Semi-elliptical ring cross tube anti-resonance hollow-core optical fiber

Abstract

The invention discloses a semi-elliptical ring cross tube anti-resonance hollow-core optical fiber, and belongs to the field of optical fiber communication. The optical fiber comprises an outer cladding, an inner cladding, a hollow fiber core and a medium filling area. A circular tube is used as an outer cladding, a semi-elliptical ring cross capillary tube structure is used as an inner cladding, and the limited loss in the anti-resonance hollow-core optical fiber is reduced by controlling geometric structure parameters and refractive index parameters of the optical fiber, so that the minimum limited loss of 1550nm optical signals in the transmission process of the optical fiber is 0.291 dB / km. In addition, the optical fiber has the bending resistance and the prepared fault-tolerant characteristic, and even if the bending radius is 2 cm, the maximum limiting loss does not exceed 0.381 dB / km. And the optical fiber structure is allowed to be within a certain error range, leakage of transmitted optical signals can still be inhibited, and low limiting loss is maintained. The invention can be applied to an ultra-high-speed and ultra-large-capacity optical fiber transmission system, and is particularly suitable for an 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 an important role as a transmission medium. The widespread application of optical fiber depends on whether it has the optical properties of ultra-low transmission loss, low bending loss and wide light-guiding passband. These characteristics determine its potential for widespread use in fields such as optical fiber communications, laser systems and spectral analysis. For future ultra-high-speed, ultra-large-capacity and ultra-long-distance optical fiber transmission systems, ultra-low-loss optical fiber will be an indispensable key component.

[0003] As a cutting-edge product of optical development, antiresonant hollow core fiber has the characteristics of low loss, low delay, high bandwidth and low nonlinear effect. This fiber has a special structure, the core part of which is a hollow core area, and the light is confined in the hollow core by the antiresonance effect of the cladding. Therefore, the transmission of light is mainly carried out in the air rather than in solid materials, which can greatly reduce the absorption loss and nonlinear effect of the optical fiber when it is transmitted in solid materials. Thus, ultra-low loss and low nonlinear light transmission can be achieved.

[0004] In an antiresonant hollow-core optical fiber, its cladding is usually composed of a plurality of elliptical thin-walled capillary inner claddings and outer claddings of the same or different sizes. Light cannot be completely constrained during optical fiber transmission, and then leaks into the cladding or other areas, increasing the optical fiber loss rate. In addition, when such optical fibers are bent, the refractive index values ​​of the inner cladding and the outer cladding change, resulting in further loss. Moreover, the cladding tube of this type of hollow-core optical fiber is prone to deformation during the preparation process, making it difficult to achieve the designed ideal structure after preparation, that is, to maintain the consistency of optical fiber preparation. This in turn causes problems such as energy leakage or mode coupling, resulting in a large difference between the actual performance of the optical fiber finally prepared and the theoretical design value. The above problems have limited the development of antiresonant hollow-core optical fibers to a certain extent. Therefore, how to reduce the confinement loss of hollow-core optical fibers, improve the bending resistance of hollow-core optical fibers, and how to improve the fault tolerance characteristics of their preparation has become an urgent problem to be solved. Summary of the invention

[0005] In order to solve the problems including the problem that the optical signal cannot be completely constrained during the transmission of the hollow-core optical fiber, resulting in leakage, the problem that the loss of the optical fiber increases sharply when it is bent, and the problem that the optical fiber does not reach the ideal structural parameters during the preparation process, resulting in the degradation of the optical fiber performance. The purpose of the present invention is 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 structure parameters and refractive index parameters of the optical fiber, the limiting loss in the anti-resonant hollow-core optical fiber is reduced, so that the limiting 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 anti-bending characteristics and fault-tolerant characteristics of preparation, and even when the bending radius is 2cm, its maximum limiting loss does not exceed 0.381dB / km. And the optical fiber structure is allowed to effectively suppress the leakage of the transmitted optical signal under a non-ideal structure, that is, within a certain error range, and maintain a low limiting loss. Compared with traditional anti-resonant hollow-core optical fiber, 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 objective of the present invention is achieved through the following technical solutions:

[0007] The present invention discloses a semi-elliptical ring cross-tube anti-resonant hollow-core optical fiber, comprising an outer cladding, an inner cladding, a hollow-core fiber core and a dielectric filling area. The outer cladding is an 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, i.e., a dielectric filling area. The hollow-core fiber core is located inside the inner cladding.

[0008] Preferably, the material of the outer cladding is 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, are 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 an outer cladding, and a semi-elliptical ring cross capillary structure as an inner cladding, and effectively controls 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 a certain preparation fault tolerance characteristic. Allowing the optical fiber structure to be within a certain error range, the optical fiber can still effectively suppress the leakage of light and maintain a 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 It is a structural schematic diagram of a cross section of a semi-elliptical ring cross-tube anti-resonant hollow-core optical fiber;

[0018] Figure 2 The radial refractive index distribution diagram of a semi-elliptical ring cross-tube anti-resonant hollow-core optical fiber;

[0019] Figure 3 It is a trend diagram of the limiting loss of a semi-elliptical ring cross-tube anti-resonant hollow-core optical fiber changing with the thickness of the inner cladding semi-elliptical tube;

[0020] Figure 4 It is a contour diagram of the confinement loss of a semi-elliptical ring cross-tube anti-resonant hollow-core optical fiber as the major and minor axes of the inner cladding semi-elliptical tube change;

[0021] Figure 5 It is a graph showing the trend of the limiting loss of a semi-elliptical ring cross-tube antiresonant hollow-core optical fiber as a function of the hollow-core fiber diameter;

[0022] Figure 6 It is a trend diagram of the limiting loss of a semi-elliptical ring cross-tube anti-resonant hollow-core optical fiber changing with the distribution angle deviation of a single semi-elliptical tube;

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

[0024] Figure 8 It is a schematic diagram of the structure of the cross section of another semi-elliptical ring cross-tube anti-resonant hollow-core optical fiber;

[0025] Fig. 9 It is a structural schematic diagram of a cross section of a comparative embodiment of a semi-elliptical ring tube anti-resonant hollow core optical fiber;

[0026] Fig.10 It is a structural schematic diagram of the cross section of another comparative embodiment of annular ring tube antiresonant hollow core optical fiber. DETAILED DESCRIPTION

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

[0028] like Figure 1 As shown, a semi-elliptical ring cross-tube anti-resonant hollow-core optical fiber disclosed in this embodiment includes a circular tube 1, a plurality of 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 an outer cladding, and the plurality of semi-elliptical ring cross-capillary structures 2 serve as an 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 intersecting with the outer cladding. Each semi-elliptical capillary structural element intersects with an adjacent semi-elliptical capillary structural element and is evenly distributed in the outer cladding, so that its cross section forms a semi-elliptical chain shape. These intersecting semi-elliptical capillary structural elements together constitute the inner cladding 2 of the hollow-core optical fiber. The center of the circle of the adjacent semi-elliptical capillary structural elements and the center of the circle of the outer cladding form a certain angle, which is evenly distributed in the outer cladding and forms a closed cavity with the outer cladding, i.e., a medium filling area 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 direction. The material of the outer cladding 1 and the inner cladding 2 is the same, which is quartz glass. Its refractive index is 1.45 and its thermal expansion coefficient is 0.55e-6 (K -1 ), relative dielectric constant is 3.75, Poisson's ratio is 0.17, and Young's modulus is 73.1 (GPa). The medium filling area 4 and the hollow core 3 are air, and its refractive index value is 1.

[0031] Embodiment 1:

[0032] like Figure 1 As shown, a semi-elliptical ring cross-tube anti-resonant hollow-core optical fiber disclosed in this embodiment includes a circular tube 1, a plurality of 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 an outer cladding, and the plurality of semi-elliptical ring cross-capillary structures 2 serve as an inner cladding.

[0033] 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 set to a plurality of semi-elliptical capillary structural elements intersecting with the outer cladding. Among them, the long semi-axis of the cross section of the semi-elliptical capillary is 30.2 μm, the short semi-axis of the cross section of the semi-elliptical capillary 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, with a total of 12 semi-elliptical capillary structural elements, which are evenly distributed in the outer cladding. And each semi-elliptical capillary and the outer cladding form a closed cavity, that is, the medium filling 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, for 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 filling area 4 and the hollow core 3 are air, and the refractive index is 1.

[0037] Furthermore, for the above-mentioned embodiment, its core technical contribution lies in the structure of the inner cladding composed of multiple intersecting semi-elliptical capillaries combined with the outer cladding. It can be understood that it is precisely thanks to the special structure of the above-mentioned inner cladding that the range in which the optical signal can be transmitted in the hollow-core optical fiber is strictly controlled, and the optical signal is effectively confined to the hollow-core fiber 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. Figure 3 As shown in FIG. 1 , 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 anti-resonant hollow core optical 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] Further, 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 with respect to other semi-elliptical capillaries is uneven. The angle formed by the center of the circle of the semi-elliptical capillary 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 when 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 is 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 anti-resonant hollow-core optical fiber can maintain a relatively low limiting loss, i.e., less than 1dB / km.

[0039] Further, for the above embodiment, if Figure 7 As shown, through calculation, the optical fiber can still maintain its limiting loss at a maximum of 0.3805 dB / km even when the bending radius is 2 cm.

[0040] Embodiment 2:

[0041] like Figure 8 As shown, a semi-elliptical ring cross-tube anti-resonant hollow core optical fiber comprises a circular tube 1, a plurality of semi-elliptical ring cross-capillary structures 2, a hollow core 3 and a dielectric filling area 4. The circular tube 1 is used as an outer cladding, and the plurality of semi-elliptical ring cross-capillary structures 2 are used as an inner cladding.

[0042] The outer cladding 1 is the outermost circular tubular structural element. The thickness is set to 3μm. The inner cladding 2 is located inside the outer cladding and is set to a plurality of semi-elliptical capillary structural elements intersecting with the outer cladding. Among them, the long semi-axis of the cross-section of the semi-elliptical ring cross capillary structural element is 29μm, the short semi-axis of the cross-section of the semi-elliptical capillary is 31μm, and the thickness is set to 0.5μm. The center of the semi-elliptical capillary structural element is located on the inner surface of the outer cladding 1, and 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 in the outer cladding. And each semi-elliptical capillary and the outer cladding form a closed cavity, that is, 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, for 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 filling area 4 and the hollow core 3 are air, and the refractive index is 1.

[0046] Furthermore, for the above-mentioned embodiment, its core technical contribution 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 thanks to the special structure of the above-mentioned inner cladding that the optical fiber can effectively reduce the limiting loss and suppress the leakage of light. That is, for the semi-elliptical ring cross-tube anti-resonant hollow-core optical fiber, by adjusting the thickness of the relevant semi-elliptical ring cross-tube, the length of the major semi-axis, the length of the minor semi-axis, the diameter of the hollow core, and the thickness of the outer cladding, the effective anti-resonance conditions of the hollow-core optical fiber are achieved, the limiting loss and bending loss of the optical fiber are reduced, and its fault tolerance characteristics are improved.

[0047] Further, for the above embodiment, when the angle formed by the center of the circle of the adjacent semi-elliptical capillaries and the center of the circle of the outer cladding deviates, that is, the relative position of the semi-elliptical capillaries is unevenly distributed. The thickness of the semi-elliptical capillaries deviates within 0.2 μm. Or the major and minor semi-axes of the cross section of each semi-elliptical capillary deviate within 0.5 μm, the semi-elliptical ring cross-tube anti-resonant hollow-core optical fiber can maintain a low limiting loss.

[0048] Comparative Example 1:

[0049] A semi-elliptical ring anti-resonant hollow core optical fiber is used as a comparative example. Fig. 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 core 3 and a medium filling area 4.

[0050] The outer cladding 1 is the outermost circular tubular structural element. The thickness is set to 2.5μm. The inner cladding 2 is located inside the outer cladding and is set to a plurality of semi-elliptical capillary structural elements intersecting with the outer cladding. Among them, the long semi-axis of the cross section of the semi-elliptical ring capillary structural element is 22.6μm, the short semi-axis of the cross section of the semi-elliptical capillary is 22.4μm, and the thickness is set to 0.5μm. The angle formed by the center of each adjacent semi-elliptical capillary structural element and the center of the outer cladding is 45 degrees, with 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 0.1μm, and they are approximately tangent. And each semi-elliptical capillary and the outer cladding form a closed cavity, that is, 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 example, the hollow core 3 and the medium filling area 4 are air, and the refractive index thereof is 1.

[0053] Further, for the above comparative example, 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 above comparative example, the minimum limiting loss is calculated by the finite element method to be 14 dB / km, and when the bending radius is 2 cm, the bending loss is 14.402 dB / km. Compared with Example 1, the semi-elliptical cross capillary structure can more effectively reduce the limiting loss, and its special interlocking structure can better support the bending side of the optical fiber when it is bent, reducing the leakage of the optical signal when it is bent. Example 1 has more advantages in reducing limiting loss and bending loss.

[0055] Comparative Example 2:

[0056] A semi-elliptical ring anti-resonant hollow core optical fiber is used as a comparative example. Fig.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 core 3 and a medium filling region 4.

[0057] The outer cladding 1 is the outermost circular tubular structural element. The thickness is set to 2.5μm. The inner cladding 2 is located inside the outer cladding and is set to a plurality of semi-elliptical capillary structural elements intersecting with the outer cladding. Among them, the cross-sectional radius of the circular capillary structural element is 21.3μm, and the capillary thickness is set to 0.5μm. The angle formed by the center of each adjacent semi-elliptical capillary structural element and the center of the outer cladding is 60 degrees, with 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 0.2μm. And each semi-elliptical capillary and the outer cladding form a closed cavity, that is, 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 example, the hollow core 3 and the medium filling area 4 are air, and the refractive index thereof is 1.

[0060] Further, for the above comparative example, 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] For the above comparative example, the minimum limiting loss calculated by the finite element method is more than 100 dB / km, and the bending loss is more than 190 dB / km when the bending radius is 2 cm. Compared with Example 1, the semi-elliptical intersecting capillary structure can more effectively reduce the limiting loss, and its special interlocking structure can better support the bending side of the optical fiber when it is bent, reducing the leakage of the signal when it is bent. Example 1 has more advantages in reducing limiting loss and bending loss.

[0062] The above-mentioned embodiments are only preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, several equivalent deformations and substitutions can be made on the content disclosed in the present invention, such as the thickness of the semi-elliptical ring cross tube, the length of the major semi-axis, the length of the minor semi-axis, the radius of the hollow core, the size of the ellipticity, the number of semi-elliptical ring capillaries, the equivalent shape of the semi-elliptical ring capillaries, the size of the cladding refractive index and the thickness of the outer cladding, and the filling gas, liquid or vacuum of the medium filling area and the hollow core. These equivalent deformations and substitutions and the adjustment of other device parameters should also be regarded as the protection scope of this patent.

Claims

1. A semi-elliptical ring cross-tube anti-resonant hollow core optical fiber, Features: It includes an outer cladding, an inner cladding, a hollow fiber core and a medium 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 medium filling area; the hollow fiber core is located inside the inner cladding.

2. A semi-elliptical ring cross-tube anti-resonant hollow core optical fiber according to claim 1, Features: The material of the outer cladding layer is quartz glass.

3. The semi-elliptical ring cross-tube anti-resonant hollow core optical fiber according to claim 1, Features: 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 anti-resonant hollow core optical fiber according to claim 3, Features: 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 anti-resonant hollow core optical fiber according to claim 1, Features: The hollow core fiber is filled with one or more gases, or is in a vacuum.

6. The semi-elliptical ring cross-tube anti-resonant hollow core optical fiber according to claim 1, Features: 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 anti-resonant hollow core optical fiber according to claim 1, Features: The medium filling area is set to be one or more gases, or a vacuum.

8. The semi-elliptical ring cross-tube anti-resonant hollow core optical fiber according to claim 1, Features: The refractive index of the medium filling area is less than that of the cladding.

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