A method of equalizing the channels of a WDM link comprises identifying an error threshold level BER.sub.Fail for the BER defined for each signal S(j) in accordance with the channel rate, and determining the attenuation A(j) of, for example, the power P(j) of each signal S(j) transmitted over the WDM link. The transmitter powers are adjusted taking into account the attenuations determined for all channels. The attenuation A(j) for channel (j) is determined by first setting the power P(j) of all signals S(j) to a maximum P.sub.Max, attenuating the power P(j) of channel (j) until the BER reaches the threshold value BER.sub.Fail, measuring the power corresponding to the BER.sub.Fail for that channel, and calculating the difference between the P.sub.Max and P(j).sub.Fail. The transmitter powers are then set according to the relationship P(j)=P.sub.Max -.eta.(A(j)-A.sub.Min), where .eta. is 0.8 for a system with 3-4 channels. The method may be used for multi-channel systems with intermediate nodes where channels are added and dropped.