Tunable three-wavelength fiber laser and transient switching between three-wavelength soliton and Q-switched mode-locked states

We report a passive mode-locked fiber laser which can realize single wavelength tuning and multi-wavelength spacing tuning simultaneously. The tuning range is from 1528 to 1560nm, up to three bands of soliton states can be output at the same time. These results are confirmed by nonlinear Schrödinger equation model based on splitstep Fourier method. In addition, we reveal a way to transform the multi-wavelength soliton state into Q-switched mode-locked state, which is period doubling. These results will promote the development of optical communication, optical sensing, multi-signal pulse emission.