BER for optical heterodyne DPSK receivers using delay demodulation and integration detection

Abstract

Previous work on the bit error rate (BER) performance of differential phase-shift keying (DPSK) including the effects of additive white Gaussian noise (AWGN) and phase noise has concentrated on the delay demodulator with narrow-band intermediate frequency (IF) bandpass filtering (BPF) and sampling detection. No similar analysis has yet been performed for the delay demodulator with wideband IF bandpass filtering and integration detection. Phase noise is an important consideration in coherent optical communication systems and the most widely accepted model is a Brownian motion process. A closed-form BER expression along with detailed Monte Carlo simulation results are presented for the DPSK delay demodulator with wideband IF bandpass filtering and integration detection filtering including phase noise effects using the Brownian motion model. Analytic expressions are also obtained for the moments of the phase noise component of the decision variable. Using these moments, estimates of the phase noise BER floor are produced. It is found that this receiver has noise performance comparable to receivers with narrowband IF bandpass filtering and sampling detectors for signal-to-noise ratio (SNR) and phase noise in the range of practical interest, but with potentially less degradation due to intersymbol interference (ISI).