相比于传统的强度调制/直接检测（IM/DD）系统，相干系统具有更高的容量和功率预算，能更好地满足高容量无源光网络（PON）的需求。近年来，如何将相干应用于PON场景以更好地支撑未来高带宽业务已成为研究热点。文章从系统架构、相干简化、上行突发模式检测以及灵活PON 4个方面对相干PON关键技术研究现状进行了总结，并展望提出了激光共享上下行滤波器组多载波（FBMC）-PON和半导体光放大器（SOA）电流调控灵活PON方案。

With the increasing demand for space optical communication security, space chaotic optical communication has attracted a great amount of attention. Compared with traditional space optical communication, a chaotic optical communication system has a higher bit error rate (BER) for its complex system design. In order to decrease the BER of space chaotic optical communication systems, we introduce two diffractive optical elements (DOEs) at a transmitting terminal (Tx). That is because the commonly used reflective optical antenna at Tx blocks the central part of the transmission beam, which leads to a great amount of power consumption. Introducing the DOEs into the optical subsystem at Tx can reshape the transmission beam from a Gaussian distribution to a hollow Gaussian distribution so that the block of the secondary mirror in the reflective optical antenna can be avoided. In terms of the DOE influence on communication quality, we give a BER model based on a minimum-shift-key (MSK) space uplink chaotic optical communication system to describe the DOE function. Based on the model, we further investigate the effect of the DOEs through analyzing the BER relationship versus basic system parameters based on the BER model. Both different mismatch conditions of chaotic systems and different atmospheric turbulence conditions are considered. These results will be helpful for the scheme design of space uplink chaotic optical communication systems.