An All-Optical Photoacoustic Spectrometer for Remote Detection of Acetyelene Gas in Power Transformer

An all-optical photoacoustic spectrometer based on the diaphragm-based extrinsic Fabry-Perot interferometer (EFPI) fiber acoustic sensor for acetylene gas continuous and real-time monitoring at atmospheric pressure and room temperature is first developed. The diaphragm-based EFPI fiber acoustic sensor is used to replace the conventional acoustic sensor in this kind of spectrometer. A first longitudinal resonant PA cell with double absorption optical path is used, and a tunable erbium-doped fiber ring laser (TEDFRL) has been employed in conjunction with an erbium doped fiber amplifier (EDFA) to achieve highly sensitive remote interrogation of acetylene gas. With the wavelength modulation and lock-in harmonic detection method, the minimum detectable limit of 1.56 parts-per-billion (ppb) volume acetylene (Signal-to-noise=1, SNR=1) at the 1530.37nm transition line has been achieved in the laboratory. The advantages of all-optical photoacoustic spectrometer are immunity to electromagnetic interference, safely in flammable and explosive situations, and long distance sensing.