Multiple dense wavelength division multiplexing (DWDM) signals are superimposed on a single channel of a multiplexed signal in a coarse wavelength division multiplexing (CWDM) system. The DWDM signals may be superimposed on the CWDM spectrum in a metro area network that has legacy optical components that are otherwise designed for use with CWDM signals. This system increases the data transmission rates that can be achieved over an existing network that has less expensive CWDM optical components. The system also provides a scalable solution for increasing data transmission capacity in new networks.