Research on methods to enhance heterodyne photons utilization efficiency in coherent detection based on GM-APD

The GM-APD photon coherent detection system is capable of extracting information such as echo distance, intensity, and phase from the frequency domain, achieving a sensitivity at the single-photon level, which makes it suitable for detecting weak signals. In this system, the heterodyne photons utilization efficiency significantly impacts the signal-to-noise ratio (SNR). Therefore, methods to enhance the heterodyne photons utilization efficiency are proposed. Firstly, a clustering method is employed to ensure that each pixel of the detector corresponds closely to an optimal value of local oscillator (LO) light intensity, this approach addresses the issue of low heterodyne photon utilization caused by uneven light spots. Secondly, the work proposes LO modulation as a solution to mitigate peak noise generated by the LO that reduces heterodyne photon utilization. Finally, an experimental setup based on GM-APD photon coherent detection is established, comparative experiments are conducted to validate the effectiveness of these two proposed methods. Through all-fiber experiments, it was verified that the application of clustering methods improved the average single-pixel SNR by 1.7 times compared to the pre-clustering scenario. Building upon this clustering approach, modulation of the LO further enhanced the system’s mean SNR by an additional 93 %.