We present a novel scheme for simultaneous measurement of temperature and refractive index by use of a single sampled fiber Bragg grating (SFBG). The intrinsic nature of a SFBG that possesses both fiber Bragg grating and long-period grating spectral responses permits the temperature effect to the measured solely from the former, whereas the refractive-index information is extracted from the latter. Using such a dual-parameter sensor, we successfully demonstrated measurement of the dependence on temperature of the refractive index of an aqueous solution of sucrose.
Shu, X., Gwandu, B. A. L., Liu, Y., Zhang, L., & Bennion, I. (2001). Sampled Fibre Bragg Grating for Simultaneous Refractive Index and Temperature Measurement. Optics Letters, 26(11), 774-776. https://doi.org/10.1364/OL.26.000774