II-VI Incorporated
Free space variable optical attenuator with integrated input/output power monitors

Abstract:

A free space variable optical attenuator (VOA) utilizes a beamsplitter to create tap beams (of both the input signal and the beam-steered output signal) that are directed into monitoring photodiodes. The beamsplitter is configured to exhibit a non-equal splitting ratio such that the tap beams are only a relatively small portion of the input/output beams. The free space configuration eliminates the need for fiber-based couplers, splices and connections to external monitors, as required in prior art VOA monitoring systems. The VOA utilizes a voltage-controlled, MEMS-based tilt mirror to provide beam steering of the propagating, free space beam in a known manner to introduce attenuation (power reduction) in the output signal.