Electronic Nonlinearity Compensation in 112-Gb/s PDM-QPSK Optical Coherent Transmission Systems

We show that implementing pre- and post-dispersion compensation in electronic nonlinearity compensation can significantly improve the performance of 112-Gb/s PDM-QPSK coherent systems. More electronic compensation stages are required for a system without optical dispersion compensators (ODCs) than that with ODCs. Introduction Optical coherent detection with digital signal processing is considered a promising technology for optical networks. It can effectively compensate many linear effects such as chromatic dispersion (CD) and polarizationmode dispersion (PMD), and offers low required optical signal-to-noise ratio (OSNR) and high spectral efficiency compared with directdetection [1]-[3]. Electronic compensation of fiber nonlinearity has also been demonstrated, ranging from a simple power-dependent nonlinear phase rotation to the more effective (but more complex) electronic backpropagation [3]-[12]. In this paper, we study a multi-stage electronic nonlinearity compensator (ENLC) with reduced complexity that performs intra-channel nonlinearity compensation. We consider a 112Gb/s polarization-division-multiplexed quadrature-phase-shift-keyed (PDM-QPSK) signal. The transmission line can incorporate optical dispersion compensators (ODCs) or be without ODCs. We show that a simple optimization of the electronic dispersion precompensation before the first stage of the ENLC can largely improve electronic nonlinearity compensation. Moreover, a large difference in the ENLC complexity for systems with and without ODCs is observed.