Study of optical switching nodes for 6G xHaul
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Date
2026-02-18
Authors
Ζησιμόπουλος, Σπυρίδων
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Abstract
The rapid expansion of next generation services is driving massive growth in fixed and mobile networks, accompanied by a consistent annual increase in network traffic. Consequently, telecommunications providers are shifting their focus toward developing networks that can handle this capacity while maintaining superior Quality of Service (QoS). Recent progress in coherent detection and transmitter-based processing enables a single optical transceiver to generate multiple smaller subcarriers. This pioneering approach, known as XR optics, introduces transformative architectural possibilities for next generation xHaul networks.
This thesis explores the transformation of current Point to Point optical networks and their restrictive electrical aggregation into flexible, scalable, and cost-effective Point to Multipoint networks, highlighting the necessity of a flexible midhaul with flexible switching nodes to support this paradigm shift. This architecture aligns with the hub and spoke traffic patterns observed in contemporary metro and access networks, achieving interoperability among transceivers of different speeds through individually routed, digitally generated subcarriers. Simultaneously, the disaggregation of the traditional Baseband Unit (BBU) into Central Units (CU), Distributed Units (DU), and Radio Units (RU), this model eliminates vendor lock in and provides enhanced flexibility in network configurations.
This thesis analyzes the feasibility of a flexible midhaul ring topology designed to support rising traffic demands. The experimental component utilizes the VPIphotonics Design Suite™ to conduct advanced network simulations. The core innovation of this study is the implementation of Mach Zehnder Interferometers with ring resonators (RAMZI), specifically a Nyquist filtering Interleaver and a Circular Subcarrier group Interlacer. These devices serve as fundamental building blocks for next generation 6G xHaul and were found to be highly efficient in realizing a scalable architecture. The results demonstrate that the proposed multi-node architecture remains robust across different fiber span lengths without being compromised by crosstalk effects. This research was conducted within the framework of the PROTEUS-6G research program, a proposal submitted to the European Commission for the development of revolutionary 6G communication architectures.
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Keywords
Passive optical networks (PONs), Digital subcarriers, Coherent detection, Reconfigurable optical add drop multiplexers (ROADMs)