The application of Shannon’s theory to the optical ‘fiber channel’ faces many challenges. The most important is that
three phenomena are simultaneously at play in fibers: amplified spontaneous emission, chromatic dispersion, and the (instantaneous)
Kerr fiber nonlinearity (see Fig. 1a). Estimations of the ‘fiber capacity’ that include fiber nonlinearity have
relied on a variety of assumptions such as weak nonlinearity [4], low dispersion [5] or heuristic [6] and information rates [7]
approaches. In these studies, no connections are made to modulation, constellations and nonlinearity compensation.