Thermal independent solution concentration sensing with tilted fiber Bragg grating

The temperature and solution concentration sensing characteristics of tilted fiber Bragg grating (TFBG) are investigated by means of theoretical analysis and experiments in this paper. It shows that the core and cladding modes exhibit nearly but not exactly the same thermal sensitivity with good linearity throughout the inquired temperature range. The dualsensitivity problem of TFBG to temperature and solution concentration is solved by calibrating every cladding mode wavelength with the core mode wavelength which is not sensitive to the solution concentration respectively to compensate the temperature effect, and this method makes thermal independent solution concentration measurement possible. It indicates that the cladding modes wavelengths linearly shift to the long wavelength direction with the increasing sucrose aqueous solution concentration, the demonstrated sensitivity is up to 5.6 pm/(g/40mL).