Development of Optical Fiber Sensor for Water Salinity Detection

This project addresses the lack of a real-time, low-cost sensor to detect salt levels in water. The authors aim to develop an optical fiber sensor for water salinity detection. The sensor employs the principles of absorption spectroscopy using a broadband light source and spectrometer to detect changes in the optical spectrum of the sensor in the presence of varying concentrations of sodium chloride ions. A D-shaped sensor is fabricated by modifying the circular structure of a plastic optical fiber. Functionalized carbon nanotubes are drop casted over the D-shaped sensing region. Both uncoated and CNT-coated POF sensors are exposed to different concentrations of sodium chloride in water, and the spectral response is recorded. The results show that the sensors exhibited a strong correlation in their intensity response towards varying concentrations of sodium chloride salt ranging from 0 to 25%. The uncoated sensor had a sensitivity of 31A.U./% salt, and the CNTcoated Sensor had a sensitivity of 114 A.U/% salt. The functionalized CNT layer increased the sensitivity of the POF sensor by approximately 4 times. The outcome of this research provides a cost-effective and reliable method for water salinity detection in industrial and environmental applications.