Fig. 1.

Frequency comb operation. a Setup for generating and measuring the comb state. The amplified spontaneous emission noise generated by the erbium-doped fiber amplifier (EDFA) is removed using a 200-GHz band-pass filter centered at the pump wavelength. The comb state is stabilized against long-term drifts by selecting a line of 460 GHz above the pump frequency using a second 200-GHz band-pass filter. b Comb spectrum measured at the through port with 0.1-nm resolution. The 20 comb lines in the shaded region between 1531 and 1566 nm are used for the communication experiments (the C band is typically specified between 1530 and 1565 nm). c Directly measured and d reconstructed intracavity time-domain waveforms using the drop port of the microresonator. The scale bars correspond to 1 ps. e The comb-line spacing measured with 1-kHz resolution