CWDM is a method of combining multiple signals at various wavelengths for transmission along fiber optic cables, such that the number of channels is fewer than in dense wavelength division multiplexing (DWDM) but more than in standard wavelength division multiplexing (WDM).

CWDM systems have channels at wavelengths spaced 20 nm apart, compared with 0.4 nm spacing for DWDM.

CWDM typically uses 8 defined wavelengths from 1470nm to 1610nm with 20nm wavelength spacing. Is used as a low entry cost to WDM icrease signaling throughput.