Comparison of system tolerance to polarization-mode dispersion between different modulation formats

The polarization-mode dispersion (PMD) tolerance of different modulation formats is studied, including ON-OFF keyed (OOK), differential phase-shift keyed (DPSK), and carrier-suppressed return-to-zero (CSRZ) formats. It is shown that, generally, for PMD uncompensated systems, the modulation formats with larger pulsewidth have larger penalty, while the modulation formats with smaller bandwidth perform better in PMD compensated systems. It is also shown that DPSK can tolerate more PMD than OOK for both PMD uncompensated and compensated systems, and that CSRZ, because of its specific spectrum characteristics, has a different feature from return-to-zero formats.