Combined Effect of Polarization-Mode Dispersion and Chromatic Dispersion on Strongly Filtered $pi/2$ -DPSK and Conventional DPSK

We show that strongly filtered /pi//2 differential phase-shift keying (DPSK) is better immuned against polarization-mode dispersion (PMD), whereas, DPSK has better tolerance toward chromatic dispersion. This provides the basis for tradeoff between PMD and group velocity dispersion tolerance through careful selection of a suitable modulation format from conventional DPSK and /pi//2-DPSK to suit different network topologies.