A terahertz special-shaped hollow-core optical fiber

Abstract

This application discloses a terahertz shaped tube hollow-core optical fiber. This terahertz shaped tube hollow-core optical fiber comprises a core and an outer cladding surrounding the core. The outer cladding comprises elliptical arc segments and circular arc segments arranged in an annular pattern around the core. The elliptical and circular arc segments are arranged alternately. The elliptical arc segments are convex when viewed from the side closest to the core, while the circular arc segments are concave when viewed from the side closest to the core. This shaped tube hollow-core optical fiber features a small size, low transmission loss, and flat dispersion.

Description

Technical Field

[0001] The present application relates to the technical field of optical fibers, and in particular to a terahertz special-shaped hollow-core optical fiber. Background Art

[0002] There are many types of hollow-core optical fibers. Among them, hollow-core antiresonant optical fibers have attracted extensive research by scientific researchers due to their simple structure, flexible design, and superior loss, dispersion, and nonlinear performance.

[0003] At present, the transmission loss of terahertz hollow-core optical fiber is 1dB / m (at 1THz frequency) or above. To further reduce the transmission loss, it is necessary to optimize the structure or manufacturing process. At this stage, it is necessary to find a simpler and lower-loss structure.

[0004] Terahertz dielectric tube waveguides have a simple structure and offer the advantages of low transmission loss and flat dispersion. They are compatible with existing extrusion processes and can be manufactured using a variety of polymers with low absorption losses in the THz band. Researchers have conducted preliminary exploration of their loss characteristics, modal features, and related optical fiber devices, but have not yet further explored their transmission loss reduction for medium- and long-distance terahertz system connections.

[0005] Among the current terahertz hollow-core optical fibers, the most promising and widely used structure is a nodeless structure consisting of a single-layer resonant ring plus an outer cladding protective sleeve. This structure increases the difficulty of molding during the extrusion process and cannot guarantee the integrity and accuracy of the structure; however, the single-layer special-shaped tube manufacturing process can maintain good structural dimensional accuracy and durability. Summary of the Invention

[0006] In view of this, the present application provides a terahertz special-shaped tube hollow-core optical fiber, which can reduce transmission loss and achieve dispersion flatness.

[0007] The present application provides a terahertz special-shaped tube hollow-core optical fiber, comprising a core and an outer cladding coated on the outer circumference of the core, wherein the outer cladding comprises elliptical arc segments and circular arc segments arranged in a ring around the core and connected to each other, the elliptical arc segments and the circular arc segments being arranged alternately, the elliptical arc segments being convex when viewed from the side close to the core, and the circular arc segments being concave when viewed from the side close to the core.

[0008] Optionally, the fiber core is respectively formed of an air layer, a single-layer dielectric tube and an air layer outwards.

[0009] Optionally, the thickness of the elliptical arc segment and the circular arc segment are equal, satisfying the anti-resonance condition in the ARROW theory, that is,

[0010]

[0011] Where λ is the designed operating wavelength, n1 represents the refractive index of the cladding material, n0 represents the refractive index of air, and m is the resonance order, which is a positive integer.

[0012] Optionally, the fillet radius at the connection between the elliptical arc segment and the circular arc segment is 0.3-0.5 mm.

[0013] Optionally, the number of the elliptical arc segments is 3-25.

[0014] Optionally, the curvature value of the elliptical arc segment, which is defined by the ratio of the major axis to the minor axis, is 1.4-2.7.

[0015] Optionally, the arc segment satisfies an arc length l<0.4r, where l is the arc length of the inner boundary of the positive curvature arc, and r is the radius of the tangent circle in the fiber core region.

[0016] Optionally, the semi-major axis of the elliptical arc segment is 0.45-0.96 of the fiber core radius.

[0017] Optionally, the arc length of the elliptical arc segment accounts for 0.175-0.5 of the arc length of the elliptical geometric shape in which it exists.

[0018] Optionally, the light-guiding material of the outer cladding is Zoenex COC, TOPAS COC, high polyethylene HDPE, polyethylene PE, Teflon Teflon, TPX, polystyrene PS, high-impact polystyrene HIPS, polyacrylic acid PP, polyvinyl chloride PVC, polytetrafluoroethylene PTFE, high-resistance silicon HRS, picarin, light-curing resin, engineering plastic ABS or polylactic acid PLA.

[0019] Due to the adoption of the above technical solution, the present invention achieves the following beneficial effects:

[0020] 1. The structure of the present application is simple, with only one layer of light-guiding medium material, and no nodes are generated around the fiber core area, which greatly simplifies the production process and robustness.

[0021] 2. The hollow-core optical fiber of the present application has the characteristics of small size, low transmission loss and flat dispersion. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The following detailed description of the specific embodiments of the present application in conjunction with the accompanying drawings will make the technical solutions and other beneficial effects of the present application apparent.

[0023] Figure 1 A schematic structural diagram of a terahertz hollow-core optical fiber is provided for an embodiment of the present application.

[0024] Figure 2 A structural schematic diagram of elliptical arc segments and circular arc segments connected is provided for an embodiment of the present application.

[0025] Figure 3 A structural schematic diagram of an optical fiber cross section is provided for an embodiment of the present application.

[0026] Figure 4 This is a structural comparison diagram of the terahertz special-shaped hollow-core optical fiber of the embodiment of the present application and the optical fiber of the prior art.

[0027] Figure 5 for Figure 4 Comparison curve of the fundamental mode loss of the three types of optical fibers.

[0028] Figure 6 A diagram of group velocity dispersion results is provided for the embodiments of this application.

[0029] The components in the figure are identified as follows:

[0030] 1-outer cladding; 2-fiber core; 11-elliptical arc segment; 12-circular arc segment. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the embodiments described are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making creative efforts are within the scope of protection of this application.

[0032] In the description of this application, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the described features. In the description of this application, "plurality" means two or more, unless otherwise specifically defined.

[0033] In the description of this application, it should be noted that, unless otherwise expressly specified or limited, the terms "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections, electrical connections, or mutual communication; they can refer to direct connections or indirect connections through an intermediate medium; they can refer to internal communication between two components or the interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on specific circumstances.

[0034] The disclosure below provides many different embodiments or examples for realizing different structures of the present application. In order to simplify the disclosure of the present application, the components and settings of specific examples are described below. Of course, they are merely examples and are not intended to limit the present application. In addition, the present application may repeat reference numbers and / or reference letters in different examples, and such repetition is for the purpose of simplicity and clarity, and does not itself indicate the relationship between the various embodiments and / or settings discussed. In addition, the present application provides examples of various specific processes and materials, but those of ordinary skill in the art will appreciate the application of other processes and / or the use of other materials.

[0035] Please refer to Figure 1 In this embodiment, the terahertz special-shaped tube hollow-core optical fiber includes a core 2 and an outer cladding 1 coated on the outer periphery of the core. The outer cladding includes an elliptical arc segment 1211 and a circular arc segment 12 arranged in a ring around the core 2 and connected to each other. The elliptical arc segment 1211 and the circular arc segment 12 are arranged alternately. The elliptical arc segment 1211 is convex when observed from the side close to the core 2, and the circular arc segment 12 is concave when observed from the side close to the core 2.

[0036] The outer cladding 1 is the outermost layer of the hollow core optical fiber, and wraps the air core 2 inside.

[0037] The outer cladding tube is usually made of a terahertz low-loss material (e.g., Zoenex, TOPAS, etc.) and has a thickness of t. The design should follow the antiresonant reflection waveguide (ARROW) principle, that is, it should meet the following requirements:

[0038]

[0039] Where λ is the operating wavelength, n1 represents the refractive index of the cladding tube material, n0 represents the refractive index of air, and m is the resonance order, which is a positive integer.

[0040] In this embodiment, if Figure 3 As shown, the terahertz hollow-core fiber is suitable for 1.0 THz band optical fiber communication. Specifically, the operating frequency is f = 1.03 THz, n1 = 1.531 + j4.7 × 10 -4 , n0=1, m=2.

[0041] The specific shape and related parameters of the outer cladding 2 are as follows: Figure 2 As shown, elliptical arc segment 1211 can be shaped like a semi-elliptical arc. The semi-elliptical arc has a negative curvature relative to the fiber core 2, that is, it curves toward the side closest to the fiber core 2. The positive circular arc segment 12 is concave when viewed from the side closest to the fiber core, that is, it has a positive curvature. The fillet radius at the junction of elliptical arc segment 1211 and circular arc segment 12 is 0.2 mm.

[0042] In this embodiment, the fiber core 2 is surrounded by 11 outer cladding layers 2 arranged in a circular shape with a negative curvature c = a / b = 1.7. The radius of the inscribed circle of the surrounding contour is the radius r of the fiber core 2. core =4.5mm.

[0043] In this embodiment, the outer cladding 1 is made of TOPAS polymer, the number of elliptical arc segments 1211 is 11 and they are arranged at equal intervals, and the core radius r core =4.5mm. Correspondingly, since the elliptical arc segments 1211 and the circular arc segments 12 are arranged alternately, the number of the circular arc segments 12 is also 11.

[0044] The shape of the cladding tube 1 is formed by connecting an ellipse with a major semi-axis a=2.05 mm and a minor semi-axis b=1.02 mm with a perfect circular arc with an inner arc length g=0.83 mm and arranging them in a ring.

[0045] Please refer to Figure 4 、 Figure 5 Finite element simulation technology was used to simulate and test this embodiment. The simulation adopted the mode analysis method of the optical fiber cross section. It was measured that the limiting loss of this embodiment was the lowest under the condition of incident wavelength of 0.288mm, which was about 0.062dB / m. Compared with the same simulation conditions, the same TOPAS material, the same tube wall thickness t, and the fiber core radius r core The hollow-core optical fiber with a circular cladding tube has a loss at this wavelength reduced by about one order of magnitude. At the same time, the loss is reduced by three times compared with a circular cladding tube (diameter of about 12.4 mm) in the same volume.

[0046] refer to Figure 6 The real part of the refractive index of TOPAS material changes little in the 0.1-5 THz band, and the material dispersion can be ignored when calculating the group velocity dispersion. In this embodiment, the group velocity dispersion value is high only near the resonant frequencies of 0.7 THz and 1.35 THz, while in the wide spectrum range of 0.8-1.25 THz, the group velocity dispersion value is within ±0.01 ps / THz / cm, which has the characteristic of low dispersion.

[0047] The above is only a preferred specific implementation method of the present application, but the scope of protection of the present application is not limited thereto. Any changes or replacements that can be easily thought of by any technician familiar with this technical field within the technical scope disclosed in this application should be covered by the scope of protection of the present application.

Claims

1. A terahertz special-shaped hollow-core optical fiber, characterized in that: The invention comprises a fiber core and an outer cladding covering the outer circumference of the fiber core, wherein the outer cladding comprises elliptical arc segments and circular arc segments arranged in a ring around the fiber core and connected to each other, the elliptical arc segments and circular arc segments being arranged alternately, the elliptical arc segments being convex when viewed from the side close to the fiber core, and the circular arc segments being concave when viewed from the side close to the fiber core; outward from the fiber core, there are an air layer, a single-layer dielectric tube, and an air layer, respectively. The number of the elliptical arc segments is 3-25, and the curvature value of the elliptical arc segments, defined by the ratio of the major axis to the minor axis, is 1.4-2.

7.

2. The terahertz special-shaped hollow-core optical fiber according to claim 1, characterized in that: The thickness of the elliptical arc segment and the circular arc segment are equal, satisfying the anti-resonance condition in the ARROW theory, that is, ； Where λ is the designed operating wavelength, n1 represents the refractive index of the cladding material, n0 represents the refractive index of air, and m is the resonance order, which is a positive integer.

3. The terahertz special-shaped hollow-core optical fiber according to claim 1, characterized in that: The fillet radius at the connection between the elliptical arc segment and the circular arc segment is 0.3-0.5 mm.

4. The terahertz special-shaped hollow-core optical fiber according to claim 1, characterized in that: The arc segment satisfies the condition that its arc length l < 0.4r, where l is the arc length of the inner boundary of the positive curvature arc and r is the radius of the tangent circle in the fiber core region.

5. The terahertz special-shaped hollow-core optical fiber according to claim 1, characterized in that: The semi-major axis of the elliptical arc segment is 0.45-0.96 of the fiber core radius.

6. The terahertz special-shaped hollow-core optical fiber according to claim 1, characterized in that: The arc length of the elliptical arc segment accounts for 0.175-0.5 of the arc length of the elliptical geometric shape in which it is located.

7. The terahertz special-shaped hollow-core optical fiber according to claim 1, characterized in that: The light-guiding material of the outer cladding layer is Zoenex COC, TOPAS COC, high polyethylene HDPE, polyethylene PE, Teflon Teflon, TPX, polystyrene PS, high-impact polystyrene HIPS, polyacrylic acid PP, polyvinyl chloride PVC, polytetrafluoroethylene PTFE, high-resistance silicon HRS, picarin, light-curing resin, engineering plastic ABS or polylactic acid PLA.

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