US Patent 10439709 Handling channel holder failures in channel holder equipped optical links

An Optical Add/Drop Multiplexer (OADM) node includes a plurality of degrees each having a multiplexer and a demultiplexer configured to interface to an optical section in an optical network; one or more channel holder sources configured to connect to corresponding multiplexers of the plurality of degrees and provide optical power at unoccupied portions of optical spectrum on the corresponding optical section to present a full-fill loading condition thereon; and control circuitry configured to locally detect a failure on the one or more channel holder sources affecting an upstream degree, and switch unoccupied optical spectrum filled with the channel holder signals from one or more downstream degrees to the upstream degree.