Fig. 5.

Experimental interferogram and spectrum. a Time-domain interferogram over a measurement time of 2 µs. The waveform repeats with a period of 25.6 ns, which is the inverse of the difference in comb line spacing (39 MHz). The waveform of one period is shaded and demonstrates good reproducibility. The multiple bursts within one period indicate that multiple solitons are generated in each microresonator within one cavity roundtrip. b Fourier-transformed spectrum of the time-domain interferogram in a, on a logarithmic scale with 24 resolved lines and an average signal-to-noise ratio of 13.8 dB (≈24). Modulation in the spectrum is also due to both comb operating in multiple soliton regime. The missing RF beat note at 0.64 GHz is due to the absence of a comb line, which is attributed to a mode crossing effect within the microresonator