A semi-elliptical ring cross pipe inverse-hemacylindrical optical fiber

Abstract

The application discloses a kind of semi-ellipse ring cross pipe anti-resonant hollow core optical fiber, belong to optical fiber communication field.The present application includes outer cladding, inner cladding, hollow core and medium filling area.By adopting circular tube as outer cladding, and by semi-ellipse ring cross capillary structure as inner cladding, while by controlling the geometric structure parameters and refractive index parameters of optical fiber, the confinement loss in anti-resonant hollow core optical fiber is reduced, so that the confinement loss of optical signal at 1550nm in the transmission process of the optical fiber is lowest 0.291dB / km.In addition, the optical fiber has bending resistance and fault tolerance characteristics, even when the bending radius is 2cm, the highest confinement loss is not more than 0.381dB / km.The optical fiber structure allows the transmission of optical signals to be suppressed within a certain error range, maintaining low confinement loss.The application can be applied to ultra-high speed, ultra-high capacity optical fiber transmission system, especially suitable for ultra-low loss optical fiber transmission system.

Description

Technical Field

[0001] The invention relates to a semi-elliptical ring cross-tube anti-resonance hollow-core optical fiber, belonging to the field of optical fiber communication. Background Art

[0002] In the field of optical communications, optical fiber plays a vital role as a transmission medium. Its widespread application relies on its optical properties of ultra-low transmission loss, low bending loss, and a wide light transmission band. These characteristics determine its potential for widespread use in fields such as optical fiber communications, laser systems, and spectral analysis. Ultra-low-loss optical fiber will be an indispensable key component for future ultra-high-speed, ultra-large-capacity, and ultra-long-distance optical fiber transmission systems.

[0003] Antiresonant hollow-core fiber, a cutting-edge development in optical technology, boasts low loss, low latency, high bandwidth, and low nonlinearity. This fiber features a unique structure with a hollow core, where the antiresonance effect of the cladding confines light. As a result, light transmission occurs primarily through air rather than solid materials, significantly reducing absorption losses and nonlinear effects associated with fiber transmission through solid materials. This enables ultra-low-loss and low-nonlinear optical transmission.

[0004] In antiresonant hollow-core fibers, the cladding is typically composed of multiple inner and outer claddings of elliptical thin-walled capillaries of equal or varying sizes. Light is not completely confined during fiber transmission, leaking into the cladding or other areas, increasing the fiber's loss rate. Furthermore, when this type of fiber is bent, the refractive index of the inner and outer claddings changes, further increasing the loss. Furthermore, the cladding tubes of this type of hollow-core fiber are prone to deformation during fabrication, making it difficult to achieve the ideal designed structure after fabrication—that is, to maintain consistency in fiber fabrication. This can lead to problems such as energy leakage and mode coupling, resulting in significant discrepancies between the actual performance of the final fiber and the theoretical design. These issues have, to a certain extent, limited the development of antiresonant hollow-core fibers. Therefore, reducing the confinement loss of hollow-core fibers, improving their bending resistance, and enhancing the fault tolerance of their fabrication have become pressing issues. Summary of the Invention

[0005] In order to solve the problems of optical signal leakage caused by the inability to be fully confined during transmission of hollow-core optical fibers, the problem of sharp increase in optical fiber loss when bending, and the problem of optical fiber performance degradation caused by failure to achieve ideal structural parameters during the preparation process, the present invention aims to provide a semi-elliptical ring cross-tube anti-resonant hollow-core optical fiber, which adopts a circular tube as the outer cladding and a semi-elliptical ring cross-capillary structure as the inner cladding. At the same time, by controlling the geometric structural parameters and refractive index parameters of the optical fiber, the confinement loss in the anti-resonant hollow-core optical fiber is reduced, so that the confinement loss of the optical signal at 1550nm during the transmission of the optical fiber is as low as 0.291dB / km. In addition, the optical fiber has bending resistance and fault tolerance characteristics of preparation, and its maximum confinement loss does not exceed 0.381dB / km even when the bending radius is 2cm. The optical fiber structure can effectively suppress the leakage of the transmitted optical signal and maintain low confinement loss under non-ideal structure, that is, within a certain error range. Compared with traditional antiresonant hollow-core optical fibers, this optical fiber has lower confinement loss and good bending resistance and fault tolerance, thus providing a reliable transmission channel for ultra-high-speed, ultra-large-capacity optical fiber transmission systems.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] The present invention discloses a semi-elliptical ring cross-tube antiresonant hollow-core optical fiber comprising an outer cladding, an inner cladding, a hollow core, and a dielectric-filled region. The outer cladding is the outermost circular tubular structure. The inner cladding, located within the outer cladding, comprises a plurality of semi-elliptical tubular structures intersecting with the outer cladding. Each semi-elliptical tubular structure intersects with adjacent semi-elliptical tubular structures and is evenly distributed within the outer cladding. A closed cavity, i.e., the dielectric-filled region, is formed between the outer cladding and the inner cladding. The hollow core is located within the inner cladding.

[0008] Preferably, the outer cladding is made of quartz glass.

[0009] Preferably, the cross section of the semi-elliptical tubular structure of the inner cladding is a semi-elliptical ring shape; the material of the inner cladding is quartz glass.

[0010] Preferably, the major semi-axis of the semi-elliptical tubular structure of the inner cladding is in the range of 22 μm to 34 μm, the minor semi-axis is in the range of 20 μm to 32 μm, and the ellipticity of the elliptical ring is in the range of 1 to 1.6.

[0011] Preferably, one or more gases or a vacuum is set in the hollow core.

[0012] Preferably, the refractive index of the hollow core is smaller than the refractive index of the cladding material; the shortest distance between the center point of the outer cladding circle and the inner cladding is the radius of the hollow core.

[0013] Preferably, the medium filling area is set to be one or more gases, or a vacuum.

[0014] Preferably, the refractive index of the medium-filled region is smaller than the refractive index of the cladding.

[0015] Beneficial effects:

[0016] The present invention discloses a semi-elliptical ring cross-tube anti-resonant optical fiber, which adopts a circular tube as the outer cladding and a semi-elliptical ring cross capillary structure as the inner cladding, while effectively controlling the geometric structure parameters and refractive index parameters of the optical fiber. It can effectively reduce the limiting loss in the anti-resonant hollow-core optical fiber, so that the limiting loss of the optical signal at 1550nm during the transmission process of the optical fiber reaches a minimum of 0.291dB / km. In addition, the finite element method is used to calculate that even when the bending radius of the optical fiber is 2cm, its maximum limiting loss does not exceed 0.381dB / km. And the optical fiber has certain preparation fault tolerance characteristics. Allowing the optical fiber structure to be within a certain error range, the optical fiber can still effectively suppress light leakage and maintain low limiting loss. The optical fiber can be applied to ultra-high-speed, ultra-large-capacity optical fiber transmission systems, and is particularly suitable for ultra-low-loss optical fiber transmission systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a structural diagram of a cross-section of a semi-elliptical ring cross-tube antiresonant hollow-core optical fiber;

[0018] Figure 2 This is the radial refractive index distribution diagram of a semi-elliptical ring cross-tube antiresonant hollow-core fiber;

[0019] Figure 3 This is a graph showing the trend of the confinement loss of a semi-elliptical ring cross-tube antiresonant hollow-core optical fiber as the thickness of the inner cladding semi-elliptical tube changes;

[0020] Figure 4 The contour diagram of the confinement loss of a semi-elliptical ring cross-tube antiresonant hollow-core optical fiber as a function of the semi-major axis and the semi-minor axis of the inner cladding semi-elliptical tube;

[0021] Figure 5 This is a graph showing the trend of the confinement loss of a semi-elliptical ring cross-tube antiresonant hollow-core optical fiber versus the hollow-core core diameter;

[0022] Figure 6 This is a graph showing the trend of the confinement loss of a semi-elliptical ring cross-tube antiresonant hollow-core fiber as a function of the distribution angle deviation of a single semi-elliptical tube;

[0023] Figure 7 This is a graph showing the trend of the limiting loss of a semi-elliptical ring cross-tube antiresonant hollow-core optical fiber versus the bending radius;

[0024] Figure 8 This is a schematic diagram of the cross-section of another type of semi-elliptical ring cross-tube antiresonant hollow-core fiber;

[0025] Figure 9 A schematic structural diagram of a cross-section of a comparative embodiment of a semi-elliptical ring tube antiresonant hollow-core optical fiber;

[0026] Figure 10 This is a structural schematic diagram of the cross section of another comparative embodiment of an annular tube antiresonant hollow-core optical fiber. DETAILED DESCRIPTION

[0027] The specific embodiments of the present invention are further described in detail below with reference to the accompanying drawings:

[0028] like Figure 1 As shown, this embodiment discloses a semi-elliptical ring cross-tube antiresonant hollow-core optical fiber, comprising a circular tube 1, multiple semi-elliptical ring cross-capillary structures 2, a hollow-core fiber 3, and a dielectric filling region 4. The circular tube 1 serves as the outer cladding, and the multiple semi-elliptical ring cross-capillary structures 2 serve as the inner cladding.

[0029] The outer cladding 1 is the outermost circular tubular structural element. The inner cladding 2 is located inside the outer cladding and is configured as a plurality of semi-elliptical capillary structural elements that intersect with the outer cladding. Each semi-elliptical capillary structural element intersects with an adjacent semi-elliptical capillary structural element and is evenly distributed within the outer cladding, forming a semi-elliptical chain of rings in its cross-section. These intersecting semi-elliptical capillary structural elements together constitute the inner cladding 2 of the hollow-core optical fiber. The center of each of the adjacent semi-elliptical capillary structural elements forms a certain angle with the center of the outer cladding, is evenly distributed within the outer cladding, and together with the outer cladding, forms a closed cavity, i.e., a dielectric-filled region 4. The hollow-core fiber core 3 is located inside the inner cladding.

[0030] like Figure 2 As shown, it is the refractive index distribution diagram along the x-axis. The outer cladding 1 and the inner cladding 2 are made of the same material, quartz glass. Its refractive index is 1.45 and its thermal expansion coefficient is 0.55e-6 (K -1 ), relative dielectric constant of 3.75, Poisson's ratio of 0.17, and Young's modulus of 73.1 (GPa). The dielectric filling region 4 and the hollow core 3 are air, whose refractive index is 1.

[0031] Example 1:

[0032] like Figure 1 As shown, this embodiment discloses a semi-elliptical ring cross-tube antiresonant hollow-core optical fiber, comprising a circular tube 1, multiple semi-elliptical ring cross-capillary structures 2, a hollow-core fiber 3, and a dielectric filling region 4. The circular tube 1 serves as the outer cladding, and the multiple semi-elliptical ring cross-capillary structures 2 serve as the inner cladding.

[0033] The outer cladding 1 is the outermost circular tubular structural element. Its thickness is set to 2.5 μm. The inner cladding 2 is located inside the outer cladding and is configured as multiple semi-elliptical capillary structural elements that intersect with the outer cladding. The semi-long axis of the semi-elliptical capillary cross section is 30.2 μm, the semi-minor axis of the semi-elliptical capillary cross section is 29 μm, and the thickness is set to 0.5 μm. The angle formed by the center of each adjacent semi-elliptical capillary structural element and the center of the outer cladding is 30 degrees. There are a total of 12 semi-elliptical capillary structural elements, which are evenly distributed within the outer cladding. Each semi-elliptical capillary and the outer cladding form a closed cavity, namely the medium-filled area 4.

[0034] Furthermore, for the above embodiment, the hollow core 3 is located inside the inner cladding and has a diameter of 42.94 μm.

[0035] Furthermore, in the above embodiment, the material of the outer cladding 1 and the inner cladding 2 is quartz glass, and its refractive index is 1.45.

[0036] Furthermore, for the above embodiment, the medium-filled area 4 and the hollow fiber core 3 are air, and the refractive index is 1.

[0037] Furthermore, for the above embodiment, its core technical contribution lies in the structure of the inner cladding and outer cladding composed of multiple intersecting semi-elliptical capillaries. It can be understood that it is precisely thanks to the special structure of the above inner cladding that the range of light signals that can be transmitted in the hollow-core optical fiber is strictly controlled, and the light signal is effectively confined to the hollow-core core through anti-resonance. The optical fiber can effectively reduce the limiting loss and suppress the leakage of light, and at the same time, the optical fiber has good anti-bending and fault-tolerant characteristics. By reasonably optimizing the geometric structure of the semi-elliptical ring cross-tube anti-resonant hollow-core optical fiber. As Figure 3 As shown in FIG, by adjusting the thickness of the relevant semi-elliptical ring cross tube, the optimal thickness of the semi-elliptical ring cross tube is 0.5 μm. Figure 4 As shown, by adjusting the length of the major semi-axis and the minor semi-axis of the relevant semi-elliptical ring cross tube, that is, by adjusting the major and minor semi-axis of each semi-elliptical capillary to meet the range of -2.75x+100.25≥y≥1.83x-23.41 and 30μm≥x≥25μm, 31.5μm≥y≥26μm, the semi-elliptical ring cross tube antiresonant hollow core fiber can maintain a limiting loss of less than 1dB / km. Figure 5 As shown, by adjusting the diameter of the hollow core fiber, the lowest limiting loss of the optical signal at 1550nm can be obtained, which is 0.291dB / km.

[0038] Furthermore, for the above embodiment, when the angle formed by the center of the circle of the adjacent semi-elliptical capillary tubes and the center of the circle of the outer cladding deviates, the relative position of the semi-elliptical capillary tubes to the other semi-elliptical capillaries is uneven. The angle formed by the center of the circle of the semi-elliptical capillary tube structure element and the center of the circle of the outer cladding deviates within the range of 25 degrees to 35 degrees. When the deviation range is within 2 degrees, the loss is limited to no more than 1dB / km, and the deviation range is within 5 degrees, the loss is limited to no more than 10dB / km. Figure 6 As shown. Figure 3 As shown in Figure 2, the thickness of the semi-elliptical capillary has a deviation within 0.2 μm. Figure 4 The major and minor axes of each semi-elliptical capillary shown satisfy the deviation within the range of -2.75x+100.25≥y≥1.83x-23.41 and 30μm≥x≥25μm, 31.5μm≥y≥26μm. The semi-elliptical ring cross-tube antiresonant hollow-core optical fiber can maintain a low limiting loss, that is, less than 1dB / km.

[0039] Furthermore, for the above embodiment, Figure 7 As shown in FIG, the optical fiber can maintain its limiting loss up to 0.3805 dB / km even when the bending radius is 2 cm by calculation.

[0040] Example 2:

[0041] like Figure 8 As shown, a semi-elliptical ring cross-tube antiresonant hollow-core optical fiber includes a circular tube 1, multiple semi-elliptical ring cross-capillary structures 2, a hollow-core fiber core 3, and a dielectric filling area 4. The circular tube 1 serves as the outer cladding, and the multiple semi-elliptical ring cross-capillary structures 2 serve as the inner cladding.

[0042] The outer cladding 1 is the outermost circular tubular structural element. Its thickness is set to 3 μm. The inner cladding 2 is located inside the outer cladding and is configured as multiple semi-elliptical capillary structural elements that intersect with the outer cladding. The semi-long axis of the cross-section of the semi-elliptical ring-intersecting capillary structural element is 29 μm, the semi-minor axis of the cross-section of the semi-elliptical capillary is 31 μm, and the thickness is set to 0.5 μm. The center of the semi-elliptical capillary structural element is located on the inner surface of the outer cladding 1. The angle formed by the center of each adjacent semi-elliptical capillary structural element and the center of the outer cladding is 40 degrees. There are a total of 9 semi-elliptical capillary structural elements, which are evenly distributed within the outer cladding. Each semi-elliptical capillary and the outer cladding form a closed cavity, namely the medium filling area 4.

[0043] Furthermore, for the above embodiment, the hollow core 3 is located inside the inner cladding and has a diameter of 40.5 μm.

[0044] Furthermore, in the above embodiment, the material of the outer cladding 1 and the inner cladding 2 is quartz glass, and its refractive index is 1.45.

[0045] Furthermore, for the above embodiment, the medium-filled area 4 and the hollow fiber core 3 are air, and the refractive index is 1.

[0046] Furthermore, the core technical contribution of the above-mentioned embodiment lies in the structure of the inner cladding and outer cladding formed by multiple intersecting semi-elliptical capillaries. It can be understood that it is precisely due to the special structure of the inner cladding that the optical fiber can effectively reduce confinement loss and suppress light leakage. Specifically, for the semi-elliptical ring cross-tube anti-resonant hollow-core optical fiber, by adjusting parameters such as the thickness of the semi-elliptical ring cross tubes, the length of the semi-major axis, the length of the semi-minor axis, the diameter of the hollow core, and the thickness of the outer cladding, the conditions for effective anti-resonance of the hollow-core optical fiber are achieved, thereby reducing the confinement loss and bending loss of the optical fiber and improving its fault tolerance.

[0047] Furthermore, in the above embodiment, when the angles formed by the centers of adjacent semi-elliptical capillaries and the center of the outer cladding deviate, i.e., the relative positions of the semi-elliptical capillaries are unevenly distributed, the semi-elliptical capillaries can maintain low confinement loss if the semi-elliptical capillary thickness deviates within 0.2 μm or the semi-major and minor axes of the cross-section of each semi-elliptical capillary are deviated within 0.5 μm.

[0048] Comparative Example 1:

[0049] A semi-elliptical ring anti-resonant hollow core fiber is used as a comparative embodiment. Figure 9 As shown, it includes a circular tube 1 as an outer cladding, a plurality of semi-elliptical ring capillary structure elements as an inner cladding 2, a hollow fiber core 3 and a dielectric filling area 4.

[0050] The outer cladding 1 is the outermost circular tubular structural element. The thickness is set to 2.5 μm. The inner cladding 2 is located inside the outer cladding and is configured as a plurality of semi-elliptical capillary structural elements intersecting with the outer cladding. The major semi-axis of the cross section of the semi-elliptical capillary structural element is 22.6 μm, the minor semi-axis of the cross section of the semi-elliptical capillary is 22.4 μm, and the thickness is set to 0.5 μm. The angle formed by the center of each adjacent semi-elliptical capillary structural element and the center of the outer cladding is 45 degrees. There are a total of 8 semi-elliptical capillary structural elements, which are evenly distributed in the outer cladding. The distance between the semi-elliptical capillaries is less than 0.1 μm, and they are approximately tangent. Each semi-elliptical capillary and the outer cladding form a closed cavity, namely the medium filling area 4.

[0051] Furthermore, for the above comparative example, the outer cladding 1 and the inner cladding 2 are made of quartz glass, and the refractive index thereof is 1.45.

[0052] Furthermore, for the above comparative embodiment, the hollow core 3 and the medium-filled region 4 are air, and the refractive index thereof is 1.

[0053] Furthermore, for the above comparative embodiment, the hollow core 3 is located in the central region of the optical fiber, has a diameter of 36.94 μm, and is filled with air with a refractive index of 1.

[0054] For the comparative example above, the minimum limiting loss calculated using the finite element method is 14 dB / km, and the bending loss is 14.402 dB / km at a bending radius of 2 cm. Compared with Example 1, the semi-elliptical cross-capillary structure is more effective in reducing limiting loss. Its unique interlocking structure better supports the curved side of the optical fiber when it bends, reducing optical signal leakage during bending. Example 1 is more advantageous in reducing limiting loss and bending loss.

[0055] Comparative Example 2:

[0056] A semi-elliptical ring anti-resonant hollow core fiber is used as a comparative embodiment. Figure 10 As shown, it includes a circular tube 1 as an outer cladding, a plurality of circular capillary structure elements as an inner cladding 2, a hollow fiber core 3 and a dielectric filling region 4.

[0057] The outer cladding 1 is the outermost circular tubular structural element. The thickness is set to 2.5 μm. The inner cladding 2 is located inside the outer cladding and is configured as a plurality of semi-elliptical capillary structural elements intersecting with the outer cladding. The cross-sectional radius of the circular capillary structural element is 21.3 μm, and the capillary thickness is set to 0.5 μm. The angle formed by the center of each adjacent semi-elliptical capillary structural element and the center of the outer cladding is 60 degrees. There are a total of 6 circular capillary structural elements, which are evenly distributed in the outer cladding. The distance between the circular capillaries is less than 0.2 μm. Each semi-elliptical capillary and the outer cladding form a closed cavity, namely the medium filling area 4.

[0058] Furthermore, for the above comparative example, the outer cladding 1 and the inner cladding 2 are made of quartz glass, and the refractive index thereof is 1.45.

[0059] Furthermore, for the above comparative embodiment, the hollow core 3 and the medium-filled region 4 are air, and the refractive index thereof is 1.

[0060] Furthermore, for the above comparative embodiment, the hollow core 3 is located in the central region of the optical fiber, has a diameter of 21.63 μm, is filled with air, and has a refractive index of 1.

[0061] Finite element method calculations for the comparative example show a minimum confinement loss exceeding 100 dB / km, and bending losses exceeding 190 dB / km at a 2 cm bending radius. Compared to Example 1, the semi-elliptical intersecting capillary structure is more effective in reducing confinement losses. Its unique interlocking ring structure better supports the curved sides of the fiber when it bends, reducing signal leakage during bending. Example 1 demonstrates superiority in reducing confinement and bending losses.

[0062] The above-described embodiments are merely preferred examples of the present invention and are not intended to limit the scope of protection of the present invention. It should be noted that, for those skilled in the art, several equivalent variations and substitutions can be made based on the content disclosed in the present invention, such as the thickness of the semi-elliptical ring cross tube, the length of the semi-major axis, the length of the semi-minor axis, the radius of the hollow core, the magnitude of the ellipticity, the number of semi-elliptical ring capillaries, the equivalent shape of the semi-elliptical ring capillaries, the magnitude of the cladding refractive index and the thickness of the outer cladding, and the filling of the dielectric filling area and the hollow core with gas, liquid, or vacuum. These equivalent variations and substitutions, as well as adjustments to other device parameters, should also be considered within the scope of protection of this patent.

Claims

1. A semi-elliptical ring cross-tube antiresonant hollow-core optical fiber, characterized by: It includes an outer cladding, an inner cladding, a hollow fiber core and a dielectric filling area; the outer cladding is the outermost circular tubular structure; the inner cladding is located inside the outer cladding and is a plurality of semi-elliptical tubular structures intersecting with the outer cladding; each semi-elliptical tubular structure intersects with the adjacent semi-elliptical tubular structures and is evenly distributed in the outer cladding; a closed cavity is formed between the outer cladding and the inner cladding, namely the dielectric filling area; the hollow fiber core is located inside the inner cladding.

2. The semi-elliptical ring cross-tube antiresonant hollow-core optical fiber according to claim 1, characterized in that: The outer cladding layer is made of quartz glass.

3. The semi-elliptical ring cross-tube antiresonant hollow-core optical fiber according to claim 1, characterized in that: The cross section of the semi-elliptical tubular structure of the inner cladding is a semi-elliptical chain shape; the material of the inner cladding is quartz glass.

4. The semi-elliptical ring cross-tube antiresonant hollow-core optical fiber according to claim 3, characterized in that: The semi-long axis of the semi-elliptical tubular structure of the inner cladding is in the range of 22 μm to 34 μm, the semi-minor axis is in the range of 20 μm to 32 μm, and the ellipticity of the elliptical ring is in the range of 1 to 1.

6.

5. The semi-elliptical ring cross-tube antiresonant hollow-core optical fiber according to claim 1, characterized in that: The hollow core of the fiber is filled with one or more gases, or is in a vacuum.

6. The semi-elliptical ring cross-tube antiresonant hollow-core optical fiber according to claim 1, characterized in that: The refractive index of the hollow core is less than that of the cladding material; the shortest distance between the center point of the outer cladding circle and the inner cladding is the radius of the hollow core.

7. The semi-elliptical ring cross-tube antiresonant hollow-core optical fiber according to claim 1, characterized in that: The medium filling area is set to be one or more gases, or a vacuum.

8. The semi-elliptical ring cross-tube antiresonant hollow-core optical fiber according to claim 1, characterized in that: The refractive index of the medium filling area is smaller than that of the cladding.

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