Theory Research Of Chaos Secure Optical Communication Based On Semiconductor Ring Laser

In the case that the security of communication of software encryption is precarious because of the development of computer technology and quantum optical communication is far from practical, consumers are in urgent need of superior communication techniques to meet their growing demand for confidentiality in the information era. Chaotic optical communication is interested in its high confidentiality, broad bandwidth, cheapness and other advantages by researchers in recent year. Semiconductor ring lasers are the ideal candidates of emitters of optical communication systems because of their abundant dynamics, small size, low power consumption, convenient integration and other advantages. This paper tries to set up a model of chaotic optical secure communication based on semiconductor ring laser numerically and explores the effect of Langevin noise for the chaotic communication systems. The main works of this paper are listed as follows:The key premise of this project is the building of the model of chaotic optical secure communication system based on semiconductor ring laser. The method of chaos masking coding technology is simulated in our model. General synchronization is employed and the Q-value is used to evaluate the quality of communication and the effect of confidentiality. When the modulation depth is fixed at 4%, the maximum communication rate is 2.38 Gbps under the condition of guaranteeing the good quality of communication and effect of confidentiality. This paper studies the work of chaotic secure optical communication system under the Manchester code modulation. It shows that relative to the NRZ code modulation, Manchester code shows superior performance in the quality of communication and effect of confidentiality. Moreover, Manchester code possesses various advantages that NRZ code can’t match, for example, no dc exists in Manchester code because rising edge(falling edge) is used for representing ‘1’(‘0’) or ‘0’(‘1’), the timing signal is easy to get and Manchester code makes the most of the high bandwidth of chaotic carriers. Therefore, the paper draws a conclusion that Manchester code is more suitable for modulating chaotic carriers than NRZ code.The paper studies the impact of Langevin noise on chaotic optical communication system. We need to find an appropriate algorithm to solve the rate equations of semiconductor ring laser subjected optical feedback. The rate equations own noise term and are different from common delay differential equations, we call them stochastic delay differential equations. We obtain the delay term by cubic Hermite interpolation algorithm and then solve the stochastic differential equations by Heun algorithm. The paper explores the influence of Langevin noise on the output of semiconductor ring lasers, chaotic synchronization and chaotic communication. We find that Langevin noise makes difference to the chaotic carriers emitted by lasers. If we amplify the Langevin noise little by little, the chaotic carriers would become random signal gradually. Moreover, the Langevin noise almost has no effect on chaotic synchronization because of the injection locking effect. Since Langevin noise is comparable with message signal, the Langevin noise can damage the communication quality without affecting the synchronization.