For the first time to our knowledge, the turbo-switched Mach–Zehnder interferometers (TS-MZIs) architecture, which includes quantum-dot semiconductor optical amplifiers (QDSOAs) and is followed by a series delayed interferometer (DI), is used in a combined scheme (QDSOAs-TS-MZIs-DI) to realise NOT-AND (NAND) and exclusive-NOR (XNOR) Boolean functions at a rate of 1 Tb/s return-to-zero data. The performance of the two considered gates is evaluated by calculating and comparing the quality factor and the cross-correlation coefficient for the QDSOAs-TS-MZIs-DI, the TS-MZIs with QDSOAs but without DI (QDSOAs-TS-MZIs) and the standard MZIs with QDSOAs (QDSOAs-MZIs). The comparison shows the superiority of the QDSOAs-TS-MZIs-DI over the other two alternatives (QDSOAs-TS-MZIs and QDSOAs-MZIs) and hence suggests that it should be preferred as a switching module when executing the NAND and XNOR Boolean functions at 1 Tb/s in the optical domain.

In this paper, carrier reservoir semiconductor optical amplifiers (CR-SOAs) are employed for the first time to design an all-optical (AO) half adder at 120 Gb/s. The CR-SOAs are incorporated in Mach–Zehnder interferometers (MZIs) configured as XOR and AND gates to execute the required SUM and CARRY logic functions,respectively. The performance of the half adder is evaluated through the quality factor (Q-factor), whose variation against the CR-SOA’s critical operating parameters, including amplified spontaneous emission noise, is theoretically investigated. The simulation results show that MZIs with CR-SOAs can implement an AO half adder running at 120 Gb/s with a high Q-factor.