Node for an optical network

The invention is preferably utilised in a ring network with nodes generating specific wavelength signals that circumnavigate the ring back to their origin. A multi-wavelength signal is received at port 104 of node 100. A wavelength is reflected using filter 106 (e.g. a fibre Bragg grating (FBG)) and redirected using circulator 122 to a monitoring detector 132 (which can check successful circumnavigation). The remaining wavelengths are passed by the filter to continue forwards on the signal line. A signal generator 128 (e.g. LED) creates a signal, connected to the signal line in a reverse direction via circulator 116 towards the filter. The filter wavelength is again reflected into the forward direction to join the remaining wavelength signal. This combined signal traverses circulator 116 to reach beam splitter 120 which directs some signal energy onwards via network output port 102 and some to receiving detector 130 (e.g. photodiode) which can check that the local signal has been combined successfully. Separate claims are made to the wavelength dropping and wavelength adding operations.