Patent ID: 7330650

Claim:
A bi-directional optical ring network having a first ring network and a second ring networks for providing a protection switching, comprising: a plurality of nodes, having optical add/drop multiplexers, each being provided on the first and second ring networks and including a demultiplexer and a multiplexer, each of which has a capacity of 1×N; a pair of switching devices provided across the first and second ring networks and connected between the optical add/drop multiplexers and fiber optic links connected with another node; and wavelength interleavers, each being provided on both ends of each optical add/drop multiplexer provided on the first and second ring networks and including three ports, of which one port is connected to each switching device and allows for passing signals of all wavelength bands, another port allows for passing only signals of some wavelength bands processed on any one of the first and second ring networks, and the third port allows for passing only signals of the other wavelength bands processed on the other, wherein the pair of switching devices is configured to loop-back optical signals related to a link failure to one of the first and second ring networks that does not have a link failure when a failure occurs between the nodes via one of the first or second ring networks, and wherein the looped-back optical signals related to the link failure bypass the add/drop multiplexer on said one the first and second ring networks so that each add/drop multiplexer only multiplexes or demultiplexes optical signals which it must add or drop.