Optical Equalization: System Modeling and Performance Evaluation

Optical equalization in fiber-optic systems is theoretically investigated. First, a wide variety of optical equalizers is presented by giving their equivalent models, by describing the basic principles of operation, and by showing analogies and differences among different structures and configurations. Then, evaluation of the bit error rate and outage probability, in the presence of optical noise, chromatic dispersion (CD), and polarization mode dispersion (PMD), is discussed by comparing different methods based either on the PMD vector and its related statistics or on Markov chain Monte Carlo (MCMC) simulations applied to a random waveplate model. As the first relevant result, the accuracy and complexity of different PMD models in compensated systems are tested and compared, and a novel reduced Bruyegravere-Kogelnik (BK) model, which is more accurate and simple than the complete BK model or other second-order models, is proposed. As an additional result, the ultimate theoretical performance for different configurations and numbers of stages of the equalizers is given, and it is shown that when a single equalizer is used for a pair of polarization-multiplexed channels, the system tolerance to PMD is highly increased