A Simple and Affordable Solution for Current Measurement Using a Polarimetric Fiber Sensor with Temperature Correction

Abstract

The objective of this study is the principle of operation, performance and practical schemes of a simple broadband optical fiber polarimetric current sensor with spectral interrogation permitting temperature-insensitive measurements using optically active Bi₁₂SiO₂₀ (BSO) crystals. Depending on the excitation source two components of the broadband spectrum have been identified: the broadband fluorescence component up to 900 nm caused by excitation under 500 nm and the transmitted component for wavelengths above 500 nm. The theoretical polarimetric analysis and performance description of the sensor is based on the Mueller-Stokes matrix method and to account for the use of a broadband light source the spectral dependence of the dispersions of the optical activity and the Verdet constant has been taken into account for which simple power law approximations have been proposed to facilitate the design of the interrogation schemes. Two interrogation solutions have been outlined based on the modulated polarimetric spectral response: the extrema wavelength shift and the \(\pi\)-shifted differential response of which the former is the focus of the present paper. The sensitivities to current, to temperature, as well as the cross sensitivities, have been experimentally measured and their spectral dependences have been established. A two-spectral points method has been proposed to perform current measurements with temperature correction. Current measurements within the 200 A to 800 A range with a minimum of 0.1 A current changes and a dynamic range of up to 34 dB can be performed.