A tunable diode laser absorption spectrometry (TDLAS) system has been developed in order to apply it to an open atmospheric path which is often suffered from heavy scintillation. A quick scanning of the laser frequency and the digital signal processing architecture are employed to cope with it. The laser frequency is scanned over 4 ms around an absorption line of CH4 in 7μm band every 31ms.
Received signal is treated with a DSP system to achieve the best SNR and also to separate the absorption signal from scintillation. Column density of CH4 is produced on every laser frequency scanning. The adjoint spectrum algorithm is employed to achieve the separating capability.
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