64-Gbit/s Optical-Domain Encrypted Chaotic Secure Communication Over 110-km Commercial Fiber

As a physical layer secure transmission scheme, optical chaotic communication has garnered significant attention for its notable advantages in transmission rate and transmission distance. However, issues like fiber link damage and hardware mismatches between transmitter and receiver hinder its advancement to higher speeds and longer distance. In this letter, we experimentally demonstrate chaotic secure communication of a 64 Gbit/s PAM-4 signal transmitted over 250km using a chaotic optoelectronic oscillator (OEO) system, achieving record-breaking capacity-distance products of 16000-Gbit/s•km in optical-domain encrypted chaotic secure communication using single-core SMF. In our laboratory validation, we utilized ultra-low-loss (~0.155dB/km), large-effective-area ( $\sim 150~\mu $ m2) SMF to reduce link losses and enhance OSNR at the receiver. A multi-span dispersion-managed fiber link, along with decision-directed least-mean square (DD-LMS) algorithm, is employed to address amplitude distortion caused by the fiber, modulation, and synchronization mismatches. Furthermore, we also successfully demonstrated in a 110-km deployed commercial optical fiber in Chengdu, China, presenting a cost-effective approach to strengthening commercial optical network security.