56 Gb/s PAM4 physical secure communication based on electro-optic self-feedback hardware temporal phase encryption and decryption.

To guarantee information security from the lowest level of optical networks, it is essential to provide physical layer security in fiber-optic communication systems. However, it is challenging to realize high speed physical secure optical communication based on advanced optical modulation formats and pure commercial hardware components. In this work, we report an experimental demonstration of a high-speed 56 Gb/s PAM4 physical-layer secure optical communication system by employing an electro-optic self-feedback hardware module for temporal self-phase encryption and decryption without consuming any additional encryption channel. An encrypted 56 Gb/s PAM4 confidential signal is successfully decrypted after transmitting over 60 km single-mode fiber. The demonstrated scheme can not only be integrated with existing optical communication networks, but can also be used as a pluggable module, which may provide a promising solution for ultra-high speed physical secure optical communication by combining with advanced multiplexing technology in future.