From order to chaos and back: Recent advances in optical cryptography of transmitted data

We outline the fundamentals of optical cryptography with coupled semiconductor lasers, and the associated tools of optical chaos generation and synchronization, as well as chaos coding of transmitted information, with special reference to CM (Chaos masking) and CSK (Chaos Shift Keying). We present different versions of such schemes which have been numerically and/or experimentally tested both with discrete component crypto-systems and with a PIC (Photonic Integrated Circuit) realization of the chaotic source. Finally, we outline some recent developments on the chaos secure transmission technique.