Random phase compensation method of coherent lidar based on symmetrical double harmonic signals

The coherent cumulative lidar based on the symmetrical double harmonic signals has been implemented and verified. In the system, the double harmonic signals are generated by the laser through an electro-optic modulator, and then the signal is divided into two paths, one of which is coupled to the transmitter as the signal light, and the other is used as the local light, which performs I/Q de-chirp processing with the echo reflected from the targets. The proposed lidar works at a wavelength of 1550 nm with a sweep bandwidth of 1 GHz, and a pulse period of 70us. This article respectively gives two processing methods in frequency domain and time domain to compensate for the random phase. Finally, the experimental results of coherent accumulation on stationary and moving targets show that the method can be excellently used to compensate for the random phase induced by atmospheric disturbance, vibration, and nonlinear effects of optical devices in the system, so that the phase can be stabilized within 0.4 rad in any complex environment, and the coherent accumulation efficiency can be improved to 90%. Therefore, this paper has great guiding significance for detecting the low detectable targets and improving detection distance.