Tapered Plastic Optical Fiber Coated With Graphene for Uric Acid Detection

A simple tapered plastic optical fiber (POF) sensor is proposed and demonstrated for the detection of uric acid concentrations in deionized water. The sensor uses a tapered POF probe coated with different concentrations of graphene in a polymer composite. The tapered fiber is fabricated using an etching method and has a waist diameter of 0.45 mm and tapering length of 10 mm. The coating improves the sensitivity of the proposed sensor as it changes the effective refractive index of the cladding and allows more lights to be transmitted from the tapered fiber. The probe is immersed in uric acid solution and it senses the relative acid concentration using intensity modulation technique. As the uric acid concentration varies from 0 to 500 ppm, the output voltage of the sensor increases linearly from 2.98 to 4.36 mV with a sensitivity of 0.0021 mV/ppm and a linearity of more than 98.88%. A more efficient and stable sensor with graphene polymer composite coating increases the sensitivity due to the effective refractive index of the deposited cladding that allows more light to be transmitted through the tapered fiber.