Research On Spread Spectrum Of Laser Chaotic Signal Based On Time Lens

Chaos in external-cavity semiconductor laser(ECSL)has attracted widespread attention in recent years for its potential applications in the fields of secure optical communications,chaotic radar,high speed random bit generator and so on.While the inherent defects of chaotic laser signal,such as uneven spectrum and limited bandwidth,restrict the application of chaos in the generation of high speed random number,chaotic secure communication and laser chaotic radar.Besides,the external cavity resonant characteristic of the chaotic laser signal,which implied some periodicity,on the one hand may divulge the feedback time delay,cause system to be deciphered,and reduce the chaotic optical secure communication security;and one the other hand,it can decrease the randomness and the reliability of the chaotic laser generation random code.As a structure that can realize time-frequency conversion of waveform,time lens can transform the time spectrum of chaotic signal into a certain extent,realizing the bandwidth enhancement of chaotic signal.This time-frequency disruption also provides a possibility for the study of time lens in chaotic secure communications.From the perspective of optical time lens,the two equivalent models in this paper are presented from the Maxwell equations and space-time duality theory,by comparison with optical lens.The optical time lens model is constructed by the VPI simulation software,and the simulation results show good performance in spreading chaotic spectrum.On the basis,this paper further studies the influence of parameters of nonstandard time lens on chaos bandwidth enhancement and time delay signature concealment,the results indicate that the spectrum can be greatly enhanced and the TDS is totally eliminated.Based on the chaotic spread spectrum technology,this paper also explored the application of nonstandard time lens module in the chaotic secure communication.Because of the reversibility of the module,the chaotic signal after spread spectrum could be recovered,which means it can be applied in the chaotic secure communication.The paper analyzed the chaotic secure communication system,we analyze from three aspects,synchronization property,communication performance and security of the system,optimize parameters.By comparing with the traditional chaotic secure communication systems,it is verified that the proposed chaotic secure communication system can effectively resist the typical attack methods,and improve the system security.