https://www.wdmlight.com/18-16....-8-4CH-CWDM-Mux-Demu
The CWDM multiplexer is based on thin-film filter (TFF) technology and operates on ITU grids with 20nm channel spacing. The CWDM wavelength ranges from 1270 to 1610 nm and supports at most 18 channels of optical signal multiplexing.