Fig. 1. Block diagram of tunable diode laser absorption spectroscopy-wavelength modulation spectroscopy (TDLAS-WMS) gas detection system

Fig. 2. Block diagram of TDLAS-WMS based on field programmable gate array (FPGA)

Fig. 3. Signal generation circuit with AD9767

Fig. 4. Generation of double square wave signal. (a) Phase division; (b) simulation generation of double square wave signal

Fig. 5. Delay circuit of AD9501

Fig. 6. Compensation result of delay circuit

Fig. 7. Driving and detecting circuit of TDLAS-WMS

Fig. 8. Measured waveforms of proposed system. (a) Waveforms of laser control signal; (b) waveforms of double frequency reference signal

Fig. 9. Detection waveforms of TDLAS-WMS system based on FPGA