Compact Fiber Optic Sensors for Dual Temperature and Refractive Index Profiling Based on Partially Etched Chirped Fiber Bragg Grating

We propose a partially etched chirped fiber Bragg grating (pECFBG) as a fiber optic sensor capable of detecting and profiling temperature and refractive index changes over the grating length. The sensor is achieved by etching a 1.4 cm-long chirped FBG by hydrofluoric acid, leaving a part of the grating unetched. In this way, we expose a part of the grating to refractive index variations in the outer medium, while the whole grating is sensitive to temperature changes. By applying spectral correlation in each grating portion, it is possible to detect profiles of temperature and refractive index, as experimentally demonstrated.