High spectral density long-haul 40-Gb/s transmission using CSRZ-DPSK format

This paper presents an experimental investigation of 40-Gb/s DWDM transmission technologies that can potentially transport multiple terabits of aggregate capacity with ultrahigh spectral efficiency over several thousand kilometers of fiber in a terrestrial optical network. By using carrier-suppressed return-to-zero (CSRZ) differential-phase-shift-keyed (DPSK) modulation format with optimized signal filtering, we have demonstrated transmission of 6.4-Tb/s capacity with 0.8-bit/s/Hz spectral efficiency over 3200 km of fiber using 100-km amplified spans. This transmission was conducted using 160 50-GHz-spaced wavelength channels, each at 42.7 Gb/s, in the standard C + L wavelength bands. Low dispersion-slope TrueWave REACH fiber plus slope-matched dispersion compensating fiber with all-Raman amplification were also employed to achieve this record 20-Pbit/s/km capacity-distance product for terrestrial 40-Gb/s systems. In addition, we used a loop-synchronous polarization controller (PC) to better emulate the polarization effects of a straight-line system.