Differential Phase-Shift Keying Receiver Design Applied to Strong Optical Filtering

The authors study, via simulation and experiments, the influence of the differential phase-shift keying decoder Free Spectral Range (FSR) when strong optical filtering is considered for the non-return-to-zero and return-to-zero modulation formats and show that larger FSR can improve performance. The Differential Phase-Shift Keying (DPSK) modulation format has attracted considerable attention in recent years due to its superior Optical Signal-to-Noise Ratio (OSNR) sensitivity and fiber non-linearity tolerance compared to on-off keying formats. It has particularly attracted attention for higher data rate applications: notably 40 Gb/s and beyond. The practical direct detection DPSK receiver architectures considered in this paper require two key components, namely a balanced photodetector and a Delay Interferometer (DI).