Cross-phase modulation

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.

Applications of XPM

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 non-linear medium. This technique is applied to fiber optic communications.

XPM in DWDM applications

In 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 XPM-effect.

Advantages of XPM

• Nonlinear Pulse Compression
• Passive mode locking
• Ultra fast optical switching
• Demultiplexing of OTDM channels
• Wavelength conversion of WDM channels

Disadvantages of XPM

• XPM leads to interchannel crosstalk in WDM systems
• It can produce amplitude and timing jitter

See also

• Self-phase modulation — SPM
• Four wave mixing — FWM
• Stimulated Raman scattering — SRS

External links

• Cross-phase modulation (RP Photonics, Encyclopedia of Laser Physics and Technology)