自参考式光纤气体传感数据处理方法

Self-Reference Type Signal Processing in Fiber Gas Sensing System

气体检测是光纤传感领域的一大研究热点.在强度吸收型气体传感系统中,吸收致光强变化的检测直接影响到气体浓度的解调精度.以内腔吸收式气体传感系统为例,采用自参考式数据处理方法实现气体吸收谱线的自动识别与浓度解调.根据朗伯-比尔(L-B)定律,理论推导了光强检测误差对浓度解调误差的影响.采用自参考式浓度解调算法,提取了乙炔气体的吸光度曲线,并从理论和实验2方面计算了气体吸收峰的吸光度.分别采用自参考式和预参考式解调算法,再结合2种不同的拟合线型,计算了500组实验数据中9条乙炔气体吸收谱线的吸光度.结果表明,采用自参考式解调算法-Lorentzian拟合时解调误差最小且不超过250×10?6.再结合波长扫描理论,浓度传感的解调精度可得到进一步提升.

Gas detection is one of the focuses in optical fiber technology. In intensity absorption type gas sensing system, the demodulation precision of gas concentration is influenced by absorption induced intensity variety. Taking intra-cavity absorption gas sensing system as an example, recognition of gas absorption spectrum and concentration demodulation can be realized by using self-reference type signal processing. According to Lambert-Beer Law, influence of optical intensity detection error on concentration demodulation error can be deduced theoretically. Using self-reference type demodulation algorithm, the absorbance curve of acetylene was obtained. And the absorbance of absorption peak was calculated theoretically and experimentally. By using self-reference and pre-reference type demodulation algorithm respectively, and by combining two fitting line-types, absorbance of nine absorption lines obtained from five hundred experiments was calculated. It is indicated by the results that the minimum demodulation error of less than 250× 10^- 6 can be obtained by self-reference type demodulation algorithm and Lorentzian fitting linetype. Combined with wavelength sweep technology, demodulation precision can be improved further.