Single-channel 170 Gbit/s transmission up to 4000 km using dispersion-managed fiber spans and all-Raman amplification

We demonstrate the first 4000 km, 170 Gbit/s DPSK transmission in a recirculating loop using dispersion-managed fiber spans and all-Raman amplification. Bit error rates of 2/spl middot/10/sup -9/ (1920 km) and 5/spl middot/10/sup -5/ W (4320 km) were obtained (less than 10/sup -12/ after FEC).