Theoretical And Experimental Study On High-Speed Long-Haul Chaotic Secure Optical Fiber Communication

High-speed long-haul transmission can be realized in optical fiber communication system.However,the security of optical fiber communication is threatened by optical fiber eavesdropping technologies.On the premise of ensuring the validity and reliability of communication,optical fiber physical layer protection technology can effectively improve the security performance.Optical chaotic system has the unique advantages of high dynamic complexity and high bandwidth,which can be used as a random entropy source with excellent characteristics.It is an effective way to meet the security requirements of high-speed information channel and has been widely concerned in recent years.However,the parameter security,synchronization robustness and implementation complexity of optical chaotic secure communication systems are the key issues that restrict its practical application.In addition,with the rapid development of optical fiber communication,the demand of higher speed and longer distance secure communication brings new challenges to chaotic system.In this thesis the theoretical and experimental research is carried out to meet the application requirements of high-speed and long-haul secure optical transmission.The capacity expansion of chaotic secure communication in the intensity modulation direct detection(IM/DD)optical transmission system is researched and realized.The long-haul synchronization based on analog-digital hybrid optical chaotic system is proposed and verified,and the high-speed long-haul chaotic secure communication method for signal in high-order modulation format is explored in coherent detection optical transmission system.The main contents and results are as follows:(1)In order to expand the capacity of chaotic secure communication in the IM/DD system,a theoretical model of wavelength division multiplexing(WDM)chaotic secure communication with phase noise source and phase-to-intensity conversion mechanism is constructed,which takes into account the security of entropy source,synchronization robustness and system implementation complexity.Besides,the multiplexing cost is reduced.The simulation verifies the feasibility of the WDM secure communication based on the optically coupled phase chaotic source.Besides,a dense wavelength division multiplexing(DWDM)secure communication system based on external entropy source is built and verified by experiments.The results show that the system supports the single wave 10 Gbps signal secure transmission in 100 km fiber link,with channel spacing of 50 GHz.It can resist the attack of autocorrelation function on the delay time key of the chaotic system.An effective method for chaotic secure communication capacity expansion is provided.(2)An analog-digital hybrid electro-optical feedback chaotic source is designed for long-haul chaos synchronization.Besides,analog-digital hybrid chaos synchronization structure and long-haul secure communication are verified by experiment.The distortion of analog optical signal after long-haul transmission will cause the traditional chaotic synchronization performance degradation.While in the proposed analog-digital hybrid chaotic system,using digital signal for long-haul transmission,the chaotic synchronization distance can be increased.Moreover,the signal processing based on the neural network improves the synchronization performance.Experimental results show that chaos synchronization can be achieved in 200 km fiber link.Based on the synchronization method,a digital key stream is generated,and two types of long-haul secure optical fiber communication schemes based on XOR encryption systems are proposed.(3)To meet the requirements of high speed and long haul in chaotic secure communication,a chaotic coherent secure communication system is designed based on analog-digital hybrid chaos and coherent optical transmission.With the theoretical model of the time-delay dynamic system,a bidirectional coupling laser chaotic system is designed using the nonlinear effect of laser injection.Long-haul chaotic synchronization is realized based on the common-injection synchronization mechanism.The simulation results show that chaotic synchronization with correlation of 0.98 can be maintained after 1000 km single-mode fiber transmission.High-order format signal is used to modulate the analog optical carrier generated from the chaotic source,synchronized chaotic signal is used for coherent detection,and digital signal processing algorithm is used for information decryption and demodulation.Simulation results show that the system can support 5Gbaud16 QAM signal secure transmission over 1000 km single-mode fiber.Besides,it can resist the attack of autocorrelation function on the delay time key of chaotic system.