Simultaneous Measurement of Thermal Gradient and Average Temperature in Concrete Blocks Using Nonuniform Long-Period Optical Fiber Gratings. - N'Guessan G. M. Koffi; Tinko A. Eftimov; Alla Arapova; Frédéric J. Lesage; Wojtek J. Bock; Amine Cherif (IEEE Trans. Instrum. Meas., 2022)