Cascade integrator comb filter-aided calibration-free Wavelength Modulation Spectroscopy Tomography

Calibration-free Wavelength Modulation Spectroscopy (CF-WMS) technique has been widely applied to sense gas characteristics, e.g., temperature, concentration, in harsh environment for suppressing the measurement noise. While increasing modulation frequency can achieve better noise suppression, it burdens the WMS signal processing and data communication. In this paper, we present a WMS signal demodulation technique aided by cascade integrator comb (CIC) filter, aiming to significantly reduce the amount of data while maintain the demodulation accuracy with easy and cost- effective hardware implementation. By using the proposed demodulation method, it enables the real-time data streaming for the high-temporal resolution. More importantly, the fitting process for WMS-2f/1f signal is significantly accelerated. A numerical simulation is conducted to compare between the CIC-aided demodulator and the traditional method, showing that the computation time is significantly reduced. This scheme is also validated by a lab-scale single-path experiment.