Research On Stress-type Polarization-maintaining Fiber And Its Polarization Beam Splitter

The transmission rate of optical fiber system and the requirements of fiber optic gyroscope and other instruments on the polarization state of optical fiber are increasing day by day,which has prompted people to study the control of polarization state system.In order to overcome the phenomenon that single-mode fiber exhibits polarization-mode dispersion during communication,we artificially design stress areas or increase the ovality of the core in the cladding of the traditional single-mode fiber.This results in an asymmetric stress field in the fiber core.Thus,a polarization-maintaining fiber having excellent polarization maintaining characteristics is obtained.Polarization-maintaining fiber plays a decisive role in the fields of coherent communication and sensing.Therefore,the analysis of polarization-maintaining fiber and the expansion of its application are crucial.This thesis is mainly on the basis of the predecessors.We analyze and summarize the optical characteristics of the panda polarization maintaining fiber and the bow-tie polarization maintaining fiber.Based on the panda-type polarization-maintaining fiber,we propose a stress-type dual-core fiber tunable polarization beam splitter.The main work content is as follows:Firstly,we introduce the research background and significance of this thesis,and analyze the domestic and international development status of polarization-maintaining fiber,dual-core fiber and polarization beam splitter.Secondly,we study the fiber wave transmission theory and the photoelastic theory,and briefly introduce the optical fiber numerical analysis method and the finite element method simulation software.Then,based on the finite element method,we establish the panda polarization-maintaining fiber and the bow-tie polarization-maintaining fiber model,and analyze the stress distribution of the fiber cross section and the cause of birefringence.By changing the structural parameters of the stress area,we explore the change trend of the birefringence of the stress-maintaining fiber.Then,we introduce the working principle and performance indexes of the stress-type dual-core fiber polarization beam splitter,and select the method of calculating the absolute value of the normalized power difference to calculate the length of the polarization beam splitter.Finally,through the analysis of the mode field and characteristics of the stress-type dual-core fiber polarization beam splitter,we propose a polarization beam splitter that can be tuned in real time by adjusting the operating temperature.The device has the advantages of smaller length and wider operating bandwidth.