Oxygen measurement via fluorescent quenching- The presence of oxygen molecules (blue sphere below) shortens the time that light is emitted from the luminophore.
Fluorescence with respect to oxygen content - The transmitted light intensity is subjected to AC modulation. Transmitted light is compared with the received light to look for a phase shift. The presence of Oxygen will decrease the phase shift.
Intensity changes with oxygen - The presence of oxygen causes a faster decay in fluorescence light intensity. The optode output must be matched to the desired oxygen measurement range.