A Quasi-Parallel DAQ Scheme for Wavelength Modulation Spectroscopy Tomography

Wavelength Modulation Spectroscopy Tomography (WMST) has been widely used for imaging of critical flame parameters, e.g. temperature distribution and species concentration distribution, in harsh environments. To better characterize turbulent flows in practical applications, it is highly desired to improve the temporal resolution of the WMST method. This paper presents a quasi-parallel data acquisition scheme for WMST, which can maintain the temporal response of a fully parallel system with cost-effective hardware implementation. The key idea is to multiplex among the channels on the fast modulated periods within each wavelength scan. The proposed method was validated by four-channel quasi-parallel data acquisition of the absorption data using a customized FPGA platform. The results show that accurate harmonics information can be extracted simultaneously for each multiplexed channel.