Optical add/drop arrangement for ring networks employing wavelength division multiplexing

Abstract

An add/drop arrangement using broadband optical couplers provides a low-loss, highly flexible add/drop capability for survivable wavelength division multiplexed (WDM) ring networks. At each node in the ring having the broadband optical coupler-based add/drop element, a portion of optical signal power of the entire WDM signal (i.e., all optical channels) is tapped off so that one or more optical channels of particular wavelengths can be dropped at the node. Information (e.g., data) to be added at the node is supplied in an optical channel that is added to the WDM signal via the broadband coupler. Because the add/drop element uses a broadband coupler, another portion of optical signal power of the WDM signal, including any added optical channels, passes through the node onto the ring. Depending on the specific ring topology being used with the broadband coupler-based add/drop arrangement, additional wavelength assignment and handling measures may be required. For example, certain ring topologies may experience interference between optical channels of particular wavelengths due to possible re-circulation of these optical channels beyond the add and drop nodes (e.g., after an optical channel passes its destination node). According to one illustrative embodiment, a node is equipped to perform wavelength conversion and/or wavelength suppression to prevent undesirable re-circulation of optical channels.