Isochronal synchronisation between the elements of an array of three mutually coupled directly modulated semiconductor lasers is utilized for the purpose of simultaneous bidirectional secure communication. Chaotic synchronisation is achieved by adding the coupling signal to the self feedback signal provided to each element of the array. A symmetric coupling is effective in inducing synchronisation between the elements of the array. This coupling scheme provides a direct link between every pair of elements thus making the method suitable for simultaneous bidirectional communication between them. Both analog and digital messages are successfully encrypted and decrypted simultaneously by each element of the array
B. M. Krishna, John, M. P., and Dr. V . M. Nandakumaran, “Multi-user bidirectional communication using isochronal synchronisation of array of chaotic directly modulated semiconductor lasers”, Physics Letters A, vol. 374, pp. 1835–1842, 2010.