Application of optical time-domain reflectometry for the interrogation of fiber Bragg sensors

A reflectometric approach is proposed for the polling and multiplexing of sensitive elements on fiber Bragg gratings (FBGs). The method is based on the power measurement of the radiation reflected by the FBG using a conventional fiber-optic time-domain reflectometer. The multiplexing of sensors is based on the time separation of signals. Requirements on the Bragg diffraction gratings that provide the linear dependence of the received signal on the FBG mechanical stress and temperature are determined. In the measurements of the FBG relative elongation and temperature, the threshold sensitivities are 0.8 × 10^?4 (80 μstrain) and 5°C, respectively. Due to its simplicity and efficiency, the reflectometric method of FBG polling and multiplexing can be used to solve various measurement problems, in particular, the safety monitoring of the stressed-strained elements in building structures.