An optical fiber interferometric refractometer

22 Mar 2007

A Suhadolnik Meas. Sci. Tech. 18 1205-1208

Dr Alojz Suhadolnik at the University of Ljubljana, Slovenia, has developed a new type of optical fiber interferometric refractometer that can measure the refractive indices of various liquids with high accuracy.

The laser interferometer system consists of a fiber-optic Mach-Zehnder interferometer combined with a conventional bulk optic Michelson interferometer. The first interferometer measures the optical path length difference of the moving sample, while the second one measures the liquid sample displacement in air.

Suhadolnik used a fringe count technique on both interferometers to obtain the refractive indices of a variety of liquids, including water, benzene and acetone, and a range of concentrations of sodium chloride in water. When the results were compared to previously recorded values, the new optical fiber interferometric refractometer was found to give highly accurate measurements of the refractive indices for the range of liquids investigated.

As well as allowing high accuracy measurements, the proposed refractometer has the advantage of being easy to assemble; the optical fiber Mach-Zehnder interferometer has a simple construction and the Michelson interferometer is commercially available.