A fibre-optic oxygen sensor for oceanography

The concentration of oxygen is one of the most important parameters for underwater life. Electrochemical sensors based on the Clark electrode provide a convenient tool for easy and fast oxygen determination. However, the drift of these sensors prevents their use for accurate long-term measurements. On the contrary, optical sensing, particularly when combined with time-resolved fluorescence, could be a solution to get a long-term-stable oxygen sensor. The sensing principle is based on the quenching of fluorescence by oxygen. In order to overcome difficulties arising from the immobilization of the dye in a solid matrix, a special set-up with ideal dye environment has been designed. Fluorescence lifetime measurements are made with two time windows set at two distinct positions along the fluorescence decay curve. The response time of our sensor is long but still compatible with our application. The effect on the sensor of several parameters specific to the marine environment, such as salinity and hydrostatic pressure, has been investigated.