Fig. 1. Schematic of the Er fiber laser. ISO, Faraday isolator; PBS, polarization beam splitter; λ/4, quarter-wave plate; λ/2, half-wave plate.

Fig. 2. Radio frequency spectrum up to 3 GHz with the resolution bandwidth of 30 kHz.

Fig. 3. (a) Soliton pulse spectrum measured in linear scale (black) and simulation result (red). (b) Spectrum measured in log scale (black) and simulation result (red).

Fig. 4. (a) Fringe-resolved autocorrelation trace of the direct output pulses. (b) Inset is the calculated intensity autocorrelation trace of transform-limited pulse is about 73 fs (blue line) and simulated pulse profile with 82 fs (red dot). In both cases, the pulse profiles are assumed to be secant hyperbolic.

Fig. 5. Evolution of pulse duration inside the laser cavity. Gain fiber, CorActive Er-doped gain fiber (Er80-8/125); NPE, saturable absorber.