The influence factors and optimization methods of the local oscillator power for coherent doppler lidar

Abstract

Coherent doppler lidar for wind is based on the heterodyne detection between local oscillator signal and the echo signal. Optimum optical local oscillator power is an important factor of the signal to noise ratio. The dynamic range of echo signal, the relative intensity noise and the photoelectric detector saturation effect are studied comprehensively as the local oscillator power influence factors for the first time. The expression of the local oscillator power and SNR is derived. Using the computer simulation, the conclusion that the dynamic range of the echo signal will not affect the optimum of the local oscillator is obtained. Selecting different values of the relative intensity noise, the curves of the SNR versus local oscillator are given. Comparing the SNR formula in the quantum limit with the derived SNR formula, the saturation effect of the photoelectric devices is studied.