Cross-phase modulation in optical fibers.

When pulse pairs copropagate in a fiber, each pulse chirps the other through cross-phase modulation (XPM). In particular, XPM causes spectral broadening of signal pulses during Raman or parametric optical pulse amplification. We have studied XPM experimentally in the fiber Raman amplification soliton laser. We show that experimentally observed spectra can be explained by a simple model that concentrates on the phase change as a function of pulse walk-off.