The Research Of The Fiber Grating Demodulating System Based On FPGA

FBG sensors can measure temperature, strain parameters, with electromagnetic interference resistance, good stability, multi-point measurement, so the building structure monitoring, aerospace and other fields has been applied. At present, China’s machinery and equipment urgently needed to provide multi-parameter, multi-point, stable and reliable condition monitoring tools, FBG sensors offer many advantages just an effective way to monitor machinery and equipment condition monitoring. However, the conventional fiber grating sensor demodulation devices, there is a larger, more expensive, restricted use conditions and other issues, such as resolution and wavelength demodulation is difficult to meet the requirements of machinery and equipment condition monitoring, limiting the fiber grating in this area.Aiming at the fiber grating sensor demodulation equipment problems in study design a more low-cost, portable, stable performance of the sensor demodulation device, by comparing the various sensors signal demodulation, select the system is highly integrated, environmental adaptability linear CCD spectral imaging method as demodulation equipment proposals, choose SOPC as an embedded demodulation kernel build this project required FBG sensor demodulation system.Fiber grating sensor demodulation system hardware design to FPGA this topic for the control circuit core, the use of technology to build Nios II soft-core microprocessor, which combines the advantages of FPGA logic control and soft-core embedded powerful digital signal processing ability. In SOPC Builder development environment to customize the CPU, PIO, memory, UART and other components, design and development of the A / D data acquisition and storage circuit, linear CCD driver circuit and a multi-channel optical switch drive circuit, and use in the FPGA Verilog HDL developed a drive logic to achieve a light switch, a photoelectric conversion spectral signal conditioning, data acquisition and storage functions. Demodulation system software part, by fitting Gaussian peak searching algorithm and spectrum-related peak searching algorithm analysis, algorithm implements the various wavelengths corresponding demodulation scheme Nios II software. Developed LabVIEW PC testing software, functional demodulation system to facilitate verification.Experiments show that the optical fiber grating sensor demodulation system based on FPGA realizes the high integration, high resolution of the demodulation system requirements, at the same time show that gaussian fitting and spectral correlation both wavelength demodulation algorithm can meet the accuracy requirements, effectively improve the center wavelength demodulation of fiber Bragg grating sensor resolution, by contrast, spectrum correlation peak algorithm has higher stability, and find peak gaussian fitting algorithm has the advantage of less computational complexity. Related wavelength using a spectrum demodulation algorithm, accuracy of ? 3pm, fiber grating temperature sensor temperature measurement accuracy of ? 0.4 ℃.The high integration, high resolution will promote fiber Bragg grating sensor demodulation system application in the field of machinery and equipment condition monitoring.