Abstract: Optical add/drop multiplexer (OADM) is a key device for fiber sensing dense wavelength division multiplexer and future all-optical-net communication to replace electronic router, which is the bottleneck of high-speed information transmission. The work principles of the OADM based on the structure of Mach-Zehnder interferometer and fiber Bragg grating(FBG), the structure of optical circulator, FBG and the structure of integrative fiber grating coupler(FGC) were introduced. Three configurations of OADM were built and were experimentally investigated to test their performance. The advantages and disadvantages were concluded and the basis for the design and fabrication of OADM was provided.