Transmission of 2.6 Tb/s Using 100-Gb/s PDM-QPSK Paired With a Coherent Receiver Over a 401-km Unrepeatered Link

We demonstrate the transmission of 26 channels at 100 Gb/s (corresponding to a total capacity of 2.6 Tb/s) over a 401-km-long unrepeatered link with a spectral efficiency of 2 b/s/Hz. This is obtained thanks to the association of polarization-division-multiplexed quadrature phase-shift keying signals detected in a coherent receiver and an optimized amplification scheme, consisting in high-power booster and third-order remote optically pumped amplifier.