Patent ID: 7133609

Claim:
In a bidirectional WDM ring network including an inner ring and an outer ring for processing N units of optical signals having a first wavelength band and a second wavelength band, a node comprising: a plurality of optical add/drop multiplexers along the inner and outer rings; a pair of switching devices interfacing the inner and outer rings and disposed between the optical add/drop multiplexers for switching a direction of the optical signals passing through the inner and outer rings; and, a plurality of WDM filters provided along the inner and outer rings and between the optical add/drop multiplexers and the switching devices, each WDM filter including a first port for permitting all wavelength bands to pass therethrough and coupled to the switching devices, a second port for permitting only optical signals processed by one of the inner and outer rings to pass therethrough and coupled to one end of the optical add/drop multiplexer, and a third port for permitting optical signals processed through the other of the inner and outer rings to pass therethrough and coupled to the other end of the optical add/drop multiplexer, wherein, upon a detection of a link failure in one of the inner and outer rings, the WDM ring network is operative to transfer optical signals to one of the inner and outer rings in a reverse direction via the switch device.