title: Relative phase noise induced impairment in M-ary phase-shift-keying coherent optical communication system using distributed fiber Raman amplifier.
abstract: We show for the first time, to the best of our knowledge, that, in a coherent communication system that employs a phase-shift-keying signal and Raman amplification, besides the pump relative intensity noise (RIN) transfer to the amplitude, the signal's phase will also be affected by pump RIN through the pump-signal cross-phase modulation. Although the average pump power induced linear phase change can be compensated for by the phase-correction algorithm, a relative phase noise (RPN) parameter has been found to characterize pump RIN induced stochastic phase noise. This extra phase noise brings non-negligible system impairments in terms of the Q-factor penalty. The calculation shows that copumping leads to much more stringent requirements to pump RIN, and relatively larger fiber dispersion helps to suppress the RPN induced impairment. A higher-order phase-shift keying (PSK) signal is less tolerant to noise than a lower-order PSK.
authors.affiliation: Wuhan National lab for Optoelectronics, Huazhong University of Science and Technology, Wuhan, China.
authors.forename: Jingchi
authors.initials: J
authors.lastname: Cheng
authors.forename: Ming
authors.initials: M
authors.lastname: Tang
authors.forename: Songnian
authors.initials: S
authors.lastname: Fu
authors.forename: Perry Ping
authors.initials: PP
authors.lastname: Shum
authors.forename: Deming
authors.initials: D
authors.lastname: Liu