Comment on "Time reversal of ultrafast waveforms by wave mixing of spectrally decomposed waves".

In a recent Letter [Opt. Lett. 25, 132 (2000)] the properties of two different techniques for time reversal of ultrafast optical waveforms were compared. Although both techniques, spectral phase conjugation and spectral inversion, perform the same function for real pulses, for pulses with complex envelope functions it was asserted that only spectral inversion gives true time reversal. I argue here for a different interpretation.