  The explosion of demand for ultra-high information transmission rates over
the last decade has necessitated the usage of increasingly high light
intensities for fiber optical transmissions. As a result, the fiber
non-linearities need to be treated non-perturbatively. Similar analyses in the
past have focused on the effects of non-linearities on existing transmission
technologies, e.g. WDM. In this paper we take advantage of the fact that, under
certain assumptions, light transmission through optical fibers can be described
using the non-linear Schroedinger equation, which is exactly integrable. As a
particular example, we show that in the low Gaussian noise limit, the Gaussian
input distribution has a higher mutual information than the transmission using
WDM over the same available bandwidth.
