Simultaneous bend and temperature sensor using tilted FBG

Abstract

We propose a simple, very reliable and fast optical sensor based on a tilted fiber Bragg grating for the simultaneous measurement of temperature and macro bending. The transmitted spectrum of a tilted Bragg grating is composed of numerous discrete dips which have two distinct origins: the dip at the longest wavelength comes from the self coupling of the core mode while the others are due to the backward coupling with the cladding modes. We apply a different demodulation technique to each of these two contributions in order to realize a dual sensor. This sensor allows the detection of small curvatures and provides a good accuracy.