US Patent 7366412 Hybrid fine-coarse carrier switching

An optical shell node is provided with an ability to perform time switching on signals received from subtending edge nodes and channel switching on signals received from other shell nodes and destined for the subtending edge nodes. The signals received from the subtending edge nodes may be aggregated into signals that are channel switched by optical core nodes or by other shell nodes toward destination edge nodes. A resultant network formed of these shell nodes along with channel-switching core nodes and subtending-upon-shell-node edge nodes is capable of expansion beyond a continental scale, can support large numbers of edge nodes and has a higher bit rate capacity than known optical network structures.