<title>Novel distributed fiber optic microbend sensor structure based on dispersion addressing</title>

Abstract

This paper presents novel fully distributed forward propagating system, suitable for use with microbend sensors. The presented principle bases on selective launch of modes in specially designed multimode fiber called OFDA (Optical Fiber for Dispersion Addressing). At the input of the OFDA fiber short, pulse is launched in fundamental mode. In presence of microbend disturbance located down the sensing fiber, light couples from fundamental to higher order modes that propagate at different group velocity as fundamental mode. The position of measurand is then determined on the basis of time delay between pulse carried by fundamental mode and by pulse carried by higher order modes. The difference of group velocities is maximized by proper construction of refractive index of the OFDA fiber profile. Experimentally produced fibers exhibited difference of group velocities in range over 1%. This allows for easy reconstruction ofposition and amplitude of microbend deformations located down the sensing fiber.