Fiber-optic photoacoustic gas sensing: a review

Fiber-optic photoacoustic (PA) sensing has important applications in trace gas detection. The fiber-optic Fabry-Perot acoustic sensor implemented applying a cantilever is a novel and highly sensitive PA detector. Demodulation technologies such as intensity demodulation, optical cross-correlation demodulation and spectral demodulation are the key to improving the performance and engineering applications of fiber-optic PA sensors. For the detection of weak PA signals, the white-light interferometry based lock-in detection method is highlighted. On this basis, the miniature fiber-optic PA sensor with the special characteristics of high sensitivity, intrinsic safety, long-distance measurement, and immunity to electromagnetic interference can be designed by combining the cantilever and PA probe. This review also outlines the application of cantilever-enhanced fiber-optic PA sensing technology in the fields of online analyzing of high-voltage electrical equipment, leakage gas monitoring, coal mine spontaneous combustion monitoring and environmental gas monitoring. Finally, the future trend of fiber-optic PA sensing is presented.