Patent ID: 7831144

Claim:
A method performed by a node of a wavelength multiplex optical network, the method comprising: detecting at the node that at least a portion of functionality of a wavelength of a first unidirectional path (first path/wavelength) of an optical circuit fails to operate, the first unidirectional path being originated from a first terminating node as a source node for reaching a second terminating node as a destination node of the first unidirectional path, the first terminating node and the second terminating node forming the optical circuit, wherein the optical circuit includes a nonterminating node; determining within the node whether the node is the second terminating node of the optical circuit in response to detecting a failure of the first unidirectional path; if it is determined that the node is the second terminating node of the optical circuit, the node signaling the first terminating node by removing a light of a second wavelength of a second unidirectional path (second path/wavelength) in an opposite direction of the first unidirectional path of the optical circuit, to indicate the failure of the first path/wavelength; and the node ignoring the failure of the first unidirectional path without removing the light of the second wavelength of the second unidirectional path if it is determined that the node is not the second terminating node of the optical circuit.