Research On Underwater Optical Communication Based On Quantum Noise Stream Cipher

With the development of Chinese marine information and communication technology,the importance of underwater communication security is increasingly prominent.In order to meet the requirements of higher security for maritime communication system,the physical layer encryption technology in optical communication system has received widespread attention.As a new physical layer encryption algorithm,Quantum Noise Stream Cipher(QNSC)is compatible with the existing optical fiber equipment and can achieve high-speed and long-distance transmission.It has a broad application prospect in submarine optical cable system,underwater optical communication and other fields.In this paper,the security risks,encryption methods and quantum noise stream encryption techniques of underwater optical communication systems have been investigated.Then the feasibility verification and experimental study of Quantum Noise Stream Cipher technology in different underwater communication systems are emphasized.The main work and innovations of this paper are as follows:At First,a two-dimensional Quantum Noise Stream Cipher scheme based on MQAM-OFDM modulation in underwater wireless optical communication based on blue/green laser is designed,and the encryption transmission experiments are carried out.Experimental results show that the transmission cost of the encryption scheme is only 1dB,and the encryption cost decreases with the increase of the transmission rate,which is feasible in high-speed underwater wireless optical communication.Secondly,the paper also analyzes the reasons for the nonlinear effect of the underwater blue-green laser communication system:1.The OFDM signal adopted has a high Peak to Average Power Ratio(PAPR);2.The high modulation depth required by the encrypted signal makes the signal nonlinear distortion.In view of the above problems,this paper adopts limiter method and Volterra-series based recursive least squre(VRLS)algorithm to compensate the system performance,which can obtain certain effect.Thirdly,this paper verifies the feasibility of IM-DD OFDM transmission scheme based on Quantum Noise Stream Cipher in long-distance submarine optical cable system,and realizes the safe transmission of 2.5Gbit/s encrypted signal for 1000km.And it is proved that MQAM-OFDM encryption scheme has a high tolerance to optical fiber dispersion effect in long-distance submarine optical cable transmission.