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

Future flexible transceivers will be able to adjust modulation format, number of subcarriers, symbol rate, and forward error correction (FEC) scheme, according to 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 transparent reach and desired net bit rate, and assuming an FEC scheme with a constant gap to capacity, the paper provides a set of modulation format, number of subcarriers, symbol rate, and code rate, which requires minimum bandwidth, while offering a conveniently low bit error rate (in optical systems, typically 10-15). We observed that optimum operating points required FEC schemes with overheads ranging from almost 0 to 145%, which is an important guideline for future flexible optical communications systems.