DWDM uses the same #multiplexing technique as Coarse Wavelength Division Multiplexing (CWDM). However, compare to CWDM ability to multiplex 8 signals, DWDM system is able to multiplex 32 signals into a single fibre. Additionally, the signals can be amplified, making them keen to be transmitted up to 250 km. The conversion between electrical signals and light are done by Fibre-Optic Transmission Systems (FOTS), which is a Modulator.