Abstract
A digital compensation scheme based on a perturbation theory for mitigation of cross-phase modulation (XPM) distortions is developed for dispersion-managed fiber-optic communication systems. It is a receiver-side scheme that uses a hard-decision unit to estimate data for the calculation of XPM fields using the perturbation technique. The intra-channel nonlinear distortions are removed by intra-channel digital backward propagation (DBP) based on split-step Fourier scheme before the hard-decision unit. The perturbation technique is shown to be effective in mitigating XPM distortions. However, wrong estimations in the hard-decision unit result in performance degradation. A hard-decision correction method is proposed to correct the wrong estimations. Numerical simulations show that the hybrid compensation scheme with DBP for dispersion and intra-channel nonlinear impairments compensation and the perturbation technique for XPM compensation brings up to 3.7 dBQ and 1.7 dBQ improvements as compared with the schemes of linear compensation only and intra-channel DBP, respectively. The perturbation technique for XPM compensation requires only one-stage (or two-stage when hard-decision correction is applied) compensation and symbol-rate signal processing.
Highlights
The performance of fiber-optic transmission systems is mainly limited by intra-channel [1,2,3] and inter-channel [4,5,6,7] nonlinear impairments
We have investigated a digital compensation scheme based on a perturbation theory to compensate for fiber nonlinearities in dispersion-managed fiber-optic systems
We considered a hybrid scheme, where the intra-channel distortions are removed by intra-channel Digital back propagation (DBP) and the XPM distortions are compensated by the perturbation technique
Summary
The performance of fiber-optic transmission systems is mainly limited by intra-channel [1,2,3] and inter-channel [4,5,6,7] nonlinear impairments. The distortion due to XPM can be compensated for using the DBP [17], in which coupled nonlinear Schrödinger equations (NLSEs) are solved using SSFS This scheme is quite effective; it requires huge computational resources since the step size should be about 3 km. We investigated the possibility of compensating inter-channel distortions using the lowcomplexity intra-channel DBP (with a step size of 40 km) and inter-channel distortions using the perturbation technique In this case, we found that the performance improvement is 2.4 dBQ as compared to the case of linear compensation for 2-channel WDM systems. Using the corrected hard-decision data, XPM distortion compensation is done again and the performance improvement over the linear compensation scheme is 3.2 dBQ We note that this method is applicable for WDM systems, and for superchannel systems with multiple carriers [22]. We have ignored the polarization dependence of the signals and limited our study to singlepolarization WDM systems
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