A method of frequency-locking in Direct Detection Doppler Wind LIDAR

We introduce a data acquisition (DAQ) system for frequency-locking in Direct Detection Doppler Wind LIDAR (DWL). In DWL, double-edge technique based on Fabry-Perot etalon is used to detect the frequency shift. Tiny frequency shift could distinctly reflected in amplitude of output pulse from Photomultiplier Tube (PMT). Nevertheless, outgoing laser frequency is sensitive to temperature changes. Moreover, vibration would intensify the influence especially on vehicle-mounted DWL. The locking channel is designed for stabling the outgoing laser frequency. An approach of detecting the self-frequency shift in commercial DWL is to measure amplitude variation by PMT. Our DAQ system is designed for pulse signals sampling and processing. The system includes a DAQ hardware system and a dedicated DAQ software. The raw data sampled by hardware would transferred to DAQ software at PC via universal serial bus (USB). We use appropriative algorithm in data processing for relatively low sampling rate. Our system reports the same results as commercial oscilloscope and the tests show that the DAQ system meets the locking requirements.