Dual Bragg grating sensor for concurrent torsion and temperature measurement

The paper discusses a dual fibre Bragg grating sensor for the independent measurement of temperature and torsion in a rotating shaft. It shows theoretically that torsion affects the differential wavelength of the gratings in the proposed configuration, whereas temperature changes only the common-mode wavelength, allowing measurement of both torsion and temperature. For the particular system investigated experimentally, the differential wavelength change due to torque was 19.4 pm (N m)?1, and the corresponding temperature sensitivity was ?0.36 pm ?C?1. In contrast to these values, the temperature sensitivity of the common-mode wavelength change was 25.3 pm ?C?1, and its torque cross-sensitivity was ?0.19 pm (N m)?1.