Polarization shift keying: an efficient coherent optical modulation

Multilevel digital coherent optical modulation schemes based on the state of polarization of a fully polarized lightwave are proposed and analyzed. Based on the complete statistical characterization of the Stokes parameters, extracted through appropriate signal processing in the presence of shot and additive Gaussian noise, the optimum maximum likelihood receiver operating symbol by symbol is derived. A spectral analysis of the IF (intermediate frequency) signals is also presented. Exact performance in terms of average error probability is found for the proposed multilevel schemes, which turn out to be promising as compared to other standard modulation techniques