Impact of filtering on RZ-DPSK reception

We discuss the influence of optical and electrical filtering on the performance of beat-noise limited balanced and single-ended direct detection of return-to-zero differential phase-shift keying (DPSK). Our simulations, supported by 40-Gb/s measurements, show that balanced DPSK detection outperforms both its singleended equivalent and ON-OFF keying by ~2.7 dB, with higher gains at narrower optical filter bandwidths.