Frequency comb generation by four-wave mixing and the role of fiber dispersion

A fiber-optic frequency comb generator utilizes four-wave mixing (FWM) to expand a modulated continuous wave (CW) lightwave into a comb of discrete, equispaced frequencies. The sign and magnitude of the fiber dispersion are shown to control comb expansion by affecting the interference among different four-wave mixing interactions at particular comb frequencies. Positive dispersion initiates comb expansion while zero and negative dispersions suppress expansion. Dispersion mapping engineers fiber links for maximum comb bandwidths. By managing dispersion in a 35 km link of dispersion-shifted fiber, a frequency comb spanning 1.1 THz is experimentally demonstrated. Promising applications include pulse train synthesis affording low-chirp, arbitrarily profiled, short pulses.