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Journal of Sensors
Volume 2016 (2016), Article ID 3475782, 6 pages
Research Article

Noncontact Optical Fiber Sensor for Measuring the Refractive Index of Liquids

1Facultad de Ciencias Físico Matemáticas, Universidad Autónoma de Nuevo Leon, Avenida Universidad S/N, Cd. Universitaria, 66455 San Nicolás de los Garza, NL, Mexico
2Centro de Investigaciones en Optica, A.C., Loma del Bosque 115, 37150 Leon, GTO, Mexico
3Centro de Investigacion en Ingenieria y Ciencias Aplicadas, Universidad Autónoma del Estado de Morelos, Avenida Universidad No. 1001, Colonia Chamilpa, 62209 Cuernavaca, MOR, Mexico
4Centro Universitario de los Lagos, Universidad Autónoma de Guadalajara, Enrique Diaz de Leon 1144, 47460 Lagos de Moreno, JAL, Mexico

Received 27 November 2015; Accepted 17 February 2016

Academic Editor: Xingwei Wang

Copyright © 2016 R. Selvas-Aguilar et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


A noncontact optical fiber sensor for measuring the refractive index of transparent liquids is proposed. It operates by calculating the path of a focused laser beam at 635 nm that travels across the boundaries of a liquid sample. The optical power Fresnel reflections are detected and, subsequently, the refractive index is determined as the ratio between the traveled beam paths when the liquid is deposited versus a reference without the liquid sample. Additionally, a mathematical analysis of the geometrical case is included. The theoretical data from our sensor are in good agreement with the experimental results. The resolution achieved by the sensor is better than 10−3 RIU.