Transmission of 1 Tb/s Unique-Word DFT-Spread OFDM Superchannel Over 8000 km EDFA-Only SSMF Link

Conventional coherent optical orthogonal frequency-division-multiplexed (CO-OFDM) system has inferior nonlinear tolerance due to high peak-to-average power ratio (PAPR). Discrete Fourier transform spread OFDM (DFTS-OFDM) has recently been proposed as a promising candidate that possesses similar spectral characteristics as conventional CO-OFDM, but has much better nonlinear tolerance. We demonstrate experimentally the transmission of 1.0 Tb/s unique-word DFTS-OFDM superchannel signal over 8000 km standard single-mode fiber with 80 km span engineering and erbium-doped fiber amplification (EDFA) using quadrature phase shift keying (QPSK) modulation, representing a record spectral efficiency and reach product in transmission systems compatible with most of the deployed links.