Data Center networking requirements have evolved rapidly in recent years. Driven by services that include the Internet of Things, Big Data processing, Cloud Services and Social Media, large-scale Data Center providers are in urgent need to develop scalable solutions that will accommodate the ever growing capacity demands in a cost- and energy-efficient manner and provide simplified data center management and automation. As a result, we have recently seen several important developments in the implementation of interconnects offering ever broader bandwidths, which have attracted fevered discussions on what may be the most effective route forward towards their adoption. Advances in silicon technology have allowed for more compact and affordable hardware implementations. However, the limits to the capabilities of current transceiver and switching technologies are already in sight, forcing Data Center providers to upgrade their hardware every few years. The wide adoption of pluggable 100 Gb/s systems and the technology push towards small form-factor transceivers with capacities that are several multiples of this, triggers the development of a whole new technological ecosystem, including new fibre and device technologies as well as networking concepts and architectures. In this rapidly evolving environment, this Special Issue offers a timely insight to some of the latest research developments in areas including: – Integrated photonic technologies, including sources, switches, silicon photonic integrated circuits and their packaging – Novel fibres to serve Data Center Interconnects – Data Center Communication links – Advanced Data Center networking concepts We hope that this collection of invited papers from some of the leading research groups working on Data Center Communications will provide the readers with a detailed appreciation of the state-of-the-art in this hot application area of optical communications, and that it will inspire further cutting-edge research in the field. We would like to thank all of the authors, as well as the anonymous reviewers of the papers for their hard work towards ensuring a high quality Special Issue. This Issue would not have been realised without the initiative, guidance and patience of Editor-in-Chief Bertrand Desthieux, whose leadership and contribution we gratefully appreciate.