Multiplexing: A multiplexer (MUX) combines wavelengths using thin-film filters or arrayed waveguide gratings (AWGs), ensuring <0. 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. They are a cost effective method to expand the capacity of existing fiber optic cables.