Frequency noise reduction performance of a feed-forward heterodyne technique: application to an actively mode-locked...

We report on the frequency noise reduction performance of a feed-forward technique. The Letter is based on frequency noise measurements that allow the spectral response of the feed-forward phase noise correction to be determined. The main limitation to the noise compensation is attributed to the local oscillator flicker noise and the noise added by the optoelectronic loop elements. The technique is applied to an actively mode-locked laser diode demonstrating, at the output of the system, an optical frequency comb source with 14 comb lines reduced to sub-kilohertz intrinsic linewidth.