Wavelength division multiplexer is a device that can divide signals into multiple single wavelength signals or synthesize multiple single wavelength signals into one signal. It can multiplex multiple wavelengths in one wavelength division multiplexer fiber, which greatly increases the transmission capacity of optical network. AWG has the advantages of wavelength selectivity, low insertion loss and compact size. It is widely used in the photosynthetic and wavelength division of DWDM system and wavelength routing system。