Mode-Hop-Free, Optical Frequency Tunable 40-GHz Mode-Locked Fiber Laser

We have successfully achieved a mode-hop-free, optical frequency tunable 3-ps 40-GHz mode-locked fiber laser by installing an optical etalon in a 6.8-m laser cavity. The laser frequency was continuously tuned over 1 GHz without mode hopping by tuning the etalon peak frequency. The oscillation wavelength was also tuned over 1535-1560 nm by tuning an optical bandpass filter installed in the laser cavity.