Patent ID: 6898376

Claim:
In a wavelength division multiplexed communication system, an apparatus for protection against a lightpath failure from a source optical node to a sink optical node, comprising: said source optical node having first and second outputs for respectively outputting single wavelength first and second optical signals; a first lightpath, with said first lightpath being coupled to the first output of said source optical node for receiving the first optical signal; a second light path, with said second lightpath being coupled to the second output of said source optical node for receiving the second optical signal; said sink optical node having first and second inputs and first and second outputs, with the first input being coupled to said first lightpath for receiving the first optical signal and for outputting the first optical signal at the first output, with the second input being coupled to said second lightpath for receiving the second optical signal and for outputting the second optical signal at the second output; a coupler having first and second inputs and an output, with the first and second inputs being coupled to the first and second outputs, respectively, of said sink optical node, and for outputting at the output an optical signal received at one of the first and second inputs; an input for inputting a third optical signal to a third input of said sink optical node, for outputting the third optical signal at a third output of said sink optical node for transmission to said source optical node; and a detector for detecting if said sink optical node is outputting the third optical signal in addition to the first optical signal, and if so, inhibiting said sink optical node from outputting the second optical signal so that said coupler outputs the first optical signal, and if not, not inhibiting said sink optical node from outputting the second optical signal so that said coupler outputs the second optical signal.