PhoxTrot is a large-scale research effort focusing on high-performance, low-energy and cost and small-size optical interconnects across the different hierarchy levels in Data Center and High-Performance Computing Systems: on-board, board-to-board and rack-to-rack. PhoxTrot will tackle optical interconnects in a holistic way, synergizing the different fabrication platforms (CMOS electronics, Si-photonics, polymers, glass, III-Vs, plasmonics) in order to deploy the optimal "mix&match" technology and tailor this to each interconnect layer. PhoxTrot will follow a layered approach from near-term exploitable to more forward looking but of high expected gain activities. The main objectives of PhoxTrot include the deployment of:. generic building block technologies (transmitters, modulators, receivers, switches, optochips, multi- and single-mode optical PCBs, chip- and board-to-board connectors) that can be used for a broad range of applications, extending performance beyond Tb/s and reducing energy by more than 50%.. a unified integration/packaging methodology as a cost/energy-reduction factor for board-adaptable 3D SiP transceiver and router optochip fabrication.. the whole "food-chain" of low-cost and low-energy interconnect technologies concluding to 3 fully functional prototype systems: an >1Tb/s throughput optical PCB and >50% reduced energy requirements, a high-end >2Tb/s throughput optical backplane for board-to-board interconnection, and a 1.28Tb/s 16QAM Active Optical Cable that reduces power requirements by >70%.To ensure high commercial impact after the end of PhoxTrot, all activities have been designed around current market roadmaps that will be updated during the course of the project and are led by industrial partners. PhoxTrot brings together the major European industrial and research players in the field. In so doing it will create a highly timely thrust and of unprecedented momentum in optical interconnects in Europe with worldwide impact.