Fourfold extended-range of coherent LiDAR based on quadrature detection with 4x4 coupler

Coherent LiDAR is a highly sensitive sensing technology with immunity to ambient light interference and the ability to measure velocity. It emits a wavelength-swept light signal and calculates the beat frequency between reference and sample light to measure the distances of targets. Recent advancements in signal modulation techniques, particularly quadrature detection, have effectively improved the detectable range of coherent LiDAR. In this study, we employ a 4x4 coupler for quadrature detection and incorporate dual reference paths with varying optical delays through an optical switch. This approach achieves a fourfold range extension compared to the conventional setup, while utilizing the same laser source and data acquisition process.