Abstract
The potential of optimum selection of modulation and forward error correction (FEC) overhead (OH) in future transparent nonlinear optical mesh networks is studied from an information theory perspective. Different network topologies are studied as well as both ideal soft-decision (SD) and hard-decision (HD) FEC based on demap-and-decode (bit-wise) receivers. When compared to the de-facto QPSK with 7% OH, our results show large gains in network throughput. When compared to SD-FEC, HD-FEC is shown to cause network throughput losses of 12%, 15%, and 20% for a country, continental, and global network topology, respectively. Furthermore, it is shown that most of the theoretically possible gains can be achieved by using one modulation format and only two OHs. This is in contrast to the infinite number of OHs required in the ideal case. The obtained optimal OHs are between 5% and 80%, which highlights the potential advantage of using FEC with high OHs.
Highlights
AND MOTIVATIONThe rapid rise in the use of the Internet has led to increasing traffic demands putting severe pressure on backbone networks
To cope with increasing capacity demands, future optical networks will use multilevel modulations and forward error correction (FEC). This combination is known as coded modulation (CM) and its design requires the joint optimization of the FEC and modulation format
For the Deutsche Telekom Germany (DTG) and NSF networks, there is no difference between HD and SD in terms of network throughput as the minimum signal-to-noise ratio (SNR) of all light paths is above the SNR threshold
Summary
The rapid rise in the use of the Internet has led to increasing traffic demands putting severe pressure on backbone networks. To cope with increasing capacity demands, future optical networks will use multilevel modulations and FEC This combination is known as coded modulation (CM) and its design requires the joint optimization of the FEC and modulation format (see Fig. 1). The optimal modulation format based on an approximation for the maximum achievable rates of HD-FEC was considered in [16]. In [35], the closed form solution of the GN model of [34] was used to adapt the routing and wavelength assignment problem, for a target pre-FEC BER, and four different modulation formats. We use information theoretic quantities (i.e., achievable rates) and a realistic model for the nonlinear interference to study the maximum network throughput of optical mesh networks.
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