The BOOM (‘Terabit-on-chip: micro and nano-scale silicon photonic integrated components and sub-systems enabling Tb/s-capacity, scalable and fully integrated photonic routers’) project received more than EUR 3 million from the ‘Information and communication technologies’ Theme of the EU’s Seventh Framework Programme’s (FP7), and brought together nano-specialists from Belgium, Germany, Greece, Italy and the Netherlands .
The researchers systematically advanced silicon-on-insulator (SOI) photonic integration technology, and as a result developed compact, cost-effective and power-efficient components that enable photonic terabyte per second (Tb/s)-capacity systems for current and new-generation high-speed broadband core networks.
BOOM, which kicked off in 2008, was set up to respond to the increasing demand for bandwidth-hungry Internet applications.
The team perceived problems with the existing available capacity and performance of optical core networks. Power efficiency, physical size and equipment cost are key issues in these networks and they are increasingly difficult to keep within acceptable limits, particularly when electronic carrier routing systems consume and expend large amounts of electrical power and heat respectively. Therefore, by bringing photonics technologies deeper within these routers, their performance can be improved and power consumption can be decreased.
The main focus of BOOM was on the development of a photonic routing platform relying on hybrid SOI photonic integrated circuits (ICs) to implement all the routing functionalities: label detection, control signal generation, wavelength conversion and wavelength routing.
Tasked with investigating the label detection functionality, the Belgian project partners, based at Interuniversity Microelectronics Centre (Imec) in Leuven, developed an optical label extractor consisting of a high-resolution demultiplexer integrated with highly efficient photodetectors. In the proposed routing architecture, the optical data packets are labelled with a wavelength code, which has to be extracted from the packet and sent to the routing unit. The label extractor consists of an optical demultiplexer with very high resolution (12.5GHz) fabricated on the Imec silicon photonics platform and integrated with high-efficiency photodetectors. The Belgian team report that reaching the required resolution turned out to be very challenging and required an in depth study of silicon microring resonators.
The researchers were able to reach the required specifications using single-ring resonator-based filters, which allow fine-tuning of the wavelength channels (bottom electrodes) through the thermo-optic effect. They were connected to fleetingly coupled indium gallium arsenide (InGaAs) photodetectors using heterogeneous integration technology. The detectors had an efficiency of close to 1A/W and were operating at the specified speed of 1GBit/s (up to 5GBit/s).
Finally, a routing machine with more than160Gb/s aggregate capacity was built; this stage of the project was managed by the German project partners from the Fraunhofer Institute for Reliability and Microintegration (IZM) group in Berlin.