Provided is a network node for a coherent
optical wavelength division
multiplex (WDM)
transmission network including at least one remote port which is adapted to receive from and / or output to neighboring network nodes an optical WDM
signal including one or more optical channel signals each
lying within an optical channel of an optical
WDM transmission band and a predetermined number N of local ports, each local port being adapted to receive from a dedicated coherent
optical transmitter an optical add channel
signal which is to be integrated in an optical WDM
signal that is output at a remote port and / or each local port being adapted to output to a respective dedicated optical
receiver an optical drop channel signal. The network node includes an
optical router device that defines the at least one remote port and further defines an internal remote port, the
optical router device being configured to
route one or more selected or
all optical channel signals included in the optical WDM signal received at a selected remote port as optical drop channel signals to the internal remote port and / or to
route one or more optical add channel signals received at the internal remote port to one or more selected remote ports or to all remote ports. The network node further includes a passive
optical filter device which is connected, at an internal remote port of the passive
optical filter device, to the internal remote port of the
optical router device, and which further defines the predetermined number N of local ports. The passive
optical filter device is configured to define N optical bandpass filter functions each of which describes a bandpass filter characteristic between the internal remote port of the passive optical filter device and a selected, respectively differing local port. The
passband of each optical bandpass filter function covers two or more neighboring optical channels. The passbands of
all optical bandpass filter functions differ from each other with respect to the optical channels covered.