An all-optical photoacoustic spectrometer for multi-gas analysis

An all-optical photoacoustic spectrometer for multi-gas analysis is reported in this paper. The spectrometer consists of a near-infrared tunable fiber laser connected with an erbium-doped fiber amplifier in series, a fiber acoustic sensor and a first order longitudinal resonant photoacoustic cell. Due to the application of the diaphragm-based Fabry-Perot interferometric fiber acoustic sensor in this system, the all-optical photoacoustic spectrometer has the advantages of immunity to electromagnetic interference, safely in flammable and explosive situations, and long distance sensing. Simultaneous and continuous detection of trace methane, acetylene, carbon dioxide, carbon monoxide and water vapor (CH4, C2H2, CO, CO2, and H2O) are implemented. The detection limits (signal-to-noise = 1) of 87 ppm for CH4, 1.3ppb for C2H2, 4.6 ppm for CO, 5.5 ppm for CO2 and 24 ppm for H2O are demonstrated at atmospheric pressure and room temperature.