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为降低电路及光路噪声等对痕量气体检测精度的影响,达到进一步提高痕量气体检测系统精度的目的,选用超窄带激光器作为系统光源并以谐波检测原理及改进希尔伯特-黄变换(IHHT)滤波算法作为数据处理的核心算法构建高精度痕量气体检测系统平台。选取甲烷作为被检测对象,理论计算得当光源输出中心波长为1650.959nm时,该系统甲烷气体体积分数C与输出光强一、二次谐波比值I2f/If的相关系数为0.084639。将一定体积分数的甲烷气体通入平台光纤气室中进行灵敏度实验,实验结果表明应用IHHT降噪处理后C与I2f/If的相关系数由使用傅里叶变换(FFT)处理的0.062585提升到0.074884,且气体体积分数越低,IHHT的降噪效果越好。
In order to reduce the influence of circuit and optical path noise on the detection accuracy of trace gases and achieve the purpose of further improving the accuracy of trace gas detection system, the ultra-narrow-band laser is chosen as the system light source and harmonic detection principle and Hilbert-Huang transform (IHHT) filtering algorithm as the core algorithm of data processing to build a high-precision trace gas detection system platform. Select methane as the object of detection, the theoretical calculations when the light source output center wavelength of 1650.959nm, the system of methane gas volume fraction C and output light intensity, the second harmonic ratio I2f / If correlation coefficient of 0.084639. A certain volume fraction of methane gas is introduced into the platform fiber chamber for sensitivity experiments. The experimental results show that the correlation coefficient between C and I2f / If after applying IHHT noise reduction increases from 0.062585 using the Fourier transform (FFT) to 0.074884 , And the lower the gas volume fraction, the better the IHHT noise reduction effect.