Sensing Property And Technology Research On Fiber Optic Sensing In High And Low Temperature Environment

With the advent of fiber and the development of fiber optic communication, fiber optic sensor has been becoming mature in recent years. And the technology popularization and formation of industry has also gradually become a reality. Optical fiber and light are used as the sensor medium and carrier to detect the force, deformation, displacement, temperature and different parameters of the object to be tested in the optical fiber sensing technology. As the optical sensor, optical fiber sensor technology possesses the unique advantages which are different from those of traditional sensors, including small size, light weight, good long-term stability, long distance transmission, immunity to electromagnetic interference and so on. According with the demand of modern sensor technology, fiber optic sensors which have the potential to be widely applied in the aircraft engine, metallurgy, fusion reactors and large superconducting magnet get continuous promotion and rapid development. High or low temperature hampers the application and popularization of the fiber optic sensing, therefore the theory and technology research on high and low temperature resistance fiber optic sensing are necessary and important.The characteristics of fiber Bragg grating in the high temperature and low temperature environment are studied. Experiments are operated to analyze microscopic theory of the fiber Bragg grating decay and to test the high temperature performance as well as temperature stability of the fiber Bragg grating. The chirp phenomenon of fiber Bragg grating in liquid nitrogen is also tested.High temperature resistance fiber Bragg grating which can be used at the temperature as high as700℃is fabricated to solve the problem of fiber Bragg grating decay at the high temperature. The encapsulation technology of the fiber Bragg grating temperature sensor is proposed and the temperature sensing characteristic of fiber Bragg grating is tested.Strain sensing technology of fiber Bragg grating at the low temperature is discussed. Fiber Bragg grating is embedded inside the pulsed magnet coil to accomplish strain measurement of the pulsed magnet coil in liquid nitrogen.Fiber optic sensors are sensitive to both strain and temperature. Fiber Bragg grating is too fragile to be used as the strain sensor at the high temperature. In order to solve these problems, the multiplexed fiber optic technology is studied, including simultaneous strain and temperature measurement, basic theory of multiplexed fiber optic sensor, high temperature resistance encapsulation technology of the multiplexed sensor and the strain characteristic of the sensor at the high and low temperature. Experiments show that the multiplexed fiber optic sensors have favorable sensing property.