Beyond Exabit Optical Communications: from new devices, via new dimensions to new systems

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The aim of this fellowship is to develop disruptive approaches through theory and experiment to unlock the capacity of future information systems. To go beyond current channel limits is arguably the greatest challenge faced by digital optical communications. To target it, the proposed research will combine techniques from information theory, coding, higher-dimensional modulation formats, digital signal processing, advanced photonic design, and machine learning to make possible breakthrough developments to ensure a robust communications infrastructure beyond tomorrow.Optical communications have to-date been able to fulfil the ever-growing data demand whilst simultaneously reducing cost and energy-per bit. However, it is now recognised that systems are rapidly approaching the fundamental information capacity of current transmission technologies, a trend with potential negative impact on the economy and social progress. To meet future demands with prospective cost and energy savings and avoid the impending exhaust of fibre capacity, the only solution is the emergent technology of spatial division multiplexing (SDM). It provides much wider conduits of information by offering additional means for transporting channels over one single fibre, using multi-mode and multi-core fibres. However, SDM has not yet found a viable path to access this much higher information capacity. State-of-the-art SDM transceivers are only compatible with few-mode/few-core fibres (~10 paths) given the requirement to multiplex/demultiplex over all the fibre pathways to successfully estimate and unravel pathways crosstalk and walk-off. This completely defeats SDM's purpose, the installation of new fibres must allow for several decades of capacity growth to offset the high deployment costs of new cables.This fellowship envisages how to transform SDM technology to drive future optical networks by addressing the key issue overlooked by the research community since the introduction of SDM concepts: optical transceivers must undergo >100-fold integration to enable the benefits of multi-mode/core. Focus on new transceivers capable of digital space modulation will enable scalability of all data pathways to reduce the cost and energy-consumption per bit. Digital spatial modulation in novel coherent transmission schemes, i.e. the pathway index itself is used to carry information, will open fundamentally new theoretical and experimental possibilities up to now unexplored. These new transceivers will be capable of exploiting the multidimensional channel properties in the linear and nonlinear regimes through new spatial modulation formats and coding guided by new information theory and nonlinear science methods. Two main challenges are to construct a high-speed digital spatial modulator capable of dynamically addressing different groups of paths (potentially with tens of paths) in massive multi-path fibres and to develop new learning algorithms (guided by new theory methods) suitable of being embedded in spatial-adaptable transceivers to reach the ultimate capacity of nonlinear multi-dimensional channels.