Research On Tunable And Switchable Erbium-doped Fiber Laser Based On Fiber Filter

Since the beginning of the 21 st century,optical fiber communication has developed rapidly,and the requirements for light sources have become higher and higher.Fiber lasers with fixed wavelengths can no longer meet the requirements of light sources for flexibility.The tunable and switchable fiber lasers can switch different wavelengths,and can realize the tunability of the wavelengths,which can greatly meet the requirements of wavelength division multiplexing(WDM)for light sources.Based on the existing tunable and switchable fiber lasers,three novel tunable and switchable erbium-doped fiber lasers(EDFLs)are designed and studied by using the characteristics of different fiber filters.The main research contents and achievements are as follows:1.A tunable and switchable EDFL based on fiber Bragg gratings(FBGs)embedded in Sagnac rings is proposed and studied.Three FBGs are embedded in the left and right Sagnac rings to select the wavelength of the fiber laser.The pump power is fixed at 250 m W,and by adjusting the polarization controllers(PC)in the fiber laser cavity,the switchable from single-wavelength to triple-wavelengths can be realized.7different laser states are emitted,including 3 single-wavelength laser states,3 dualwavelength laser states and 1 triple-wavelength laser state,both dual-wavelength and triple-wavelength laser states are combinations of the above 3 single-wavelength states.The optical signal-to-noise ratios(OSNRs)are higher than 52 d B.The output power conversion efficiency of the fiber laser is 7%.In addition,by changing the temperature applied to the FBG,the center wavelength can be tunable,and the tunable range is 1.20 nm.2.A tunable and switchable EDFL based on an in-line Mach-Zehnder interferometer(MZI)is proposed and studied.The fiber filter used is an in-line MZI based on a spherical structure and polarization-maintaining fiber(PMF)fusion to achieve wavelength selection.The pump power is fixed at 250 m W,and by adjusting the PC in the fiber laser cavity,the switchable from single-wavelength to triplewavelengths can be realized.A total of 26 laser states are emitted,including 10 singlewavelength laser states,12 dual-wavelength laser states and 4 triple-wavelength laser states.Both the dual-wavelength and triple-wavelength laser states are combinations of10 single-wavelength states.The OSNRs are higher than 52 d B.In addition,by changing the stress applied to the in-line MZI,the central wavelength can be tunable,and the tunable range is about 1.34 nm.3.A tunable and switchable EDFL based on a composite filter with FBGs embedded in Sagnac rings and an in-line MZI parallel structure is proposed and studied.The filter used is a composite filter with a parallel structure.One branch is two FBGs embedded in Sagnac ring filter,the other branch is an in-line MZI filter.The pump power is fixed at 250 m W,and by adjusting the PC in the fiber laser cavity,the switchable from single-wavelength to quadruple-wavelengths can be realized.A total of 36 laser states are emitted.7 different single-wavelength laser states are obtained from the fiber laser,16 different dual-wavelength laser states are excited,11 different triple-wavelength laser states are excited,2 different quadruple-wavelength laser states are excited.All the dual-wavelength,triple-wavelength and quadruple-wavelength laser states are combinations of 7 single-wavelength states.The OSNRs are higher than 42 d B.In addition,by changing the temperature applied to the FBG,the center wavelength can be tunable,and the tunable range is 1.10 nm.