Considering a numerical example, we analyse the performance of Return-to-Zero (RZ) Differential Phase Shift Keyed (DPSK) transmission when deployed in a large scale transmission system. It is shown that at high distances, RZ-DPSK performs well whilst being limited by nonlinear effects. We also show that when nonlinear effects become dominant, we can still estimate channel statistics to reasonable accuracy.
We present a simplified model for a simple estimation of the eye-closure penalty for amplitude noise-degraded signals.
Using a typical 40-Gbit/s return-to-zero amplitude-shift-keying transmission, we demonstrate agreement between the
model predictions and the results obtained from the conventional numerical estimation method over several thousand
Applying direct error counting, we assess the performance of 20 Gbit/s wavelength-division multiplexing return-to-zero differential phase-shift keying (RZ-DPSK) transmission at 0.4 bit/(s Hz) spectral efficiency for application on installed non-zero dispersion-shifted fibre based transoceanic submarine systems. The impact of the pulse duty cycle on the system performance is investigated and the reliability of the existing theoretical approaches to the BER estimation for the RZ-DPSK format is discussed.