Our CWDM products separate wavelength into bands of 20 nanometers to cover the complete fiber optical communication spectrum from 1270 nm to 1610 nm. These CWDM products cover 4-channel, 8-channel, and 16-channel mux and demux applications, with upgradeability for both four and. A CWDM SFP module is an optical transceiver that uses Coarse Wavelength Division Multiplexing (CWDM) technology to transmit multiple data channels over a single strand of single-mode fiber, helping networks expand capacity without deploying additional fiber. Compared to dense wavelength division multiplexing (DWDM), its wavelength spacing is coarser (typically 20nm), hence the.