Hi Abdallah,
When you say single vector representation do you mean that the different wavelength channels are now represented as a single channel with a center wavelength that is close to the average?
I think this simplifies your work as there is only one channel to worry about. For example, XPM becomes only SPM. The only difficulty is that your sampled signal needs to have a large enough bandwidth (I.E. sample rate) to contain the entire range of channels.
Regards