A Robust, Multiplexable Fiber Sensor for Simultaneous Measurement of Bend and Strain

We report on the design and implementation of a novel optical fiber sensor for simultaneous measurement of bending and longitudinal strain. An all-fiber transducer is comprised of a fiber Bragg grating preceded by a short region of conventional fiber. Peak Bragg reflections experienced by orthogonal linearly polarized modes traveling within the sensor region shift identically with strain and temperature but oppositely with fiber bending. A novel switching interrogator allows isolation of the common mode strain signal to facilitate a robust measurement of both bend and strain, while retaining the grating-based transducer's capability for serial multiplexing.