Benefits and limits of modulation formats for optical communications

Abstract

This paper is focused on benefits and limits of intensity and phase modulation formats used in optical communications. The simulation results are obtained using OptSim software environment, employing Time Domain Split Step method. Non-Return to Zero, Return to Zero, Chirped Return to Zero and Carrier-Suppressed Return to Zero formats are compared in terms of Bit Error Rate and spectral efficiency to find the limits for selected transmission network topologies. It is shown that phase modulation formats offer many advantages compared to intensity formats. Differential Phase-Shift Keying and mainly Differential Quadrature Phase-Shift Keying improve the Bit Error Rate and transmission reach, among others. A promising solution is the application of Polarization Division Multiplexing Quadrature Phase-Shift Keying, which primarily benefits in spectral efficiency, estimated reach, optical signal to noise ratio and chromatic dispersion tolerances.