Many explanation such as oxygen, dissolved oxygen, and sensor are described inside the paper. In the paper we can learn explanation like application, sensors, and intensity.
This paper contains info about detection, phase, and probe. These are excerpted from the paper:
The determination of oxygen concentration is important in many areas of industry, medicine and the environment. The amount of oxygen dissolved in water is an indication of the quality of the water and careful control of oxygen levels is important in waste-water management and in fermentation processes. Optical dissolved oxygen (DO) sensors  are more attractive than conventional amperometric devices, because, in general, they have a fast response time, do not consume oxygen and are not easily poisoned. Sensor operation is usually based on the quenching of ¯uorescence in the presence of oxygen. In this work, the ¯uorescent ruthenium complex, [RuII-Tris(4,7-diphenyl-1,10-phenanthroline)]2, (Ru-(Ph2phen)32) was chosen because of its highly emissive metal-to-ligand charge-transfer state
Even more, the paper contains discussion things like optical oxygen, and oxygen concentration.