Calibration and enhancement of an intensity-coded NIR laser single-photon system for quantitative methane leak monitoring

Methane (CH₄) leakage monitoring represents a critical research direction for the accurate quantification of carbon emissions. This paper introduces an active laser detection technique that employs an InGaAs single-photon detector (SPD) combined with a continuous-wave laser and pseudo-random binary sequence (PRBS) modulation to simultaneously measure CH₄ concentration and distance. To mitigate the signal distortion caused by detector dead time in single-photon counting, an experimental validation system was established. A dedicated signal correction algorithm was developed to effectively reconstruct the received signals. The calibration characteristics of detector dead time and signal intensity under varying CH₄ concentrations were systematically investigated. By evaluating correction coefficients across different operational parameters, the PRBS-modulated CH₄ absorption signal was accurately restored, leading to significantly improved recovery of gas absorption intensity. Comparative validation with a reference photodiode detector showed average relative deviations of 2.8% and 5.1% for two different concentration levels, confirming the effectiveness of the proposed correction method. This work successfully demonstrates a signal reconstruction framework for single-photon detection and offers a novel solution and theoretical basis for future applications of InGaAs SPD in CH₄ and other greenhouse gas leakage monitoring.