Patent ID: 8139476

Claim:
A method for optical protection switching in a dual-fiber optical ring network in which a plurality of network nodes is interconnected by a first fiber optic cable for signals propagating in a clockwise direction and a second fiber optic cable for signals propagating in a counterclockwise direction, the method including the following steps: (a) generating and terminating, at a first of the plurality of network nodes, a first and second circulating optical probe signal that propagate to each of the plurality of network nodes along the respective first and second fiber optic cables, wherein the first and second optical probe signals are retransmitted without undergoing an optical to electrical conversion at each of the plurality of network nodes, and are generated at optical wavelengths different from those of optical wavelength-division multiplexed (WDM) signals carrying data and control information that must be retransmitted by undergoing the optical to electrical conversion at each of the plurality of network nodes; (b) monitoring the first and second optical probe signals to detect the presence of an optical failure in the optical ring network, wherein the detection of an optical break point in at least one of the optical probe signals indicates the presence of an optical failure in the optical ring network, and wherein the absence of an optical break point in both the first and second optical probe signals indicates normal operation of the optical ring network; and (c) controlling a protection switch mechanism, in response to the detection of an optical failure, to sustain communications in the optical ring network outside a location of the optical failure, and to restore communications in the optical ring network in response to the subsequent detection of normal operation of the optical ring network, indicating that the optical failure has been repaired.