Reduction of four-wave mixing noises in FDM optical fiber transmission systems with quaternary bit-phase arranged return-to-zero

To reduce four-wave mixing (FWM) noises in long-haul frequency-division-multiplexing optical fiber transmission systems, quaternary bit-phase arranged return-to-zero (Q-BARZ) is proposed as a modulation format, and FWM noises are analyzed by considering pulse overlapping in both time and frequency regions. It is found that FWM noises with channel frequencies are drastically reduced in Q-BARZ.