Optical frequency comb generation with ultra-narrow spectral lines.

We demonstrate an optical comb source that generates 550 ultra-narrow spectral lines with a spectral linewidth of 1.5-3 kHz, spanning over the C-band. The source originates from a single-mode Brillouin laser processed with phase modulation, pulse compression, and four-wave mixing. As a result, the narrow linewidth of the Brillouin laser improves the phase noise of every spectral line of the frequency comb.