Performance Assessment of All-Optical NAND and XNOR Gates at 120 Gb/s Using a Single Optically Pumped Semiconductor Optical Amplifier Mach–Zehnder Interferometer

This paper presents a numerical investigation of all-optical NAND and XNOR logic gates implemented with a single optically pumped semiconductor optical amplifier integrated into a Mach–Zehnder interferometer (OP-SOA-MZI) at 120 Gb/s. Conventional approaches require two cascaded MZI stages to obtain both logic functions. The present work demonstrates that a single OP-SOA-MZI suffices for both gates under appropriate operating conditions. The quality factor (QF) serves as the primary performance metric. The NAND gate yields a QF of 28.6, while the XNOR gate yields a QF of 18.7. A comparison with the conventional electrically pumped SOA–MZI (EP-SOA–MZI) configuration shows that the OP-SOA–MZI architecture consistently produces higher QF values and exhibits superior tolerance to noise and high-speed operation. This improvement stems from enhanced carrier replenishment and improved phase stability provided by optical pumping. The study further examines the dependence of the QF on five operational parameters: absorption coefficient, pump power, data rate, phase noise, and amplified spontaneous emission noise. The results quantify the parametric sensitivity of each logic gate and establish operating regimes for reliable high-speed performance.