Fig. 1. Schematic of laser structure. (a) Dumbbell-shaped all-polarization-maintaining mode-locked fiber laser; (b) NRPS

Fig. 2. Output characteristics of the laser under the pump power of 1.8 W. (a) Optical spectrum; (b) single pulse waveform; (c) radio frequency spectra in the span of 9 MHz and 0.8 GHz (inset); (d) pulse train waveform

Fig. 3. Variations of the pulse waveforms, average power, pulse width, and peak power with pump power. (a) Variations of output pulse waveforms; (b) variation curves of the output average power, pulse width, and peak power