Date Added: May 2012
The evolution from point-to-point Dense Wavelength Division Multiplexing (DWDM) systems towards Wavelength-Switched Optical Networks (WSON) was mainly driven by the consolidation of all-optical technology such as the Reconfigurable Optical Add-Drop Multiplexer (ROADM) and the Optical Cross-Connect (OXC). These network nodes are capable of routing and switching in the optical domain, avoiding the expensive Optical-Electronic-Optical (OEO) conversions at the intermediate transponders for each wavelength. This yields the main benefits of transparency to the bit-rate and format of optical signals. However, the lack of electronic regeneration implies the presence of two drawbacks: the accumulation of physical impairments and the Wavelength Continuity Constraint (WCC) throughout the optical connection.