Research On Sagnac Loop Optical Fiber Photonic Devices Based On Fiber Bragg Gratings

Fiber Bragg grating can be applied in the field of optical fiber communication.With the maturity of fiber Bragg grating fabrication technology,more and more kinds of fiber Bragg gratings(long period fiber gratings,tilted fiber Bragg gratings,microfiber Bragg gratings,etc.)have been successfully fabricated,and applications have been more and more widely.Fiber Bragg gratings have been studied by more and more researchers.Sagnac effect was first proposed by G.Sagnac in 1913 and verified by experiments.Optical fiber Sagnac loop is widely used in optical fiber communication and optical fiber sensing because of its advantages of high stability,easy manufacturing and low cost.With the rapid development of optical fiber communication and optical fiber sensing technology,the structure of fiber Sagnac loop has become an important research field in optical fiber communication and fiber sensor parts.The main work of this thesis is as follows:1.Using the classical theory of coupled mode to analyze the theory of fiber grating Sagnac loop comb filter to deduce the formulas of fiber grating reflectivity and transmissivity.Then,the filtering characteristics of 2×2 single mode optical fiber coupler and fiber grating Sagnac loop structure have been analyzed by Jones matrix theory,respectively.The reflectivity and transmissivity formula of fiber fiber grating Sagnac loop structure have been calculated.2.Starting from the concept of microfiber and evanescent field,the relationship between the electric field intensity and the transmission depth of evanescent wave is derived.The theoretical characteristics of microfiber Bragg grating are introduced and the influence conditions of effective index of microfiber grating are analyzed.The influence of temperature and external refractive index on effective index of fiber grating is discussed.Study on the gate region which fundamental mode and highe order mode coupling will occur in,according to the relevant theory of fiber M-Z interference,the effects of microfiber grating interference peak has been discussed.3.In this part,the reflectivity and transmissivity formulas of uniform fiber grating Sagnac loop structure have been calculated.According to the software simulation,the transmission spectrum in the fiber grating Sagnac loop has been simulated.Then,the transmission spectrum of different parameters in fiber grating Sagnac loop have been analyzed.Finally,the suitable experimental parameters are selected and the actual uniform fiber Bragg grating Sagnac ring filter is designed by experiment.4.The effects of temperature and refractive index on the effective refractive index and the interference peak of microfiber Bragg grating are analyzed,respectively.Then,a dual parameter microfiber Bragg grating sensor in Sagnac loop has been designed.The sensitivity of temperature and refractive index have been got,and the transfer matrix is obtained to simultaneous measurement of temperature and refractive index.