Overview and Comparison of Nonlinear Interference Modelling Approaches in Ultra-Wideband Optical Transmission Systems

Abstract

The recent advances in modelling nonlinear interference of systems operating beyond the C-band are discussed. Estimation accuracy as well as computational complexity of current approaches are compared and addressed. Keywords: optical fibre communication, ultra-wideband transmission, nonlinear interference, inter-channel stimulated Raman scattering INTRODUCTIONLightwave transmission extending beyond the C-band, exploiting the entire bandwidth of installed fibres, is increasingly being considered as a cost-effective alternative to deploying new multi-core/-mode fibres. However, for such ultra-wide bandwidths, the non-instantaneous nature of the nonlinear fibre response becomes significant, giving rise to inter-channel stimulated Raman scattering (ISRS). ISRS effectively transfers power from high to lower frequencies within the same optical signal. Although the physics of the interaction between the Kerr effect and ISRS are well understood [1], [2], efficient low-complexity performance models for modern coherent systems were (until recently) not available. Such models are key for efficient link design, real-time optimisation and physical layer-aware networking. Recently, much attention has been drawn to the development of such models, particularly by extending the modulation format independent Gaussian noise (GN) model to account for ISRS [3]- [11]. Extensions of the closed-form formalism for arbitrary, non-Gaussian modulation formats have been reported in [12]. Experimental demonstrations on the interaction between Kerr effect and ISRS followed up, in order to validate the theoretical predictions [5], [6], [13], [14]. To date, a number of modelling approaches exist in integral as well as in closed-form, varying in accuracy and complexity.In this paper, an overview of the recently proposed approaches of modelling nonlinear interference in ultrawideband transmission is presented. The estimation accuracies are compared to split-step simulations and their mathematical and computational complexity are briefly discussed.

Modeling and mitigation of fiber nonlinearity in wideband optical signal transmission [Invited]

“…Numerical solutions have been presented in [13][14][15][16][17][18], while closed-form approximations are described in [19][20][21]. A direct comparison can be found in [22]. It has been analytically shown that the induced nonlinear distortions are dependent on the transmitted modulation format, where significantly more complex models have been proposed to include such dependence for C-band systems (i.e., without ISRS) [23][24][25][26][27].…”

“…( 4) is written in terms of frequency while the result in [30] is written in terms of wavelength (resulting in a sign difference in the exponent and a different regression slope of the Raman gain function). As described in [22], Eq. ( 4) is used in the integral equations of the GN model to obtain an expression for η n ( f i ) as used in Eq.…”

Modelling the Delayed Nonlinear Fiber Response in Coherent Optical Communications

“…In addition to accurate integral formulations, fast closed-form approximations have been proposed to enable real-time performance estimations [32], [44]- [46]. A quantitative comparison between both approaches in integral and closed-form can be found in [47]. Furthermore, the link function of the ISRS GN model can be combined with the formalism derived in [48], to account for arbitrary (non-Gaussian) modulation formats [49]- [52].…”