Time-domain analysis of optical comb offset frequency variations: phase-only line-by-line shaping approach

Abstract

We investigate the effect of shifting an optical frequency comb on the resultant time-domain waveform generated via phase-only line-by-line pulse shaping. By considering a particular spectral line-by-line filter, comb shifts, i.e., offset frequency variations, are evaluated in a simple way from the changes in the temporal intensity waveform. Theoretical predictions are confirmed by experimental results. As a practical application, we estimate the magnitude of comb offset frequency fluctuations of a harmonically mode-locked fiber laser from noise in the waveforms measured with a sampling scope.