数字平均滤波是信号处理中一种常用的方法.在小信号检测中,使用数字平均滤波可以获得较高的信噪比,提高检测的灵敏度.本文提出了一种利用光学器件来实现数字平均滤波的新方法,应用于基于差分吸收检测原理的窄带扫描光源光纤气体传感系统.系统的输出是一段连续的光谱,包含有被测乙炔气体的多个特征吸收峰.系统使用法珀标准具ETALON和参考光栅提供波长参考,完成对输出信号的光谱重建.对相同波长范围的信号进行平均滤波,使气体的相同特征吸收峰重合,提高检测的灵敏度.利用光谱重建,克服了可调谐Fabry-Perot滤波器驱动电压和透射波长不稳定因素的影响.实验结果表明,本系统可以方便有效地实现光谱意义上的数字平均滤波,检测到较低浓度的乙炔气体,比较适用于工业化气体检测系统.%Digital average filtering is a widely used signal processing method. In small signal detection,digital average filtering can obtain higher signal-to-noise ratio and can improve the detection sensitivity. This paper puts forward a new method using optical device to realize the digital average filtering. Basing on difference absorption principle,a new optical fiber gas sensor system based on a scanning light source is presented, and a novel optical gas sensor system is designed. By utilizing ETALON and reference grating,it can provide reference wavelength,and realize the spectrum reproducing of the output signal. Therefore,the same spectral signals can be superposed. This method is able to overcome the uncertainty effect caused by the transmission wavelength of tunable Fabry-Perot filter and filter's driving voltage. Experimental results show that the gas detection sensitivity is remarkably improved and can detect fairy low concentration acetylene gas. The system is suitable for industrial gas monitoring.
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