Synchronization performance comparison of vertical-cavity surface-emitting lasers with two different feedback chaos schemes

Abstract

Most of the previous treatments of chaos synchronization use common optical feedback. In this paper, we introduce a new feedback type called phase conjugate feedback in vertical-cavity surface-emitting lasers (VCSEL) to achieve synchronization. For comparison, models of synchronization using both phase conjugated feedback (PCF) and common optical feedback (COF) are given, where the nonlinear and dispersion effects on transmitted signals in a fibre link are also considered. Numerical simulation shows two peaks when calculating the shifted correlation coefficient. In the phase conjugate feedback scheme, the larger peak always corresponds to anticipating synchronization while this does not hold true in the common optical feedback scheme. When anticipating synchronization takes place, the value of the correlation coefficient for phase conjugate feedback is larger than that for common optical feedback, and their discrimination is more than 0.1. Decoded messages in chaotic shift keying undergo less distortions when the phase conjugate feedback scheme is considered, because of the distortion correction characteristics of phase conjugate light. All this indicates that the synchronization performance of the former scheme is better than that of the latter.