A theoretical model using ray tracing method is developed. The results predicted by the model were confirmed by experimental results. The model could explain the experimentally observed fact that the maximum signal for a given realistic tapered length is at a probe radius smaller than that expected from V-number matching condition. It is shown that for obtaining maximum fluorescence signal from an evanescent wave fiber optic biosensor a realistic optimum taper length needs to be chosen. We found that different detection environments require different taper lengths at a given taper angle. These facts were confirmed experimentally.

A fiber-optic oxygen sensor with enhanced dynamic range is reported. The quenchable fluorophore is coated on the probe surface in such a way that the more than 95% molecules should be exposed to the analyte.