Characterization of Poisson Channel for Deep Space FSO Based on SNSPD Technology by Experimental Demonstration

摘要

Free Space Optical (FSO) systems rapidly increase their importance in very long-distance deep space communication scenarios. However, the high performance requirements of deep space FSO systems demand preliminary experiments, which are unmanageable in real conditions. Regarding this issue, an innovative approach for testing deep space optical communication links in controlled laboratory environment is developed. The proposed testbed is based on fibre optics technology and combines a couple of units, which represent a real deep space FSO link. The parameters of several different photon-counting receivers are discussed. Similar to already demonstrated deep space missions, the implemented optical receiver is Superconducting Nanowire Single Photon Detector (SNSPD) characterized with high single photon sensitivity and detection efficiency. Consequently, in this paper an authentic deep space Poisson channel is emulated and examined. The Poisson channel is theoretically defined as a special focus is put on its information capacity. Moreover, the description of the Poisson point process is supported by real SNSPD measurements in terms of high efficiency single-photon detection. The experimental results show clearly the single photon counts and dark count rate in dependence on applied SNSPD bias current. In addition, a figure presenting the SNSPD detection efficiency is provided.