Full-range CO₂ detection using dual-path WMS-DAS and multi-regime adaptive fusion

Tunable diode laser absorption spectroscopy (TDLAS) offers high sensitivity, selectivity, robustness, and real-time detection. However, most TDLAS-based sensors have a limited dynamic range, typically below 10⁴. Here, we propose a TDLAS-based method for full-dynamic-range CO₂ detection. A dual-path absorption cell is combined with a wavelength modulation spectroscopy-direct absorption spectroscopy (WMS-DAS) measurement strategy to realize full-range detection. A dual-logistic adaptive weighting algorithm is developed to fuse adjacent channels and suppress range-boundary discontinuities, enabling smooth and continuous transitions across adjacent detection regimes without hard switching. Experiments demonstrate that the proposed configuration and detection scheme enable CO₂ measurements from sub-ppm levels to 100% concentration, with a dynamic range of 3.3 × 10⁶, while achieving a 1σ detection limit of 0.3 ppm at an integration time of 72 s. The proposed method shows strong potential for applications ranging from trace-level environmental monitoring to industrial gas purity analysis.