Photonic processing of all-optical Johnson counter using semiconductor optical amplifiers

This study presents a novel design of Johnson counter using D flip-flops. The performance of D flip-flop is carried out by exploiting the cross-gain modulation effect in semiconductor optical amplifier (SOA), purging the use of components like polarisation controllers, switches and so on. Performance is evaluated in terms of various variants like operational speed, cost effectiveness of design, rise time/fall time, quality of signal received and the system is found to give better results in terms of extinction ratio even without any feedback path. The Johnson counter or twisted ring counter is implemented using three all optical D flip-flops producing six states. The D flip-flop incorporates travelling wave SOA and all-optical NOT gate. The proposed counter is reasonably valuable as it desires half of the flip-flops in association to other ring counters which directly reduce the cost of the system.