Research And Application Of Large Capacity Fiber Grating Sensor Demodulation System

With the developments of the embedded technology and internet technology, we focus more attention on the building large-scale distributed fiber sensor network with more stable performance and powerful function because of the requirements of more extensive and complicated configuration monitor system. As the key technology of the network, the research of large scale real-time fiber sensor system is necessary. The principle and technology of fiber grating sensor are illustrated deeply in this article. And base on the study, a demodulation solution for large-scale, real-time fiber grating sensor with tunable narrow source, which has been tested in the healthy monitor system for some large scale equipment, has been designed. The contents below are discussed in this article:(1) After analyzing the typical fiber sensor demodulation solution, a new large scale fiber grating demodulation solution based on the fiber grating sensor multiplexing technology is designed. Higher system capacity and better SNR have been realized in the experiments compared with the traditional demodulation solution.(2) The performances of traditional sensor source are analyzed and compared. Based on the deep study of EDFA and SOA working theory, the tunable ring cavity laser with EDFA and the tunable ring cavity frequency domain mode locked laser with SOA are designed respectively and used as source for fiber sensor demodulation system. The experiment result showed greater output optical power compared with the traditional source. Besides, the SNR and the capacity of system are enhanced greatly. The total system performance is improved obviously.(3) Based on the principle, characteristic and specification of fiber F-P filter, the tunable FP filter is developed in the experiment. The output spectrum of F-P filter based on V-groove collimation has 90nm free bandwidth,0.32nm 3dB bandwidth and less than 5dB insertion loss. The F-P cavity length can be adjusted with piezoceramics drive voltage. And the passband wavelength is variable with variable cavity length corresponding. The all specification can meet the requirements of fiber sensor system.(4) The real-time large scale FBG sensor demodulation system is studied and designed. Novel FPGA and high speed DSP chip, instead of traditional MCU, are applied in detecting grating signal. FPGA is used to realize the real-time signal detection of parallel fiber grating in high speed, and the high speed DSP can complete the system wavelength computing. The system has the capacity of high speed and real time process and could provide enough interface types to meet the requirements of Ethernet application. Because the application of tunable narrow band laser source and high resolution detection technology, the system has higher compute speed and resolution. And the high speed process and data conservation are combined, which improve the system performance greatly.(5) The application test of fiber sensor demodulation system in healthy monitoring of coal handling equipment was carried out. The system can work safely and stably, and the test result show well real-time monitor performance on dynamic response of the key test point, which achieve the performance testing in laboratory.