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. When the optical power from a wavelength impacts the refractive index, the impact of the new refractive index on another wavelength is known as XPM.

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 nonlinear medium. This technique is applied to fiber-optic communications. If both beams have the same wavelength, then this type of cross-phase modulation is degenerate.

XPM is among the most commonly used techniques for quantum nondemolition measurements.

Other advantageous applications of XPM include:

• Nonlinear optical Pulse Compression of ultrashort pulses

• Passive mode-locking

• Ultrafast optical switching

• Demultiplexing of OTDM channels

• Wavelength conversion of WDM channels

• Measurement of nonlinear optical properties of the media (non-linear index n2 (Kerr nonlinearity) and nonlinear response relaxation time)

Disadvantages of XPM

XPM in DWDM applications

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.

• 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

• Cross-polarized wave generation XPW

References

External links

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