Multilevel Optical Systems With MLSD Receivers Insensitive to GVD and PMD

• Published in: Journal of lightwave technology Vol. 26; no. 10; pp. 1263 - 1273
• Main Authors: Colavolpe, G., Foggi, T., Forestieri, E., Prati, G.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 15.05.2008; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Applied sciences; Channels; Coding, codes; Differential encoding; Dispersions; electrical equalization; Exact sciences and technology; group velocity dispersion (GVD); Information, signal and communications theory; intersymbol interference (ISI); maximum-likelihood sequence detection (MLSD); Microprocessors; Modulation; Modulation, demodulation; Optical distortion; Optical fiber communications; Optical modulation; Optical noise; Optical receivers; Optical telecommunications; optical transmission systems; Optical transmitters; Phase modulation; phase-shift keying (PSK); Polarization mode dispersion; polarization mode dispersion (PMD); Quadrature amplitude modulation; quadrature amplitude modulation (QAM); Receivers; Reduction; Signal analysis; Signal and communications theory; Statistics; Studies; Systems, networks and services of telecommunications; Telecommunications; Telecommunications and information theory; Transmission and modulation (techniques and equipments); Viterbi algorithm; Viterbi algorithm (VA); Phase noise; Performance evaluation; Polarization diversity; Quadrature amplitude modulation; Processor; intersymbol interference (ISI); maximum-likelihood sequence detection (MLSD); Viterbi algorithm (VA); Transmitter; Polarization mode dispersion; Implementation; Degradation; optical transmission systems; Laser noise; Optical transmission; phase-shift keying (PSK); Coding; group velocity dispersion (GVD); Optical fiber communication; Multilevel system; Damaging; polarization mode dispersion (PMD); quadrature amplitude modulation (QAM); Receiver; Equalization; Velocity dispersion; Differential encoding; Phase shift keying; Group velocity; Intersymbol interference; Integrated circuit; electrical equalization; Maximum likelihood
• ISSN: 0733-8724; 1558-2213
• DOI: 10.1109/JLT.2008.917052

This paper analyzes optical transmission systems based on high-order modulations such as phase-shift keying signals and quadrature amplitude modulations. When the channel is affected by group velocity dispersion (GVD), polarization mode dispersion (PMD), and phase uncertainties due to the laser phase noise, the optimal receiver processing based on maximum-likelihood sequence detection and its practical implementation through a Viterbi processor is described without a specific constraint on the receiver front end. The implementation issues are then faced, showing that at least a couple of widely known front ends, with proper modifications, can be used to extract the required sufficient statistics from the received signal. The aspects related to the receiver adaptivity, the complexity reduction of the Viterbi processor, and the possibility of employing polarization diversity at the transmitter end are also discussed. It is demonstrated that, as long as a sufficient number of Viterbi processor trellis states is employed, GVD and PMD entail no performance degradation with respect to the case of no channel distortions (the back-to-back case).