Measurement of Nonlinear Temporal Phase Shifts Using a Spectral Foucault Technique

Temporal phase shifts induced by cross-phase modulation in an optical fiber are directly characterized with a spectral equivalent of the Foucault technique used to spatially resolve wavefronts. The temporal phase induced by high power pulsed pump on a monochromatic probe via cross-phase modulation is converted in a temporal intensity modulation via spectral filtering. A measurement of the modulated instantaneous power of the filtered signal allows to directly determine the time-resolved nonlinear phase shift. An experimental demonstration is performed on a highly nonlinear fiber.