A four-channel FDM system using Mach-Zehnder filters is equalized by the transversal filters to realize cosine roll-off band-limiting characteristics for no inter-symbol interference. The channel compensation is split equally between the transmitter and receiver filters. The equalization filters consist of adaptively designed finite impulse response filters.
The tap coefficients are determined in order to satisfy the design objective transfer function. The eye is fully open even when a neighboring channel spacing becomes narrow. The inter-symbol interference results in almost zero and the inter-channel interference powers decrease. Thus, the signal to inter-channel interference ratio increases more than 24 dB in the case of roll-off factor of 0.2.