Noise properties of cascaded optical majority gates

All-optical signal processing remains an active field of research [1] , [2] . The fundamental challenge is the nature of photons that do not interact with each other but require a nonlinear medium. Majority gates have been proposed in a number of arrangements [3] , [4] , including injection-locked lasers [5] . Recently, we have demonstrated such an all-optical majority gate based on a vertical-cavity surface-emitting laser (VCSEL) [6] . Here we demonstrate numerically operation of a set of consequent majority gates based on injection locking technique taking into account noise in lasers. The operation principle is to transmit and process Phase-Shift Keyed (PSK) optical signal, and at the same time suppress the amplitude variation after each majority gate (make a normalization procedure, Fig. 1 ). We use here a special operation mode of a phase-locked laser suppressing the amplitude variations while keeping the phase modulation.