Self-propagated chaotic dynamically enhanced optical physical layer encryption communication system based on bidirectional long short-term memory neural network

The physical layer chaotic encryption of optical communication is considered as an effective secure communication technology, which can protect data and be compatible with existing networks. Theoretically, any chaotic system or chaotic map has ideal complex dynamics. However, due to the limited precision of simulation software and digital equipment, the chaotic system often degrades dynamics, which hinders the further application of digital chaotic system in many fields. In this paper, we propose a self-propagated nonlinear chaotic dynamical enhanced optical physical layer encryption scheme based on bidirectional long short-term memory neural network (Bi-LSTM-NN). The Bi-LSTM-NN is used to train and learn the dynamical enhanced chaotic sequences with different initial values iteratively, and finally the chaotic sequences with self-propagated dynamical enhancement are output. The correlation coefficient (CC) of chaotic sequences by the enhanced chaotic system and Bi-LSTM-NN are more than 0.98. Compared with the original chaotic system, the range of sample entropy above 0.8 is more than 2 times, and the sensitivity of the initial value x0 is up to 2.28 times, and y0 is up to 1.3 times, making the key space reaches 10520. The scheme successfully encrypts constellation points and information in the frequency domain. In addition, the scheme achieves encrypted 16 quadrature amplitude modulation-orthogonal frequency division multiplexing (16QAM-OFDM) signal transmission of 65.9 Gb/s using 2 km 7-core optical fiber. The experimental results show that the scheme can ensure data security, and in the future optical network has a good application prospect.