Impact of Phase Noise and Compensation Techniques in Coherent Optical Systems

One of the most severe impairments that affect coherent optical systems employing high-order modulation formats is phase noise due to transmit and receive lasers. This is especially detrimental in uncompensated links, where an ideal compensator for channel distortions and laser phase noise should fi...

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Bibliographic Details
Published in:Journal of lightwave technology 2011-09, Vol.29 (18), p.2790-2800
Main Authors: Colavolpe, G., Foggi, T., Forestieri, E., Secondini, M.
Format: Article
Language:English
Subjects:
Applied sciences
Coherent detection
Detection, estimation, filtering, equalization, prediction
Dispersion
Equalizers
Exact sciences and technology
group velocity dispersion (GVD)
Information, signal and communications theory
Laser noise
Modulation, demodulation
Multiplexing
OFDM
optical communication
Optical noise
Optical receivers
Optical telecommunications
orthogonal frequency division multiplexing (OFDM)
Phase noise
Signal and communications theory
Signal, noise
Telecommunications
Telecommunications and information theory
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Summary:One of the most severe impairments that affect coherent optical systems employing high-order modulation formats is phase noise due to transmit and receive lasers. This is especially detrimental in uncompensated links, where an ideal compensator for channel distortions and laser phase noise should first eliminate receive phase noise, then equalize channel distortions, and only later compensate for transmit phase noise. Unfortunately, the simultaneous presence of transmit and receive phase noise makes very difficult to discriminate between them, even in the presence of a pilot tone. Moreover, the picture is different for optical systems using single-carrier or orthogonal frequency division multiplexing, where transmit and receive phase noise components may have a different impact. All these aspects are analyzed and discussed in this paper. A novel digital coherence enhancement (DCE) technique, able to significantly reduce the phase noise of transmit or receive lasers by using an interferometric device plus a very simple electronic processing, is also described. The performance of this technique and the statistical properties of the residual phase noise are analytically derived and verified by simulations, showing a high increase of the maximum bit-rate-distance product. The practical implementation of DCE is finally discussed and some alternative implementation schemes are presented.
ISSN:0733-8724
1558-2213
DOI:10.1109/JLT.2011.2164237