Abstract
By injecting an external sinusoidal electronic drive, bistable laser diodes can generate chaotic light output. The steady-state rate equations describing the bistable laser diodes are numerically simulated to explore optical chaotic behaviors. Nonlinear effects of the bistability that leads to chaos are demonstrated. Different schemes including Poincare maps, bifurcation diagrams, and Lyapunov exponents are calculated to assert the existence of the chaos. Period doubling routes to chaos are established by increasing the modulation current. Furthermore, discontinuous change of the chaotic behaviors is achieved by alerting the modulation frequency. A synchronization scheme using bistable laser diodes in optical chaotic communication is proposed. To synchronize between two identical chaotic system with different initial conditions, a drive and response system model is constructed according to Pecora and Carroll's theory. Synchronization can be achieved for optical simplex transmissions provided that the conditional Lyapunov exponents for the drive and response systems are all negative. This approach offers a key step toward the optical chaotic modulation and demodulation. Optical chaotic transmission of digital signal is investigated by the input parameter switch using the drive-response model according to Pecora and Carrol's theory. The digital message can in the receiving end. In addition, the first conditional Lyapunov exponent of the system is shown to be directly the tansmission rate. Adding an AM signal to the drive system, the two systems become asymptotically synchronized. The AM signal can be recovered by utilizing the property of the asymptotic synchronization. Chaotic AM noise is present as a direct result of the chaotic AM demodulation. 2.Chaos………………………………………………………………………..4 2.1 Formulation……………………………………………………………4 2.2 Chaotic behavior……………………………………………………5 2.2.1 Poincare map……………………………………………………6 2.2.2Bifurcation diagram…………………………………………7 2.2.3 Lyapunov exponents………………………………………………8 2.3 Crises on various modulation frequencies……………………………9 3. Synchronization…………………………………………………………9 3.1 Formulation………………………………………………………9 3.2 Synchronization in simplex transmission……………………………10 4. Application in optical communication……………………………………11 4.1 Optical digital communication………………………………………11 4.2 Optical chaotic AM demodulation by asymptotic synchronization..............................................13 5. Conclusion………………………………………………………………14 6. Reference………………………………………………………………16 7. Appendix………………………………………………………………18