Add-and-drop node for a WDM optical network

An add and drop node for a WDM optical network comprises an optical input section (21), an optical output section (22), a selective transit section (31) comprising a wavelength demultiplexer (33), a wavelength multiplexer (35) and a plurality of lines (20) each dedicated to a wavelength channel, an optical gate (34) being arranged on each dedicated line and controlled on a packet-by-packet basis for selectively passing or blocking each optical packet as a function of control data, an add module (40) for generating second optical packets adapted for superimposition to the passed optical packets for WDM transmission to a second network segment, and a light source (51, 66) adapted to generate time-continuous optical power in the input section in response to detection of a failure state, wherein the optical gate (34) is controlled to create gaps during time intervals reserved for the second optical packets and to shape the time-continuous optical power into dummy optical packets during the remaining time intervals.