Patent ID: 6853811

Claim:
A method for operating an optical ring, the optical ring including a plurality of nodes, the method comprising: propagating a plurality of optical signal pairs over a plurality of wavelength connections between the nodes, wherein each such optical signal pair includes a first signal having a first wavelength λ a and a second signal having a second wavelength λ b that differs from λ a , and wherein at least one of the plurality of nodes the first signal acts as a transmit signal and the second signal acts as a receive signal; and redirecting at least one of the optical signal pairs over a protection path in response to a failure in the optical ring, wherein the protection path propagates signals with respect to the at least one of the plurality of nodes without changing the wavelengths of the transmit and receive signals. wherein, for each optical signal pair, the first and second wavelengths are selected from a set of N discrete wavelengths ordered sequentially by wavelength from λ 1 to λ N and divided into m subsets such that λ b(mod N/m) =λ a±n(mod N/m) , with a common fixed integer value of n≧1 for the plurality of optical signal pairs.