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. Using the DWDM technology can add effctively WDM capability to their existing and new networks, and extend the optical signals transmission distance. DWDM OADM modules are available in single-sided (East or West) and dual-sided (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 up to 4 data channels at any point along the trunk.