| Fiber Bragg Grating (FBG) sensor is a new kind of optical passive components, it has unique advantages such anti-electromagnetic interference capability, light, corrosion resistance, high detection sensitivity and so on. Recently, the development of sensor detection technology is becoming mature gradually based on FBG. The FBG sensor has been widely used in the field of spacecraft industry, petrochemical, power electronics, civil engineering structures, biological chemistry and medical fields and so on. Currently, a large number of sensors are needed for structural monitoring and controlling in large-scale projects. For example thousands of sensors are necessary to monitor the large building structure. Therefore single FBG sensor can not fulfill these practical needs. Now domestic and foreign scholars began to pay more attention to the distributed FBG sensor system. A variety of distributed fiber Bragg grating sensing demodulation schemes has been proposed. However these schemes are mostly based on active demodulation technologies. In these methods, the wavelength of light is scanned by a single wavelength in the range of sensing spectrum and the optical signal is converted to electrical signal followed by wavelength. It can not be satisfactory in terms of demodulation rate, response speed, spectrum resource utilization. So it is necessary to develop a distributed multi-channel FBG demodulation system with high responsive, high accuracy and moderate cost.In this thesis, the wavelength demodulation technology of multi channel distributed FBG sensing network has been studied deeply. On the basis of analyzing the advantages and disadvantages of several common FBG demodulation methods, this paper proposes a multi-channel FBG sensor demodulation system based on Arrayed Waveguide Grating (AWG). This system consists of a broadband light source, isolator, optical coupler, circulator, FBG sensors, AWG, photoelectric detection circuit, amplifying circuit, low pass filter circuit, AD sampling circuit, ARM control circuit and PC monitoring software, etc. By the method of the strength, the temperature of the FBG sensor is demodulated. The STM32F107 is used as the control chip and the high-speed 8 channel ADS8345 is used to sample the real-time signal in this system. The multi-channel sensing data can be collected by the method of selecting ADS8345 chip in a poll mode. The main interactive mode software is completed based on LabVIEW2014, which achieves the function of the display, storage and analysis. Experiment has been carried out to test the single channel 8 FBG sensors. The experiment results show that the sampling rate is 1 KHz for each channel, the range of wavelength demodulation is 1545.30-1560.50nm, the demodulation error is not more than ±0.3?, the precision of wavelength demodulation is ±3pm and the wavelength resolution is 1pm. By extending the number of channel plate can realize more FBG sensor measurement. |
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