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.

The remarkable success of the internet is unquestioned, touching all aspects of our daily lives and commerce. This success is fundamentally underpinned by 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 that allowed ready access to information otherwise inaccessible. Similarly, the remarkable growth of social media is supported by the introduction of optical fibres into data centres, allowing their tremendous growth. Exponential growth has been a characteristic of data communications since their first introduction in the 1970's and has been fuelled by the gradual introduction of radical technologies, such as optical amplification, wavelength-division multiplexing and coherent modulation. All of these technologies are today routinely deployed and it is widely acknowledged that fibres are becoming full. The limit to fibre capacity has its origin in the fact that the intense signals are significantly distorted by nonlinearly (a similar effect to overdriving loudspeakers). 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. Faced with the ongoing exponential growth in demand, unless these restrictions are lifted many parallel systems will be required, resulting in exponentially increasing energy consumption, until the cost of this resource becomes prohibitive and finally curtails growth. Only one technology, optical phase conjugation (acting like a mirror for colours), has been shown to offer the prospect of supporting continued internet growth without the need for widespread use of multiple fibres and the associated growth in energy consumption. Very much like Newton's Prisms, optical phase conjugation allows the distortion of one fibre (analogous to spectral spreading in Newton's prisms) to be compensated by a second identical fibre. In PHOS, we will - Optimise the devices which perform this conjugation, both in terms of the assessment of fundamental nonlinear materials and in terms of optimised sub-system configuration. - Demonstrate orders of magnitude increase in the capabilities of optical fibres for both practical point-to-point links with non-uniform span lengths and for optical networks with a plethora of diverse routes. - Verify that the use of optical phase conjugation is cost effective, both in terms of reducing the cost of a network deployment compared to existing products and in terms of enhancing the service provided to customers through higher capacity with lower latency. Furthermore, as optical phase conjugation will transform the capabilities of the network, PHOS will work to remove bottlenecks within the network transmitters and receivers, increasing their performance by an order of magnitude, resulting in 10 times faster connections. The approach of compensating impairments in the optical domain, combined with simplified digital signal processing and enhanced exploitation of fibre bandwidth will reduce the cost, size and power consumption associated with providing 10's of Tbit/s of capacity per optical fibre. If successful, PHOS will enable massively increased data capacities from the employment of Optical Phase Conjugation, giving the UK the most advanced optical communication network and a strong position to become a leading supplier of the technology worldwide.

Optical fibres lie at the heart of our increasingly technological society, for example: supporting the internet and mobile communications that we all now take for granted, saving lives through medical diagnosis and interventions using fibre-optic endoscopes, and enabling the mass production of a huge array of commercial products through fibre laser based materials processing. However, current fibre optics technology has its limitations due largely to the fact that the light is confined to a solid glass core. This places fundamental restrictions on the power and wavelength range over which signals can be transmitted, the speed at which signals propagate, and in terms of sensitivity to the external environment. These limits are now starting to impose restrictions in many application areas. For example, in telecommunications, nonlinear interactions between wavelength channels limit the maximum overall data transmission capacity of current single mode fibres to ~100-200 Tbit/s (for amplified terrestrial systems). Moreover, nonlinear, thermal and material damage thresholds combine to limit the maximum peak and average powers that can be delivered in a tightly focusable beam. This restricts the range of potential uses, particularly in the important ultrashort pulse regime increasingly used for a wide variety of materials processing applications These limitations can in principle be overcome by exploiting new light guidance mechanisms in fibres with a hollow core surrounded by a fine glass microstructure. Such fibres are generally referred to as Hollow Core Fibres (HCFs). Within this Programme we will seek to reinvent fibre optics technology and will replace the glass core with air or vacuum to produce Optical Fibres 2.0, offering vastly superior but largely unexplored potential. Our ultimate vision is that of a Connected World, where devices, machines, data centres and cities can be linked through these hollow light pipes for faster, cheaper, more resilient and secure communications. A Greener and Healthier World, where intense laser light can be channelled to produce goods and run combustion engines more efficiently and to image cancer tissues inside our bodies in real time. And an Explorative World, where hollow lightguides will enable scientific breakthroughs in attosecond science, particle physics, metrology and interplanetary exploration. Our overall ambition is therefore to revisit the way we think about light guidance and to develop a disruptive technology that challenges conventional thinking. The programme will provide the UK with a world-leading position both in HCF technology itself and in the many new applications and services that it will support.

Photonics is one of six EU "Key Enabling Technologies. The US recently announced a $200M programme for Integrated Photonics Manufacturing to improve its competiveness. As a UK response, the research proposed here will advance the pervasive technologies for future manufacturing identified in the UK Foresight report on the Future of Manufacturing, improving the manufacturability of optical sensors, functional materials, and energy-efficient growth in the transmission, manipulation and storage of data. Integration is the key to low-cost components and systems. The Hub will address the grand challenge of optimising multiple cross-disciplinary photonic platform technologies to enable integration through developing low-cost fabrication processes. This dominant theme unites the requirements of the UK photonics (and photonics enabled) industry, as confirmed by our consultation with over 40 companies, Catapults, and existing CIMs. Uniquely, following strong UK investment in photonics, we include most of the core photonic platforms available today in our Hub proposal that exploits clean room facilities valued at £200M. Research will focus on both emerging technologies having greatest potential impact on industry, and long-standing challenges in existing photonics technology where current manufacturing processes have hindered industrial uptake. Platforms will include: Metamaterials: One of the challenges in metamaterials is to develop processes for low-cost and high-throughput manufacturing. Advanced metamaterials produced in laboratories depend on slow, expensive production processes such as electron beam writing and are difficult to produce in large sizes or quantities. To secure industrial take up across a wide variety of practical applications, manufacturing methods that allow nanostructure patterning across large areas are required. Southampton hosts a leading metamaterials group led by Prof Zheludev and is well positioned to leverage current/future EPSRC research investments, as well as its leading intellectual property position in metamaterials. High-performance special optical fibres: Although fibres in the UV and mid-IR spectral range have been made, few are currently commercial owing to issues with reliability, performance, integration and manufacturability. This platform will address the manufacturing scalability of special fibres for UV, mid-IR and for ultrahigh power sources, as requested by current industrial partners. Integration with III-V sources and packaging issues will also be addressed, as requested by companies exploiting special fibres in laser-based applications. In the more conventional near-infrared wavelength regime, we will focus on designs and processes to make lasers and systems cheaper, more efficient and more reliable. Integrated Silicon Photonics: has made major advances in the functionality that has been demonstrated at the chip level. Arguably, it is the only platform that potentially offers full integration of all the key components required for optical circuit functionality at low cost, which is no doubt why the manufacturing giant, Intel, has invested so much. The key challenge remains to integrate silicon with optical fibre devices, III-V light sources and the key components of wafer-level manufacture such as on line test and measurement. The Hub includes the leading UK group in silicon photonics led by Prof Graham Reed. III-V devices: Significant advances have been made in extending the range of III-V light sources to the mid-IR wavelength region, but key to maximise their impact is to enable their integration with optical fibres and other photonics platforms, by simultaneous optimisation of the III-V and surrounding technologies. A preliminary mapping of industrial needs has shown that integration with metamaterial components optimised for mid-IR would be highly desirable. Sheffield hosts the EPSRC III-V Centre and adds a powerful light emitting dimension to the Hub.