波长调制技术在掺铒光纤腔内吸收气体传感中的应用

Application of Wavelength Modulation in Erbium-Doped Fiber Laser Intra-Cavity Absorption Gas Sensor

在掺铒光纤腔内吸收气体传感系统进行气体检测时,由于受到放大自发辐射噪声、标准具效应等因素影响,气体浓度检测信号强度和检测浓度极限受到了很大的限制。为了解决上述问题,将广泛应用于可调谐二极管激光器吸收光谱的波长调制技术应用到掺铒光纤腔内吸收传感系统,利用实验分析了二次谐波信噪比与泵浦驱动电流、调制频率以及调制深度的关系,从理论上分析推导的最佳波长调制深度也与实验得到的调制深度非常吻合。采用波长调制技术得到气体传感系统的检测浓度极限为140×10-6。

Erbium-doped fiber intra-cavity absorption gas sensor（ICAGS） system has been experimented and reported. But the sensitivity of gas detection and the minimum detectable gas concentration are limited by the existences of amplified spontaneous emission（ASE） noise, the etalon effects, as well as background noise of amplifier. In order to solve these issues, wavelength modulation technique, which has been used widely in tunable diode laser absorption spectroscopy, is applied to ICAGS system. The relationships between signal-to-noise rate of the second harmonic and pump current, modulation frequency and modulation depth have been analyzed based on experiments and the optimal values of them are also stated. The modulation depth which is based on experiments specially corresponds to the result of theory. The minimum of detectable gas concentration is nearly 140× 10^-6.