A narrow linewidth terahertz dual-comb spectrometer with an all-fiber adaptive clock and a real-time feedback loop

•A broadband, mode-resolved terahertz comb spectrum is obtained with narrow linewidth.•The adaptive-clock signal is obtained by all-fiber optical path and electronic signal processing.•The real-time feedback loop with active frequency stabilization is used to realize the long-term stability of the system.•Adaptive sampling effectively suppresses terahertz time-domain intensity jitter.