Non-linear function for a Gaussian photo-reception in standard IM/DD systems

Abstract

In this paper, a set of mathematical transformations is developed to obtain the nonlinear function that recovers the Gaussian statistics after the square law distortion produced by the photodetector in Intensity Modulated/ Direct Detected IM/DD systems. Linear impairments in the optical domain like the Amplified Spontaneous Emission (ASE) or the Rayleigh Backscattering (RB) noise are considered the predominant. Here for the first time, a mathematical non-linear function is obtained without assuming any predefined function form. The result is that the noise distribution can be considered more signal-independent Gaussian after this non-linear transformation, than by using any other previously published operation. Applying this function in post-detection enables to make the system more linear, and then would improve the performance of the conventional electronic equalizers (EE). When using Maximum Likelihood Sequence Estimators (MLSE), a simplified metric can be used. Since the channel transfer function can be easily reproduced, computational cost and complexity are reduced.