CWDM (Coarse Wavelength Division Multiplexing) is an easy way to expand the capacity of an existing fiber network. Based on a mux / demux, which mixes and separates wavelengths. A link consists of two units. The technology is standardized in ITU G.695 and 694.2 and is used in Ethernet, FC, SAN and SONET. Up to 18 duplex channels can be mixed in a single fiber pair.