A single fiber CWDM multiplexer allows for up to 9 channel over a single strand of fiber. WDM is usually divided into two categories, Coarse WDM (CWDM) and Dense WDM (DWDM). They both come with their own channel configurations, advantages and disadvantages. In fiber-optic communications, wavelength-division multiplexing (WDM) is a technology which multiplexes a number of optical carrier signals onto a single optical fiber by using different wavelengths (i. The light from each fiber is first collimated. Tailored for professionals sourcing solutions from CommMesh, it. The true heart of the WDM system is the multiplexer, also known as a mux.