In an optical transmission system, data is transmitted via an optical beam modulated with an arbitrary waveform. The optical beam is transmitted through at least one optical element. Transmission through at least one optical element degrades the signal quality of the initial optical beam. The signal characteristics of at least one optical beam at the output of least one optical element are used as feedback to shape the arbitrary waveform to improve signal characteristics. An arbitrary waveform may be used to compensate signal degradation caused by a multiplexer/demultiplexer in a wavelength division multiplex system.