Here's how fiber optic sensors work: The system includes a light source, optical fiber, sensing element (or transducer), and a detector. Radiation absorption excites an orbital electron to a higher energy level. Heating the material enables the trapped states to interact with phonons and decay into lower-energy. A fiber optic sensor measures a physical quantity by modulating the intensity, spectrum, phase, or polarization of light traveling through the optical fiber system. They can detect very small objects, are particularly flexible to mount and are extremely resistant in harsh environments – even in high temperatures.