Patent ID: 8116623

Claim:
A multi-ring network operating method of cross-connecting at least two ring networks, the method comprising: cross-connecting an input working ring and an input protection ring of a first ring network to an output working ring and an output protection ring of a second ring network; splitting an input multi-wavelength optical signal of the first ring network into at least one portion each having a specific wavelength, by using an optical coupler; and transmitting the input multi-wavelength optical signal to at least one wavelength selective switch, wherein the wavelength selective switch selectively passes at least one of the portions of the input multi-wavelength optical signal through at least one output of the second ring network, wherein a multi-casting function is provided both in an optical domain and in an electrical domain so that if the input signal does not require signal reproduction or wavelength conversion, it is cross-connected in the optical domain, and if the input signal requires signal reproduction or wavelength conversion, it is cross-connected in the electrical domain.