US Patent 7308201 Optical communication system

A node is provided in an optical communications network that utilizes a first set of add/drop filter elements for extracting and combining optical signals that are carried on wavelength division multiplexed channels in a first wavelength band. Additionally, an extraction element and a combining element for dropping and adding a service channel associated with the wavelength division multiplexed channels. The extraction element is arranged downstream of the add/drop filter elements. The extraction and combining elements are additionally adapted to drop and add, respectively, at least one further wavelength band carrying at least one optical traffic data channel.