a wavelength division multiplexed optical communication method and apparatus uses a pre - emphasis technique to adjust the attenuation or amplification of a particular optical channel at a transmitter terminal to produce identical signal - to - noise ratios for all of the optical channels at a receiver terminal . the pre - emphasis adjustments to the transmitted signals are made on the basis of signal - to - noise ratio measurements performed at the receiver terminal . the signal - to - noise ratio values for each channel are transmitted through a facing line that is also used to transmit data along optical communication lines from the receiver terminal back to the transmitter terminal . the present invention also provides a method and apparatus for monitoring optical transmission paths for the deterioration of optical amplifier repeaters or an optical fiber . the optical signals are then adjusted to account for the location of the particular amplifier or fiber that has deteriorated .