Long-haul transmission of WDM signals with in-line phase-sensitive amplifiers

We demonstrate the use of in-line low-noise phase-sensitive amplifiers (PSAs) in a wavelength-division multiplexing long-haul transmission link with a recirculating loop experiment. We quantify how replacing phase-insensitive amplifiers with PSAs can improve the reach of one-, two-, and three-channel transmission systems both numerically and experimentally.