A micromachined pressure sensor with fiber-optic interferometric readout

Abstract A high sensitivity, batch fabricated, fiber-optic pressure sensor has been fabricated using silicon micromachining technology. The transducer consists of a fiber positioning v-groove, a 45° stationary mirror and a silicon membrane, micromachined in silicon by anisotropic etching in KOH solution, and a single mode optical fiber. The membrane and optical fiber end form a Fabry-Perot cavity whose length varies with pressure. The generated optical interference fringes are used to detect and measure the change in membrane deflection. Pressure range of operation is dictated by the thickness, size and material of the membrane. The sensor described here was designed for low pressure range (0–25 mm Hg) applications. Temperature sensitivity and stability problems which are commonly encountered with currently available piezoresistive and capacitive pressure sensors are significantly reduced by the inherent differential nature of interferometric measurement and the use of all silicon construction. The fabrication, packaging and testing of the sensor are described in this paper. The performance of the sensor was evaluated and found to compare favorably with theoretical predictions.