Numerical studies on bi-directionally coupled directly modulated semiconductor lasers

Results of a numerical study of synchronisation of two directly modulated s emiconductor lasers, using bi-directional coupling, are presented. The effe ct of stepwise increase in the coupling strength (C) on the synchronisation of the chaotic outputs of two such Iasers is studied, with the help of par ameter space plots, synchronisation error plots, phase diagrams and time se ries outputs. Numerical results indicate that as C increases, the system ac hieves synchronisation as well as stability together with an increase in th e output power. The stability of the synchronised states is checked by appl ying a perturbation to the system after it becomes synchronised and then no ting the time it takes to regain synchronisation. For lower values of C the system does not regain synchronisation. But, with higher values synchronis ation is regained within a very short time. (C) 2000 Elsevier Science B.V. All rights reserved.