DWDM Optical Add/Drop Multiplexer (OADM) is a passive optical device used in WDM networks for adding and dropping one/multiple 100 GHz DWDM channels in the C-band into one or two fibers, while letting the rest of the wavelengths bypass to the needed destination. DWDM OADM modules are available in single-side (East or West) and dual-side (East and West) configurations. With matching MUX/DEMUX units placed at each end of an optical link, multiple data channels can be combined and transmitted over a single-mode fiber trunk. The passive OADM modules can add or drop 2, 4, 8 data channels at any point along the trunk.