Delayed Electro-optic Chaotic System With Extra Optical Feedback And Its Application In Secure Communication

Chaotic laser sources have the advantages of broad-spectrum,high-dimensional hyperchaos and high data transmission rate,so they have been widely researched for secure communication.Compared with the chaotic laser sources based on their internal optical nonlinearities,the electro-optic chaotic systems make use of external nonlinearities and have the advantages of controllable parameters,high encoding/decoding rate and can be easily implemented.Therefore,the latter is more practical in the deployment of future commercial communication networks.The problems exist:(1)they haven't shown more superiority than the chaotic lasers with its internal nonlinearities in complexity and it remains to improve;(2)their output will leak the time delay signature in the systems so the problem of security should be solved;(3)the parameters space and scale await to extend.All the efforts to the three problems aim at the improvement of security in communication.An electro-optic intensity chaotic system(EOICS)with an extra optical feedback is proposed in this paper.The introduction of the optical feedback method realizes the complex variation of electro-optic feedback strength and a new delay is added,thus the parameters scale has been extended.The Hopf bifurcation dynamics are identified in theory and numerical simulation.Then we study the bifurcation diagram,permutation entropy and the Lyapunov exponents for complexity and the auto-correlation function(ACF)and the mutual information(MI)for security.And the synchronization of the communication system in a chaos modulation encryption scheme based on the proposed system is also discussed.Results show that the EOICS with an extra optical feedback can improve complexity and the output optical chaos could be enhanced by increasing the optical feedback strength.On the other hand,it can effectively suppress the time delay analysis,which implies the enhancement of security.Furthermore,the high quality synchronization is realized in a certain range of parameters detuning except the two time delays and the encoding/decoding rate can reach several GHz to tens of GHz.The last but not the least,the proposed system allows convenient implement and shows good controllability in almost all the system parameters.