Two-wavelength interferometric technique for measuring the refractive index of salt-water solutions.

An experimental test system capable of measuring the refractive index variation of a salt-water solution at two wavelengths, with temporally varying temperature and concentration, is constructed by using a Mach-Zehnder interferometer. An experimental data-reduction method is developed to take the data generated in the experimental test program and to determine the variation of the refractive index with temperature and concentration. The experimental data obtained from the test system are reduced and the results are fitted by using a nonlinear regression algorithm to determine the functional dependence of the refractive index with temperature and concentration.