| In recent years,with the exploration of marine resources and the increase of subma-rine military activities,technologies such as underwater exploration,underwater sensor networks,and submarine communications have developed rapidly.The important sup-port for the development of these technologies is effective and high-speed underwater communications.Compared with underwater acoustic communication and underwater radio frequency communication,underwater optical wireless communication(UOWC)technology can achieve ultra-high data transmission rate and ultra-low transmission de-lay with low cost,so it has become a research hotspot in recent years.In addition,the security of communication is also one of the basic requirements of communication.For UOWC,in order to prevent the theft of information during the communication process,to ensure the security of information transmission,and to meet the requirements of the military field and other scenarios with higher security requirements,it is necessary to encrypt the transmission of information.This article mainly adopted quantum key dis-tribution(QKD)technology to generate security keys,encrypted classic UOWC,and solved the security problem of classic communication.At the same time,we designed underwater QKD system as well as underwater classical and quantum hybrid trans-mission system,and verified the communication performance of the system through experiments.First of all,this article introduced some basic concepts of quantum information and clarified the principle basis for ensuring the security of QKD.At the same time,two kinds of QKD protocols were introduced,and their lower bounds of security key rate were analyzed.In addition,for the classical UOWC system,the system model and channel characteristics were analyzed,which lays the foundation for the subsequent system design.For the underwater QKD system,the feasibility of underwater QKD was verified by experiments,and then a 10 meter underwater QKD system based on polarization coding was built.The experiments of BB84 protocol QKD and decoy state protocol QKD were completed,and the offline post-processing of QKD system was performed.Finally,the achieved security key rate of BB84 protocol QKD is 563.41 Kbps,the quan-tum bit error rate(QBER)is 0.36%,the security key rate of decoy state protocol QKD is 711.29 Kbps,and the corresponding QBER is 0.95%.At last,the maximum secure transmission distance of the system under different experimental conditions was sim-ulated and predicted theoretically,and the security key rate and the maximum secure transmission distance of non-decoy state,single decoy state,double decoy state and infinite dimensional decoy state were compared.The simulation results show that the double decoy state protocol is better than several other decoy state protocols.In addition,this article also designed and built an underwater classical and quantum hybrid transmission system.In this system,the classical light source and quantum light source use blue light and green light respectively,and the idea of wavelength division multiplexing was used to achieve hybrid transmission.In order to complete the signal synchronization of QKD link,a signal synchronization scheme based on the synchro-nization head of the classical optical communication was designed.For the classical optical communication channel,an adaptive stochastic resonance signal synchroniza-tion scheme for weak received signals under long-distance condition was designed to improve the synchronization performance under weak signals.Finally,the interaction between classical and quantum communication systems was analyzed,and the commu-nication performance of the system under different transmission distances was verified by experiments. |
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