A novel fiber-optic chemical sensor based on change of sample refractive index

A novel unclad optical chemical sensor is reported. This sensor is operated by the detection of the mode-filtered light emanating from an optical fibe r based on the changes of analyte refractive index(RI). Compared with measu ring changes in the transmitted light at the end of the fiber optic, it has a great advantage in signal to noise ratio(S/N) against a low background. In this paper, response characteristics of the sensor are discussed by meas urement of ethanol and acetic acid respectively. The sensor is hoped to hav e good prospects of applications in practice.