A high-sensitivity compact dual-T-type resonant fiber-optic photoacoustic sensor for simultaneous detection of multiple gases

We propose a high-sensitivity compact dual-T-type resonant fiber-optic photoacoustic(DTR-FOPA) sensor for simultaneous detection of two gases. The designed DTR-FOPA sensor contains two T-type photoacoustic cells (PACs) and a cantilever-based fiber-optic acoustic sensor (CFOAS). The two T-type PACs are connected and the CFOAS is located in the middle of the two resonant cavities so that the photoacoustic signals from two resonant cavities can be measured simultaneously. Two collimators are mounted at each end of the two T-type PACs buffer chambers for transmitting the excitation light source. The performance of T-type PAC and CFOAS has been analyzed by theory and FEA software to obtain a highly sensitive dual gas sensor. The design high-performance CFOAS has a first-order intrinsic frequency of 2415 Hz and a sensitivity up to 17288 nm/Pa. Two distributed feedback lasers (DFBs) with wavelengths of 1532.8 nm and 1650.96 nm, a spectral demodulator, and a DTRFOPA sensor are used to realize a high-sensitivity simultaneous detection of methane (CH4) and acetylene (C2H2) gases. The minimum detection limits (MDLs) for CH4 and C2H2 are 65.7 ppb and 4.3 ppb, respectively with the integration time of 100 s, and the corresponding NNEA are 6.648 x 10-9 W center dot cm- 1 center dot Hz- 1/2 (CH4), 9.71 x 10-9 W center dot cm- 1 center dot Hz- 1/2 (C2H2). The miniaturized DTR-FOPA sensor features sensitivity and all-fiber optic connectivity, providing direction for long-range trace multi-gas simultaneous sensing.