Fibre optic glucose sensor

This paper reports the principle of operation, the design aspects, experimentation and performance of a fibre optic probe for sensing the variation of refractive index with concentration of glucose in distilled water. The device consists of fibre optic transmitter, fibre optic probe, reflecting mirror, temperature controller, photodiode detector and a digital multimeter. The variations in refractive indices of glucose for a range of concentrations varying from distilled water are studied. The measurements are carried out for glucose solutions with concentrations of 5, 10, 15, 20 and 25 g per 100 ml of distilled water. For a concentration change from 0 to 25 g per 100 ml, the refractive index varies from 1.3322 to 1.3617, the displacement corresponding to peak voltage changes by 1000 µm and the variation detected in peak voltage is 182 mV. The results show that the displacement corresponding to maximum intensity observed at different concentrations is a function of the refractive index of the medium and there is a linear relationship between them. From the experimental results it is concluded that as the concentration or density of a solute increases, the refractive index increases proportionately. The stability of the sensor, high sensitivity and the simplicity of the design, low cost of fabrication, make it suitable for chemical, biomedical, pharmaceutical and process control applications.