Chaotic Non-Orthogonal Matrix-Based Encryption for Secure OFDM-PONs

We propose and experimentally demonstrate a novel encryption scheme to enhance the physical layer security in broadcast passive optical networks (PONs). We exploit, for the first time, a new dimension using non-orthogonality for encryption. Different from the conventional masking of data, the proposed chaotic non-orthogonal matrix (CNOM) can also dynamically scramble the number of subcarriers in an orthogonal frequency division multiplexing (OFDM) signal while maintaining the same bandwidth to further deceive potential eavesdroppers. By simultaneously using faster-than-Nyquist signaling and redundant precoding, the proposed scheme can achieve the compromise between spectral efficiency (SE) and resilience against system impairments, while increasing the overall key space. We then carry out a proof-of-concept experiment to verify the feasibility of the proposed CNOM-based encryption. Results showed that the transmission performance could be improved in addition to the security enhancement.