Research On High Birefringence Characteristics Of Hollow Core Anti-resonance Fiber For High Precision Fiber Optic Gyroscope

High precision fiber optic gyroscopes have extremely significant military and commercial applications.High birefringence fibers are key component in fiber optic gyroscope and have been the focus of scientific research.Hollow Core Anti-resonance Fiber（HC-ARF）has attracted more and more attention because of simple cladding structure,wide transmission band,and special light guiding mechanism.We can increase birefringence,reduce loss,and change the transmission band by designing the cladding of HC-ARF.In addition,it is possible to design polarization filtering devices required for optical communication,optical sensing and lasers by combining HC-ARF with metal and using the surface plasmon resonance effect of metal.The polarization filtering devices have higher polarization extinction ratio and may replace polarization splitters in fiber optic communication systems.In this paper,two kinds of glass HC-ARF are designed,and the loss,birefringence,mode,and polarization filtering characteristics of the HC-ARF are studied in depth.These two types of HC-ARF have excellent performance in polarization maintenance and polarization filtering,which can provide ideas for the research of high precision fiber optic gyroscopes and polarization filtering devices based on polarization maintaining fibers.The main work and related research contents of this thesis are as follows:Firstly,a high birefringence HC-ARF with a semi-circle cladding is proposed to meet the needs of high-precision fiber optic gyroscopes for polarization-maintaining fibers.At the wavelength of 1550 nm,the confinement loss of the x and y polarized fundamental modes guiding in this HC-ARF are 1.76 d B/m and 0.93 d B/m,respectively.The birefringence can reach 1×10^-4 and the bandwidth that birefringence is greater than 10^-4 can cover 60 nm.If increasing the confinement loss,the maximum birefringence can reach 1.6×10^-4 at the wavelength of 1550nm.The HC-ARF also has good bending characteristics.When the bending radius is greater than 5 cm,the bending loss of the y polarization fundamental mode is less than 1 d B/m when bending in the x direction.It can well satisfy the requirements of high precision fiber optic gyroscopes.And different parameters of the proposed HC-ARF can meet high-precision fiber optic gyroscopes with different characteristics.This HC-ARF can be extended to other applications that require polarization maintaining devices.Secondly,according to the needs of optical communication systems for polarizing filters,a HC-ARF with coating gold film in cladding is proposed.The HC-ARF can filter out x polarized LP₀₁,LP₂₁,and LP₀₂ modes at different wavelengths through optimizing the position and thickness of the gold-coated films,the size and thickness of the rings,and the size and thickness of the elliptical rings.At a wavelength of 1550 nm,the maximum polarization extinction ratio of LP₀₁ can reach 293.At a wavelength of 1570 nm,the maximum polarization extinction ratio of LP₂₁ is 116.At a wavelength of 1574 nm,the maximum polarization extinction ratio of LP₀₂ is 30.And the polarization filtering wavelength of different modes can be tuned in the C-band and L-band by changing the ellipticity of elliptical rings.The gold-coated HC-ARF can be used as a multi-mode,multi-wavelength polarization filter,and is applied in polarization-mode multiplexing,mode division multiplexing,and wavelength division multiplexing optical communication systems.