Research On All-fiber Tunable Filter Based On Acoustic And Optical Control Scheme In Optical Fiber

Optical fiber communication technology has become a very important part of modern communication technology,the optical fiber communication system(OFCS)is constantly moving towards larger capacity and higher speed.Because of their easy integration with the OFCS and flexible wavelengths,all-fiber devices play a very important role in the OFCS.Among many kinds of tuning methods,acousto-optic and optical tuning method attracts more and more attention due to its rapid response speed and no anisotropic effects.Moreover,fiber doesn't need to be destructive written and a dynamic grating structure with a flexible tunablity can be formed.In this dissertation,we propose and demonstrate a new optical tuning method for Er/Yb co-doped fiber Bragg gratings based on side pumping.And we successfully fabricate an all-fiber acousto-optic tunable filter(AO TF)based on acousto-optic interaction in optical fiber.The main research contents are as follows.(1)The research background and significance of all-fiber structured filter are analyzed.Then we start from the all-fiber tunable filter,and introduce several kinds of methods that can achieve tunable filters.And then we compare these methods with each other.(2)Some basic theories and analysis models of fiber gratings are introduced.Theoretical derivation of the fiber grating temperature and strain characteristic is shown to il ustrate how the temperature changes can affect central wavelength of fiber grating.(3)A side pumping doped chirped fiber grating method is proposed and demonstrated by Matlab simulation.Through the analysis of the experimental results,an all-fiber optically tunable filter is achieved.(4)A side pumping doped uniform fiber Bragg grating method is designed and tested,the experimental results are theoretically explained and demonstrated by Matlab simulation.(5)The principle of all-fiber acousto-optic tunable filter based on acousto-optic interaction in optical fiber is introduced.We successfully fabricated an AO TF in the experiment and also measured its wavelength and notch-depth tunability.