Tunable figure-of-eight fiber soliton laser incorporating an all-fiber frequency shifter

We constructed and characterized a figure-of-eight fiber soliton laser that incorporates an all-fiber frequency shifter/tunable filter based on a two- mode fiber. The laser produced 0.88-ps short soliton pulses that were tunab le over a wavelength range of 23 nm. The self-starting threshold was as low as 12 mW of 0.98-mu m pump power, which was very close to the self-sustain ing and lasing threshold. The laser exhibited better stability for solitons than the conventional configuration did, which was found to be due to supp ression of cw lasing by frequency-shifted feedback. In addition, we propose d and demonstrated a new and simple method of pulsewidth measurement based on a self-heterodyne autocorrelation that used the intracavity frequency sh ifter existing in this laser configuration.