Quantum-enhanced AFDM: a six-dimensional encryption scheme for reliable and secure optical fiber transmission

In this study, we address the challenges of performance and security in passive optical networks (PON) by proposing and experimentally validating a quantum-enhanced affine frequency division multiplexing (AFDM) PON system. Through comparative experimental analysis of chromatic dispersion tolerance characteristics, we demonstrate that AFDM signals achieve receiver sensitivity gains of 0.5 dB, 1 dB, and 3 dB over conventional orthogonal frequency division multiplexing (OFDM) systems in 30-km, 50-km, and 80-km standard single-mode fiber (SSMF) transmissions, respectively. For secure PON transmission, we introduce a six-dimensional (6-D) signal encryption scheme, where the generated random sequence with true randomness masks AFDM signals across multiple physical dimensions to resist brute-force attacks. Experimental validation in a 10-km 7-core fiber system verifies the synergistic integration of multi-core signal distribution and key management, with AFDM exhibiting a 1-dB performance advantage in crosstalk-dominated environments. Notably, the proposed framework demonstrates exceptional inter-core interference suppression while maintaining complete physical layer security, establishing a technological foundation for high-capacity secure optical access networks.