Abstract: Disclosed is a sensor capable of measuring motion in a harsh environment. The sensor uses a fiber optic sensor element formed within a core of an optical fiber that is disposed within an enclosure made of a high strength, corrosion-resistant material. The optical fiber is attached to a supporting fixture in a cantilever fashion so that the intrinsic internal mass of the optical fiber has the freedom to be affected by gravity so that an environmental disturbance acting on the sensor results in a bending strain being applied to the optical fiber. A Bragg grating is located at the bending portion of the optical fiber. The modulation of an optical signal promulgating through the optical fiber is sensed using conventional means and used to measure the magnitude of the environmental disturbance.