All-optical encryption/decryption of DmPSK signals with key steganography for photonic layer security

In the 5th Generation Fixed networks (F5G) era, full-fiber-connected optical networks support emerging bandwidth-hungry services. However, optical networks are vulnerable to attack by tapping or other methods, which has been paid more and more attention in modern optical infrastructure. Therefore, optical Exclusive OR (XOR) encryption/decryption for advanced modulation formats used for F5G appears as one of the promising technologies to guarantee security. Some current solutions either leave potential security hazards because of the degenerate four-wave mixing and keys without special treatment or are cost-consuming due to employing multiple wavelengths and coherent receivers. In this paper, a novel all-optical encryption/decryption system for Differential m-Phase Shift Keying (DmPSK) signals occupying only a single wavelength with key steganography is proposed and simulated. The proposed system mainly consists of a generalized XOR (GXOR) part and a steganography part. We implement the GXOR part by the cascaded IQ Mach-Zehnder Modulators and the steganography part by the Equvilent-Phase-Shifted Super-Structured Fiber Bragg Grating (EPS-SSFBG). The numerical simulation results demonstrate that the GXOR implementation can achieve reconfigurable encryption/decryption of DQPSK (m = 4) or D8PSK (m = 8) signals merely with a single wavelength and a differential direct-detection receiver. And the EPS-SSFBG can enhance key security in a cost-efficient method as well. The system can work at the recorded bit rate of 260Gbps, which can be applied to enhance the photonic layer security in F5G and beyond.