Fiber optic temperature measurement is a new technology developed only in the past decade or so. At present, fiber optic temperature measurement is still in the stage of research, development and gradual popularization. In temperature measurement scenarios that traditional methods cannot handle, it has gradually shown its outstanding characteristics. It can accurately measure target objects in strong magnetic fields, where ordinary infrared thermometers may cause large errors or even fail to work normally — such as the furnace temperature in high-frequency metal smelting, rubber vulcanization, and microwave baking of wood, textiles, food and medicine. Fiber optic temperature measurement has great advantages in these fields.

The principle of the fiber optic temperature sensor is mainly based on the optical time-domain reflectometry principle of optical fiber and the backward Raman scattering temperature effect. When a light pulse enters the fiber from one end, it propagates forward along the fiber. Because the inner cavity of the fiber is like a mirror, reflection occurs at every point during propagation, and a small part of the reflected light travels in exactly the opposite direction to the incident light. The intensity of this backward reflected light has a certain correlation with the temperature of the reflection point: the higher the temperature of the reflection point, the stronger the reflected light. In other words, the intensity of the backward reflected light reflects the temperature of the reflection point. Using this phenomenon, if the intensity of the backward reflected light can be accurately measured, the temperature of the reflection point can be calculated — this is the basic principle of temperature measurement with optical fiber.

A distributed fiber optic temperature sensor uses the entire transmission fiber as the sensor; every point on the fiber serves both "transmission" and "sensing" functions. In a distributed fiber optic temperature sensing system, when a strong pulse light signal is transmitted in the fiber, every point produces extremely weak backward scattering of the laser signal. According to the wavelength of the scattered light, it can be divided into Rayleigh scattering, Raman scattering and Brillouin scattering. Among them, the intensity of Raman scattering is strongly correlated with the temperature at that point. By detecting the intensity of the scattered light signal at each point, the temperature information at that point can be obtained, thereby obtaining the temperature distribution along the entire fiber.