OPTICAL-SYSTEM FOR PRESSURE AND TEMPERATURE SENSING

An optical sensing system based on a micromachined silicon resonator h as been developed and has been successfully field tested in a harsh ae rospace environment. Two vibrating silicon beams mounted above a diaph ragm are addressed by the same optical fibre. As pressure is applied, the diaphragm generates stress changing the resonance frequency of a b eam clamped at both ends. Additionally, a cantilever beam is located v ery close to the first beam which is only sensitive to the ambient tem perature. Detailed investigations were undertaken to obtain a better i nsight into the photothermal activation and interferometric detection of the resonating beams. The sensor itself was fabricated from monocry stalline silicon using silicon to silicon fusion bonding and electro-c hemical etch stop techniques. For packaged sensors with a pressure ran ge from zero to 130 kPa or 3 MPa an overall accuracy of 0.05% full sca le was achieved.