Strain and temperature discrimination using a fiber Bragg grating concatenated with PANDA polarization-maintaining fiber in a fiber loop mirror

A highly sensitive strain and temperature sensor which is formed by concatenating a fiber Bragg grating (FBG) with a section of PANDA polarization-maintaining fiber (PMF) in a fiber loop mirror (FLM) has been proposed and experimentally demonstrated to perform temperature and strain measurement. The sensing principle of high birefringence fiber loop mirror (HiBi-FLM) and FBG has been analyzed with formula derivation. Due to the different temperature and strain sensitivities of HiBi-FLM resonant dip and FBG resonant peak, the changes in applied strain and ambient temperature can be simultaneously determined by measuring the two resonance wavelengths shifts. High temperature sensitivity of −1.93 nm/℃ and strain sensitivity of 37.5 pm/μe have been achieved respectively over the range of 20∼55 ℃ and 0∼789.6 μe. The discrimination errors for temperature and strain are measured to be ± 0.5 ℃ and ± 18 μe, respectively. The proposed sensor enjoys simple structure, good linearity, high sensitivity and low cost, and thus shows a good application prospects in various fiber-optic sensing applications.