We report the first demonstration of 640-Gb/s return-to-zero ON-OFF keying channel transmission over a 100-km standard single-mode fiber link employing midspan phase conjugation. A frequency-degenerate conjugate field spanning more than 20 nm is created in a low-birefringence parametric mixer for the first time. Physical separation of the conjugate field from the original field is enabled by utilizing pump polarization nondegeneracy. Rigorous link characterization using a high-quality 640-Gb/s transmitter and a high-sensitivity receiver revealed error-free (bit error ratio
Tobias Kippenberg, Maxim Karpov, Martin Hubert Peter Pfeiffer, Arne Kordts, Fatemeh Alishahi, Ahmad Fallahpour, Cong Liu