Stream 6: Telecommunications II
Scalable Optical Access Architectures in 6G Front-Haul
Alexandros Stavdas, OpenLightComm Ltd
The role of fiber optic connectivity in access is indispensable to support the emerging 6G applications and services. This assertion is supported by a number of techno-economic factors, such as the fact that there are multiple 6G functional splits available with dissimilar transportation line-rate and processing trade-offs, while the higher the RF bandwidths in FR2 deployments, the shorter the distance between small cells. In a landscape where the connectivity technologies are converging, there are many interdependent issues that must be resolved via co-design, ranging from the eventual small-cell densification to the possibility of fiber exhaustion in the trunk and distribution segments. In this work, we present scalable optical access architectures, and we assess how these can accommodate different 6G functional splits. Moreover, we present the results of a network dimensioning studies, and we quantify how these architectures address the challenges associated with 6G small cell deployments.
Co-authored by: Alexandros Stavdas, Evangelos Kosmatos, Christos Matrakidis, and Ian Cooper; OpenLightComm Ltd.
Advanced Characterization of Optical Modulators and Coherent Receivers for Multi-Band Transmission Systems Beyond C- and L-Band
Robert Emmerich, HHI
We present a comprehensive review of the performance of currently available optical dual-polarization I/Q modulators and dual-polarization coherent receivers for multi-band transmission systems. Our evaluation covers various implementations of these technologies, facilitating the selection of components for prototype development aimed at efficient and sustainable capacity enhancement of already deployed single-mode fibre links. Our analysis includes measurements of individual components while focusing on their key performance indicators as a function of wavelength. Key findings of this investigation at the transmitter end include the identification of LiNbO3 and TFLN modulators as promising candidates for these systems, while InP modulators suffer from strong and undesirable wavelength dependencies. On the receiver side, discrete coherent receivers based on free-space technologies enable operation over a range of 200 nm, from E- to U-band. With additional components such as lasers, filters, wavelength-selective switches, and amplifiers now readily accessible, this will further drive research into multi-band systems.
End-to-End Learning based Probabilistic Constellation Shaping in High-Capacity Optical Fibre Communication Systems
Tianhua Xu, University of Warwick
The end-to-end learning approach has shown strong potential in achieving robust constellation shaping for optical fibre communication systems. However, current end-to-end probabilistic constellation shaping (PCS) methods, which utilise binary cross-entropy combined with source entropy to estimate generalised mutual information (GMI) as the loss function, fall short in fully realising the shaping gain. This limitation arises because, in PCS, both binary cross-entropy and source entropy are influenced by shifts in the probability distribution of square QAM constellation points, leading to a learned distribution that remains close to uniform. In response, this work introduces a novel end-to-end based PCS approach that incorporates a modified loss function, which includes an adaptive weight factor to adjust the impact of binary cross-entropy and source entropy on GMI dynamically. The GMI optimised with the proposed PCS aligns closely with the Maxwell-Boltzmann distribution for AWGN channels, for high-capacity optical fibre communication systems.
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