The Intra-Cavity QEPAS Sensor Using Fiber-Ring Laser for C2H2 and CO2 Detection

An intra-cavity quartz-enhanced photoacoustic spectroscopy (QEPAS) sensor using fiber-ring laser is demonstrated. The sensor includes an erbium-doped fiber (EDF) intra-cavity laser and a quartz tuning fork (QTF), and realizes wavelength scanning through a piezoelectric transducer (PZT). The acousto-optic modulator (AOM) is used to modulate laser intensity at a frequency of 32.758 kHz. We use optical switches to detect acetylene (C2H2) and carbon dioxide (CO2) at 1530.37 and 1572.66 nm, respectively, based on the time division multiplexing (TDM) technology. The two-component gas sensor showed good linearity of 0.9996 and 0.9966, and could achieve a minimum detection limit (MDL) of 180.64 ppbv and 145.45 ppmv for C2H2 and CO2 detection, respectively.