Estimation of a calibration relation of TDLS spectrometer to measure a gas concentration of NH3 gas near-infrared region

A theoretical study has been implemented to enhance the detection limit of methane gas by tuning the wavelength of the open path tunable diode laser spectrometer (TDLS) in the near infrared region. MatLab code has been written to tune the accurate wavelength in the NIR region. Then, the frequency domain measurements have been carried out to extract the second harmonic as an indicator of gas existence. The results show the accurate wave length in NIR region is (1543.027 nm) and the measurement have been demonstrated at L = 100 m, the gas concentration was N = 0.05 to 0.5 ppb in 0.2 step for all gas measurement.