, from the outside in, consists of an optical fiber outer sheath 1, six circular nested cladding tubes 2, and an air fiber core 5. The optical fiber outer sheath 1 is the outermost layer of the hollow-core anti-resonant optical fiber, enclosing the cladding tubes, support plate, and air fiber core within it. The circular nested cladding tubes and support plate are typically made of silicon dioxide and should be designed according to the anti-resonant waveguide (ARROW) principle, i.e., satisfying: The air region enclosed by the circular nested cladding tubes is the fiber core, with a radius of R;

[0038] There are two forms of circular nested cladding tubes: one is two resonant tubes (3) nested within the cladding tubes on the x-axis; the other is four supporting plates (4) nested within the cladding tubes. The nested resonant tubes are also made of silicon dioxide and are designed according to the principle of resonant reflection waveguides, i.e., satisfying the following: When the thickness of the nested tube is at the resonant thickness, the fundamental mode of the fiber core will couple with the nested tube mode, thereby increasing the confinement loss of the fundamental mode. Here, λ is the designed operating wavelength, n1 represents the refractive index of the glass cladding tube material, n0 represents the refractive index of air, and m is a positive integer. The cladding tubes nested in the four support plates are centrally symmetrical in pairs. The distance z between the support plate and the bottom of the circular cladding tube can be changed, thereby adjusting the coupling between the higher-order modes of the fiber core and the cladding tube mode, and increasing the confinement loss of the higher-order modes.

[0039] Figure 2 This describes the relationship between the confinement loss of each mode in a hollow antiresonant fiber nested with a support plate and the distance z from the bottom of the cladding tube. This is for transmitting LP... 11 Model, inhibit LP 21 and LP 02 In this embodiment, z1 and z2 are set to 0.8R and 0.85R, respectively.

[0040] Figure 3 In the embodiments of the present invention, the fundamental mode and a single LP 11 The ratio of the mode to the hollow beam varies with wavelength. Simulation results show that, in this embodiment, at a wavelength of 1.539 μm, the ratio of the fundamental mode to the LP mode... 11 The loss ratio of the two modes is as high as 5770; near this band, the bandwidth with a loss ratio of more than 100 is about 5nm, which can achieve good single dark empty mode transmission characteristics.

[0041] The hollow-core anti-resonant fiber used in the above embodiment for transmitting a single-mode dark hollow beam has a structure consisting of an outer cladding tube, a circular nested cladding tube, and an air core, arranged from the outside in. Two circular cladding tubes on the x-axis contain a small circular cladding resonator tube to suppress the fundamental mode; the remaining circular cladding tubes contain a support plate to suppress other higher-order modes. This increases the confinement loss of the fundamental mode, enhances the suppression effect on specific higher-order modes, and enables stable transmission of a single-mode dark hollow beam.

[0042] The embodiments of the present invention have been described above in conjunction with the accompanying drawings. However, the present invention is not limited to the above embodiments. Various changes can be made according to the purpose of the invention. Any changes, modifications, substitutions, combinations or simplifications made based on the spirit and principle of the technical solution of the present invention shall be equivalent substitutions. As long as they meet the purpose of the invention and do not deviate from the technical principle and inventive concept of the present invention, they shall fall within the protection scope of the present invention.

Claims

1. A hollow core anti-resonant optical fiber transmitting a single dark hollow mode, characterized in that: From the outside to the inside, it consists of an optical fiber jacket (1), a circular nested cladding tube (2), and an air fiber core (5). The fiber optic jacket tube (1) is the outermost layer of the hollow anti-resonant fiber, and the cladding tube (2) and the air fiber core (5) are wrapped inside it; The circular nested cladding tube (2) is composed of a series of circular glass tubes disposed in an annular interlayer cavity between the optical fiber outer tube (1) and the air fiber core (5). Adjacent circular glass tubes in the circular nested cladding tube (2) are disposed without contacting each other, and the thickness of the glass tube is t. AR The radius is R tube One side of the glass tube is fixed to the inner wall of the optical fiber outer tube (1), thereby forming an integrated optical fiber stable structure that connects the optical fiber outer tube (1) and the circular nested cladding tube (2). The air core (5) is composed of a central region surrounded by multiple circular nested cladding tubes, and the radius of the air core surrounded by it is R; The circular nested cladding tube (2) comprises two nested structures, wherein the circular nested cladding tube (2) in the x-axis direction has nested small circular resonant tubes (3) inside, and the thickness of the resonant tube is t. R The radius is R res One side wall of the resonant tube (3) is fixed to the inner wall of the circular nested cladding tube (2), thereby forming a fiber optic stabilization structure of the small circular resonant tube (3) and forming a transmission structure that suppresses the fundamental mode; the remaining circular nested cladding tubes (2) have nested structures with a thickness of t inside. AR The support plate (4) is fixedly connected at both ends to the inner wall of the circular nested cladding tube (2) in each direction, thereby forming another small circular resonant tube (3) fiber optic stable structure. The distance between the support plate (4) and the bottom of the inner cavity of the circular nested cladding tube (2) is z. The circular glass tubes with the support plate (4) and the air-separated fiber core (5) are symmetrical in pairs. A group is formed by the adjacent symmetrical air-separated fiber cores (5) with the support plate (4) to form a structure that realizes the suppression of higher-order modes and transmits a single-mode dark hollow beam. The thickness t of the support plate (4) AR The anti-resonant reflecting waveguide (ARROW) principle is followed, i.e. the following is satisfied: ; The thickness t of the small circular resonator tube (3) R Also follows the anti-resonance reflection waveguide ARROW principle, that is, satisfies the following: ； Where λ is the designed operating wavelength, n1 represents the refractive index of the glass cladding tube material, n0 represents the refractive index of air, and m is a positive integer, with a value range of 1, 2, ...

2. The hollow-core anti-resonant optical fiber for transmitting a single dark hollow mode according to claim 1, characterized in that: For the resonant tube with the nested small circular resonant tube (3) in the x-axis direction, the wall thickness of the small circular resonant tube (3) is t. R One side wall of the small circular resonant tube (3) is fixed to the circular cladding tube, and the fixed position coincides with the connection position of the outer glass tube and the fiber optic outer tube (1), forming a stable fiber optic structure; the radius R of the small circular resonant tube (3) is... res The wall thickness t of the small circular resonant tube (3) R This ensures that the fundamental mode of the fiber core is coupled with the resonant tube wall mode, thereby forming a structure that increases the limiting loss of the fundamental mode.

3. The hollow core anti-resonant optical fiber transmitting a single dark hole pattern according to claim 1, wherein: For a circular glass tube with a support plate (4), the distance between the support plate (4) and the bottom of the inner cavity of the circular nested cladding tube (2) is z. The bottom of the inner cavity is the intersection of the line connecting the center of the circular glass tube and the air fiber core (5) with the inner side of the tube wall of the circular glass tube. The intensity of the suppression of higher-order modes can be adjusted by changing the distance z between the support plate (4) and the glass tube.

4. The hollow core anti-resonant optical fiber transmitting a single dark hole pattern according to claim 1, wherein: For transmission LP 11 modes, the hollow core anti-resonant optical fiber that transmits the fundamental dark hollow mode suppresses the mode transmission of the other high order modes including LP 21 , LP 02 modes.

5. The hollow core anti-resonant optical fiber transmitting a single dark hole pattern according to claim 1, wherein: The small circular resonant tube (3) and the support plate (4) are made of silicon dioxide.

Images