Abstract: An optical receiver suitable for use in a wavelength division multiplexing (WDM) system is able to tolerate shifts in the transmitting lasers' wavelength. During a periodically repeated wavelength synchronization phase, only a single transmitter laser is operating, and a peak finder locks onto the wavelength having greatest power and notes the corresponding detector pixel's position. Thus, the receiver knows the relative wavelength of the transmitting laser in terms of the detector pixel illuminated with the brightest light, and can store this information for later reference. The active transmitter lasers take turns synchronizing their wavelengths during successive synchronization phases. During the multi-wavelength data transmission phase, many lasers in the system transmit information at the same time, at different wavelengths.