In this chapter, a temperature sensor is demonstrated based on four different techniques; intensity modulated fiber optic displacement sensor (FODS), lifetime measurements, microfiber loop resonator (MLR) and stimulated brillouin scattering. These sensors utilize light transmission properties through optical fibers to detect temperature. Fiber-optical thermometers can be used in electromagnetically strongly influenced environment, in microwave fields, power plants or explosion-proof areas and wherever measurement with electrical temperature sensors are not possible. Unlike traditional electrical temperature sensors (e., thermocouples, RTDs), fiber optic sensors offer significant advantages such as immunity to electromagnetic interference. To illustrate the principle of operation of this temperature sensor, consider the following diagram: In reference to the above figure, phosphor is excited by an ultraviolet light source (which limits the length of the silica-based feed fiber to a few tens meters) and the return spectrum is divided. Fiber optic temperature sensors are innovative tools that offer several advantages over traditional temperature sensors. Primarily used in challenging environments where standard sensors fail to deliver, these sensors have gained considerable traction in various industries.
