Fig. 1. Schematic of the experimental setup. WDM, wavelength division multiplexer; BP, bandpass filter.

Fig. 2. Single-wavelength operation under DS condition output: (a) mode-locking pulse train, (b) the corresponding pulse width, (c) tunability of output spectra. Single-wavelength operation under DSR condition output: (d) pulse train operating in DSR region at a pump power of 192 mW, (e) rectangular pulses of the mode-locked fiber laser under different pump power, (f) tunability of single-wavelength DSR operation.

Fig. 3. Oscillator output power versus launched pump power.

Fig. 4. Dual-wavelength DS output: (a) spectrum on logarithmic scale, (b) corresponding mode-locking pulse train with pump power of 62 mW.

Fig. 5. (a) Optical spectrum of dual-wavelength DSR operation with different pump power, and (b) corresponding step-like pulse.