Analyses of all-optically regenerated transmission system using nonlinear interferometric switches

We derive, for the first time, a simple formula for calculating the signal-to-noise ratio (SNR) in the transmission system where all-optical nonlinear interferometric switches are periodically inserted as all-optical regenerators. This formula predicts that even after the signal traveling over an infinite distance, the SNR can be maintained at a certain value, as long as the optical amplifier noise is smaller than a critical level.