METHOD AND SYSTEM FOR TIME SEPARATED QUADRATURE DETECTION OF DOPPLER EFFECTS IN OPTICAL RANGE MEASUREMENTS

In some implementations, a light detection and ranging (LIDAR) system includes a transmitter configured to transmit an optical signal that is output from a laser and modulated based on a modulating signal, a receiver configured to receive a returned optical signal in response to transmitting the optical signal, and a processor. The processor is configured to produce a first optical signal based on the returned optical signal and a first version of the modulating signal, produce a second optical signal based on the returned optical signal and a second version of the modulating signal, generate a digital signal based on the first optical signal and the second optical signal, determine a Doppler frequency shift of the returned optical signal based, at least in part, on the digital signal, and provide data indicative of the Doppler frequency shift to a vehicle.