Calculation of Mutual Information for Partially Coherent Gaussian Channels With Applications to Fiber Optics

Bernhard Goebel, René-Jean Essiambre, Gerhard Kramer, Peter J. Winzer, Norbert Hanik
2011 IEEE Transactions on Information Theory  
The mutual information between a complex-valued channel input and its complex-valued output is decomposed into four parts based on polar coordinates: an amplitude term, a phase term, and two mixed terms. Numerical results for the additive white Gaussian noise (AWGN) channel with various inputs show that, at high signal-to-noise ratio (SNR), the amplitude and phase terms dominate the mixed terms. For the AWGN channel with a Gaussian input, analytical expressions are derived for high SNR. The
more » ... r high SNR. The decomposition method is applied to partially coherent channels and a property of such channels called "spectral loss" is developed. Spectral loss occurs in nonlinear fiber-optic channels and it may be one effect that needs to be taken into account to explain the behavior of the capacity of nonlinear fiber-optic channels presented in recent studies.
doi:10.1109/tit.2011.2162187 fatcat:3fwwsnccqzaazhve4uyertc2ju