Metro-aggregation networks are undergoing a major transformation to accommodate the exponential growth in data traffic, requiring scalable and cost-effective solutions. On the transceiver side, coherent pluggable optics are set to be the dominant transmission solution, in view of the cost, footprint, power consumption, and interoperability benefits. On the line system side, filterless optical networks (FONs) offer architectural simplicity and potential CAPEX savings, despite introducing challenges such as spectrum waste, channel power imbalance, and increased impact of outof- band noise. Conversely, reconfigurable optical adddrop multiplexer (ROADM) architectures based on wavelength blocker (WB) using wavelength selective switch (WSS) mitigate these limitations, albeit at the expense of higher insertion loss (IL) and complexity. A comprehensive comparative analysis of FON and WBbased ROADM architectures considering a horseshoe topology in metro-aggregation network scenarios is presented. Customized algorithms to optimize optical amplifier (OA) settings are proposed for each architecture. The resulting network design framework is used to characterize the scalability of metro-aggregation networks based on each architecture when considering different network sizes and offered capacity per node. Results highlight that adopting higher-performance multi-source agreement (MSA) transceivers and implementing tailored OA settings optimization mitigates the limitations of FON architectures. Moreover, the study demonstrates that the most suitable solution, in terms of transceiver type and line system architecture combination, depends on the network size and target capacity.

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• Electrical Engineering, Electronic Engineering, Information Engineering - Engineering and Technology