Multidimensional Modulation and Coding in Optical Transport

This paper reviews the performance of optimized modulation formats in two, four, and eight dimensions. We present performance (lower bounds) for higher dimensions by exploiting known performance of binary block codes. Ultimately, the achievable information rates of given modulation formats and receiver types are limited by the mutual information and generalized mutual information. We exemplify how these metrics can be used for system performance as well as to quantify the performance differences between four types of systems, using hard or soft decision on bits or symbols.