Time delay calibration techniques for receiving arrays in SNSPD-based optical communication systems

Superconducting nanowire single photon detectors (SNSPDs) have attracted considerable attention in the field of free-space optical communications, especially for ultra-long-distance communications. Calibrating the inherent time delay in the optoelectronic circuit of SNSPD arrays is critical to enabling photon detection with high time accuracy. In this paper, we propose two methods for estimating the inherent timing error: Gaussian fitting calibration (GFC) and maximum-likelihood calibration (MLC). In particular, MLC estimates the timing error by taking into account the deadtime and jitter characteristics of SNSPD. Experimental results demonstrate the effectiveness of the proposed methods.