Conversion Between Anticipating And Lag Chaos Synchronization In Mutually Coupled Semiconductor Lasers

Message transmission through bidirectional, multidirectional, and even network is the inevitable developing trend with the development of the technologies of the optical chaos communication. Therefore, bidirectional optical chaotic secure communication has become a new research focus. For completely symmetrical mutually delay-coupled semiconductor lasers (SLs), the chaos synchronization characteristics behave in an unstable way due to spontaneous symmetry-breaking phenomena. By introducing an additional optical feedback or extremely asymmetrically mutually coupled SLs, stable chaos synchronization can be realized. However, it will make the system more complex. So, the easy-controlled mutually coupled system, with simple structure, stable chaos synchronization will have more actual application value.This paper proposes an easier scheme. Based on a simple mutually coupled scheme constructed by two similar SLs with asymmetrical bias currents, the stable anticipating or lag chaos synchronization has been experimentally observed, and we also study the influence of bias currents on anticipating or lag synchronization. For the two similar SLs used in the experiment which have consistent internal parameters to construct a mutually coupled system, the chaos synchronization performance has been studied due to the changes of the bias currents. The results show that:when the bias currents of the SLs are equal, the chaos outputs have two approximately equal maxima, this means the chaos outputs are unstable synchronization, and the anticipating or lag synchronization will occur random changes. Through adjusting the bias current of a SL and fixing that of the other one, the two SLs will behave stable anticipating or lag synchronization, and with the changes of bias currents, the stable anticipating or lag relationship will change. The chaos output in the SL biased at a relatively higher bias current level anticipates that of the other SL. Considering that the SL with a higher bias current level will oscillate at a longer wavelength, so we can think the SL with a longer wavelength becomes the leader. Furthermore, the corresponding theoretical analyses have been given, and the theoretical results coincide with the experimental results.Finally, the secure communication performances in the mutually coupled system are theory investigated under CSK scheme. For 250MHz random signal loaded into the bias current of transmitter laser, messages can be well hidden and extracted satisfactorily from receiver laser.