Strain and temperature measurements based on superimposed Long and Short Period Fiber Bragg Grating sensors
Résumé
We propose a fiber Bragg grating based optical sensor to measure and localize strain and temperature effects simultaneously. Long period grating (LPG) and fiber Bragg grating (FBG) exhibit different responses to an applied solicitation, thus, strain and temperature influences can be determined separately by measuring the corresponding wavelength shifts. In this paper we present a configuration based on the use of these two gratings types: a LPG and a FBG written in the same fiber section which allows us to discriminate the contributions of these two main solicitations. The sensor is calibrated in temperature range from 25°C to 120°C, and in strain range from 0 to 2300 µ-strain. The reported errors are estimated to be within ± 0.2°C and ± 2.7 µ-strain respectively. These sensors were embedded and tested in both metallic and composite material plates