The successful two-channel WDM transmission of optically multiplexed 4
0 Gbit/s RZ signals with properly managed fibre dispersion is demonstr
ated. The dispersion dependence of the signal-to-noise-ratio for each
signal channel is measured and it is found that the optimum total disp
ersion value, including dispersion compensation fibres, is not zero bu
t is anomalous, which is slightly smaller than the value predicted by
the soliton condition with uniform dispersion.