Higher Order Harmonics of Modulational Instability Induced by Vacuum Fluctuations

We study the higher order harmonics of scalar modulational instability in the regime where it arises spontaneously through amplification of vacuum fluctuations. We obtain detailed predictions concerning the detunings, intensities, growth rates and spectral widths of the harmonics. These predictions are well verified by experimental results obtained by propagating high intensity light pulses through optical fibers.