Accurate measurements of aqueous glucose concentrations have been made in a double chamber Fabry-Perot etalon that can be miniaturized for subcutaneous implantation to determine the concentration of glucose in interstitial fluid. In general, optical approaches to glucose detection measure light intensity, which in tissue varies due to inherent scattering and absorption. In our measurements we compare the spectral positions of transmission maximums in two adjunct sections of an etalon in order to determine the refractive index difference between these sections and can tolerate large changes in intensity. With this approach, we were able to determine aqueous glucose concentrations between 0 mg/dl and 700 mg/dl within the precision of our reference measurement ( 2.5 mg/dl or 2% of the measurement value). The use of reference cavities eliminates interference due to temperature variations, and we show the temperature independency over a temperature range of 32 C to 42 C. Furthermore, external filters eliminate interference from large molecule contaminants.
Martini, J.; Kiesel, P.; Roe, J.; Bruce, R. H. Glucose concentration monitoring based on a small fabryperot etalon . Journal of Biomedical Optics. 2009 May/June; 14 (3): 034029.