Study On Fiber Grating Temperature Sensor Technology In Airborne Environment

Today's aerocraft, playing an important role in military affairs and national defense of a nation, is an important manifestation of the comprehensive national strength. The working environment of aerocraft, which is a very complicated structure, is always extremely harsh and inconstant. So it seems more important to monitor the aerocraft's structure and working condition effectively and rapidly for its safe and steady working.The temperature is a vital parameter for the aerocraft. The traditional temperature measuring components, such as thermocouples, thermometer bulbs, resistance thermometer sensors and so on, which have made great contributions to the development of aerocraft , have all kinds of deficiencies and disadvantages. It is very fit for the safety monitoring of the aerocraft structure and its working condition, because the fiber grating temperature sensor has many excellent features compared to traditional sensors, such as small size, light weight, better resistance of electromagnetic interference, good corrosion resistance, easy multiplexing and so on.In this paper, firstly, the basic theory of fiber grating sensor technology is simply analyzed, and then FBG temperature sensor with thin stainless steel tube encapsulation and FBG temperature sensor with nickel tube after being plated with gold package are introduced mainly. Because of the harsh working environment of aerocraft, the low and high temperature properties of FBG temperature sensors have been researched, and the temperature properties of FBG temperature sensors with different capsulations have been compared. In the low temperature experiment, it is found that the bare FBG and the FBG plated with gold package have good repeatability and linearity, but under -60℃the FBG with thin stainless steel tube encapsulation has a central wavelength breaking, and the cause of the breaking has been expounded in details. The FBG plated with gold package is better to be applied to aerocraft. In the high temperature experiment, the high temperature properties of three kinds of FBGs which are made respectively from communication standard single mode fiber, high Germanium co-doped fiber and high Boron co-doped fiber have been studied. The temperature sensitivities of these three types of FBGs have been improved greatly after being plated with gold. Three kinds of FBGs have good repeatability and linearity, but at a large temperature area the nonlinearity appears; when being heated to a certain temperature, the FBGs will be destroyed, optical characteristics disappearing, and the three kinds of FBGs have different destroying temperatures. The failure mechanism and the cause of nonlinearity have been analyzed.The performance of the FBG demodulator as a key technology in FBG measuring system influences the performance of the whole measuring and monitoring system to a large degree. The DSP has been used in the demodulating system based on F-P cavity to increase the demodulating speed and improve the performance of the whole system.