  In this paper, a new method for the separation of noise categories based on
Four-Wave Mixing is presented.
  The theoretical analysis is grounded in the Gaussian Noise model and verified
by split step simulations. The noise categories react differently to the
introduced perturbations, by performing a set of perturbations the behaviour of
the different categories can be separated by means of a least-square fitting.
Given ASE is independent of the induced perturbations, it is possible to
separate noise contributions. The analysis includes constant and variable power
perturbations.
  The estimation of the noise categories is discussed from two points of view:
NSR evolution post-DSP processing, and over the power spectral density in a
notched region. The NSR estimation can only be performed at reception, whereas
the power spectral density approach can be performed along the optical link if
a high resolution Optical Spectrum Analyzer is available.
  Additionally, we perform a simple experimental verification considering of
two WaveLogic 3 transceivers for the NSR, successfully estimating the noise
contributions.
