Optimizing of laser source parameters for FMCW automotive LiDARs

Integrated FMCW LiDARs and their application in Advanced Driver Assistance Systems besides photonic integration involve meeting the vital requirements for accuracy, range detection and object velocity. Automotive LiDARs need to provide a high detection probability and ranging accuracy of moving objects at distances up to hundreds of meters. Precision control of the modulation waveform keeping a high degree of coherency is the pre-requisition for reliable ranging. We have separated the terms of frequency linearization and stabilization, which are responsible for the linearity of the detected response, accuracy, and detection probability of a LiDAR. The required phase-locked loop bandwidth maximum of 500 kHz for the laser control system is specified for a 300-meter measurement range. Requirements for a laser modulation waveform linearity for FMCW LiDAR could be simplified by introducing the scaling factor that is strictly determined by the residual deviation function. Additionally, the practical aspects of laser linewidth and frequency noise density spectrum distribution influence on the detection probability are demonstrated. As a result, optimized criteria for laser swept source performance are proposed, which can be used for the development of long-range detection systems. Finally, the practical results of frequency chirp characterization and ranging performance over 100 meters are demonstrated.