Impact of very large cumulated dispersion on performance of 40 Gbit/s submarine systems over nonzero dispersion shifted fibres

Submarine systems based on nonzero dispersion shifted fibres are numerically investigated at 40 Gbit/s channel bit rate over 10500 km in the whole C-band. High dispersion excursions up to 12000 ps/nm, appearing in such systems, do not impair the performance of differential phase-shift keyed modulation formats at 40 Gbit/s. Alternate-polarisation return-to-zero differential phase-shift keying maintains its ∼3 dB advantage over return-to-zero differential phase-shift keying.