A new kind of wavelength scanning spectroscopy was proposed and demonstrated, based on a free-running fiber laser frequency comb centered at 1560 nm with bandwidth of 25 nm working as a highly coherent broadband light source. A phase-shifted fiber Bragg grating (PS-FBG) was used with a tunable filter to form an ultra-narrow-bandwidth transmission module and to generate narrow-linewidth probe light, scanning across the gas absorption line. The absolute gas absorption spectrum was measured by using the radio-frequency (RF) pulse intensity demodulation in the forms of frequency beating and lock-in amplification. Gaussian process regression (GPR) algorithm was developed for spectrum recovery and gas concentration retrieval, especially for conditions with low signal-to-noise ratio (SNR). The absorbance detection limits were tested as 2 × 10 for integration time of 0.4 s and 8.1 × 10 at 100 s. Multi-channel gas monitoring for CO, CO and NH was conducted via cascading PS-FBGs with different π-phase-shift wavelengths. The proposed wavelength scanning spectroscopy with capacity of absolute gas absorption spectrum measurement has advantages of calibration free, broadband, high precision and high stability, which is suitable for multi-channel gas sensing applications.

中文翻译：

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基于自由运行激光频率梳和高斯过程回归算法的灵敏、免校准、多通道波长扫描光谱学，用于气体传感

提出并演示了一种新型波长扫描光谱，其基于中心为 1560 nm、带宽为 25 nm 的自由运行光纤激光频率梳作为高度相干宽带光源。相移光纤布拉格光栅（PS-FBG）与可调谐滤波器一起使用，形成超窄带宽传输模块，并产生窄线宽探测光，扫描气体吸收线。通过使用频率跳动和锁定放大形式的射频（RF）脉冲强度解调来测量绝对气体吸收光谱。高斯过程回归 (GPR) 算法专为光谱恢复和气体浓度反演而开发，尤其适用于低信噪比 (SNR) 的情况。积分时间为 0.4 s 时，吸光度检测限为 2 × 10 ，积分时间为 100 s 时，吸光度检测限为 8.1 × 10 。通过级联具有不同π相移波长的PS-FBG对CO、CO和NH进行多通道气体监测。所提出的具有绝对气体吸收光谱测量能力的波长扫描光谱仪具有免校准、宽带、高精度和高稳定性等优点，适合多通道气体传感应用。