Enhancing Precision in Off‐Axis Integrated Cavity Output Spectroscopy Sensors Through Optimal White Noise Power Injection

Abstract Residual cavity mode noise is a primary limiting factor in the detection performance of off‐axis integrated cavity output spectroscopy (OA‐ICOS). The radio‐frequency white noise (WN) perturbation technique has emerged as a highly effective method for suppressing this noise. However, optimizing the WN injection power remains a critical challenge: insufficient power fails to adequately reduce cavity mode noise, while excessive power induces spectral distortion and hampers calibration, compromising measurement reliability. Here, for the first time, an optimal WN prediction model is presented that accurately simulates the suppression of cavity mode noise and spectral distortion under different injection powers. Using methane gas measurement as an example, a systematic trade‐off analysis and extensive simulations are conducted, determining the optimal WN injection power to be −33.98 dBm. At this power level, spectral distortion is kept <0.1% and cavity mode noise is suppressed by > 99%. A 10 h continuous stability test further confirms the effectiveness of this power setting: concentration drift remains <3.8 ppb, detection precision improves by 25.5%, and the response time for the minimum detectable concentration is shortened by a factor of 7.5. This work provides valuable theoretical guidance for the design of next‐generation cavity‐enhanced trace gas analyzers.