The theory, design, fabrication, and characterization of MEMS (micro electrical mechanical system) Fabry-Perot diaphragm-fiber optic microphone are described in the present invention. By using MEMS technology in processing and packaging, a square 1.9 mm.times.1.9 mm, 2 .mu. thick SiO.sub.2 diaphragm with a 350 .mu. square embossed center of silicon is mechanically clamped to the ferrule of a single mode fiber to keep its closeness (5 .mu.) and perpendicular orientation with respect to the diaphragm. Static measurement of optical output power versus the pressure on membrane reveals more than one period of Fabry-Perot interference, thereby generating a Fabry-Perot diaphragm-fiber interferometer device accurately reproducing audible acoustic wave.