The invention proposes a system and method for selecting an optimal optical path through which to transmit an optical signal, the optimal optical path is one of a plurality of optical paths in a transparent optical network. Each of the plurality of optical paths includes a plurality of optical elements. For each of the plurality of optical paths, a first optical signal to noise ratio is determined for each optical element in the respective optical path. Then, for each of the plurality of optical paths, nonlinear distortions caused by each optical element in the respective optical path are modelled as Gaussian noise and a second optical signal to noise ratio associated with the modelled Gaussian noise is determined. Finally, the optimal optical path is selected using the sums of the first and second optical signal to noise ratios, respectively.