The fibre optical sensor is completely non-conductive and offers complete immunity to RFI, EMI, NMR and microwave radiation with high temperature operating capability, intrinsic safety, and non-invasive use. The principle of operation is based on the temperature. High-temperature measurements above 1000 °C are critical in harsh environments such as aerospace, metallurgy, fossil fuel, and power production. Fiber-optic high-temperature sensors are gradually replacing traditional electronic sensors due to their small size, resistance to electromagnetic. 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. One type of fibre optic temperature probe consists of a gallium. Since the measuring chain is a functional combination of optical methods, optical fiber properties, and other photonic elements together with control electronic circuits, it is necessary to nd a suitable compromise between the chosen measurement method, fi measuring range, accuracy, and resolution. Fiber optic temperature sensors are immune to the many environmental effects that compromise other measurement technologies, can be embedded and installed in locations traditional temperature sensors cannot and deliver an unprecedented level of spatial detail and data without sacrificing precision. Distributed Temperature Sensing System (DTS) uses light as a carrier of temperature information, uses optical fiber as a medium for transmitting temperature information, and obtains temperature distribution at various points on the fiber. In addition, optical time domain reflectometry (OTDR) is.