Extremely Wideband Optical Fibre Communication Systems

The exponential growth in the use of bandwidth-hungry internet services such as high-definition video streaming, cloud computing, artificial intelligence, Big Data and the Internet of Things requires new advances in optical data transmission technologies to achieve ultra-high throughputs and minimal latencies. To go beyond current channel limits is arguably the greatest challenge faced by digital optical communications. To target it, the proposed research programme will develop new approaches to significantly increase the capacity of future communication systems focusing on the ultrawideband optical transmission and amplification in combination with adaptative coded modulation and digital signal processing, to ensure a robust communications infrastructure beyond tomorrow.

Systems capacity is bounded by three dimensions: bandwidth, information spectral density and space. Whilst much research has focused on maximising the information spectral density and investigating space division multiplexing, little attention has been paid to the bandwidth domain. We propose to significantly extend the channel bandwidth with transceivers, broadband optical amplifiers, beyond the well-established erbium doped fibre amplifier (EDFA), focusing on bismuth and thulium doped fibre amplifiers with the assistance of Raman-amplification. Together with space division multiplexing, based on multiple fibres or new multi-core fibres, will ensure system capacities of tens of Petabit/s will be possible in the future. In EWOC research, we will gain a deeper understanding of the fundamental nonlinear effects that govern the upper limit on capacity in such ultra-wide systems, never previously investigated. Three main challenges are: (i) to fully utilise the bandwidth of the ubiquitous silica fibres low-loss window, overcoming the single mode fibre constraints, to reach bit rates of up to 250 Tb/s per core; (ii) to operate beyond the Raman gain shift - means that the associated nonlinear signal-to-signal interference in the widely diverse dispersion and nonlinearity regimes must be understood, quantified and effectively mitigated and (iii) experimentally demonstrate the combination of the significantly increased bandwidth with novel coded modulation, advanced DSP and nonlinearity mitigation in a wide variety of distance and bitrate transmission scenarios and applications in core, access and data centre networks.

The EWOC proposal is a collaboration between UCL's Optical Networks Group and the University of Southampton Optoelectronics Research Centre and 6 world-leading industrial partners spanning network and service providers (BT and KDDI), equipment systems (Xtera and Nokia) and optical fibre/amplifier (Corning/OFS) manufacturers, a testament to the strategic importance of this research.

The importance of ubiquitous, broadband, high-capacity, low delay and secure telecommunications infrastructure is critical to the UK's future and economic success. The recently published report of the National Taskforce on Telecoms Equipment Diversification Task Force (https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/975007/April_2021_Telecoms_Diversification_Taskforce_Findings_and_Report_v2.pdf) has highlighted the need for R&D to ensure this: 'Research, development and innovation are central to the development of new telecoms solutions and technologies and a major competitive advantage for incumbent vendors. Therefore, R&D activity and investment is vital in driving diversification' recommending 'The Government should invest in projects aimed at early development and growth of systems integration skills in the UK. Such projects will ensure it builds a competitive advantage in this domain, and as an early element of its ambition to build UK capability'. The EWOC proposal is focused on both of these goals.