Enhancing the Reliability and Security of OFDM-PON Using Modified Lorenz Chaos Based on the Linear Properties of FFT

This paper proposes a technique for enhancing the reliability and security of the orthogonal frequency division multiplexed passive optical network (OFDM-PON) based on modified Lorenz chaos. The chaotic mapping uses a modified three-dimensional Lorenz mapping, adding feedback factors to the common Lorenz mapping, generates 3 masking factors, and uniformly encrypts the three dimensions (3D) of the constellation diagram, subcarrier frequency, and symbols in OFDM, which effectively improves the security of the system. Owing to the linearity of the (inverse) fast Fourier transform (FFT/IFFT) operation in the OFDM system and the mismatch between the number of subcarriers and the number of Fourier points, the use of idle subcarriers in the FFT/IFFT operation can reduce peak-to-average power ratio (PAPR). The proposed high-security OFDM-PON is experimentally verified. In the experiments, the OFDM signal is modulated by the quadrature amplitude modulation and achieves a 14.7 Gb/s data rate, which is tested against the fiber span of 25 km single-mode fiber (SMF). In comparison with the normal OFDM-PON, concerning the PAPR and security performance, this scheme improves the PAPR performance by 1.6 dB and has high chaotic initial sensitivity and safety performance.