基于直接探测相干接收阵列的空间分集高灵敏度空间激光通信研究

Free-space coherent laser communication has unique advantages in high-speed information transmission due to its high spectral efficiency, but it requires higher receiving sensitivity in principle, especially under the atmospheric turbulence. Space diversity based on arrayed receivers is effective to improve the receiving sensitivity. However, the existing arrayed coherent receivers are all based on the principle of balanced detection, and a pair of balanced photodetectors have to be used to receive a branch signal. In this project, we plan to study the high-sensitivity free-space laser communication using the space diversity based on single-photodetector direct-detection coherent receivers. Coherent modulation formats will be directly detected by a single detector, and the space diversity technology based on arrayed direct-detection coherent receivers will be explored to improve the receiving sensitivity. The receiving sensitivity of 10 dB PPB is pursued for 20 Gb/s high-speed coherent signals. Also, the receiving performance of the spatial diversity based on direct-detection coherent reception will be tested using high-speed coherent modulation formats under simulated atmospheric environment and outdoor long distance conditions. This project will be the first exploration of the space diversity based on direct-detection coherent receivers. It will provides important theoretical guidance and practical techniques for long-distance and high-speed coherent free-space laser communications, and provides references for the future space communication applications in the fields of military and civilian.

相干空间激光通信因其高频谱利用率在高速信息传输方面具有独特优势，但从原理上需要更高的接收灵敏度，特别是在大气湍流影响下提高灵敏度至关重要。基于接收机阵列的空间分集可以有效提高接收灵敏度，但现有的相干接收机阵列都是基于平衡探测原理的，接收一个分支信号需要一对平衡光电探测器。本项目拟研究基于单探测器直接探测相干接收空间分集的高灵敏度空间激光通信，利用单个探测器直接探测多进制相干编码信号，将直接探测相干接收机组成接收阵列，研究其空间分集对多进制相干编码信号接收灵敏度的提高，将20 Gb/s以上高速信号的接收灵敏度提高到10 dB PPB，并在模拟大气和室外长距离条件下实验测试基于直接探测相干接收空间分集技术的高灵敏度相干空间激光通信链路性能。本项目是对直接探测相干接收空间分集问题的首次探索，将为长距离高速相干空间激光通信提供重要的理论指导和实用技术，为未来军事和民用领域的空间通信应用提供参考。

相干空间激光通信因其高频谱利用率在高速信息传输方面具有独特优势，但从原理上需要更高的接收灵敏度，特别是在大气湍流影响下提高灵敏度至关重要。基于接收机阵列的空间分集可以有效提高接收灵敏度，但现有的相干接收机阵列都是基于平衡探测原理的，接收一个分支信号需要一对平衡光电探测器。本项目研究了基于单探测器直接探测相干接收空间分集的高灵敏度空间激光通信。分析了使用单个光电探测器从混频光场中恢复完整相干信号的原理，并建立了多进制相干编码信号从发射端到接收端的完整大气传输理论模型，得到了基于单探测器直接探测相干接收阵列的优化配置方案，并实验实现了20 Gbit/s的QPSK信号空间分集接收，采用双SPD相干接收机阵列实验获得了2~3 dB的性能增益；将OFDM信号与空间分集接收相结合，进一步提高了空间激光通信的系统性能；建立了无人机空间激光通信的链路模型，分析了空间分集接收对无人机光通信链路的性能提升。本项目是对直接探测相干接收空间分集问题的首次探索，这些研究工作的开展，为实现高灵敏度的长距离高速相干空间激光通信奠定了理论和实践基础，为未来军事和民用领域的空间通信应用提供参考。