Optimization for full optical chaotic synchronization by hybrid feedback and injection

A novel secure optical communication system is investigated in this experimental work. The scheme is based on dynamical chaotic encryption, i.e., optical chaos is generated using hybrid feedback (HF) technique. Accordingly, both transmitting and receiving units included a pair of lasers, such that a master–slave regime was implemented in both of those two units. Optical injection (OI), optical feedback (OFB), and optoelectronic feedback (OEFB) all interacted to increase the security level. The key measured parameter is the correlation coefficient (CC) between the signals emitted from the first unit and the second one. The CC is optimized from 0.24 to 0.80 by decreasing the mismatch parameters during observations of time series and frequency spectra. Detuning, frequency modulation, and feedback strength (optical and radio frequency types) all changed in order to increase CC and optimize the resulting synchronization. The master laser (ML) plays the role of driver laser, while all three remaining lasers are considered slaves. In this scheme, a laser network is simulated experimentally to build a laser neural network as an application.