A method and apparatus for controlling the signal/noise ratio of optical add/drop
signals in an optical WDM transmission system having a transmitter unit, a receiver
unit and at least one optical add/drop multiplexer for transmitting optical express
signals and at least one optical add/drop signal wherein the power spectrum of
the pre-emphasized express signals is determined, and the signal level of the at
least one optical add/drop signal is adapted to the power spectrum determined for
the express signals.
