Fiber nonlinearity limits the use of coherent optical orthogonal frequency division multiplexing (CO-OFDM) to upgrade wavelength-division multiplexing (WDM) systems using legacy non-return-to-zero-on-off-keying (NRZ-OOK) channels. This letter proposes to compensate for the fiber nonlinearity of CO-OFDM with NRZ-OOK neighbors by combining digital signal processing (DSP)-based self-phase modulation (SPM) post-compensation with pilot-tone-based cross-phase modulation (XPM) compensation. The simulation results demonstrate that the optimum low-pass filter bandwidth for pilot-tone-based XPM compensation depends on the pilot-to-signal ratio value and launch optical power. Our method allows a 4-dB increase in the launch power for a 40-Gb/s single polarization CO-OFDM channel placed in the middle of six 10.7-Gb/s NRZ channels in a 50-GHz space and 1 200-km WDM system.
© 2012 Chinese Optics Letters
(060.1660) Fiber optics and optical communications : Coherent communications
(060.2330) Fiber optics and optical communications : Fiber optics communications
(060.4080) Fiber optics and optical communications : Modulation
(060.4370) Fiber optics and optical communications : Nonlinear optics, fibers
Fiber Optics and Optical Communications
Mingliang Deng, Xingwen Yi, Jing Zhang, Hongbo Zhang, and Kun Qiu, "Fiber nonlinearity compensation for CO-OFDM transmission with 10.7-Gb/s NRZ-OOK neighbors," Chin. Opt. Lett. 10, 110602-110602 (2012)