Design And Experimental Investigations Of Dual-wavelength Single-longitudinal-mode Erbium-doped Fiber Standing-wave Lasers

In recent years,fiber lasers have played an important role either in the laser measurement or in the fiber communication,with the rapid development of fiber laser techniques.As a member of them,dual-wavelength single-longitudinal-mode fiber lasers have been used as the key part in many fields.The fiber lasers can provide light sources for two-channel optical fiber communication,whose wavelength matches with the transfer window of fiber communication.And the dual-wavelength single-longitudinal-mode fiber lasers can produce optical beat signals as the carriers of measurement signal for absolute distance measurement.Therefore it is of great significance to design and study the two-wavelength single-longitudinal-mode fiber laser.The main work of this thesis is to study and design the dual-wavelength single-longitudinal-mode erbium-doped fiber standing-wave lasers,and the main contents of this thesis include the following four parts:Firstly,the research situation of dual-wavelength single-longitudinal-mode fiber laser and the fundamental principles as well as the main features of fiber laser have been briefly introduced.Secondly,the methods of the common longitudinal-mode selections and dual-wavelength selections of fiber lasers have been introduced in this thesis.The longitudinal-mode selector and dual-wavelength selector which satisfy the requirements have been chosen for the fiber laser.The structure of dual-wavelength single-longitudinal-mode standing-wave fiber laser has been designed,and the feasibility of the fiber laser has been verified.Tuning method of wavelength difference with transversely applied force on the polarization-maintaining fiber Bragg grating(PMFBG)element has been theoretically analyzed,and a device for tuning of wavelength difference has been provided.Thirdly,some important characteristics of the dual-wavelength single-longitudinal-mode standing-wave fiber laser system based on PMFBG have been investigated experimentally,which include the longitudinal-mode selection and dual-wavelength single-longitudinal-mode oscillating.The feasibility of the tuning device has been demonstrated.The research results have shown that the standing-wave fiber laser can steadily output dual-wavelength single-longitudinal-mode laser at 1550 nm,the wavelength spacing between two wavelengths primarily depend on the interval of both reflective peaks of PMFBG.The single-longitudinal-mode laser oscillating at 1549.550 nm and 1549.908 nm have been shown by experiment.Finally,a dual-wavelength single-longitudinal-mode fiber laser system based on fiber polarizing beam splitter(FPBS)has been designed.The feasibility of this fiber laser has been analyzed,and the characteristics have been studied experimentally,including the output power,oscillating mode,polarization and so on.This fiber laser can output orthogonally and linearly polarized dual-wavelength single-longitudinal-mode laser,the wavelengths of which are 1550.027 nm and 1540.079 nm,respectively,with a wavelength space of 9.948 nm.The wavelength spacing between both wavelengths primarily depend on the interval of both reflective peaks between the two FBGs.In a word,the experiments validate the feasibility of the dual-wavelength single-longitudinal-mode standing-wave fiber lasers designed in this thesis,which has laid the solid foundation for the further studies of frequency tuning,laser frequency stabilization and interferometric measuring techniques.