An optical WDM transmission system including a plurality of first optical transceivers at a first end of an optical WDM transmission link, each including a tunable optical transmitter being adapted to create a first digital optical channel signal within the bandwidths of a set of first optical channels of the system according to tuning control information. The first channels are multiplexed in to a first WDM signal and supplied at the first end of the WDM link. Second optical transceivers at a second end link each include a transmitter adapted to create a second digital optical channel signal within a channel bandwidth of a second set of optical channels of the system. The second channels are multiplexed into a second WDM signal for transmission to the first transceivers, and demultiplexing there. A central tuning device creates the tuning control information for the first optical transceivers by tapping off an optical WDM detection signal from the first signal, extracting tuning status information from the optical WDM detection signal and determining tuning control information for at least one of the first transceivers. The central tuning device also supplies the tuning control information to the at least one first transceiver by modulating the second signal according to the tuning control information applying an amplitude modulation of the second signal using a dedicated WDM tone frequency.