A Lorentzian narrow-linewidth demodulation scheme based on a short fiber delayed self-heterodyne technique

We propose a narrow-linewidth demodulation method which utilizes a short-fiber-delayed self-heterodyne structure and coherent envelope spectral properties to restore the Lorentzian line shape of the laser output. The Lorentzian spectrum obtained using our scheme is consistent with that obtained using a traditional long-delay method, and here, the utilization of a short fiber avoids the broadening caused by 1/f noise. Both simulated and experimental results demonstrate that our scheme is effective and accurate. We demonstrate the recovery of a Lorentzian linewidth of 6.0 kHz, while maintaining higher accuracy than that achieved using traditional schemes (31.7 kHz). Our approach provides a feasible means of improving the accuracy and computational efficiency of narrow linewidth measurements.