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.

Eighty 42.7-Gb/s, 100-GHz-spaced WDM channels were transmitted over 52 times 100 km of UltraWavetrade fiber. We employed dispersion-managed fiber spans, return-to-zero differential-phase-shift-keyed modulation, balanced detection, and all-Raman amplification to achieve this capacity times distance record of 16.6 petabit-km/s for 40-Gb/s transmission

Results for a new inverse dispersion fiber are presented yielding dispersion matched fiber sets that provide both higher equivalent effective area and similar attenuation as non-zero dispersion shifted fibers for submarine applications

80 × 10.664 Gbit/s wavelength division multiplexed transmission over 5200 km of fibre with 100 km amplified spans and 50 GHz channel spacing is demonstrated. Error-free operation of all 80 channels is achieved by using dispersion-managed fibre spans, distributed Raman amplification, and forward error correction.

80 /spl times/ 10.664 Gbit/s wavelength division multiplexed transmission over 5200 km of fibre with 100 km amplified spans and 50 GHz channel spacing is demonstrated. Error-free operation of all 80 channels is achieved by using dispersion-managed fibre spans, distributed Raman amplification, and forward error correction.

42 × 10 Gbit/s wavelength division multiplexed transmission over 4000 km of UltraWave fibre with 100 km dispersion-managed spans and 50 GHz channel spacing is demonstrated. A new dispersion map and all-Raman distributed amplification are employed to obtain error-free transmission of all 42 channels without the use of forward error correction.

Dispersion compensating fibres for dispersion-flattened hybrid transmission lines based on non-dispersion shifted fibres have been experimentally investigated. Average values obtained from the production of thousands of kilometres of fibres with different dispersions and thereby different compensation length ratios are given. Optimisation of hybrid lines for minimisation of span attenuation and fibre nonlinearity is described.