“Reconfigurable Optical Add/Drop Multiplexer (ROADM) A new form of add/drop multiplexer that essentially adds the ability to switch individual networks. The key differentiating feature of a ROADM is the ability to switch traffic and both the wavelength and SONET/SDH layers. ROADM functionality is not new; most long-haul DWDM equipment has built-in ROADM functionality. What’s new is the appearance of these features in purpose-built metro optical gear, an application that has been long hyped but is only now beginning to gain support.”