Pump Hysteresis And Wavelength Tuning In Passively Mode-locked Er³⁺-doped Fiber Laser

Fiber communication technology play an very important role in the process of informationization of socialty due to its high speed and huge capacity. The fiber laser based on nonlinear polarization rotation technique draw lots of attention because of its potential purpose in the fiber communication system such as DWDM, OTDM as an economical, steady fiber source. Pump power hysteresis affects the stabilization of the repetition rate of a fiber laser based on nonlinear polarization rotation technique, and the importance of characteristic of wavelength tuning is distinct when fiber laser apply to communication optical source. The article has analysized the mechanism of the pump power hysteresis and wavelength tuning theoretically and experimentally, and validate the analysis result of the pump power hysteresis in simulation. The main research results are listed below:Firstly, The mechanism of the pump power hysteresis effect is analyzed by the nonlinear transmission model. It is found that the pump hysteresis arises from the nonlinear loss property of the laser cavity and the hysteresis becomes larger as the number of the solitons increases. Both simulation and experimental results confirm the analytical conclusion, and clearly demonstrate that not only the soliton operation of the laser, but also the generation and annihilation of each individual soliton in the laser exhibit the pump power hysteresis.Secondly, the mechanism of wavelength tuning is analyzed theoretically and experimentally. Experimentally, while disconnecting isolator and increaseing the pump power to 325mw we find the central wavelength of spontaneous radiation spectrum of the fiber is 1532nm. And then, the isolator is connected and the pump power is stabilized to 325mw, the power of long wavelength increase and the laser come into dual-wavelength state after tuning polarization controller. Continuing tuning polarization controller, the laser come into soliton state and the central wavelength of soliton spectrum is 1558nm. Besides, it can be tuned between 1558nm and 1570nm simplly tuning polarization controller. At last, analyzing the mechanism of wavelength tuning with nonlinear transmission mode, the research result indicate that the mechanism of wavelength tuning arise from the combination of fiber birefraction, fiber non-linearity and cavity filter.