High sweeping linearity and optical intensity control of broadband FMCW laser source generation for 4D imaging LiDAR

Frequency-modulated continuous-wave (FMCW) light source is a key component in light detection and ranging (LiDAR) systems with high sensitivity and precision. In this paper, we report a triangular-waveform broadband FMCW light source based on pre-distorted injecting current of a distributed feedback (DFB) laser diode and a feedback control loop for keeping optical intensity constant during the frequency sweeping. A pre-distorted injecting current waveform generated by adaptive pre-distortion method is used to drive a DFB laser to generate FMCW light source. After 100 iterations, we achieved the effective frequency sweeping excursion about 31 GHz within 90% region of interest. The frequency sweeping nonlinearities of the down- and up-ramp were 3.10×10⁻⁹ and 5.32×10⁻⁹, respectively. The corresponding relative nonlinearities for down- and up-ramp were 0.00157% and 0.00206%. Due to the modulation of injecting current, the lasing optical intensity of DFB underwent undesired intensity modulation. To achieve constant optical intensity, we utilized a feedback control loop in combination with a Mach-Zehnder interferometer. By comparing the beat-note with and without feedback control loop, the intensity of waveform in the time domain was obviously corrected, which could further improve the ranging resolution from 4.59 mm to 4.30 mm.