Information capacity of optical channels

The chapter starts with a brief introduction of some basic concepts of information theory, introducing the notion of channel capacity and focusing on some issues that are particularly relevant for the optical fiber channel but often only briefly touched in classical textbooks on information theory: how to deal with waveform channels, with memory, and with the unavailability of an exact channel model. The optical fiber channel is then described by presenting the main equations governing the propagation of light in optical fibers and by discussing a few different approximated channel models that can be deployed for an information theoretical analysis, providing different trade-offs between accuracy and complexity. The last part of the chapter is devoted to the study of the capacity of the optical fiber channel, providing both easy-to-compute capacity bounds and more accurate but complex bounding techniques, and considering different scenarios and link configurations. Future perspectives and open problems are finally discussed.