Design Of Optical Fiber Bragg Grating Sensor Demodulation System For Smart Grid

With the development of optical communication technology, optical fiber sensing technology has attracted more and more attention, and has became an important research topic in the field of sensing. Fiber Bragg grating(FBG) is a new type in the field of optical fiber sensing technology, it has electrical insulation, anti-electromagnetic interference, high sensitivity, small volume and light weight etc. advantages, and it is easy to set up a sensor network by using multiplexing technology, realize the distributed measuring system, so it is widely used in the field of aerospace, energy, chemical industry, power monitoring etc. It is the premise of the application that how fast and effective to demodulate fiber grating sensing signal. However, the cost and the volume of the demodulation system limits its development in engineering. Therefore, it is a key point to design a practical fiber Bragg grating demodulation system with low cost, miniaturization.This paper analyzed the development of fiber grating sensing technology at home and abroad contrasted the advantages and disadvantages of commonly used demodulation method based on the deep understanding of the principle of fiber grating demodulation. And selected the tunable F-P filter as the demodulation method for this paper with the consideration of practicability and feasibility, and constructed distributed sensing network by the technology of wavelength division multiplexing.The hardware circuit part in this paper introduced optical components used in the system,and chose the type of these optical components according to the requirements of the system. Completed the hardware circuit structures using FPGA as core processor, the hardware circuit includes F-P filter drive circuit, photoelectric detection circuit, A/D conversion circuit. Finally, this paper completed the design of monitoring circuit software with the development platform of LabVIEW. The monitoring software realized on-line monitoring function, it can display the real-time data collected form lower machine through the serial port.The signal processing part is the core of the whole system. Firstly, this paper carried on the wavelet threshold denoising algorithm to the collected signal in order to remove the high frequency noise, and improve the signal to noise ratio. This paper constructed a new threshold function based on the soft and hard threshold function and existing threshold function from the existing literature. This function has better advantages in the treatment of noise. Then calculated the value of measured materials throuth the center wavelength, which was obtained by the peak searching algorithm.Finally, this paper analyzed the detection results of the whole demodulation system, and simulated the new wavelet threshold function. And through the temperature sensing experiment, the threshold function denoising algorithm proposed in this paper was applied to the demodulation system. The results show that the system has good linearity to temperature detection, and the detection accuracy meet the needs of the project, has achieved the anticipated design goal. It also has the significance of further research and development.