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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[disambiguation needed] 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.[1]
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)[1]
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
- ^ a b Petrov, Nikolay V.; Sergei S. Nalegaev; Andrei V. Belashov; Igor A. Shevkunov; Sergei E. Putilin; Yu-Chih Lin; Chau-Jern Cheng (2018). "Time-resolved inline digital holography for the study of noncollinear degenerate phase modulation" (PDF). Optics Letters. 43 (15): 3481. Bibcode:2018OptL...43.3481P. doi:10.1364/OL.43.003481. S2CID 51893588.
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