Low-Cost CDC ROADM Architecture Based on Stacked Wavelength Selective Switches

A highly flexible, stacked, switch module is proposed, wherein multiple independent 1×N wavelength selective switches (WSSs) can be realized on a single 4k liquid crystal on silicon device. The stacked WSS module can be configured in different ways for application at either the transit side or the add/drop side of a colorless, directionless, and contentionless (CDC) reconfigurable optical add/drop multiplexer (ROADM). Two ROADM architectures are proposed based on the stacked WSS modules. Their costs are analyzed for both a 4-deg network node and a larger 8-deg node. The first proposed ROADM architecture with full CDC features is shown to realize a cost reduction of at least 35% in these two test network nodes, when compared with the conventional CDC ROADM architecture based on the standalone WSSs and multicasting switches (MCSs). The second ROADM architecture proposed has a small probability of wavelength contention, which could be prevented by a local wavelength assignment algorithm. According to our cost estimation, we are able to aggressively reduce the number of components at the add/drop side and make an overall cost reduction of >70% and >80% in the 4- and 8-deg network nodes, respectively.