Highly sensitive in-band OSNR monitors based on phase-matched four-wave mixing

This paper presents a novel all-optical in-band optical signal-to-noise (OSNR) monitoring method based on phase-matched four-wave mixing (FWM). The monitoring ability arises from the power transfer function (PTF) giving preferential gain to clean pulses when compared to noisy pulses. By selecting the phase match condition a much higher monitoring sensitivity can be achieved at a reduced input power compared to other PTF-based methods proposed before. Numerical simulations are used to quantify the sensitivity enhancement for signals with different modulation formats.