Abstract: A study of denoise for spectrum signal is conducted for solving huge noise problem of direct absorption oxygen spectroscopy. Mass flow measurement of gas illustrates that the oxygen spectrum needs higher signal noise ratio (SNR). In the process of spectrum measurement，signal was interrupted by several steps，such as signal generator. After analyzing these step noises，the sources of sinusoidal noise were excluded. Using auto-balanced detection，the ‘sinusoidal noise’ was cleaned. By calculating the oxygen concentration by denoised signal，the precision is higher than 1%. This has demonstrated the suitable application in this field. At last，small oxygen spectrum signal detection was explored，and the absorbance is at the level of 10-3.

Key words: Direct absorption spectroscopy；Gas mass flux；Noise cancellation；Small oxygen spectrum signal

摘要： 针对直接吸收氧气光谱信号噪声较大的问题，开展了光谱信号降噪研究。以气流质量流量测量为例，说明氧气光谱信号的SNR(信噪比)要求较高。在光谱信号的测量过程当中，信号受到信号发生器等多个环节的干扰。经过对信号发生器噪声等信号进行分析，排除了“正弦噪声”的上述来源。采用自平衡检测方法，去除了该“正弦噪声”。通过对降噪后信号进行氧气浓度计算，其结果精度优于1%，证明了该方法的适用性。利用上述研究成果拓展了微小氧气光谱信号的检测能力，其光谱吸光度在10-3量级。

关键词: 直接吸收谱技术；气流质量流量；噪声消除；微小氧气光谱信号