Optical fiber sensors using luminescent probes located along an optical fiber in the cladding of this fiber are of great interest\r\nfor monitoring physical and chemical properties in their environment. The interrogation of a luminophore with a short laser\r\npulse propagating through the fiber core allows for the measurement of the location of these luminophores. To increase the\r\nspatial resolution of such a measurements and to measure multiple analytes and properties in a confined space, a crossed optical\r\nfiber sensing platform can be employed. Here we describe the application of this platform to measuring the concentration of\r\ndissolved oxygen. The sensor is based on luminescence quenching of a ruthenium complex immobilized in a highly crosslinked\r\nfilm and covalently attached to the optical fibers. Both luminescence-intensity and luminescence-lifetime changes of the sensor\r\nmolecules in response to changes in the concentration of oxygen dissolved in water are reported. For luminescence-intensity\r\nmeasurements, a second adjacent sensor region is employed as reference to account for laser pulse energy fluctuations. Enhanced\r\nquenching response in water is demonstrated by the use of organically modified poly(ethylene glycol) precursors, which increase\r\nthe hydrophobicity of the film surface.
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