Comprehensive Study and Experimental Validation of U-shaped Probe Extrinsic Fiber Optic Sensor for the Measurement of Refractive Index at Various Temperatures using a Tunable Light Source

Abstract

Extensive detection performances due to sensitivity to external and internal perturbations in the fiber structure makes the optical fiber sensors highly superior over the conventional sensors. The fiber optic sensors with clad removed fibers at some portion along its length play a vital role in the determination of refractive index of various liquids at several wavelengths and at several temperatures. In the present paper a refractive index sensor has been developed to investigate the performance and experimental validation in the measurement of R.I. values of liquids at various temperatures using a tunable light source capable of emitting light at the wavelengths of 630nm, 660nm, 820nm and 850nm. The U-shaped glass probe connected between the tunable light source and an optical detector using two multimode PCS fibers of 200/230μm, acts as a clad removed portion of the sensor which is called as sensing zone or sensing region. In the working principle of the sensor, the U-shaped glass rod immersed into each mixture prepared with the combination of Toluene and Acetonitrile, the light launched from the source reaching the detector was noted at various temperatures and by tuning the wavelength of the source to 630nm, 660nm, 820nm and 850nm. From the data obtained, the sensor was calibrated to measure the refractive index of various liquids at different temperatures and wavelengths. Exploiting all the advantages offered by the fiber optic communication systems, the sensor was expected to be rugged, robust, reliable, and durable offering the sensitivity in the range of the order of 10^-5.