Performance enhancement of an all-optical XOR gate using quantum-dot based reflective semiconductor optical amplifiers in a folded Mach-Zehnder interferometer

The feasibility of implementing an All-Optical (AO) XOR gate for 320 Gb/s data pulses using Quantum Dot (QD) based Reflective Semiconductor Optical Amplifiers (RSOAs) in a Folded Mach–Zehnder Interferometer (FMZI) is investigated using detailed numerical models. Detailed performance comparisons are made between the conventional QD-SOA based MZI XOR and the specific scheme. The influence of various parameters such as SOA length, input optical powers, rear-facet reflectivity, and bias current on the XOR gates output quality are investigated. The results indicate that the gain recovery time in the QD-RSOA can be reduced to approximately 50% of its value in the QD-SOA, which can help avoid restoring sophisticated gain recovery acceleration techniques. It is shown that at low input powers and high bit rates the MZI XOR fails to perform the logic operation, while the FMZI XOR can deliver a good performance at data rates as high as 320 Gb/s with reducing the power consumption of the structure. The simulations demonstrate an about 5 dB (1 dB) improvement on the XOR output extinction ratio (amplitude modulation) for 320 Gb/s input bit sequence. The combination of the ultrafast gain dynamics of QD materials with the inherent advantages of RSOA devices and using the former in the latter inside the high-performance FMZI can be utilized to realize power-efficient ultrafast signal processing and switching functions while being cascadable and scalable for constructing more complex AO circuits.