Signal constellation shaping  

Zhi Zhang et al. from the School of Communication and Information Engineering, University of Electronic Science and Technology of China designed a constellation Reshaping chaotic encryption (CSCEn) scheme with statistical distribution controllable, as shown in FIG 2.  Firstly, orthogonal amplitude modulation (QAM) symbol sequences were divided into several sub-sequences, and probabilistic shaping (PS) was performed based on the statistical information (SI) (through constellation region substitution). Then, SI sequences were encoded and encrypted into chaotic signal phases using key distribution algorithm.  SI was extracted at the receiving end to recover the original signal [2].  The researchers successfully transmitted the encrypted ps-16-qam signal over a standard single mode fiber (SSMF) of 25km.  Because this scheme can not only realize flexible deployment with low complexity and improve the performance of sending and receiving signals, but also provide enough security to resist the attack from illegal optical network unit (ONU), it will undoubtedly have a good application prospect in the future.