Dual Output Approach in Dye Concentrations Determination Using Non-Adiabatic Tapered Fiber

A non-adiabatic tapered optical fiber sensor based on interferometric approach was developed by tapering a singlemode fiber using flame brushing technique. Two output variables in the form of absorption and spectral shift were used to infer the dye concentration of an analyte containing Remazol Black B. The system could measure the dye concentration of the analyte within a range of 50 to 250 ppm with sufficient sensitivity and configurability. A sensitivity of 7.61 × 10^-5 abs/ppm and 0.0045 nm/ppm was obtained for the output derived from the absorption of light and spectral shift, respectively. A new predictive model was formulated by combining the predicted dye concentrations of absorption and spectral shift with equal weightings. Then, an experiment was performed to measure the accuracy of the models that use absorption, spectral shift, and their combination to predict the concentration of an analyte in the range of 50 to 250 ppm. The differences between the actual and the predicted dye concentration values were evaluated in terms of the correlation coefficient (R²), root-mean-square error (RMSE), and mean absolute percentage error (MAPE), respectively. The results show that by combining the two parameters, a better estimate (R² = 0.9875, RMSE = 7.6761, MAPE = 4.1257) of the dye concentration with higher correlation and lower error can be achieved. Finally, an additional experiment is conducted to validate the accuracy of the sensors.