Displacement sensor based on bent optical fiber with structural imperfections on the outer side

The concept of highly sensitive fiber optic displacement sensors is presented. It is based on macrobending plastic fiber with structural imperfections on the outer side. The theoretical principles of optical power losses in such fibers due to multiple curvatures are based on a surface that serves as a model for an imperfect layer and has the same optical properties. The sensor was tested using two different types of roughness topologies. We discuss some experimental results that confirm our prediction of considerable dependence of the output numerical aperture (the output signal) on the changing imperfections caused by bending the fiber.