The present document relates to optical communication systems. In particular, the present document relates to high efficiency wavelength division multiplexing (WDM) optical communication systems. An optical transmitter (210) adapted to transmit an optical signal on an optical wavelength division multiplexed, referred to as WDM, transmission channel (111) to a corresponding optical receiver (230) is described. The optical transmitter (210) comprises a profiling unit (217) adapted to receive information regarding an equalization filter (270) adapted at the corresponding optical receiver (230), based on a first optical signal received from the optical transmitter (210); a pulse shaping filter unit (212) adapted to filter a sequence of data symbols (211) using a pulse shaping filter, thereby yielding a filtered sequence of data symbols (211); wherein a frequency response (404, 405) of the pulse shaping filter depends on the information regarding the equalization filter (270); and a digital-to-optical converter (214, 215 216) adapted to convert the filtered sequence of data symbols (211) into a second optical signal to be transmitted to the optical receiver (230).