STM32 Based Real-time Peak Detection Of FBG

Fiber grating sensors can be used to measure physical quantities such as temperature,pressure,chemical composition and so on.Fiber grating sensors have some unique advantages such as high sensitivity,low preparation cost,easy reuse,no electromagnetic interference,good insulation,strong explosion-proof performance and corrosion resistance.These advantages make them gradually replace the traditional sensors.Therefore,FBG is very suitable for the measuring in high-intensity electromagnetic interference,explosive,flammable and high-voltage electric field environment.The demodulation of the traditional FBG sensor is usually realized by an Optical Spectrum Analyzer.However,this method is expensive and complex,So it cannot meet the needs of practical automatic control.In this paper,in order to reduce the size of the demodulator,tunable laser was used to obtain spectral data,which can not only meet the needs of practical automatic control,but also have the advantages of small size and low price.`At the same time the STM32F4 system instead of the computer was used to process data.It is convenient for use in some construction sites.Due to the tunable laser scanning interval is 10 pm,with this method the maximum accuracy can only reach 10 pm.In order to improve the accuracy,we need to use data fitting.The main contents of this dissertation are as follows:1.In this paper,the sensing mechanism of the sensor is introduced in detail,and then several commonly used demodulation techniques and related working principles are described.Finally,their advantages and disadvantages are analyzed in depth.2.The principle and development software of STM32F4 development board was summarized,and the structure of the whole system was introduced in detail.3.The demodulation algorithm was introduced.The reflection spectrum data of FBG is detected in real-time sent to storage devices,then the Levenberg-Marquardt(LM)algorithm was perform for Gaussian fitting to get the peak reflection wavelength.Finally,the fitting speed and fitting accuracy wasmeasured,The demodulation time is only 70 ms.The uncertainty of the peak detection is 0.87 pm when the tuning step is 10 pm.It is suitable for field use where real-time measurement is needed.4.Finally,the advantages and disadvantages of the design scheme based on FBG demodulation system was summarized.