Analysis of energy monitoring for a double-pulsed CO 2 integrated path differential absorption lidar at 1.57  μm.

For double-pulsed 1.57 μm integrated path differential absorption lidar, the transmitted pulse energy measurement is an important factor that can influence the uncertainty of CO ₂ concentration measurement. An energy monitoring experiment was performed to determine how to improve the measurement precision of the transmitted pulse energy. Ground glass diffusers were used to reduce the speckle effect during energy monitoring. The roughness and rotational speed of the ground glass diffusers were considered and compared. The normalized energy ratios between on-line and off-line echo pulses and on-line and off-line energy monitoring pulses were analyzed, and the Allan deviation was used to evaluate the energy monitoring results. Averaging 148 shots, the standard deviation of the normalized energy ratio reached 0.0757%, whereas the correlation between the energy ratio of the on-line and off-line energy monitoring pulses and the energy ratio of the on-line and off-line echo pulses was higher than 90%.