As recently discussed by the Wall Street Journal, the remarkable success of the internet may be attributed to the tremendous capacity of unseen underground and undersea optical cables and the associated technologies. Indeed, the initial surge in web usage in the mid-1990s coincides with the first optically amplified transatlantic cable network allowing ready access to information otherwise inaccessible. Tremendous progress has been made since then, and since the introduction of the single mode optical fibre network by BT in 1983 all developments have exploited the same physical infrastructure, enabling return on investment over three decades in time and almost five orders of magnitude in capacity. However, of equal importance have been the "last mile" actually connecting customers to the network. Whilst growth in the last century was supported by the existing copper infrastructure, todays networks are more technologically fractured, split between (in order of capacity, ranging from a few kbit/s to a few Gbit.s) this legacy network, satellite distribution (plagued by poor latency), wireless networks, hybrid fibre/copper (eg BT Infinity), coaxial networks (cable TV), passive optical networks and point to point optical networks. Each of these solutions offer unique features suited to today's market, enabling competition between network operators (eg BT, Virgin, EE) as well as service providers. However, with the exception of fibre based solutions the potential for further capacity growth is limited. As demand for communication services applications continue to grow in number (e.g. Twitter, YouTube, Facebook, etc.) and in bandwidth (e.g. HDTV, 4k video...), all parts of the communication systems carrying this traffic must be able to operate at higher and higher speeds. This ever-growing capacity demand can only be handled by continually upgrading the capacity of all parts of the network, including long-haul links between major cities, as well as the critical 'last mile' distribution networks ending at or near the customer premises which are the focus of this project. In UPON, rather than continuing to introduce this series of platforms, each optimised for a specific application and data rate, we will identify the network configuration which allows the maximum possible capacity per user (with a single connection), considering both the limitations of the access network itself (arising from trade-off between nonlinearity and noise) and the practically achievable capacity in the core network. This unique approach will allow the development of a single, optimised network configuration with the highest possible growth potential. By considering techno-economic modelling as a fundamental component of the network design, with equal weight to technological constraints, will also identify, propose and demonstrate cost effective evolution scenarios. These scenarios will enable the gradual roll out of network capacity and customer demand and bandwidth intensive applications are developed over the next decades. This will be achieved in three phases: Experimental and theoretical analysis, of the impact of geographical layout on the signal loss, of the impact of various forms of optical distortions - most importantly nonlinear distortions where the light intensity alters the refractive index of the fibre itself, and cost; Development of novel technologies to enhance the achievable data rates for each customer, specifically exploiting the unique properties of a new form of optical amplifier the "Fibre Optic Parametric Amplifier", and new transmission fibres specifically designed for access applications; Experimental demonstrations proving the feasibility of the UPON configuration and influencing the decision making processes within major network operators. If UPON is successful, it will pave the way for the highest possible connectivity between people, offering unprecedented quality of experience, at the optimum cost.

As recently discussed by the Wall Street Journal, the remarkable success of the internet may be attributed to the tremendous capacity of unseen underground and undersea optical fibre cables and the technologies associated with them. Indeed, the initial surge in web usage in the mid 1990s coincides with the commissioning of the first optically amplified transatlantic cable network, TAT12/13 allowing ready access to information otherwise inaccessible. Tremendous progress has been made since then, with the introduction of wavelength division multiplexing, where multiple colours of light are used to establish independent connections through the same fibre and coherent detection, the optical analogue of an advanced radio receiver able to detect both amplitude and frequency (or phase) modulation simultaneously enabling the information carrying capacity to be doubled and the required signal power to be reduced. To manage the costs, communication networks typically aggregate connections between many users onto a single communications link within the core of the network, avoiding the tremendous costs associated with dedicated links for all users across vast distances. Typically the trade of between cost and reliability has resulted in traffic from several thousand customers being aggregated onto a single fibre resulting in bit rates in the region of 100 Gbit/s per wavelength channel to support broadband connections of around 10 Mbit/s. However, this has resulted in intensities in optical fibres that are a million times greater than sunlight at the surface of the Earth's atmosphere and so the signal is significantly distorted by nonlinearly (a similar effect to overdriving load speakers). This distortion limits the maximum amount of information which may be transmitted across and optical fibre link, and unless combated, the nonlinear response will result in a capacity crunch, limiting access to the internet to today's levels. This project aims to allow the continued increase of the bandwidth of these fibre networks underpinning modern communications, including 17.6 million UK mobile internet connections and 70% penetration of home broadband connections. To increase capacity we will maximise spectral use, by adapting techniques found in mobile phones for use in fibre networks, resolving the significant issues associated with processing data with 1,000,000 times greater bandwidth using a balance of digital and analogue electronic and optical processing. This will reduce cost, size and power consumption associated with producing Tb/s capacities per wavelength. Critically, the project will develop techniques to understand and mitigate the nonlinear signal distortions. Nonlinear distortions occur within a channel, between channels and between each channels and noise originating in the optical amplifiers. By transforming the signal mid way along the link, we will exploit the nonlinear response of the second half of the fibre link to cancel the nonlinear distortion of the first to minimise the impact of nonlinear distortion associated with the channels themselves, and optimise the configuration of the system to minimise the nonlinear interaction with the noise, resulting in orders of magnitude increases in the maximum capacity of the optical fibre system.