40 Gb/s Secure Coherent Optical Communication Based on Electro-Optic Phase Feedback Encryption

In the current context of information explosion, securing the physical layer in the backbone networks of coherent optical communication is vitally important. In this letter, we experimentally validate a secure communication scheme for coherent optical communication systems based on electro-optic phase feedback encryption, thereby successfully transmitting a 40 Gb/s dual-polarization quadrature phase shift keying (DP-QPSK) signal over a distance of 180 km. By strategically incorporating a delay line interferometer and a dispersion component within the electro-optic feedback loop, it is possible to generate random phase scrambling at a moderate modulation depth. With the utilization of commercial hardware, the encryption of DP-QPSK signals can be seamlessly accomplished in a plug-and-play manner, removing the necessity for additional synchronization or key distribution systems. The proposed scheme paves a new way to protect the polarization-multiplexing signals and offers a promising approach for secure coherent optical communication system.