An optical MEMS sensor system

In recent years, the optical application of MEMS (MOEMS, micro-opto-electro-mechanical-system) is widely studied, because of its intrinsic benefits [P. Rai-Choudhury, 2000][Hiroyuki Fujita et al., 2000]. One of most striking development is MOEMS sensors. The feature size and motion of MEMS devices are in the range of sub-micrometer, which make MEMS an effective mechanism to realize optical interference, hence a sensor system can be achieved by monitoring these micro-interferometers. This work reports a whole process of modeling, fabrication, and measurement of an optical MEMS sensor system. The sensor tip is designed as a Fabry-Perot cavity etched on the silicon chip, light is incident from the optical fiber, and simultaneously the reflected optical signal from the cavity is monitored. When certain ambient change forced on the tip, the membrane of the cavity vibrates deviating from resonance; consequently the reflected light is changed by means of central wavelength shift, and power degradation. CMOS modeling tools are used, to design the tip prototype and the fabrication process. Single mode fiber links between the tip and source/detector, the light source is 1550 nm broadband. Both OTDR and OSA are used to precisely decode the magnitude of ambient change. Next, the analogous sensor tips are reproduced and arrayed to realize a sensor network, thus a momentary impact will be positioned as well as quantified through spatial division multiplex [K.T.V Grattan et al., 2000]. Upon the performances, MOEMS sensor is compared with other possible sensing mechanisms, with regard to the physical features, sensing results, fabrication easiness, and application limits.