4/spl times/2.5 Gb/s transmission over standard singlemode fiber with amplifier spacing of 160 km

A 4/spl times/2.5 Gb/s WDM transmission system was demonstrated over 740 km of standard singlemode fiber with amplifier spacing of 160 km. The four line amplifiers used have saturated output power of 12 dBm and non-equalized gain profile. To the authors' knowledge, this is the largest repeater spacing demonstrated for a WDM system without ASE filtering. Bit error rates as low as 10/sup -16/ were measured for received power ranging between -30 and -27 dBm, depending on the channel. The power penalties are below 2 dB for a bit error rate of 10/sup -9/. This penalty is mainly due to accumulated noise from the amplifiers.