A tunable wavelength add/drop (t-WDM) device utilizes a multiwavelength
input (which serves as a data input port), a low loss optical circulator
or an optical coupler, a wavelength division de-multiplexer which splits
the input multi-wavelength data stream into itsd individual components, a
modified multi-channel DOS, a telecommunications grade optical fiber, and
a wavelength multiplexer for adding optical data channels. The input
multi-wavelength data stream from a network is sent to a wavelength
de-multiplexer where it is demultiplexed into individual wavelengths which
are applied to an array of Y-branch digital optical switching devices
controlled by a computer. If a specific wavelength is to be dropped, it is
diverted towards a branch of a given switch which has a fiber pig tail
attached. If a specific wavelength is to be sent through (neither dropped
or added) then the signal is diverted towards a mirrored end of the
Y-branch, where it is reflected back towards the wavelength
de-multiplexers to the circulator and goes out the output end of the
t-WADM. If a wavelength `slot` has ben vacated by a dropping channel then
a new data stream may be added in that slot.
