Research On Key Problems Of Few-mode Large-capacity Optical Communication System Based On Chaotic Perturbation

With the rapid development of communication networks,people's demand for communication bandwidth is only increasing.In addition to the transmission rate,more and more attention has been paid to the capacity of the communication network and the security of data transmission.While using high-order modulation technology to improve the spectral efficiency of the system,the mode division multiplexing technology has been widely studied as an effective scheme to improve the optical fiber communication capacity.At the same time,the use of chaotic encryption technology to encrypt data to improve data security has become one of the most popular data encryption strategies.In this paper,the transmission capacity and data security issues of optical communication systems are discussed.Combining the above technologies,with the goal of improving the transmission performance and signal security of the system,a large-capacity and high-security optical communication system based on chaotic disturbance is studied,which breaks through the limitation of traditional chaotic vector space and solves the problem of using data information itself to achieve physical layer security,and reduces the complexity of the system.The specific research contents are as follows:(1)For orthogonal frequency division multiplexing passive optical network,a physical layer security strategy based on four-dimensional iterative cascade chaotic encryption model is proposed in this paper.Combined with probability shaping technology,improved Logistic and delay-Tent-Sine double chaotic mapping are used to iteratively cascade to generate scrambling vector,and the transmitted signal is encrypted to enhance the physical layer security of the system.The large key space of this scheme is enough to resist exhaustive attacks and improve the problems of low randomness and weak scalability caused by traditional low-dimensional chaos.At the same time,the reusability of the chaotic system can be improved by changing the dimension of the iterative equation.After encrypting the signal using the proposed model,transmission of 16.48 Gb/s can be achieved using standard single-mode fiber over a fiber span of 25 km,and a gain of 1 d B can be obtained using probability shaping techniques.(2)In order to improve the physical layer security of the filter bank multi-carrier/offset quadrature amplitude system,a chaotic encryption strategy based on diversity DNA encryption is proposed in this paper.After encrypting the input original binary bit stream,modulate it to generate a transmission signal,among them,the DNA diversity rules,the encoding and decoding rules between binary data and base pairs,the key base sequence and the DNA base sequence scrambling rules are dynamically controlled by different chaotic sequences.And the DNA code is extended to 3 bits,realizing a substantial expansion of the key space to the order of 10e180,enhancing the robustness to malicious attacks by illegal attackers,and ensuring the security of the physical layer of the system.The proposed chaotic encryption-based filter bank multicarrier/offset quadrature amplitude system security strategy is experimentally transmitted on a25 km standard single-mode fiber,the experimental results show that the encryption method has good bit error rate performance in transmission,can effectively prevent eavesdropping,and has high sensitivity and security.It has a certain beneficial effect on the peak-to-average power ratio of the filter bank multi-carrier/offset quadrature amplitude system.(3)For the secure transmission of large-capacity modulo division multiplexing systems,this paper proposes a parallel bit interleaving security strategy based on four-dimensional chaos.After perturbing the constellation point distribution probability of the signal,the bits and symbols of the modulated signal are interleaved and scrambled,so as to improve the security performance of the physical layer of the signal.By optimizing and calculating the chaotic sequence generated by the four-dimensional hyperchaotic system,the disturbance process is controlled,and the correlation between the encrypted information sequence and the original sequence is significantly reduced.The used parallel bit interleaving algorithm effectively reduces the complexity of the system and increases the encryption efficiency by 1.43 times.At the same time,the multi-plane optical conversion technology is combined to realize few-mode transmission,and the 3×10 Gb/s MIMO-free transmission is realized on a 5 km weakly coupled four-mode fiber.The scheme can effectively improve the security performance of the system,and combines the few-mode multiplexing technology with the advanced modulation technology,which can be well applied in the future large-capacity,high-security optical transmission system.