Cross-phase modulation (XPM) is a nonlinear optical effect where one wavelength of light can affect the phase of another wavelength of light through the optical Kerr effect.
Cross-phase modulation can be used as a technique for adding information to a light stream by modifying the phase of a coherent optical beam with another beam through interactions in an appropriate nonlinear medium.
Other advantageous applications of XPM include: In dense wavelength-division multiplexing (DWDM) applications with intensity modulation and direct detection (IM-DD), the effect of XPM is a two step process: First the signal is phase modulated by the copropagating second signal.
In a second step dispersion leads to a transformation of the phase modulation into a power variation.
Additionally, the dispersion results in a walk-off between the channels and thereby reduces the effect of XPM.