Fig. 4
Experimental RF spectrum obtained with our 2 μm dual-comb spectrometer. a RF spectrum recorded with a 5 m long HNLF with Ppump = 5.5 W and Pidler = 25 mW in each arms. When zoomed in, this spectrum reveals b the Δfrep = 57 kHz line spacing and c the 3.3 Hz half-width at half-maximum of one line of the RF comb
