title: Relative phase noise induced impairment in CO-OFDM optical communication system with distributed fiber Raman amplifier.
abstract: In this Letter, we demonstrate that the interplay between Raman pump relative intensity noise and cross-phase modulation leads to a relative phase noise (RPN) that brings non-negligible performance degradation to coherent optical orthogonal frequency-division multiplexing (CO-OFDM) transmission systems with co-pumped Raman amplification. By theoretical analysis and numerical simulation, we proved that RPN brings more system impairment in terms of Q-factor penalty than the single carrier system, and relatively larger walk-off between pump and signal helps to suppress the RPN induced impairment. A higher-order modulated signal is less tolerant to RPN than a lower-order signal. With the same spectral efficiency, the quadrature-amplitude modulation format shows better tolerance to RPN than phase-shift keying. The reported findings will be useful for the design and optimization of Raman amplified CO-OFDM multi-carrier transmission systems.
authors: Jiadi
authors: J
authors: Wu
authors: Jingchi
authors: J
authors: Cheng
authors: Ming
authors: M
authors: Tang
authors: Lei
authors: L
authors: Deng
authors: Fu
authors: F
authors: Songnian
authors: Perry Ping
authors: PP
authors: Shum
authors: Deming
authors: D
authors: Liu