Research On High-security Optical Communication Technology Based On Chaotic Nonlinear Dynamic

With the commercial use of 5G technology and the continuous development of diversified services,data traffic has exploded and the number of users has also surged.In recent years,our country has been increasing attention to the Internet,implementing the strategy of cyber power,implementing the"Internet Plus"action plan,developing the sharing economy and implementing the national strategy of big data.The cornerstone of the global network is the optical communications network,which carries 85 percent of the world’s data traffic.As the data flow of optical network surges,the information security between different users is particularly important.At present,the data security of optical network is mainly the upper layer protocol encryption,and the physical layer encryption of optical network is less studied.The physical layer encryption can protect data fundamentally and avoid the risk of exposure of data frame headers.Therefore,it is of great significance to study the physical layer encryption of optical communication networks.The main research work of this paper is as follows:（1）In order to realize the data security protection under the Multi-carrier modulation architecture,a high-security Universal Filtered Multicarrier（UFMC）transmission system based on a new three-dimensional（3D）discrete chaos model is proposed in this article.The cascade of counters and the 3D discrete chaotic system is used to generate three masking factors and update these factors to encrypt bitstream,constellation and the information of subcarriers.Using this structure,the key space is 10²⁷⁰ and the key is updated timely.In this work,the encryption scheme solves the dynamic degradation of chaotic cryptography.Experimental results show that there is no significant difference in error performance to before encryption.Compared with orthogonal frequency division multiplexing（OFDM）system,spectrum efficiency of the UFMC system is higher,which reduces out-of-band leakage and interference between services.Considering the complexity constraints of the receiver,the inter-symbol interference caused by fiber dispersion is alleviated by optimizing the distribution of data subbands,and the bit error rate performance is improved.It is shown that UFMC system obtains 1.9 d B gain than the OFDM system in terms of receiver sensitivity when the bit error rate is 10^-3.This encryption scheme has a promising application prospect in short-distance optical access systems in the future.（2）To realize the key and ciphertext transmission together,we propose a physical layer encryption scheme based on OFDM power-domain non-orthogonal multiple access（NOMA）technique for the dynamic key hiding transmission and multi-dimensional disturbance.The encryption scheme realizes multi-point mutual-coupling key transmission and multi-dimensional disturbance encryption by a 3D discrete chaotic model.The encrypted data and the dynamic key are transmitted together by multichannel signals in NOMA,then,the chaotic signal generated by chaotic generator is used to mask the dynamic key.3D chaotic sequences generated by the dynamic key are used to encrypt bits,symbols and carriers of the original signal.The initial key,the dynamic key and the chaotic signal realize multi-point mutual-coupling.We conduct a 74.6 Gb/s encrypted signal transmission over 2 km 7 core fiber.The key space of encrypted scheme can reach 10⁴⁶².Finally,experimental results show that the original data can be recovered accurately,and the bit error rate of the dynamic key is close to zero.The security and reliability of the system have been verified,and this scheme has an important application prospect in the future optical communication system.（3）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）.The Bi-LSTM 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 are more than 0.98.Compared with the original chaotic system,the range of sample entropy above 0.8 is more than2 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（QAM）OFDM signal transmission of 65.9 Gb/s using 2 km 7-core optical fiber.