MEMS interferometer-based reconfigurable optical add-and-drop multiplexor

An apparatus for selectively passing and dropping first component signals of a first wavelength division multiplexed (WDM) signal and for selectively adding second component signals of a second WDM signal to the first WDM signal, the apparatus comprising:

• a. a first optical train to direct each component signal of the first WDM signal along a corresponding one of a plurality of first optical paths;
• b. a second optical train to direct each component signal of the second WDM signal along a corresponding one of a plurality of second optical paths;
• c. an array of interferometers configured to receive the first component signals along the plurality of first optical paths and the second component signals along the plurality of second optical paths, each interferometer including a beam splitter to receive a first signal along the first optical path and a second signal along the second optical path, and to split each signal into a first portion and a second portion, a first mirror to reflect the first portion of each signal wherein an optical path length of the first portion is fixed, a phase modulator including a selectively actuated reflective layer to reflect the second portion of each signal wherein an optical path length of the second portion is variable, the phase modulator including a support structure and a substrate, the reflective layer forming a single elongated element suspended above the substrate, the reflective layer being configured to deflect in a direction substantially normal to the substrate;
• a first de-multiplexer configured to de-multiplex the first WDM signal into the first component signals, a second de-multiplexer configured to de-multiplex the second WDM signal into the second component signals;
• a first multiplexer configured to multiplex all first and second component signals directed back along the first optical path and a second multiplexer configured to multiplex all first and second component signals directed back along the second optical path;
• wherein the first de-multiplexer and the second de-multiplexer each comprise a diffraction grating configured to direct a component signal to a corresponding beam splitter by way of a transform lens and a second mirror;
• whereby the reflective layer is selectively actuated between a first position and a second position to vary the optical path length of the second portion such that when the reflective layer is in the first position, the first portion and the second portion of the first signal constructively interfere and the first portion and the second portion of the second signal constructively interfere thereby directing the first signal back along the first optical path and the second signal back along the second optical path, and when the reflective layer is in the second position, the first portion and the second portion of the first signal destructively interfere and the first portion and the second portion of the second signal destructively interfere thereby directing the first signal along the second optical path and the second signal along the first optical path.