Parameter selection in optical networks with variable-code-rate transceivers

Future flexible transceivers will be able to adjust modulation format, symbol rate and FEC scheme according to the channel and network conditions. This paper uses a combination of theoretical derivations and experimental results to recommend the best set of parameters to satisfy a specific demand to be routed along the network. In particular, for a given required OSNR (which is related to reach) and desired net bit rate, and assuming a capacity-achieving FEC scheme, the paper provides the set of modulation format, symbol rate and code rate which requires the minimum bandwidth, while offering an arbitrarily low bit error rate. We observed that optimum operating points required FEC schemes with overheads ranging from almost 0 to 100%, which is an important guideline for future flexible optical communications systems.