Differential pseudo-random phase-modulated continuous-wave coherent LiDAR

This study presents a differential pseudo-random phase-modulated continuous-wave (DPR-PMCW) coherent LiDAR system designed for high-precision ranging of dynamic remote targets. The system employs a differential pseudo-random binary sequence (PRBS) to drive high-speed electro-optic phase modulation (EOPM). This approach eliminates the need for an independent local oscillator (LO) via what we believe to be a novel self-referenced interferometric receiver architecture. The receiver integrates a free-space unequal-arm-length Mach-Zehnder interferometer (UAL-MZI) with a polarization-maintaining 2 × 4 90° optical hybrid, achieving 1-bit delayed self-interference via precisely matched optical path differences (OPD) while enabling quadrature coherent detection. A matched filtering algorithm processes the interferometric signals to achieve millimeter-level ranging precision after analog-to-digital conversion (ADC). Importantly, the system exhibits inherent immunity to wavefront distortion through phase noise compensation, effectively suppressing random phase noise (RPN). The differential detection scheme passively compensates for Doppler frequency shift (DFS) without necessitating active frequency tracking. Collectively, these advancements address three critical challenges in dynamic target ranging: DFS interference, coherence length limitations, and RPN accumulation. Experimental validation confirms the system's capability for real-time, high-precision metrology of long-range non-cooperative targets under operational conditions. These results inspire an approach to implement real-time high-precision ranging of long-range rapidly-moving non-cooperative targets.