Optically interrogated MEMS pressure sensors for propulsion applications

Pressure sensors suitable for propulsion applications that utilize interrogation by fiber optics are described. To be suitable for many propulsion applications, sensors should have fast response, have a configuration that can be readily incorporated into sensor arrays, and be able to survive harsh environments. Microelectromechanical systems (MEMS) technology is utilized here for sensor fabrication. Optically interrogated MEMS devices are expected to eventually be more suitable than electrically interrogated MEMS devices for many propulsion applications involving harsh environments. Pressure-sensor elements are formed by etching shallow cavities in glass substrates followed by anodic bonding of silicon onto the glass over the cavity. The silicon is subsequently etched to form the pressure-sensitive diaphragm. Light emerging from a fiber is then used to interferometrically detect diaphragm deflection due to external pressure. Experimental results for static and dynamic pressure tests carried out in a shock tube demonstrate reasonable linearity, sensitivity, and time response. (C) 2001 Society of Photo-Optical Instrumentation Engineers.