The Detection Technology And Hardware Design Of Distributed Optical Fiber Sensor Systems

The rapid development of the intelligent sensor network has driven the research for the distributed fiber optical sensors in the field of long-haul intelligent controlling. As an important part of the distributed fiber optical sensor, the quality of the detection system is directly involved with the system performance, such as the measurement accuracy, the measurement range and the spatial resolution characteristics. Consequently, the improvement of detection performance has been the key factor for developing the distributed fiber optical sensor technology.This article focuses on the detection system of the distributed fiber optical sensor with two aspects:one is the distinction between the temperature and strain; the other is the design of the system board for high-speed data acquisition and signal processing. At first, the relation between the backward Rayleigh scattering optical power and stimulated Brillouin scattering (SBS) optical power as well as the relation between the temperature and strain is analyzed. Then, SBS combined with backward Rayleigh scattering distributed optical fiber sensing program for simultaneously demodulating the temperature and strain are proposed and discussed in theory. Secondly, according to the characteristics of backscattering signal of Raman scattering based distributed fiber optic sensor, we propose a high-speed data acquisition and signal processing system where the high-speed acquisition and signal processing designs of digital signal processor (DSP) and field programmable gate array (FPGA) including their hardware implementation methods in detail. Finally, we establish a 3 km distributed fiber sensor system based on Raman scattering by using the designed hardware components. Furthermore, experiment results are analyzed.The analyzed experimental results demonstrate that:Firstly, the distributed fiber sensor model combining the SBS and the Raman scattering is effective to demodulate the temperature and stress of the aim object. The resolution of the temperature is not only affected by the SNR (signal noise ratio) of the SBS signal and the backward Raman scattering signal but also the stress value and the stress demodulation resolution; Secondly, the DSP+FPGA program which possesses both the advantages of DSP and FPGA can improve the efficiency of the system and make the system work stably. Moreover, the system can offer a excellent platform for the software design; Thirdly, at room temperature, the 3℃temperature accuracy and 50 m spatial resolution are realized in the experiment.