Q-factor assessment of SOA-based ultrafast nonlinear interferometer

The performance of the semiconductor optical amplifier (SOA)-based ultrafast nonlinear interferometer (UNI) gated by an ultra high speed pseudorandom binary sequence is theoretically analyzed. For this purpose, a comprehensive model formed by a set of equations that describe the gain and phase evolution inside a SOA deployed as the nonlinear element in an interferometric switch is appropriately applied to this particular configuration. By undertaking a detailed numerical simulation, the impact of the SOA and input data key parameters on the Q-factor is thoroughly investigated and assessed enabling to extract useful design rules for their proper selection so as to optimize this metric. The calculations confirm the experimental evidence that the main technical limitation is imposed by the SOA carrier lifetime, which must be reduced below the bit period in order to avoid the deleterious consequences of the pattern effect on the switched-out pulses. Provided that this condition is satisfied and the rest of the parameters fulfill their specified requirements, the output amplitude fluctuations can be effectively eliminated resulting in a high quality eye diagram and error-free operation. The adopted model can be exploited for studying more sophisticated all-optical circuits and subsystems of enhanced functionality that rely critically on the SOA-based UNI as switching module.