The Cisco Metro 1500 series system uses the technology of dense wavelength division multiplexing (DWDM) to enable high performance data communication. The channels of optical communication are converted to separate wavelengths of the ITU-T grid for DWDM. The demultiplexer (DMX) module receives the combined signal from the MUX at the remote end of the link. In the DMX the combined optical signal is separated into the original wavelengths of optical communication.