<title>Displacement measurements over a wide range utilizing a simple intensity-based fiber optic sensor</title>

Abstract

A fiber optic sensor has been developed and tested for static and dynamic strain and displacement measurements. The sensor incorporates an extremely simple design, light source, and detector. The sensor utilizes a continuous piece of multimode optical fiber 'tied' into the shape of a figure of eight which functions as an intensity based optical fiber strain or displacement sensor. It is bonded to a body at two points, one on each side of the loops in the eight. The inherent stiffness of the fiber maintains a constant shape for the sensor throughout a wide range of displacements. Since multimode fiber is used in the construction, a simple LED/PIN diode is used for the light source/detector with a basic amplification circuit for each. The experiments have shown that the sensor is simple to construct, has a linear range of approximately 20 mm extension, and responds to frequencies from the quasi-static into the kilohertz range.