Range expansion of FMCW LiDAR by using a swept optical frequency comb and phase noise compensation

In frequency-modulated continuous-wave (FMCW) ranging, there exist fundamental limitations on the measurement distance, refresh rate, and depth resolution imposed by the bandwidth of the photodetector. In addition, the coherence of the light source degrades interferometric performance in long-range measurements, thereby constituting another limiting factor on the achievable measurement distance. In this paper, we propose a wavelength-swept optical frequency comb-based approach to overcome the bandwidth-imposed limitation. Furthermore, by applying a phase noise compensation (PNC) method originally developed for optical frequency domain reflectometry (OFDR), the coherence-related limitation is simultaneously mitigated, enabling long-range and high-precision FMCW LiDAR. The theoretical framework of the proposed scheme is presented, and proof-of-principle experiments under fiber-emulated long-delay conditions are performed to demonstrate mitigation of the bandwidth limitation using a wavelength-swept frequency comb with three discrete frequency components. In addition, the coherence-limited range is extended to 12 times that achievable with conventional FMCW schemes.