A LiDAR system includes an optical subsystem with an optical axis. The optical subsystem includes an optical source to emit an optical beam, a first optical lens to transmit the optical beam, an optical window to reflect a first portion of the optical beam to generate a LO signal, an optical scanner to transmit a second portion of the optical beam to a target to scan the target to generate a target return signal, where the LO signal is disposed to be decentered from the optical axis on a second optical lens in front of a photodetector (PD) to increase a percentage of an overlap of the LO signal and the target return signal on the PD.