1050-km WDM transmission of 8/spl times/10.709Gb/s DPSK signal using cascaded in-line semiconductor optical amplifier

We have performed eight-channel wavelength-division-multiplexing transmission over 1050-km single-mode fiber using cascaded in-line semiconductor optical amplifier and differential phase-shift keying modulation format for the first time; more than 6 dB of power margin was achieved over forward-error correction threshold. Factors that affect the transmission performance were discussed. It was found that four-wave mixing is the main factor that limits the maximum transmission distance. Larger capacity distance product can be realized by further optimizing the configuration of transmission link.