H2S浓度检测的发展趋势是实时检测, 基于光谱吸收原则是其中一个发展方向。 用宽带光源替代以往使用的成本较高的窄带光源, 降低整个系统的成本, 可以提高检测系统的实用性。 宽带光源经过Bragg光纤光栅滤波后可以得到窄带光。 此方法得到的光波必然会有噪声和波动, 然后对其进行滤波, 消除一部分系统的噪声和波动, 再通过光线分束器分别通入检测光路和参考光路后做差。 此差分信号不仅消除了一部分系统噪声和波动, 还消除了基波分量, 增大了信噪比。 用数学分析的方法推导出二次谐波信号, 利用SIMILINK仿真观察此信号, 不同浓度的H2S气体会有不同的输出信号, 也就得到了气体的浓度。 双光路差分法、 谐波检测技术和窄带滤波技术综合起来的优势是降低了成本, 增加了信噪比, 提高了系统的检测能力。 实验仿真结果表明, 在LED宽带光源基础上采用提取谐波信号的双光路差分方法检测H2S气体浓度正确可行, 此方法降低了系统成本, 为大范围实际应用提供了可能性。

Nowadays, the development trend of H2S concentration detection is real-time detection. The method based on spectral absorption principle is one of the development directions. The broadband light source was used to replace the high cost narrow band light source used in the past, so as to reduce the cost of the whole system and improve the practicability of the detection system. Narrow band light can be obtained by Bragg grating filtering for broad band light source. The light wave obtained by this method must be noise and fluctuate. So it was filtered to eliminate the noise and fluctuation of part of the system, and then the light beam splitter was used to make the difference between the detected optical path and the reference optical path. The differential signal not only eliminated part of the system noise and fluctuation, but also eliminated fundamental wave component. The useful signal value was relatively large, and the signal-to-noise ratio was increased. The second harmonic signal was deduced by mathematical analysis. The second harmonic was observed by SIMILINK simulation. Different concentrations of H2S gas would have different output signals, and the concentration of gas would be obtained. The advantages of the dual optical path difference method, harmonic detection technique and narrow band filtering technology were that the cost was reduced, the signal-to-noise ratio was increased, and the detection capability of the system was improved. The experimental results showed that it was feasible to detect H2S gas concentration by using the dual optical path difference method to extract harmonic signal on the basic of LED broad band light source. This method will reduce the system cost and provide the possibility for large-scale practical application.