Direct generation of subpicosecond chirp-free pulses at 10 GHz from a nonpolarization maintaining actively mode-locked fiber ring laser

0.7-1.3 ps highly stable, transform-limited, sech/sup 2/-shaped pulses at 10 GHz in the 1536-1569 nm wavelength region from a nonpolarization maintaining (PM), single intensity modulator, actively and harmonically mode-locked fiber ring laser have been directly generated. Little degradation of long-term stability of the laser operation was observed due to the non-PM nature of the laser cavity.