Design And Characteristics Of Multilayer Anti-Resonant Hollow Fiber

Compared with the traditional solid-core fiber,hollow-core photonic crystal fiber can not only transmit light in the air core,but also has the advantages of low loss,high damage threshold and low delay.And the structure of hollow-core fiber is simplified,the loss is lower,the drawing is easier and the design is more flexible,the fiber has a wide range of applications,including Fiber-optic communication and sensing,high-power laser transmission.Based on the COMSOL software,the hollow core anti-resonant fibers with different structure are designed by using the finite element analysis method,and the transmission properties such as loss,single-mode and birefringence are studied in detail.The main research contents are as follows:Firstly,the basic principle of anti-resonant hollow fiber is analyzed,the optical guiding principle is explained by using the model of anti-resonant reflective waveguide and mode-coupling suppression.At the same time,the main transmission characteristics of anti-resonant fiber are analyzed systematically.Secondly,a kind of hollow core anti-resonant fiber with a cladding ring and a nested semicircle semi-ellipse is studied.Compared with the fiber with circular and elliptical structure,it is found that the embedded part can reduce the loss of the fiber and improve the single-mode performance.In addition,the loss of the fiber can be reduced by adding a cladding ring on the outside of the cladding tube.The error analysis of the length,thickness of the connecting rods between the cladding rings and the depth of the embedded elliptical part through the cladding tube is carried out.Thirdly,based on the above research,a layer of cladding tube structure is added,and the nested part is replaced by a concentric circle structure to study the influence of the structure parameters on the fiber performance.Compared with single-cladding structure with nested concentric circles and single-cladding structure with nested circles,it is found that the designed fiber structure can reduce the loss and improve the single-mode performance,to optimize its performance.In the course of the research,it is found that there are oscillations in different degrees in the transmission characteristic curve,the causes of this phenomenon are expounded in detail.Finally,based on the above two structures,a high-birefringence,double-cladding hollow-core anti-resonant fiber is obtained by adding a nested resonator tube and a nested silicon tube in the vertical polarization direction.In order to verify the good birefringence performance of the structure,it is compared with the structure with only a nested resonant tube and only a nested silicon tube.Considering the drawing process,the cladding tube near the core may deform.The effect of the micro-rotation of the cladding tube on the fiber performance is analyzed.The fiber has small fundamental mode loss and excellent birefringence,so it can be used in fiber optic gyroscope,fiber polarizer and other optical devices.