The gradual shrinkage of cell sizes in mobile cellular networks and applying frequency reuse techniques has been the main approach to cope with the exponential growth of capacity demands over the last few decades. However, the outdoor deployment of 5G cells will require a large-scale expansion of the backhaul network. The most preferred backhaul solution is based on highly reliable and high-speed fibre optic links; however, their use is limited to a fraction of the current backhaul network because of overwhelming installation costs. Free space optical (FSO) communication is an attractive alternative solution that provides high-capacity but cost-effective wireless backhaul connectivity without interfering with radio frequency (RF) communication systems. However, despite decades of technological advances, FSO links still suffer from availability issues in the form of occasional long outages in adverse weather conditions. This is because classical high-speed FSO receivers such as avalanche photodiodes (APDs) may totally fail under low visibility weather conditions. The important question is, therefore, whether we can build high-speed atmospheric optical communication links that can reliably operate over all weather conditions while providing data rates beyond their RF counterparts. ARROW aims to address the question above by combining classical and quantum optical receptions to allow for adaptive operation of FSO receivers within a wide range of sensitivity levels while keeping high-speed communication. However, highly sensitive quantum detectors such as single photon avalanche diodes (SPADs) are not practically suitable for terrestrial FSO links as they can easily saturate at typically high irradiance levels experienced at such links while their bandwidth is limited by effects such as dead time. ARROW's hybrid receiver employs an APD along with a large array of SPADs integrated into a single chip. The large size of array effectively relaxes the saturation issue of the SPAD-based detector while allowing for spectrally efficient modulations that can significantly improve its achievable data rate. ARROW receivers will combine the functionality of the classical and quantum detectors using hard and soft optical switching and efficient digital signal processing to support adaptive operation based on the slow varying weather condition. In order to design efficient switching and signal processing, we will develop an accurate but tractable theoretical model that describes the hybrid channel in terms of different atmospheric effects (e.g., visibility and background light level) and their interaction with the hybrid receiver's characteristics (e.g., SPAD dead time, detectors field of view, and optical splitting ratio). Based on this model, a number of optical frontend designs and advanced modulation and joint coding schemes will be proposed to enhance both data rate and reliability of the receiver. Finally, the adaptive functionalities of the hybrid receiver will be experimentally demonstrated and validated. ARROW FSO receivers are expected to provide carrier grade availability for a wide range of practical link geometries and geographical locations.

From the earliest invention of the camera, humans have been seeking to observe processes that are too fast or too complex for the human eye to follow. The first time-lapse images of a running horse, taken by Eadweard Muybridge in the 19th century, allowed us to understand its motion, freezing a moment in time so that we can examine minute details. It showed that a horse's feet all leave the ground when galloping, a controversial question hotly debated at the time. Importantly, the time lapse images were a full-frame view - a key concept which we will also employ in the instrument to be developed here. Today, in cellular biology, our understanding of cellular function continues to evolve as we observe complex dynamic processes played out under a microscope. The optical microscope is a non-invasive, non-destructive and non-ionising tool which can be used to study living cells and tissues. No other method can study molecules in living cells with anything remotely approaching its combination of spatial resolution, selectivity, sensitivity and dynamics. Modern sensitive and sophisticated electronic cameras can capture dynamic processes at high speed, revealing intricate details of these processes. Indeed, detector development is a very important aspect of progress in the field of microscopy. The aim of our project is to develop extremely sensitive and fast full-frame view cameras which will allow us to observe molecules and proteins in their natural habitat, the cell, without disturbing them - in a way the 21st century equivalent of Muybridge's galloping horse. We are interested in molecules that play a role in inflammation, which is the body's response to some kind of harm or injury. These molecules are called proteins, and they are many different ones in our cells. We specialise in finding out about a protein called the coxsackie virus adenovirus receptor (CAR). We want to know how they move around in time, bump into each other and stick together. So we have labelled them with a fluorescent label to observe them under a microscope. The special cameras we are going to develop will be able to see them with a very high resolution, and also very quickly and very precisely, by measuring the polarization of the fluorescence emitted by its label. They will allow us to observe the moment a cell responds to a chemical stimulus at the level of single proteins. This will help us to understand how inflammation occurs, on a molecular basis - which, at the moment, is still unknown. Imaging living cells is the best available approach to study this kind of biological question, and others, and, ultimately, the knowledge and insight gained by doing this work will enable us to design and develop drugs against inflammation, for the benefit of all of humankind.

In the near future, light emitting diodes (LEDs) will replace all other sources of light - from the lamps that light homes and offices to the headlights of cars. As well as providing illumination, these LEDs can be used to transmit data, and so offer an opportunity to create a new wireless infrastructure for data transmission. The demand for wireless communications to smartphones, watches, tablets and other devices is growing at a rate of 50% per year, and new technologies are needed to augment the capacity of conventional WiFi. Using LEDs in visible light communications offers a huge potential capacity to support this growth and to provide new services that use localised wireless communications. While LEDs can transmit the information, an optical receiver is needed to collect the transmitted light, convert it to an electrical signal and extract the transmitted data. The maximum amount of light that can be transmitted is limited by the illumination brightness and concerns for the eye safety and comfort of users. The sensitivity of the receiver therefore ultimately determines the range over which optical data can be transmitted and/or the maximum possible data rate. The sensitivity of existing receivers for visible light communications is limited by a combination of the methods used to collect light and the devices used to convert this light to an electrical signal. In this project we aim to create new super receivers that are significantly more sensitive than existing optical receivers; that overcome conventional limits for combining speed, sensitivity and easy alignment; that are thin and flexible enough to be easily integrated onto any device. A dramatic change in performance will be achieved by combining two technologies- fluorescent concentrators and arrays of single-photon avalanche photodiodes- in a receiver for the first time. The first will use fluorescent materials to absorb the transmitted light signal and re-emit it at a different wavelength onto the detector. Using this method we will collect light over large areas using a thin, flexible layer which guides and concentrates the emitted light to its edges. The second technology is a light detector capable of detecting individual photons. We will develop methods to count photons from the transmitter in the presence of ambient light. We will explore how to optimise the fluorescent materials and light collecting layer to efficiently concentrate light onto one or more light detectors, and develop methods to maximise the amount of data transmitted by optimising how the data is represented. These super receivers will be tested in free-space visible light communications links to quantify their performance. Our estimates suggest that this approach could lead to a 100 times improvement in performance over current receivers, enabling faster data transmission, longer transmission ranges and the ability to operate in difficult environments, such as in the presence of bright ambient light.

The use of in vivo microscopic imaging is widespread for fundamental research using animal models in biomedicine, for drug discovery and tracking disease progression. Deep-tissue imaging is, however, highly invasive and so termination of the animal normally occurs after each measurement. For experiments involving testing with multiple timepoints, for example for studying disease progression or cell migration, termination of an animal for each timepoint can require the use of a large number of animals to achieve a reliable research outcome. Furthermore this provides only snapshots of phenomena, hampering understanding of cell fate and function. We will develop a multi-modal, miniaturised microscope and develop techniques for surgically implanting the microscope into an animal for multimodal microscopic imaging over extended time periods. The microscope will be sufficiently small and configured to be minimally intrusive for animal comfort. For example the microscope objective will be anchored with cement to vertebrae or bones around joints and optical image guides will transmit images to detector arrays that can be remotely located within body cavities with minimal or no discomfort to the animal. The microscope can be recovered at the end of the study. The research project will provide the following advantages that align with the aims of NC3Rs: -For longitudinal studies there will be a clear proportionate reduction in the number of animals sacrificed. -The improved control provided by the use of only a single animal for each longitudinal measurement will enable reliable research outcomes to be achieved with fewer animals. -Real-time imaging during normal animal behaviour will provide for improved quality of data for certain experiments and will reduce the animal stress associated with anaesthesia. Taking these two first aspects into account we aim to reduce the number of animals used by a factor of ten for longitudinal studies in each of three active research programmes involving spectral imaging and fluorescence imaging of the spinal cord and of joint tissue.

This project is all about multi-disciplinary collaboration - and capitalisation in a clinical setting of the many new vistas and opportunities that will arise. As such this research programme brings together a group of world class scientists (physicists, chemists, engineers and computer experts) and clinicians to design, make and test a cutting-edge bedside technology platform which will help doctors in the intensive care unit (ICU) make rapid and accurate diagnoses that would inform therapy and ensure patients get the right treatment, quickly. While we are developing our technology platform with a focus on ICU, it will also be applicable to a wide range of other healthcare situations. ICU patients suffer high death and disability rates and are responsible for a disproportionate financial burden on the health service. Potentially fatal lung complications are a common problem in ventilated ICU patients and doctors caring for these patients in the ICU face many challenges, often needing to make snap decisions without the information necessary to properly inform those decisions. The technology platform developed in this programme will provide doctors with important information on the state of ICU patients and whether they have infections, inflammation or scarring in their lungs. Currently there are no methods to do this accurately. This information will aid them in making decisions about treatment. A new approach to rapidly diagnose lung complications in ICU would enable doctors to target the correct drugs to the appropriate patients and to withdraw drugs with confidence, with resultant improvement in patient outcomes and major cost efficiencies - thus revolutionising ICU care. Using advanced fibre optic technology and micro-electronics and new sensor arrays our ground-breaking solution is to create a novel fibre-based probe that can readily be passed into the gas exchanging areas of the lung and blood vessels of ICU patients. The probe will house a variety of special optical fibres, some of which allow clinicians to "view" inside the lung while others will be modified with sensors that can measure important parameters such as oxygen concentration and acidity in both blood and lung. In addition the fibre will deliver tiny amounts (microdoses) of 'smart reagents' that fluorescently detect specific bacteria and other agents that can damage the lung. When integrated together these signals will provide highly specific information about the degree or type of lung damage and the potential causative 'bug' if an infection is suspected. Because of the large amount of information generated and in order to make it easily interpreted by doctors, computing experts will convert these signals into easy-to-understand disease readouts for our clinicians. Work on the different elements needed to create this technology platform will be undertaken by groups of chemists, physicists, engineers, computer scientists and biologists working at Bath, Heriot Watt and Edinburgh universities. Crucially, this programme will bring these scientific disciplines together in a "hub" where they will work side-by-side, promoting integration of purpose and to ensure that advances are rapidly translated into the clinical setting. This interdisciplinary hub will also provide a fertile training base for new PhD students who will learn the cross-disciplinary skills that will equip them to meet the challenges of translating the current 'revolution' in physical sciences into benefit for UK healthcare. In summary this project will generate; 1) a new cohort of scientists trained in physical and biological science that have a full appreciation of clinical translational and commercialisation pathways and who are equipped to meet the challenges of converting advances in basic science into healthcare benefit and; 2) a cutting-edge bedside technology platform which will help doctors in the ICU make rapid and accurate diagnoses.