“…The mechanisms for pulse-contrast degradation have been widely studied. Except the background noises such as amplified spontaneous emission (ASE) [1] or optical parametric fluorescence (OPF) [9,10], which are always present in optical amplifiers, almost all of other proven contrast degradation mechanisms are directly or indirectly associated with modulations of the spectral amplitude or spectral phase. Spectral clipping from the acceptance of stretcher [2], pump-noise transfer [11][12][13] and the presence of weak post-pulses [14,15] are typical sources of spectral amplitude modulations.…”