| Fiber Bragg Grating (FBG) has been widely applied in the sensing field because of its special advantages such as small volume, ease for multiplexing, immunity of electromagnetic interference and so on. Based on some multiple technologies, FBGs are distributed in the environment to be monitored, which is named as distributed FBG sensing system. How to demodulate the sensing signal, precisely and quickly, is the key of FBG sensing system. Although traditional methods, such as the method based on high-precision optical spectrum analyzer (OSA), can achieve the high precision and sensitivity, its big volume, high cost, and the lack of unit to translate optical signal to electric signal have greatly restricted practical application of FBG in the project field. Thus, research on high-sensitivity, low-cost and small-volume distributed demodulation technology is a hotspot in the FBG sensing field.Demodulation technology of distributed FBG sensing system based on matching filtering FBG was presented in this paper. The demodulation system is based on STM32F103 MCU with the core of ARM CortexTM-M3. Four serial FBGs in an optical fiber simulate distributed sensing network, while FBGs fixed on the surface of equi-intensity cantilever beam (EICB) act as matching device. Running mode of motorized precision translation stages, which is used to move EICB to match the sensing FBG, is dominated by MCU. Photodiode is used to convert the optical signal from transmitting port of matching FBG to eletrical signal provided to AD module of MCU. After the processing of MCU, the demodulation results, the environmental variables such as temperature and strain, are displayed on the LCD interface. The circuit part of the paper includes main control PCB, signal detecting PCB, source PCB and LCD interface PCB. The application program of demodulation system based on PC is designed to analyse the sensing data futher, which realize data exchange through USART communicaiton interface. |
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