Theoretical and experimental study of pulse-amplitude-equalization in a rational harmonic mode-locked fiber ring laser

A simple technique, based on nonlinear polarization rotation, for the amplitude equalization of high repetition rate pulses generated from a rational harmonic mode-locked fiber ring laser was demonstrated. Amplitude equalized pulses at 10 GHz (the fourth rational harmonic) were obtained with a harmonic component suppression ratio up to 30 dB. A theoretical explanation was given in detail, which indicates that, after pulse amplitude equalization, the situation of unequal pulse spacing can be improved to a certain extend.