The concentration of trace ethyne gas dissolved in transformer oil can adequately reflect whether overheating and discharge failures occur inside the transformer. Photoacoustic spectroscopy is becoming an effective monitoring method for online gas detection. However

in traditional photoacoustic spectroscopy

electric microphones are usually used to detect the photoacoustic signals. Weak electrical signals are easily affected by the strong electromagnetic field environment around the transformer

which seriously affects the stability and sensitivity of trace gas detection. We researched the detection of trace ethyne by photoacoustic spectroscopy based on fiber-optic acoustic sensors.Combined with fiber laser power amplification technology

the excitation light power at an absorpti

on wavelength of ethyne was increased from 20 m W to 200 mW. The fiber-optic cantilever acoustic sensor head was made to match the resonance frequency of the resonance photoacoustic cell

which realized the dual resonance enhancement of the cantilever and the resonance photoacoustic cell. Wavelength modulation technology was used to detect the gas concentration with the second harmonic amplitude of the photoacoustic signal. The photoacoustic spectroscopy system based on fiber-optic acoustic sensors was built for trace ethyne detection

and stable detection of trace ethyne with good linearity

goodness of fit of 0.99

and detection limit of 15×10

-9

could be realized.