Theoretical Analysis And Experimental Study On Filtering And Frequency Stabilization Characteristics Of Multi-wavelength Fiber Lasers

As a kind of laser,fiber laser has the advantages of simple structure,stable output beam,good beam quality,no calibration,strong heat dissipation and low maintenance cost.Compared with traditional lasers,it has good performance of tunability,stability,and multi-wavelength output,and can meet the requirements of high speed and large capacity in optical communication systems.In addition,fiber lasers are also widely used in the industrial field,including welding,cutting,soldering,marking,cleaning,etc.,biomedicine,defense and safety.Stable multi-wavelength fiber lasers(MWFL)with tunable wavelength spacing and uniform spacing are important for dense wavelength division multiplexing(DWDM),optical sensing(OS),and photogenerated microwave signal(PMS).Therefore,this thesis conducts a series of theoretical analysis and experimental research on the filtering and frequency stabilization characteristics of multi-wavelength fiber lasers,including the following parts:(1)The research background and application scenarios of fiber lasers are introduced,and the development of frequency stabilization technology and filtering characteristics of multi-wavelength fiber lasers in recent years are listed.Then the research contents of this paper are summarized.(2)For MWFL with erbium-doped fiber(EDF)as gain medium,analyze its performance and defects,and introduce the filtering principle and frequency stabilization mechanism of MWFL.The filtering principle includes Sagnac loop and Brillouin effect,frequency stabilization method includes four-wave mixing effect(FWM)and polarization hole burning effect(NPR).(3)A multi-wavelength Brillouin erbium-doped fiber laser(MWBEFL)with adjustable 1×5 brillouin spacing is designed.By combining two double frequency shift cavitys and one single frequency cavity,the pump power of three erbium doped fiber amplifiers(EDFA)is adjusted to control the Brillouin effect in each sub-cavity,achieving a Brillouin frequency shift interval(BFS)with a wavelength interval of 1 to 5 times.The switched MWBEFL has wavelength intervals of 0.086 nm,0.172 nm,0.258 nm,0.344 nm,and 0.430 nm,respectively,and the corresponding Stokes light(BS)orders are 18,7,5,2,and 1,respectively.(4)The FWM effect is introduced in the MWBEFL system.The stability characteristics of the FWM effect are theoretically analyzed.The FWM effect is compared before and after the introduction of the FWM,and the conclusion that the FWM effect can enhance the output stability of the MWBEFL is obtained.(5)A MWFL based on NPR effect is designed.The filtering characteristics of the Sagnac loop and the frequency-stabilizing characteristics of the NPR effect are used to filter the laser output on the basis of the original Sagnac loop filter interval.With a highly tunable MWFL,the MWFL has a dual wavelength spacing adjustable from 0.67 nm to 27.4 nm,the center wavelength tuning range of single-longitudinal mode lasing output is 30 nm,and has excellent output stability.