Microfabricated Optical Compressive Load Sensors

We demonstrate novel optically-addressable compressive load sensors consisting of bulk micromachined single-crystal silicon transducers integrated with fiber Bragg grating (FBG) sensing elements. These devices constitute a new class of compact optical sensors realized through the integration of mechanical components constructed via microelectromechanical systems (MEMS) fabrication technologies and strain sensitive elements based on FBGs. In this work we present experimental results for an "optical force probe" (OFP) capable of sensing compressive loading transverse to the long-axis of the fiber. Given the transduction mechanism in our design - whereby a compressive load is converted to an axial strain in the fiber - it is possible to use a standard FBG readout system to measure the imparted load. Furthermore, the sensitivity is tunable for any desired load range. Results are presented for compressive loads up to 200 psi, resulting in axial strains approaching 1000 muepsiv in the fiber.