2.6Tb/s (26 × 100Gb/s) unrepeatered transmission over 401km using PDM-QPSK with a coherent receiver

The combination of PDM-QPSK with a coherent receiver and an optimized amplification scheme (high power booster and third order pumped ROPA) enables the transmission of 26 channels at 100 Gb/s over a 401 km long unrepeatered link. We use this modulation format at 50 GHz channel spacing to achieve 2.6 Tbit/s capacity with a spectral efficiency as high as 2 b/s/Hz. To the best of our knowledge, this is the highest capacity demonstrated over such an unrepeatered distance.