Salinity Sensing by the Radio-Frequency Power Based on the Michelson Interferometer

The salinity sensing technology based on the microwave photonic method is proposed and experimentally verified. The microwave photonic filter is formed by the microwave photonic interferometry of the Michelson interferometer. Contrast to the traditional method based on the optical spectrum measurement, the salinities information can be measured by extracting the minimum values of radio frequency(RF) response curves of microwave photonic filter(MPF). Due to amount of noise and the nonlinearity in the MPF, the minimum values of RF response of MPF vary with time, so the averaged values of several measurements are utilized in data analyzing process. Experimental results show that the salinity sensitivity of 0.284dB/‰ is achieved with the brine concentration in the range of 31‰-40‰ and the value of R-square can reach 0.88 by linearity fitting for salinity sensing, and the value can be improved to 0.979 by Cubic fitting.