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. 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.
{{cite journal
|last = Petrov
|first = Nikolay V.
|author2 = Sergei S. Nalegaev
|author3 = Andrei V. Belashov
|author4 = Igor A. Shevkunov
|author5 = Sergei E. Putilin
|author6 = Yu-Chih Lin
|author7 = Chau-Jern Cheng
|date= 2018
|title=Time-resolved inline digital holography for the study of noncollinear degenerate phase modulation
|journal=Optics Letters
|volume=43
|issue=15
|pages=3481
|doi=10.1364/OL.43.003481
|pmid = 30067690
|url= https://www.researchgate.net/publication/326424496
|bibcode = 2018OptL...43.3481P
|s2cid = 51893588
}}
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
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External links
- [https://www.rp-photonics.com/cross_phase_modulation.html Cross-phase modulation (RP Photonics, Encyclopedia of Laser Physics and Technology)]
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