Arrayed waveguide grating (AWG) is a kind of planar integrated waveguide (PLC) WDM device with multiplexing and demultiplexing functions. The principle of using AWG to realize WDM devices was first proposed by M.K. Smith in 1988. AWG has the function of focusing and dispersing at the same time. That is to say, the same wavelength of light can be focused on one point, and the focus of different wavelengths can be shifted by dispersion.