The growing popularity of cloud and multimedia services is increasing the traffic volume that datacentres need to handle, leading to serious bottlenecks in datacentre networks in terms of both capacity and energy consumption. Reducing the power required by the inter- and intra-rack communication inside the datacentre through use of optical technology opens a way to solve this problem. However, the current optical switching technologies are not able to support the dynamic datacentre traffic, and hence, new optical interconnect architectures are needed. The purpose of this project is to enable a highly scalable, flexible and energy-efficient network inside the datacentre by a novel optical datacentre network architecture, based on integration of broadcast-and-select and elastic spectrum allocation. We will tackle several fundamental research problems, in order to achieve the following challenging goals of the project: (1) Ultra-high capacity inside the datacentre, (2) Reduced energy consumption of the datacentre network, and (3) Flexible provisioning of connectivity inside the data centre. A successful completion of the project goals requires a cross-layer approach, combining physical layer modeling with logical layer techniques into a universal framework for analysis, simulation, and optimization. The team behind this application, i.e., the research groups at KTH, Chalmers and LiU, possesses a unique combination of expertise for addressing these challenging research problems.