Forthcoming optical x-haul infrastructure supporting 6G mobile network requirements

The sixth generation of communication networks necessitates a series of significant technological innovations to accommodate ultra-high rates, ultra-low latency, high energy efficiency, and software-defined programmability for supporting the emerging use cases and the exponential growth in traffic demands. Ultra-wideband (UWB) and spatial division multiplexing technologies have emerged as key enablers in meeting these challenges, offering both scalable network capacity and improved energy efficiency. In this paper, we propose an advanced optical transport architecture designed to fulfill the rigorous performance criteria of next-generation optical networks covering all critical network segments. At the core of this infrastructure—the backhaul segment—we introduce a three-layered UWB/SDM-based multi-granular optical node architecture that utilizes photonic integrated circuit (PIC)-based waveband selective switches, enabling scalable network performance and delivering over 10 Pb/s of flexible optical switching capacity while maintaining a high optical signal-to-noise and interference ratio. At the network edge—the fronthaul segment—we introduce a spatially diverse point-to-multipoint PIC-based optical subcarrier interconnectivity architecture that incorporates a low-loss module—referred to as the interlacer—which interconnects cascaded half-band Nyquist-shaped interleaver filters in order to flexibly perform routing at the subcarrier group level. Across all network segments, we consider innovative, energy-efficient optical digital-to-analog converter-based transceivers capable of achieving transmission rates in the order of terabits per second per channel, while ensuring a small footprint and low power consumption. These transceivers can be flexibly reconfigured to either direct detect or coherent operation, serving the specific needs of the different network segments. Extensive numerical simulations are conducted, with parameters mostly derived from experimental data, to assess the feasibility, scalability, and cascadability of the subsystems that are incorporated to optimize the overall performance of the proposed architecture. Finally, the overall design ensures full compatibility with a service management and orchestration framework, enabling software-defined programmability across all interconnected segments.