Optical sensor for two-phase cooling vapor level measurement

An immersion cooling system includes an immersion tank defining an immersion chamber therein, an immersion working fluid, an energy source, an optical sensor, and a microcontroller. The immersion working fluid is positioned at least partially in the immersion chamber and the immersion working fluid has a liquid phase and a vapor phase. The energy source is positioned and oriented to direct an infrared beam through a portion of the vapor phase with a beam path and path length. The optical sensor is positioned in the beam path. The microcontroller is configured to determine vapor concentration in the immersion chamber based at least partially on data from the path length, the optical sensor, and the energy source.