Simultaneous Amplitude and Phase Measurement for Periodic Optical   Signals Using Time-Resolved Optical Filtering
  Time-resolved optical filtering (TROF) measures the spectrogram or sonogram by a fast photodiode followed a tunable narrowband optical filter. For periodic signal and to match the sonogram, numerical TROF algorithm is used to find the original complex electric field or equivalently both the amplitude and phase. For phase-modulated optical signals, the TROF algorithm is initiated using the craters and ridges of the sonogram. 
KeangPo Ho, Hsi-Cheng Wang, Hau-Kai Chen, Cheng-Chen Wu