240-km repeater spacing in a 5280-km WDM system experiment using 8 x 2.5 Gb/s NRZ transmission

A repeater spacing of 240 km was experimentally demonstrated over a distance of 5280 km in an 8/spl times/2.5 Gb/s wavelength-division-multiplexing (WDM) transmission experiment. This long-span length was achieved by a combination of Raman amplification, a locally pumped erbium-doped fiber (EDF), and two remotely pumped EDFs. The total gain obtained from those four gain elements was about 50 dB. The performance demonstrated in this experiment was comparable to that of a system of similar length and capacity using conventional erbium-doped fiber amplifier (EDFA) technology at a repeater spacing of 80 km.