MEMS retro-phase-modulator for free-space coherent optical communications

This paper describes an electrostatically actuated microelectromechanical systems (MEMS) device combined with small-scale retroreflective elements to produce a hybrid MEMS retro-phase-modulator suitable for use in a retroreflective free-space coherent optical communications system. In contrast to other MEMS retromodulators reported, which have concentrated on intensity modulation, the device reported in this paper produces an optical phase modulation. Two types of retroreflective elements, namely, a ball lens and an off-the-shelf retroreflective strip have been incorporated into the modulator., This paper reports a transmission system operating at higher bit rates than those that were previously published for similar schemes. Modulation has been achieved at 400 bits/s with a transmission cost of 80 pJ/bit.