Opto-electronic systems for addressing Ru oxygen sensors: their design optimization and calibration process

Description/Abstract

The paper describes research at Southampton University, aimed at optimising the design of fibre-remoted dissolved-oxygen sensors, using immobilized fluorescent Ru²⁺ indicators. The design and construction of two types of fluorescence lifetime monitoring units, one type using phase-delay-monitoring and the other using photon counting, is described. Results from a detailed theoretical study of a photon-counting RLD fluorescence lifetime sensor are presented, with specific attention to noise aspects. By numerical modeling of an analytical solution, the optimum time-window boundaries for the photon-counting system are identified. A surprising result is that the signal/noise can actually be improved by not using photon counts from all of the exponential decay, but leaving a time-gap in the measurement improves lifetime accuracy. Our previously reported Ti³⁺-doped sapphire fluorescence-lifetime calibration probe is described, and a new method for RLD interrogator verification using the probe is demonstrated.