Low Cost Refractive Index Sensor Based on Optical Lensed Fiber

Abstract

A refractive index (RI) sensor based on back reflection of an optical lensed fiber is demonstrated. The sensing device is fabricated by splicing a tiny gradient index fiber (GIF) on the tip of a single mode fiber. Symmetry mirror modeling and fiber coupling efficiency are utilized to estimate the dependence of reflection power on lens pitch. As for sensing test experiments, we measured the reflection power of RI sensor with different concentrations of glycerol solution from 0 to 100% in steps of 20% increasing. The results are consistent with theoretical curve. In terms of the experimental data, important characteristics including resolution and sensitivity are obtained. The RI sensor exhibits high sensitivity −884.62 dB for high RI sensed solution. As the high index GIF spliced on tip of the sensor, it helps to extend the sensing range from 1.45 to 1.472. Due to properties of easy fabrication and low material cost, we believe the RI sensor has potential in mass production and wide application. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1744–1746, 2013