Differential FMCW-LiDAR for breaking the limit of laser coherence

Abstract

One of the serious limitations in frequency-modulated continuous wave light detection and ranging (FMCW-LiDAR) is the maximum ranging distance as imposed by the coherence of light sources. The author proposes and demonstrates a new technique for overcoming the limitation using differential detection scheme between the frequency-fixed carrier and frequency-modulated subcarrier, which are generated from a single laser source. In the proof-of-principle experiment, two reflection points with a 3 m separation are clearly resolved at distances 192.2 m and 1.504 km using a distributed feedback (DFB) laser with the coherence length of 70 m.