Security Enhancement And Long Distance Synchronous Chaos Communication System Technology Research

Chaos theory,relativity,and quantum mechanics are known as the three greatest theories of the 20 th century in the scientific community,and can be applied to many fields such as meteorology,aerospace,and secure communications.Chaos theory can be used to achieve optical chaos security communication.The security of optical chaos communication mainly comes from the internal parameters of the laser(non-linear gain,line width enhancement factor,photon lifetime,etc.)and external parameters(feedback time delay,etc.)of the transmitter and receiver.Highly consistent,this kind of hardware physical parameters that guarantee high consistency is equivalent to providing a security key for both communication parties without channel transmission.This is also the difference from traditional confidential communication.Traditional optical chaos security communication based on hardware parameters can be cracked by specific algorithms.For example,autocorrelation algorithm,delayed mutual information algorithm,etc.can be used to calculate the feedback time of optical external cavity,which increases the risk of system security.In addition,the chaotic synchronization waveform generated by the receiving end is very dependent on the phase of the chaotic signal at the sending end.In long-distance transmission,the phase change caused by the nonlinear effect of optical fiber will also cause the sending and receiving parties to fail to synchronize.Based on the chaotic synchronization principle,this paper proposes a signal encoding scheme and a photoelectric cascaded chaotic system,which avoids unsafe factors that may cause information leakage,thereby enhancing the security of the system.The long-distance synchronization effect of chaotic signals is studied,the robustness of system synchronization is analyzed,and the above scheme is verified by simulation.The main research contents are as follows:(1)Using chaotic light as the carrier light source of the Mach-Zehnder modulator,under the appropriate carrier injection strength,the Mach-Zehnder modulator is modulated by the delayed feedback method to generate a chaotic waveform that suppresses time delay characteristics and ensures communication security.The system robustness and the impact of parameter changes on system security are studied emphatically.(2)Aiming at the means of cracking optical chaos communication such as autocorrelation algorithm,delayed mutual information algorithm or reserve pool calculation,a multi-ary encoding method is proposed,which characterizes the signal as a high-order signal presented in multi-ary system.Completely eliminate the chaotic noise left after synchronization and the noise-sensitive characteristics of high-order signals,and use chaotic noise as an interference source to submerge the adjacent "orders" of high-order signals to ensure information security.Realized the safe transmission of 1.25 Gbps information rate,and focused on the security of this scheme for some cracking methods.(3)Aiming at the problem that the long-distance transmission of chaotic signals cannot be synchronized due to phase changes and cannot be compensated in the electrical domain,a scheme for compensating the nonlinear phase shift of chaotic signals in the optical domain is proposed.Before the time-domain waveform of the chaotic signal is significantly distorted,the optical amplifier and phase modulator are used to compensate the attenuation and nonlinear phase shift brought about during the transmission,and the dispersion compensation fiber is used to make the average dispersion of the entire transmission line close to 0.When the signal rate is 1Gbps,a high-quality synchronous carrier can be generated at a distance of 1000 km.The influence of system parameter changes on the synchronization distance is emphatically studied.