Impact of Chromatic and Polarization-Mode Dispersions on DPSK Systems Using Interferometric Demodulation and Direct Detection
Journal of Lightwave Technology
We study the impact of chromatic dispersion (CD) and polarization-mode dispersion (PMD) on systems using binary or quaternary differential phase-shift keying (2-DPSK or 4-DPSK) with non-returnto-zero (NRZ) or return-to-zero (RZ) formats. These signals are received using optical preamplification, interferometric demodulation and direct detection. We consider the linear propagation regime, and compute optical power penalties at fixed bit-error rate (BER). In order to evaluate the BER precisely
... he BER precisely taking account of amplifier noise, arbitrary pulse shapes, arbitrary optical and electrical filtering, CD and PMD, we introduce a novel model for DPSK systems and compute the BER using a method recently proposed by Forestieri for on-off keying (OOK) systems. We show that when properly applied, the method yields highly accurate results for DPSK systems. We have found that NRZ-2-DPSK exhibits power penalties similar to NRZ-OOK in the presence of CD and PMD. NRZ-4-DPSK, as it has twice the symbol duration of these other techniques for a given bit rate, incurs CD and PMD power penalties only about one quarter as large as NRZ-2-DPSK. RZ-2-DPSK, as compared to NRZ-2-DPSK, incurs smaller penalties due to PMD, but offers no advantage in terms of CD. RZ-4-DPSK offers CD and PMD penalties significantly smaller than all other techniques.