| Since a chaos synchronization method was realized by Pecora in 1990, chaos synchronization in nonlinear systems has been the topic of intensive research in the past decade, and many kinds of synchronization systems have been studied. And because of the importance of optical communication, synchronization between laser systems has become a focus. Meanwhile, Vertical cavity surface emitting laser (VCSEL), as a new type of micro-cavity laser, has many excellent features such as circular beams, low divergence angles that can coupled with fiber convenient, surface-emitting easy to integrate high density 2D arrays, single longitude mode operation. And it will be the ideal light source for chaos communication.Based on the master-slave rate equations and optical injection theory, the simulation model of chaos synchronization system using VCSELs with external optical feedback has been established. Also the features of micro-cavity lasers have been taken into account. The effective range of modulation index and the influence of some typical parameters such as the spontaneous emission factor are studied by this model. Also the effect of noise of VCSEL is discussed in the last section. Results indicate that the model is competent for simulating this chaos system, and simulation results are agree with the experimental results reported in document. It is found that the chaotic carrier masks the signal successfully if the modulation index lower than its upper limit. And higher modulation frequency can be achieved with small current aperture and adequate spontaneous emission factor. Inside noise of VCSEL and dismatch of parameters have much effect on synchronization, effect of the former can be reduced by decreasing the current aperture and enhancing the injection, the latter can be solved by limiting parameters' dismatch degree.Furthermore, consider the characteristics of mutually coupling, the theoretical model of mutually injected system using VCSELs has been established. The analytical expression of mutually injection locking range is deduced by this model. Also the types of synchronization and the influence of injection delay are studied. Results indicate that for the ideal condition without parameters dismatch and noise, complete synchronization can be achieved, and injection delay has much effect on the state of VCSEL. For the real condition with parameters dismatch and noise, complete synchronization will be replaced by delay synchronization, andsynchronization error changes in step shape as injection delay changes. Simulation results also validate the expression of locking range. |
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