A MICROOPTODE ARRAY FOR FINE-SCALE MEASUREMENT OF OXYGEN DISTRIBUTION

A new microoptode array is presented that provides simultaneous measur ement with eight oxygen microoptodes using a simple optical setup and a phase-angle detection principle. The measuring system consists of: ( 1) an optical unit with eight oxygen microoptodes, a special fiber-cou pler array, optical filters, lenses, light sources (light-emitting dio des) and light detectors (photodiodes, photomultiplier tube); (2) a si gnal-processing unit with analog signal processing (phase-angle detect ion, filtering) and digital signal processing (central, data storage a nd display). The oxygen concentration is measured with tapered silica- glass fibers (tip diameter 20-30 pm) by the dynamic quenching of a lum inophore. A phase-modulation technique is used to determine the phase- angle shift that is caused by the fluorescence Lifetime when the indic ator is excited sinusoidally. In a time multiplex mode each sensor sig nal is sampled. This multisensor array system is designed for the inve stigation of the oxygen distribution in biofilms and aquatic sediments . The new measuring system and first applications in artificial and na tural systems are presented.