MIRAGE - a new project supported by the Seventh Framework Programme (FP7), Information and Communication Technologies (ICT) of the European Commission (EC) - was launched recently with the goal of developing next-generation optical interconnect technology for terabit data links.

Focusing on optical rack-to-rack and board-to-board interconnects, the three-year research project brings together seven academic and industrial partners in the optical value chain. Headed by Greece’s National Technical University of Athens, partners also include the Aristotle University of Thessaloniki in Greece; nanoelectronics research institute Imec of Leuven, Belgium; UK-based OptoScribe Ltd; Austriamicrosystems AG; and Aachen-based AMO GmbH and Technische Universität München in Germany. The project’s total budget is €4.17m, including €3m from the EC.

The internet is morphing into a content-centric network with billions of users demanding ubiquitous, instant access to vast amounts of data. In this new networking paradigm, the hot spots are the data centers, where the bulk of the information is residing. These data centers may consist of hundreds or even thousands of servers interconnected with each other. The content providers are in a constant race to increase this interconnection speed to improve the delivery of the data to the end user.

MIRAGE’s aim is to increase the optical interconnect speed, which currently tops at around 140Gb/s per link, and bring it to the terabit realm. To do so, the program will tackle the issues that still have to be solved to develop technology suitable for commercial adoption. For example, it will look into high-speed VCSELs (vertical-cavity surface-emitting laser), low-energy electronic drivers, a flexible motherboard technology that allows new functionalities such as wavelength multiplexing, multi-level modulation and multi-core fibre coupling, and ways to introduce new degrees of parallelization into the optical interconnects. In addition, project partners will develop new assembly processes based on 3D integration of electronic and optical components to effectively blend silicon, glass and III-V photonic elements with CMOS silicon electronic drivers.

As part of the project, Imec’s associated lab at Ghent University will develop the dedicated high-speed low-power VCSEL driver array and the transimpedance amplifier (TIA) array. In these IC designs, Imec will focus on the close integration and matching of the drivers with the corresponding VCSEL/photodiode arrays. Its team aims to co-optimize the electronic circuits, parasitic elements, interconnects and optical-electronic-optical component parameters to take advantage of the various new technologies developed by the MIRAGE consortium.

In addition, Imec will develop a methodology to simplify bonding the MIRAGE active add-ons to the silicon platform. Particularly for the VCSEL and photodiode bonding, tight alignment tolerances usually require costly equipment, whereas the large distance between VCSELs and waveguides necessitates the use of microlenses to account for beam divergence. MIRAGE will tackle these cost factors with a self-alignment assembly process based on microbumps.