Fiber-optic photoacoustic gas sensor with temperature self-compensation

A high-precision fiber-optic photoacoustic (PA) gas sensor with temperature self-compensation is reported. The target gas diffuses into a micro-chamber and absorbs the laser energy to generate a PA signal, which is detected by a Fabry–Perot interferometric cantilever. The temperature affects not only the acoustic sensitivity of the cantilever, but also the PA conversion efficiency. The test result of the PA frequency response demonstrates that there is a temperature-insensitive operating frequency of 1208.4 Hz in the range of 0–80°C. The temperature self-compensated measurement was realized by setting the laser modulation frequency to 604.2 Hz and using the second-harmonic detection technique.