The invention relates to an optical WDM transmission system including a plurality of first optical transceivers (11) at a first end (7) of an optical WDM transmission link (5, 5′), each of the first optical transceivers (11) including a tunable optical transmitter (17) being adapted to create a first digital optical channel signal (S1ch,i) within the bandwidths of a set of first optical channels of the optical WDM transmission system (1, 1′) according to a tuning control information, multiplexing means (13) for multiplexing the first digital optical channel signals (S1ch,i) into a first optical WDM signal (S1WDM), which is supplied to the first end (7) of the optical WDM transmission link (5, 5′), a plurality of second optical transceivers at a second end (9) of the optical WDM transmission link, each of the second optical transceivers including an optical transmitter being adapted to create a second digital optical channel signal (S2ch,i) within the bandwidth of a predetermined optical channel of a second set of optical channels of the optical WDM transmission system (1, 1′), multiplexing means for multiplexing the second digital optical channel signals into a second optical WDM signal (S2WDM), which is supplied to the second end (9) of the optical WDM transmission link (1, 1′), demultiplexing means (15) for demultiplexing the second optical WDM signal (S2WDM) into the second digital optical channel signals (S2ch,i) and providing each of the second digital optical channel signals (S2ch,i) to a dedicated first optical transceiver (11), and a central tuning device (3, 3′) adapted to create the tuning control information for one or more selected or all of the first optical transceivers (11) by tapping off an optical WDM detection signal (SWDM) from the first optical WDM signal (S1WDM), extracting tuning status information from the optical WDM detection signal (Sdet,WDM) and determining tuning control information for at least one of the first transceivers (11), the central tuning device (3, 3′) being further adapted to supply the tuning control information to the at least one first transceiver (11) by modulating the second optical WDM signal (S2WDM) according to the tuning control information applying an amplitude modulation of the second optical WDM signal (S2WDM) using a dedicated WDM tone frequency.