A Discrete-Time Polynomial Model of Single Channel Long-Haul Fiber-Optic Communication Systems

To mitigate various physical impairments of long-haul dense wavelength division multiplexing (DWDM) systems and exploit their system capacity, there is a need to develop a two-dimensional (time and wavelength) discrete-time input-output model which can become the foundation of signal processing for optical communications. As the first step, this paper develops a model for single channel multipulse multispan systems based on the Volterra series transfer function (VSTF) method. This model is suitable for high-bit-rate time-division multiplexing (TDM) transmission in the pseudo-linear regime and is easily extendable to the multichannel case. We overcome the well-known triple integral problem and reduce it to a simple integral. This model takes into account fiber losses, frequency chirp and photodetection, which are ignored in the literature. Furthermore, with this model we introduce the intersymbol interference (ISI), self phase modulation (SPM), intrachannel cross phase modulation (IXPM) and intrachannel four wave mixing (IFWM) coefficients to characterize the impact of these effects on the system performance. The model is in excellent agreement with SSF (split-step Fourier) simulation. To illustrate its application, we develop a constrained coding scheme based on the system model to suppress the impact of various impairments.