An Optical Tapped Delay Line (OTDL) is combined with other known optical
apparatuses to provide an add-drop multiplexer for a wavelength division
multiplexing fiber optic network. Each output beam of the OTDL is
spatially distinguishable in free space. This wavelength accessibility
enables selection of one or more of the optical beams for adding or
dropping. The system can be a fixed or tunable single channel add/drop
system, a fixed or tunable multi-channel add/drop system, or a fully
programmable add/drop system.