Next-to-leading order corrections to capacity for nondispersive   nonlinear optical fiber channel in intermediate power region
  We consider the optical fiber channel modelled by the nonlinear Shr\"{o}dinger equation with zero dispersion and additive Gaussian noise. Using Feynman path-integral approach for the model we find corrections to conditional probability density function, output signal distribution, conditional and output signal entropies, and the channel capacity at large signal-to-noise ratio. We demonstrate that the correction to the channel capacity is positive for large signal power. Therefore, this correction increases the earlier calculated capacity for a nondispersive nonlinear optical fiber channel in the intermediate power region. 
A. A. Panarin, A. V. Reznichenko, and I. S. Terekhov
cs.IT math.IT