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Non-contact refractive index measurement based on fiber optic beam-through technique

H. A. RAHMAN1,2,3, S. W. HARUN1,2,* , M. YASIN2,4, H. AHMAD3

Affiliation

  1. Department of Electrical Engineering, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia
  2. Photonics Research Centre, Department of Physics, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia
  3. Faculty of Electrical Engineering, Universiti Teknologi MARA (UiTM), 40450 Shah Alam, Malaysia
  4. Department of Physics, Faculty of Science and Technology, Airlangga University, Surabaya 60115, Indonesia

Abstract

A simple refractive index sensor for various concentrations of sodium chloride (NaCl) in de-ionized water is proposed and demonstrated. The beam-through technique is used to obtain output voltage of liquids with known refractive indices, namely methanol, de-ionized water, acetone and ethanol. Based on the output voltage of these liquids, the sensor characteristic curve is determined and the refractive indices of 2 % to 12 % sodium chloride concentrations are obtained. A sensitivity and detection limit of 23.07 mV/refractive index unit (RIU) and 2.28 x 10-3 RIU have been derived from measurements, respectively, with a linearity of more than 97 %. The fiber optic sensor is a promising alternative to other well-established methods for the measurement of liquid refractive index due to its simplicity of design, linearity, non-contact sensing, ruggedness and low fabrication cost..

Keywords

Fiber optic, Fiber optic displacement sensor, Refractive index measurement, Beam-through technique, Sodium chloride in de-ionized water.

Citation

H. A. RAHMAN, S. W. HARUN, M. YASIN, H. AHMAD, Non-contact refractive index measurement based on fiber optic beam-through technique, Optoelectronics and Advanced Materials - Rapid Communications, 5, 10, October 2011, pp.1035-1038 (2011).

Submitted at: Aug. 24, 2011

Accepted at: Oct. 20, 2011