“…Different techniques to attach the header to a packet can be used: transmission on a separate wavelength, subcarrier multiplexing (SCM) (e.g., CORD [9], OPERA [7]), serial transmission of header, and payload on the same wavelength (e.g., WASPNET [3], KEOPS [1]). As this header is decoupled from the payload, its bit rate can be substantially lower than that of the payload-thereby allowing to keep the header processing in the electrical domain, as explained before.…”