Dual parameters discrimination comparison between two types of optical fiber sensors during the operation of a Li-ion battery

Abstract

In this work, a comparison between the temperature and strain decoupling performed by a bare polarization-maintaining FBG (PM-FBG) sensor and by a hybrid sensing setup, involving the slow peak of the PM-FBG and the fringe shift of the fiber loop mirror (FLM) interferometer (FLM+FBGslow), was studied and discussed. To promote such comparison, the sensors were submitted to temperature and strain variations at the surface of a cylindrical Li-ion battery (LiB), cycling between 3.0 V and 4.2 V. The data spread of the FLM+FBGslow indicates a root mean square deviation of ± 0.1 °C and ± 7.8 µε, against ± 0.5 °C and ± 9.7 µε in PM-FBG, for temperature and strain, respectively. The matrixial method through the sensitivities values of each sensor was used for data processing. Although both sensing configurations showed similar trend behavior of strain and temperature variations during all the experiment, the FLM+FBGslow setup presented better accuracy when compared to the PM-FBGs, however, it could only perform measurements in all the LiB extension, while the PM-FBG could provide data regarding a specific spot of the LiB. The highest temperature and strain variations were achieved in the end of the discharge processes.