Research On High Temperature Sensing System Of Optical Fiber Fabry-Perot

Nuclear safety verification test is an activity to verify whether the performance of an item conforms to the specified requirements by placing the item under a group of chemical,physical,environmental or certain operating conditions during nuclear safety correlation analysis,among which thermal-hydraulic verification test is the most common.The thermal and hydraulic experiments of the fuel assembly of nuclear power equipment generally use the electric heating element with the same shape and size to simulate the nuclear fuel element's nuclear release.Through temperature monitoring and analysis,the heat transfer mode in the core and inside the components,the heating law in the core,the relationship between the normal operation of each circuit and system and the temperature can be studied,which is crucial to the development of nuclear power equipment.FabryPerot(F-P)high temperature sensor is an all optical fiber sensor,which has the advantage of simple structure,small volume,high precision,oxidation resistance,EMI immunity,corrosion resistant and so on.It is a good candidate to realize high temperature measurement in working condition of the thermal-hydraulic experiment with high pressure and strong electromagnetic interference.In this paper,based on the basic principle of optical fiber F-P sensor,a non-scan correlation demodulation structure based on phase demodulation was established,and the mathematical model of the non-scan correlation demodulation system was derived.The principle of temperature measurement of fiber F-P high temperature sensor was analyzed,and the coupling model of temperature-structure-light of the sensor was also derived.According to the special working environment of optical fiber F-P high temperature sensor,the structure and package that meet those requirements are designed,the 4J29 cutting alloy metal capillary tube was selected as the sensitive material,and the fabrication process of the sensor is summarized.The optical structure design and hardware circuit design of the six-channel demodulation system are carried out.The six-channel demodulation system can realize the demodulation rate of 5KHz,the six-channel synchronization accuracy is 10 ns,the sensor range is from room temperature to 600?,the response time is fast,the temperature sensitivity is 35.96nm/?,the resolution is 0.18%FS.The experimental results show that the designed fiber optic high temperature sensor system basically meets the expected design requirements and can be used to monitor the temperature of fuel assembly in simulated thermal water experiment.