CH₄/C₂H₆ Dual Gas Detection System for Urban Natural Gas Inspection Based on Off‐Axis Integrated Cavity Output Spectroscopy

ABSTRACT

A near‐infrared off‐axis integrated cavity output spectroscopic (OA‐ICOS) dual‐gas sensor for methane (CH₄) and ethane (C₂H₆) measurement was developed. Utilizing time‐division multiplexing (WDM) technology, dual‐gas detection was realized via the sensor system. The power distribution circuit was improved to make power distribution more reasonable and ripple smaller. The limit of detection (LoD) of C₂H₆ was effectively reduced by a new calibration method. With an averaging time of 1 s, the LoD is 1.2 parts‐per‐billion (ppb) for CH₄ and 12.1 ppb for C₂H₆. Extensive urban measurement unveiled three CH₄ anomalies, while the measured C₂H₆ levels demonstrated good capability of the sensor system for dual‐gas measurement.