Microfiber Optics Liquid Refractometer: The Effect of Taper Waist

A simple tapered multimode fiber (MMF) optic sensor is proposed and demonstrated as a refractometer for liquid samples application. The working mechanism of such device is based on the intensity modulated transmission of the tapered fiber when it is immersed in solutions with increasing refractive index. The tapered fiber is fabricated using heat-pulling method to achieve a waist diameter of 40, 50 and 75μm over the length of 18 mm. The performance of the tapered fiber with different waist has been evaluated on samples of ethylene glycol solution and glycerol. The obtained results show good correlation with the data provided by a commercial refractometer. The main advantages of this sensor are its enablement of miniaturization and simplification, ease to fabricate and handle while providing high accuracy measurement.