Analysis of DQPSK signals performance in upgrading metropolitan area networks to 40 Gbit/s per channel

The always increasing traffic demand requires the upgrade of current 10 Gbit/s per channel metropolitan area networks (MANs) to higher bit rate per channel. Differential quadrature phase shift keying (DQPSK) appears as one of the most promising modulation formats for this upgrade. In this paper, 40 Gbit/s per channel DQPSK signals performance is assessed through numerical simulation in presence of the main limitations of deployed 10 Gbit/s MANs. It is shown that DQPSK signals have high tolerance to the limited available bandwidth and better robustness to nonlinear impairments than optical single sideband (OSSB) signals, another very promising modulation format for the MANs upgrade. However, OSSB signals show higher tolerance to residual dispersion (when electrical dispersion compensation is used) and better performance when transmitted together with 10 Gbit/s intensity modulated signals.