The principle of optical fiber temperature sensor

Temperature is an important parameter for quality control and smooth production in metallurgical, steel, welding and chemical industries. The traditional methods of temperature measurement are thermocouple and optical pyrometer, the thermocouple method is contact temperature measurement, such as platinum rhodium thermocouple, tungsten rhenium thermocouple, etc., the probe is placed in the measured environment, the temperature difference voltage passes through the circuit. After conversion, the temperature is directly displayed on the instrument, and the high temperature sintering furnace uses this method. Although the temperature sensors are easy to operate, the performance is stable, but because of the contact temperature measurement, the thermocouple is far away from the cold and hot ends, the volume is large, and the rare precious metals are used, the cost is expensive, the service life is short, the optical pyrometer method is In contact temperature measurement, the temperature is measured by comparing the color temperature of the radiation source and the color temperature of the filament, or a laser beam is emitted. The temperature sensor of the body is measured by the reflected beam of the body. The optical fiber temperature sensor has the advantages of high measurement precision, anti electromagnetic interference, small volume and free bending, and can be applied to flammable, explosive and empty. It is too narrow to aim at difficult situations directly, so it is widely valued.

Fiber optic temperature sensors are generally divided into two categories: one is to make use of some sensitive functions of the optical fiber itself to measure the temperature of the fiber, which belongs to the function type. The optical fiber can not only perceive information and transmit information, but the other is that the optical fiber only plays the role of transmitting light, and other sensitive elements must be added to the end of the fiber. The two types of sensors are very smart and have deep research work.

The optical fiber temperature sensor uses a polymer thermosensitive material matching the refractive index of the optical fiber to the outside of two fused fibers, so that the light energy is input from one fiber to the other fiber. Because the temperature sensitive material is affected by the temperature, the refractive index changes, so the output light power is obtained. It has a functional relationship with the temperature. Its physical nature is to use the characteristic parameters of the light wave transmitted in the optical fiber, such as amplitude, phase, polarization state, wavelength and mode, etc., and have sensitive characteristics to the external environment, such as temperature, pressure, radiation and so on. It belongs to the non - contact temperature measurement.