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

• Main Authors: Rahman, Husna Abdul, Harun, Sulaiman Wadi, Yasin, Moh, Ahmad, Harith
• Format: Article
• Published: INOE 2011
• Subjects: QC Physics; TK Electrical engineering. Electronics Nuclear engineering
• Online Access: http://eprints.um.edu.my/19879/; https://oam-rc.inoe.ro/index.php?option=magazine&op=view&idu=1682&catid=67
• Institution: Universiti Malaya

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 × 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.