Unrepeatered 515Gb/s Nyquist PDM-128QAM transmission over 120km SSMF with backward Raman amplification

We experimentally demonstrate Nyquist superchannel transmission of 515Gb/s (8×64.4Gb/s) PDM-128QAM over single span of 120 km SSMF, using backward Raman amplification at the receiver-side. We achieve a record distance of unrepeatered transmission for the spectral efficiency (SE) as high as 10.31b/s/Hz.