A method to digitize the intensity of ultrashort laser pulses for high-speed optical signal processing is described. This digitization was based on the spectral broadening of a weak probe (carrier) pulse by a more intense pump (signal) pulse through the nonlinear optical process of cross-phase modulation (XPM). The signal pulse intensity was varied to generate different spectral widths that can be encoded into digital form. Using a 50-ps time-divided multiplexing pulse train with a waveguide splitter, combiner, and an array of fibers with variable lengths, a unary XPM encoding approach is demonstrated. The spectral encoding scheme can be used to achieve a 5-GHz sampling rate at a 16-level accuracy.
© 1997 Optical Society of America
P. P. Ho, Q. Z. Wang, J. Chen, Q. D. Liu, and R. R. Alfano, "Ultrafast optical pulse digitization with unary spectrally encoded cross-phase modulation," Appl. Opt. 36, 3425-3429 (1997)