CWDM (Coarse Wavelength Division Multiplexing) channels are the specific wavelengths of light used in a CWDM system to transmit multiple signals over a single fiber optic cable. CWDM technology can support up to 18 channels, each operating at a different wavelength. The standard ITU-T G.694.2 specifies the 18 CWDM channels, which are numbered from 1270nm to 1610nm with a spacing of 20nm between each channel.  Each CWDM channel operates within a specific wavelength range, and multiplexers and demultiplexers are used to combine and separate the channels at either end of the fiber optic link. This enables different data streams or services to be transmitted simultaneously over a single fiber optic cable.