Sistema de interrogação com compensação de temperatura para sensores baseados em FBG utilizando um atuador termoelétrico

Abstract

It is presented the development of an optoelectronic interrogation system (OIS) in a closed-loop control for Fiber Bragg Grating (FBG) sensors applied to AC signal measurements. It is based on the twin grating technique, in which an FBG is modulating a sensing-FBG. A microcontroller is employed to perform reflection measurements of the FBGs, and a closed-loop control is implemented in firmware to keep the filter-FBG tracking the sensing-FBG under temperature variations, with a thermoelectric actuator (TEC). The OIS was tested with a high-voltage sensor prototype under the thermal variation of 29◦C to 50◦C and the experimental results showed that the interrogation system is capable of keeping the filter-FBG tracking the sensing-FBG with a maximum deviation of 5×10−3 pm from the optimum point even under the influence of temperature. An analysis of the frequency domain of the AC signals showed that the OIS is able to perform accurate measurements at the operating point of least distortion possible. In addition, it can also be adapted for the monitoring of vibrations, such as in the maintenance of engines and turbines, and in the seismic vibrations.