  We use dispersive Fourier transformation to measure shot-to-shot spectral
instabilities in femtosecond supercontinuum generation. We study both the onset
phase of supercontinuum generation with distinct dispersive wave generation, as
well as a highly-unstable supercontinuum regime spanning an octave in
bandwidth. Wavelength correlation maps allow interactions between separated
spectral components to be identified, even when such interactions are not
apparent in shot-to-shot or average measurements. Experimental results are
interpreted using numerical simulations. Our results show the clear advantages
of dispersive Fourier transformation for studying spectral noise during
supercontinuum generation.
