EE Seminar: Mitigation of Nonlinear Interference in Fiber-Optic Communications
Speaker: Omri Geller,
M.Sc. student under the supervision of Prof. Mark Shtaif and Prof. Meir Feder
Wednesday, November 2nd, 2016 at 13:00
Room 011, Kitot Bldg., Faculty of Engineering
Mitigation of Nonlinear Interference in Fiber-Optic Communications
Abstract
Nonlinear interference noise (NLIN) that is caused by the nonlinear interactions between different channels in a Wavelength Division Multiplexed (WDM) system is a major factor in limiting the capacity of fiber-optic systems. Often, it is convenient to treat NLIN in the same way as one treats amplified spontaneous emission (ASE) noise. However, when it comes to system design this approach is clearly sub-optimal as it does not take into account the fact that NLIN, unlike ASE, is not white noise and can in fact be mitigated. Therefore, methods for mitigation of the NLIN are highly desired in order to improve system performance.
In this work we consider the problem of mitigating NLIN in the fiber-optic channel where the goal is to design practical algorithms for NLIN reduction in realistic systems that transmit Quadrature Amplitude Modulated (QAM) symbols. We first present the analytic model of the NLIN and focus on two of its features - its long temporal correlations and its dependence on the modulation format. Then we demonstrate NLIN mitigation using a practical decision directed recursive least-squares algorithm which takes advantage of the temporal correlations of the NLIN. We then take advantage of the modulation format dependence of the NLIN and propose several practical shaping algorithms for mitigating the effect of NLIN. We show that the resulting shaping gain in the presence of nonlinearity is considerably larger than the gain predicted in the literature on the basis of linear considerations. Finally, using these shaping algorithms, we show that in certain scenarios the total shaping gain in the fiber-optic channel may be higher than 1.53 dB, a value that is known to be the ultimate shaping gain limit in the linear AWGN channel.
