Addressing multiple indicators on a single optical fiber - Digital signal processing approaches for temperature compensated oxygen sensing

A digital signal processing approach for hybrid fiberoptical microoptodes based on the measurement of the luminescence lifetime of appropriate indicators is presented. Numerical algorithms are applied to resolve individual decay times in a heterogeneous luminescence emission to enable the application of optodes with multiple indicators combined on a single fiber tip. We applied a hybrid optode that senses the oxygen concentration in line with the temperature, and used the latter information to compensate for the temperature drift of the oxygen measurement. We used a blue light-emitting diode to generate the excitation signal, and a standard photodiode with integrated pre-amplifier stage to detect the luminescence signal. Both signals were sampled using a stereo audio codec, and the further signal processing routines were entirely implemented on a commercially available digital signal processing evaluation board