All-Optical Clocked Flip-Flops Exploiting SOA-Based SR Latches and Logic Gates

All-optical flip-flops are key components of photonic digital processing in next generation optical network and computing. In most digital applications, signal synchronization with a reference clock is a basic feature. In this paper, an entire set of all-optical clocked flip-flops, including SR, D, T. and JK types is proposed and demonstrated, each employing a single SR latch and optical logic gates previously introduced in literature. The bi-stable element is based on gain quenching mechanism between SOAs of two coupled fiber ring lasers. Three logic gates are carried out by exploiting four wave mixing (FWM) and cross gain modulation (XGM) nonlinear effects in SOA. Different flip-flop functionalities are obtained by adding one of the logic gates, or a combination of them, to the latch scheme. Performance evaluation in terms of extinction ratio demonstrates the effectiveness of proposed schemes. Speed limitation of flip-flop operation is also investigated and photonic integration is identified as a feasible solution to increase the operation speed beyond GHz.