2-MODE OPTICAL FIBER ACCELEROMETER

A novel interferometric accelerometer is described and demonstrated by using a two-mode, elliptical-core optical fiber. A loop of fiber bends when subjected to acceleration normal to its plane, which causes a differential phase shift between the LP01 and LP11 modes. This optical phase shift is directly measured at the output of a phase-sensitive detector by using an in-fiber double-frequency conversion technique. Preliminary results indicate a scale factor of 2 rad/g, with a sensitivity and bias stability of 30 mg. Signal-processing electronics employed to measure the rotation rate in a fiber gyroscope could potentially be used to reduce short-term noise to the 1-10-mug range. Cross talk between the sensitive axis and one of the transverse axes is virtually null.