Low-Cost Refractive Index Sensor With Optical Fibers Attached to a U-Shaped Glass Tube

A low-cost multimode optical fiber based sensor has been reported for measuring the refractive index (RI) of liquid samples. In this sensor, a light is coupled from a multimode optical fiber to a customized U-shaped glass tube, and light emerging out of the U-shaped glass tube is guided onto a photodetector with the help of another multimode fiber. The intensity of light detected by the photodetector is found to vary with the RI of liquid sample that comes into contact with the U-shaped glass tube. A sensor response has also been observed by changing the bending radius of the glass tube and the depth of surrounding liquid medium. The proposed sensor is expected to be more rugged and reliable, as compared to a tapered optical fiber and the U-shaped optical fiber refractometers.