Arrayed waveguide gratings(AWG) are commonly used as optical (de)multiplexers in wavelength division multiplexed(WDM) systems. These devices are capable of multiplexing many wavelengths into a single optical fiber, thereby increasing the transmission capacity of optical networks considerably. The devices are based on a fundamental principle of optics that light waves of different wavelengths do not interfere linearly with each other. This means that, if each channel in an optical communication network makes use of light of a slightly different wavelength, then the light from many of these channels can be carried by a single optical fiber with negligible crosstalk between the channels. The AWGs are used to multiplex channels of several wavelengths onto a single optical fiber at the transmission end and are also used as demultiplexers to retrieve individual channels of different wavelengths at the receiving end of an optical communication network.

The AWG  Mux/DeMux is manufactured with the silica-on-silicon.  The silica-on-silicon(SoS) is a type of Planar Lightwave Circuit(PLC) that are fabricated on planar substrates by depositing layers of glass with high silica content on the wafer. This results in low coupling and insertion loss.