40-Gb/s return-to-zero alternate-mark-inversion (RZ-AMI) transmission over 2000 km

We report on the transmission of 40-Gbit/s modified duobinary return-to-zero (RZ-MDB) signals over more than 2000 km (20x100 km) at a bit-error ratio of 10 sup -9. The RZ-MDB signal is generated using a single, non-return-to-zero-driven modulator in combination with an optical delay interferometer.