Asymmetric cladding structure single-polarization anti-resonance optical fiber working in terahertz wave band

Abstract

The invention relates to a single-polarization anti-resonance optical fiber, in particular to an asymmetric cladding structure single-polarization anti-resonance optical fiber working in a terahertz wave band, six longitudinal double-layer nested cladding tubes and two transverse double-layer nested cladding tubes are arranged in an optical fiber cladding, a protective tube is arranged outside the optical fiber cladding, and a perfect matching layer is arranged outside the protective tube; the six longitudinal double-layer nested cladding pipes are divided into two groups with the same number by the two transverse double-layer nested cladding pipes, and the six longitudinal double-layer nested cladding pipes and the two transverse double-layer nested cladding pipes are uniformly distributed on the circumference; the longitudinal double-layer nested cladding tube is composed of a first inner cladding tube and a first outer cladding tube, and the transverse double-layer nested cladding tube is composed of a second inner cladding tube and a second outer cladding tube. The loss of X polarization FM and the loss of Y polarization FM at 1 THz are 9.07 dB / m and 2.59 * 10 <-5 > dB / m respectively, and the PLR reaches up to 349318. The structure can effectively reduce the transmission loss and increase the polarization loss ratio, and the single polarization effect is good.

Description

Technical Field

[0001] The invention relates to a single polarization anti-resonance optical fiber, in particular to a single polarization anti-resonance optical fiber with an asymmetric cladding structure operating in a terahertz band. Background Art

[0002] The emergence of hollow core antiresonant fibers (HC-ARFs) provides a new method for the design of low-loss, low-nonlinear, low-dispersion, and high-damage threshold optical fibers. Hollow core antiresonant fibers use coherent reflections between tubular glass films in the fiber cladding to confine light to the air core and transmit it along the axis. They can be used in high-power optical transmission, optical communications, fiber gyroscopes, pulse compression, and fiber sensing. In the process of applying HC-ARFs, in order to improve the transmission quality of optical signals, it is necessary to design single-polarization optical fibers to effectively control the polarization state of light waves.

[0003] In order to obtain high-performance single-polarization optical fiber, it is necessary to break the symmetrical distribution of the optical fiber refractive index. There are two main types of existing single-polarization optical fibers: the first is to coat or fill the cladding tube in a certain direction with a high refractive index material to enhance the coupling between the cladding mode and the fundamental mode in this direction, thereby increasing the loss, while the other orthogonal direction is not affected, thereby improving the polarization loss ratio (PLR). The second is to design an asymmetric cladding structure, construct a cladding tube structure that meets the resonance conditions in a certain direction, use resonance to enhance the loss of the polarization mode in this direction, and design a cladding structure that meets the anti-resonance conditions in another orthogonal direction, thereby constraining the mode in this polarization direction and reducing the transmission loss. The single-polarization optical fiber designed in this way can effectively avoid polarization crosstalk and polarization mode dispersion caused by the fundamental modes in the two polarization directions. S. Yan et al. designed a single-mode single-polarization optical fiber with six double-ring nodeless structures, introducing different wall thicknesses in two orthogonal directions, so that its PLR at 1550nm reached 17662, and realized two single-polarization transmission bands of 1545-1553 nm and 1591-1596 nm. S. Yan et al. reported a double-ring cladding structure, in which a layer of high-refractive-index silicon material was coated on the inner layer of the cladding tube in the Y-axis direction, which enhanced the coupling between the Y-polarized fundamental mode and the cladding mode, and the PLR ​​reached 14232 at 1520 nm. Y. Gong et al. designed an asymmetric five-tube nested double C-type structure, which broke the axisymmetric distribution of the refractive index by covering the inner surface of the cladding tube in the X-axis direction with a layer of high-refractive-index silicon material, and the PLR ​​at 1550 nm reached 162486, with a single-polarization bandwidth of 150 nm. However, in the terahertz band, the optical fiber material strongly absorbs terahertz waves, making it difficult to improve the PLR. IM Ankan et al. proposed a four-tube nested semi-elliptical structure, in which a single-layer semi-elliptical tube was used in the Y-axis direction and a double-layer semi-elliptical tube was used in the X-axis direction, achieving a loss of about 4.8 dB / m at 0.9 THz, and a PLR of only 2.5. In the same year, MA Mollah et al. proposed a four-tube nested structure based on Zeonex. By designing an asymmetric structure in the two orthogonal directions of X and Y, they obtained a minimum loss of 0.34dB / m at 1.1THz, and a PLR of 13. In 2023, L. Xue et al. designed a terahertz hollow-core antiresonant fiber with four nested semi-elliptical tubes. The resonant wall thickness was used in the X-axis direction to couple the X-polarization fundamental mode, and the antiresonant wall thickness was used in the Y-axis direction to bind the Y-polarization fundamental mode, so that the PLR ​​reached 156 at 0.5THz. In 2023, Q. Liu et al. disclosed a polarization filter based on antiresonant hollow-core fiber, which adopted a double-tube cladding structure. The polarization extinction ratio reached 100dB at 1THz, and the insertion loss of the Y-polarization fundamental mode at 1THz was less than 0.66dB.

[0004] As can be seen from the above, the existing single polarization anti-resonance optical fiber in the terahertz band has the problem of high transmission loss and low polarization loss, and the single polarization performance is not outstanding. Therefore, it is of great significance to design a high-performance single polarization anti-resonance optical fiber with low loss and high polarization loss ratio. Summary of the invention

[0005] In order to further solve the above problems, the present invention provides an asymmetric cladding structure single polarization antiresonant optical fiber operating in the terahertz band. The HC-ARF with an asymmetric double-layer nested semi-elliptical tube structure can increase the transmission loss of the X-polarization fundamental mode and effectively reduce the transmission loss of the Y-polarization fundamental mode. The structure effectively reduces the transmission loss and increases the polarization loss ratio, achieving a good single polarization effect.

[0006] The technical solution adopted by the present invention is: an asymmetric cladding structure single polarization anti-resonance optical fiber working in the terahertz band, the cladding of the single polarization anti-resonance optical fiber is provided with 6 longitudinal double-layer nested cladding tubes and 2 transverse double-layer nested cladding tubes, the outside of the optical fiber cladding is provided with a protective tube, and the outside of the protective tube is provided with a perfect matching layer; the 2 transverse double-layer nested cladding tubes are arranged on the x-axis, the 6 longitudinal double-layer nested cladding tubes are divided into two groups of equal number by the 2 transverse double-layer nested cladding tubes, and the 6 longitudinal double-layer nested cladding tubes and the 2 transverse double-layer nested cladding tubes are evenly distributed around the circumference; the longitudinal double-layer nested cladding tubes are composed of a first inner cladding tube and a first outer cladding tube, and the transverse double-layer nested cladding tubes are composed of a second inner cladding tube and a second outer cladding tube; the inner radius of the single polarization anti-resonance optical fiber R =6.15 mm, the diameter of its core D c =6.2 mm, thickness of protective tube JT = 0.3 mm, thickness of the perfectly matched layer T =0.5 mm; the first outer cladding tube and the second outer cladding tube are both semi-elliptical tubes, with their long semi-axis r a =3.05mm, ellipticity u = r b / r a =0.61 mm, where the wall thickness of the first outer cladding tube is t 1 =0.035 mm; the first inner cladding tube is a semi-elliptical tube, with its long semi-axis r e =2.3 mm, ellipticity w = r f / r e = 0.4, the wall thickness is 0.035 mm; the second inner cladding tube is a semi-elliptical tube, its long semi-axisr c =1.1 mm, ellipticity v = r d / r c = 0.8, the second inner cladding tube is a tube of equal wall thickness, its wall thickness t 2 = 0.1 mm; the second outer cladding tube is a gradient wall thickness tube, with a maximum wall thickness of t 2 = 0.1 mm, minimum wall thickness t 0 =0.039 mm.

[0007] Furthermore, the second inner cladding tube and the second outer cladding tube are both tubes of equal wall thickness. t 2 = 0.1 mm.

[0008] Furthermore, the second inner cladding tube and the second outer cladding tube are both tubes with a gradient wall thickness, and the maximum wall thickness t 2 = 0.1mm, minimum wall thickness t 0 = 0.039 mm.

[0009] Furthermore, the substrate material of the asymmetric cladding structure single polarization anti-resonance optical fiber operating in the terahertz band is high-resistance silicon.

[0010] Furthermore, the inner and outer semi-elliptical tubes in the Y-axis direction are used to confine the Y-polarization fundamental mode (FM) in the core region to prevent the Y-polarization FM from entering the interior of the cladding tube or the gap between the cladding tubes. The outer cladding tube in the X-axis direction suppresses the loss of the Y-polarization FM while enhancing the loss of the X-polarization fundamental mode. The uniformly-walled semi-elliptical tubes nested inside are used to enhance the coupling effect between the X-polarization fundamental mode and the cladding mode, thereby increasing the transmission loss of the X-polarization fundamental mode.

[0011] Furthermore, the terahertz band single polarization anti-resonance optical fiber operates at 1 THz and has a bandwidth of 0.98-1.02 THz.

[0012] The beneficial effects of the present invention are as follows: a terahertz band single polarization antiresonant optical fiber is provided that can achieve ultra-low transmission loss and ultra-high polarization loss ratio. A HC-ARF based on a double-layer nested cladding tube with a mixture of gradient wall thickness and uniform wall thickness is used. The finite element method is used to analyze the influence of the wall thickness and structural parameters of the nested tube on the transmission characteristics of the optical fiber. The results show that the asymmetric double-layer nested cladding structure can reduce the confinement loss of the optical fiber and obtain an ultra-high polarization loss ratio. At 1 THz, the losses of X-polarization FM and Y-polarization FM are 9.07 dB / m and 2.59 × 10 -5 dB / m, PLR up to 349318, and PLR greater than 100 in the range of 0.98-1.02THz, which is significantly better than the existing antiresonant fiber. It provides important technical guidance for the design and optimization of low-loss, high-PLR terahertz HC-ARFs. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is a schematic cross-sectional view of a terahertz band single polarization antiresonant optical fiber having a structure of type (c); Figure 2 is a schematic cross-sectional view of a terahertz-band single-polarization antiresonant optical fiber having a structure of type (a); Figure 3 is a schematic cross-sectional view of a terahertz band single polarization antiresonant optical fiber having a structure of type (b); Figure 4 Mode field comparison of single-polarization antiresonant fibers ARF-A (a), ARF-B (b), and ARF-C (c) in the terahertz band; Figure 5 This is the effective material loss, confinement loss and total loss curve of single polarization antiresonant fiber ARF-A in the terahertz band; Figure 6 This is the effective material loss, confinement loss and total loss curve of single polarization antiresonant fiber ARF-B in the terahertz band; Figure 7 This is the effective material loss, confinement loss and total loss curve of single polarization antiresonant fiber ARF-C in the terahertz band; Figure 8 It is the polarization loss ratio PLR of three double-layer nested structures: ARF-A, ARF-B, and ARF-C; Fig. 9 It is a structure (c) type antiresonant fiber with a long semi-axis of 1 THz at an operating frequency r a Comparison of the impact curves on limit loss, effective material loss and total loss; Fig.10 It is a structure (c) type antiresonant fiber with a long semi-axis of 1 THz at an operating frequency ra Impact diagram on polarization loss ratio PLR; Fig.11 It is a structure (c) type antiresonant fiber with an ellipticity of 1 THz. u Comparison of the impact curves on limit loss, effective material loss and total loss; Fig.12 It is a structure (c) type antiresonant fiber with an ellipticity of 1 THz. u Impact diagram on polarization loss ratio PLR; Fig.13 It is a structure (c) type antiresonant fiber with a long semi-axis of 1 THz at an operating frequency r c Comparison of the impact curves on limit loss, effective material loss and total loss; Fig.14 It is a structure (c) type antiresonant fiber with a long semi-axis of 1 THz at an operating frequency r c Impact diagram on polarization loss ratio PLR; Fig.15 It is a structure (c) type antiresonant fiber with an ellipticity of 1 THz. v Comparison of the impact curves on limit loss, effective material loss and total loss; Fig.16 It is a structure (c) type antiresonant fiber with an ellipticity of 1 THz. v Impact diagram on polarization loss ratio PLR; Fig.17 It is a structure (c) type antiresonant fiber with a long semi-axis of 1 THz at an operating frequency r e Comparison of the impact curves on limit loss, effective material loss and total loss; Fig.18 It is a structure (c) type antiresonant fiber with a long semi-axis of 1 THz at an operating frequency r e Impact diagram on polarization loss ratio PLR; Fig.19 It is a structure (c) type antiresonant fiber with an ellipticity of 1 THz. w Comparison of the impact curves on limit loss, effective material loss and total loss; Fig. 20 It is a structure (c) type antiresonant fiber with an ellipticity of 1 THz. w Graph showing the impact on polarization loss ratio (PLR). DETAILED DESCRIPTION Example

[0014] like Figure 1 As shown, a single-polarization antiresonant optical fiber with an asymmetric cladding structure operating in the terahertz band is provided with 6 longitudinal double-layer nested cladding tubes 1 and 2 transverse double-layer nested cladding tubes 2 in the cladding of the single-polarization antiresonant optical fiber, a protective tube 3 is provided outside the optical fiber cladding, and a perfect matching layer 4 is provided outside the protective tube 3; the 2 transverse double-layer nested cladding tubes 2 are arranged on the x-axis, the 6 longitudinal double-layer nested cladding tubes 1 are divided into two groups of equal number by the 2 transverse double-layer nested cladding tubes 2, and the 6 longitudinal double-layer nested cladding tubes 1 and the 2 transverse double-layer nested cladding tubes 2 are uniformly distributed around the circumference; the longitudinal double-layer nested cladding tube 1 is composed of a first inner cladding tube 11 and a first outer cladding tube 12, and the transverse double-layer nested cladding tube 2 is composed of a second inner cladding tube 21 and a second outer cladding tube 22; the inner radius of the single-polarization antiresonant optical fiber R =6.15 mm, the diameter of its core 5 D c =6.2 mm, thickness of protective tube 3 JT =0.3 mm, the thickness of the perfect matching layer 4 T =0.5 mm; the first outer cladding tube 12 and the second outer cladding tube 22 are both semi-elliptical tubes, and their long semi-axis r a =3.05mm, ellipticity u = r b / r a =0.61 mm, where the wall thickness of the first outer cladding tube 12 is t 1 =0.035mm; the first inner cladding tube 11 is a semi-elliptical tube, its long semi-axis r e =2.3 mm, ellipticity w = r f / r e = 0.4, the wall thickness is 0.035 mm; the second inner cladding tube 21 is a semi-elliptical tube, the long semi-axis r c =1.1 mm, ellipticity v = r d / r c = 0.8, the second inner cladding tube 21 is a tube of equal wall thickness, and its wall thickness t 2 = 0.1 mm; the second outer cladding tube 22 is a gradual wall thickness tube, and its maximum wall thickness t 2 = 0.1 mm, minimum wall thickness t 0= 0.039 mm. The substrate material of the asymmetric cladding structure single polarization antiresonant optical fiber is high-resistance silica.

[0015] In this embodiment, the second inner cladding tube 21 in the X-axis direction is a tube of uniform wall thickness. t 2 = 0.1 mm; the second outer cladding tube 22 is a gradual wall thickness tube, and its maximum wall thickness t 2 = 0.1 mm, minimum wall thickness t 0 = 0.039 mm, forming a terahertz-band single-polarization antiresonant fiber (ARF-C) with structure (c). Example

[0016] like Figure 2 As shown, based on the technical solution of Example 1, the second inner cladding tube and the second outer cladding tube are both tubes with equal wall thickness, and their average wall thickness is t 2 = 0.1 mm. A terahertz-band single-polarization antiresonant fiber (ARF-A) of structure (a) is formed. Example

[0017] like Figure 3 As shown, based on the technical solution of embodiment 1, the second inner cladding tube and the second outer cladding tube are both gradual wall thickness tubes, and their maximum wall thickness t 2 = 0.1 mm, minimum wall thickness of the second inner cladding tube t 3 = 0.035 mm, minimum wall thickness of the second outer cladding tube t 0 = 0.039 mm. A terahertz-band single-polarization antiresonant fiber (ARF-B) of structure (b) was formed.

[0018] like Figure 4 The following are the comparison diagrams of the mode fields of three types of ARF-A (a), ARF-B (b) and ARF-C (c), where Figures (d) and (g) are the mode field diagrams of ARF-A (a), Figures (e) and (h) are the mode field diagrams of ARF-B (b), and Figures (f) and (i) are the mode field diagrams of ARF-C (c). Figure 5 , Figure 6 and Figure 7 The limiting loss, effective material loss and total loss of three antiresonant optical fibers, ARF-A (a), ARF-B (b) and ARF-C (c), respectively. Figure 8 is the polarization loss ratio (PLR) of the three structures.

[0019] Figure 5The limiting loss (CL), effective material loss (EML) and total loss of the ARF-A structure in the range of 0.7-1.3THz are given. As can be seen from the figure, the effective material loss of X and Y polarization FM is low, and the effective material loss of the Y polarization fundamental mode is lower than that of the X polarization fundamental mode. The limiting loss plays a major role in the total loss. At around 1THz, due to the resonance effect of the X-axis cladding tube, the limiting loss of the X polarization fundamental mode and the Y polarization fundamental mode increases, and the PLR ​​value is small, such as Figure 8 This is because the inner and outer layers of the two double-layer nested cladding tubes in the X-axis are both made of thick t 2 = 0.1 mm uniform semi-elliptical tube, because the wall thickness is near the resonant frequency at 1 THz, the X-polarized fundamental mode is coupled to the cladding, as shown in Figure 4 (d) shows that the transmission loss increases. Although the wall thickness of the six double-layer nested semi-elliptical tubes in the Y-axis direction is t 1 = 0.035 mm, so that the Y polarization fundamental mode is in the anti-resonance region, suppressing its transmission loss, but part of the fundamental mode energy is still coupled to the cladding, such as Figure 4 As shown in (g), the Y polarization fundamental mode is lost, resulting in a low PLR value. It can be seen that simply using a double-layer nested cladding tube structure with uniform wall thickness in the X-axis direction cannot effectively enhance the PLR.

[0020] like Figure 3 As shown, it is a double-layer nested semi-elliptical tube structure with a gradient wall thickness. The maximum wall thickness of the outer and inner layers of the two nested cladding tubes on the X axis is t 2 = 0.1 mm, and the minimum wall thickness is t 0 = 0.039 mm and t 3 = 0.035 mm. Since the gradient wall thickness changes the resonance conditions of the X-polarization and Y-polarization fundamental modes, the mode fields of the X-polarization and Y-polarization fundamental modes are better bound in the fiber core at 1 THz, such as Figure 4 (e) and (h). Compared with the ARF-A structure, the transmission loss of the ARF-B structure is reduced overall, and the resonant frequency region moves, as shown in Figure 6 As shown. At this time, the PRL is Figure 8 As shown in , the PLR ​​is not significantly improved near 1 THz.

[0021] like Figure 1 As shown in the figure, it is a hybrid double-layer nested structure with a gradient outer layer wall thickness and a uniform inner layer wall thickness. The mode fields of the X-polarized and Y-polarized FM at 1 THz are shown in Figure 4As shown in (f) and (i), the X-polarization fundamental mode is strongly coupled to the cladding due to the wall thickness of the inner cladding tube meeting the resonance condition. Compared with the ARF-A and ARF-B structures, its loss is significantly increased, while the gradient wall thickness of the outer cladding tube confines the Y-polarization fundamental mode to the core region. Figure 7 The loss spectrum of ARF-C in the range of 0.7-1.3THz is given. Compared with the ARF-A and ARF-B structures, its effective material loss changes less. The mixed nested structure of the X axis mainly affects the limiting loss, which in turn determines the total loss. Near 1THz, the total loss of the X-polarization fundamental mode increases significantly, and the maximum value appears at 1THz, reaching 9.07 dB / m. At the same time, the total loss of the Y-polarization fundamental mode is as low as 2.59 × 10 -5 dB / m. Figure 8 The PLR ​​was calculated, and it can be seen that the maximum PLR near 1THz is 349318, and the PLR ​​values ​​in the range of 0.98-1.02THz are all greater than 100, with excellent single polarization performance.

[0022] For the ARF-C structure, the major axis of the semi-elliptical tube of the outer cladding r a The impact on the polarization loss ratio, Fig. 9 for r a Taking the loss spectrum at 2.50-3.15 mm, it can be seen that when r a =2.5 mm is smaller than the outer cladding tube in the resonant wall thickness, which plays a major role in coupling the X-polarized fundamental mode with the outer cladding tube. Fig. 9 As shown in the middle illustration ⅰ, r a The increase of the distance between the outer cladding tube and the inner cladding tube increases, resulting in the X-polarized fundamental mode coupling to the resonant inner cladding tube with uniform wall thickness, as shown in Figure 9, which increases the limiting loss. r a When it increases to 3.05 mm, the X-polarized FM is further coupled to the cladding, such as Fig. 9 As shown in the middle illustration ⅲ, the limiting loss further increases to 9.07 dB / m. r a It will also affect the Y polarization FM loss. r a =2.5 mm, Fig. 9 The middle illustration ⅳ shows that a small part of the Y-polarized FM is coupled to the apex of the outer cladding tube, but the loss is small. r a As it increases gradually, the Y-polarized FM is gradually coupled to the outer cladding tube, such as Fig. 9 As shown in Figure ⅴ, when ra =2.7mm, the loss peaks. r a As the Y polarization FM increases further, it is no longer affected and is confined in the core region. Fig. 9 As shown in Figure ⅵ, the Y polarization FM loss is small. r a =3.05 mm, the minimum value is 2.59 × 10 -5 dB / m, at this time PLR=349318, reaching the maximum value, such as Fig.10 Therefore, select r a =3.05 mm is the optimal value.

[0023] The influence of cladding tube ellipticity u on polarization loss ratio, Fig.11 The figure shows the loss spectrum when u is 0.58-0.69. It can be seen that within this range, the X-polarized FM is coupled to the cladding to varying degrees, such as Fig.11 As shown in the middle illustrations i, ii and iii, the limiting loss is large, but the loss value variation range is small. However, the Y polarization FM is well confined in the fiber core, as shown in Fig.11 As shown in Figures ⅳ, ⅴ and ⅵ, only when u = 0.66, a small part of the Y-polarized FM is coupled to the outer cladding tube, and the loss is slightly larger. u When it is in the range of 0.58-0.69, the impact on the X-polarization and Y-polarization FM loss is small, so its PLR changes little, such as Fig.12 To obtain the best PLR value, select u = 0.61.

[0024] Long axis of the semi-elliptical tube with uniform wall thickness nested in the inner layer of the X-axis r c The impact on the fundamental mode loss of X polarization and Y polarization is as follows Fig.13 As shown. r c When the range is 0.8-1.4 mm, the total loss of the X-polarization fundamental mode increases first and then decreases. This is because the spacing between the inner nested tube and the outer nested tube directly determines the coupling between the core mode and the cladding mode. Fig.13 As shown in the illustrations ⅰ, ⅱ and ⅲ, when r c =1.1 mm. The coupling is strongest when the X-axis inner layer nested tube long axis has little effect on the Y-polarization FM loss, and the Y-polarization FM is well confined in the core area, such as Fig.13 As shown in illustrations ⅳ, ⅴ and ⅵ. Fig.14 Given the polarization loss ratio, it can be seen that when r c = 1.1 mm. The PLR ​​value is the highest. The influence of the elliptical tube ellipticity v, such as Fig.15 As shown, it can be seen that it has no effect on the loss of the Y-polarization fundamental mode, but only affects the coupling between the X-polarization fundamental mode and the cladding mode. v =0.8 when PLR reaches its maximum value.

[0025] The long axis of the six inner nested semi-elliptical tubes in the Y-axis direction r e and ellipticity w Impact on PLR. Fig.17 Given r e Taking the loss spectrum at 1.6-2.8 mm, it can be seen that within this range r e It has almost no effect on the loss of the X-polarization fundamental mode, that is, the total loss remains unchanged. However, it affects the loss of the Y-polarization fundamental mode. Since it is an inner cladding tube, it can further reduce the loss of the Y-polarization fundamental mode, resulting in a large fluctuation in the Y-polarization FM limiting loss curve. r e =2.3 mm, the constraint on Y polarization FM is the strongest, and the maximum PLR value is obtained at this time, such as Fig.18 As shown, select r e = 2.3mm is the optimal value. w The impact on X-polarization and Y-polarization FM is as follows Fig.19 As shown, it also does not affect the X polarization fundamental mode, but only affects the Y polarization fundamental mode. w When the ellipticity increases within the range of 0.25-0.8, the limiting loss of the Y polarization fundamental mode first decreases and then increases, that is, the appropriate ellipticity can better limit the Y polarization FM. When the ellipticity is too large, it will cause mode field leakage, as shown in ⅳ, ⅴ and ⅵ. w = 0.4, the Y polarization fundamental mode loss is the smallest and the PLR ​​value is the largest. Fig. 20 Therefore, select w = 0.4 as the optimal value.

[0026] The ARF-C structure of Example 1 not only achieves a higher PLR, reaching 349318 at 1 THz, but also has a low transmission loss of 2.59 × 10 -5 dB / m can be used to design polarization filters as well as to transmit single-polarization light waves, and has broad application prospects.

[0027] The HC-ARF with an asymmetric double-layer nested semi-elliptical tube structure, in which the X-axis direction uses a double-layer nested structure with a gradient wall thickness and a uniform wall thickness semi-elliptical tube, can increase the transmission loss of the X-polarization fundamental mode; the Y-axis direction uses a double-layer semi-elliptical tube cladding structure with a uniform wall thickness, which can effectively reduce the transmission loss of the Y-polarization fundamental mode. At 1 THz, the losses of the X-polarization FM and Y-polarization FM are 9.07 dB / m and 2.59 × 10 -5 dB / m, and the PLR ​​is as high as 349318. At the same time, the PLR ​​in the range of 0.98-1.02THz is greater than 100. This structure can effectively reduce the transmission loss and increase the polarization loss ratio, achieving a good single polarization effect.

[0028] The above content is a further detailed description of the present invention in combination with specific implementation methods, and it cannot be determined that the present invention is limited to the above specific implementation. Without departing from the overall concept of the present invention and the protection of the claims, several simple deductions or substitutions can be made, which should be regarded as falling within the protection scope of the present invention.

Claims

1. An asymmetric cladding structure single polarization antiresonant optical fiber operating in the terahertz band, characterized in that: Six longitudinal double-layer nested cladding tubes (1) and two transverse double-layer nested cladding tubes (2) are arranged in the cladding of a single polarization anti-resonance optical fiber, a protective tube (3) is arranged outside the optical fiber cladding, and a perfect matching layer (4) is arranged outside the protective tube (3); the two transverse double-layer nested cladding tubes (2) are arranged on the x-axis, the six longitudinal double-layer nested cladding tubes (1) are divided into two groups of equal number by the two transverse double-layer nested cladding tubes (2), and the six longitudinal double-layer nested cladding tubes (1) and the two transverse double-layer nested cladding tubes (2) are evenly distributed around the circumference; the longitudinal double-layer nested cladding tubes (1) are composed of a first inner cladding tube (11) and a first outer cladding tube (12), and the transverse double-layer nested cladding tubes (2) are composed of a second inner cladding tube (21) and a second outer cladding tube (22); the inner radius of the single polarization anti-resonance optical fiber R = 6.15 mm, the diameter of its core (5) D c =6.2 mm, the thickness of the protective tube (3) JT = 0.3 mm, the thickness of the perfectly matched layer (4) T =0.5 mm; the first outer cladding tube (12) and the second outer cladding tube (22) are both semi-elliptical tubes, with their major semi-axis r a =3.05mm, ellipticity u = r b / r a =0.61 mm, where the wall thickness of the first outer cladding tube (12) is t 1 =0.035 mm; the first inner cladding tube (11) is a semi-elliptical tube, the long semi-axis of which r e =2.3 mm, ellipticity w = r f / r e = 0.4, the wall thickness is 0.035 mm; the second inner cladding tube (21) is a semi-elliptical tube, the long semi-axis r c =1.1 mm, ellipticity v = r d / r c =0.8, the second inner cladding tube (21) is a tube of equal wall thickness, and its wall thickness t 2 = 0.1 mm, the second outer cladding tube (22) is a tube with a gradient wall thickness, and its maximum wall thickness is t 2 = 0.1 mm, minimum wall thickness t 0 = 0.039 mm。 2. The asymmetric cladding structure single polarization antiresonant optical fiber operating in the terahertz band according to claim 1, characterized in that: The substrate material of the asymmetric cladding structure single-polarization anti-resonance optical fiber working in the terahertz band is high-resistance silicon.

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