POLYSYS - Ultra-high speed photonics drives forward in Berlin

Within the Fraunhofer mission "to undertake applied research of direct utility to private and public enterprise and of wide benefit to society", Fraunhofer Heinrich Hertz Institute (FhG-HHI) offered production and development services in all activities to the German and international industry. Nearly every second bit now carried on the internet is based on a photonic component developed by FhG-HHI. Powerful optical components can help avoid the high costs associated with the laying of new fiber optic cables and the duplication of equipment, while also allowing for more energy-efficient data transmission. The Photonic Components department of HHI is specialized in optoelectronic semiconductor components for data transmission at rates of up to 100 Gbit/s and beyond.

On October 2010  the project POLYSYS was started on the 6th Photonics Concertation meeting that took place in Brussels. POLYSYS was a specific-target research program (STREP) co-funded by the European Commission under the 7th Framework Program (FWP 7 / ICT Call 5). The aim was to disrupt the capacity upgrade in data communication systems by providing an integration technology based on polymers for straightforward serial 100 Gb/s rack-to-rack and chip-to-chip connectivity and 400 Gb/s connectivity via short range links up to 800m.

POLYSYS, that means direct 100G connectivity with optoelectronic POLYmer-InP integration for data center SYStems with photonic and electronic components for direct operation at 100 Gb/s. Development has relied on the hybrid integration of ultra-fast electro-optic polymer modulators with ultra-fast InP-DHBT electronics on the transmitter side and InP receivers.

2nd Annual Review Meeting in November 2012 in Berlin - Project Reviewer Dr. Pierre-Yves Fonjallaz and Dr. Noori Nourshargh,  Project Officier Tanya Nikolova  and Projekt-Coordinator Prof. Hercules Avramopoulos, National Technical University Athens, NTUA (from left to right) © FhG-HHI     

The consortium consisted of five beneficiaries: one academic partner (Institute of Communication and Computer Systems/National Technical University of Athens‐ICCS/NTUA), one research institute (Fraunhofer Heinrich Hertz Institute‐FhG-HHI) and three companies (Alcatel Thales III‐V Lab (F), GIGOPTIX-HELIX (CH) and LINKRA-TELEOPTIX (I). The  five partners have formed a team aiming at optoelectronic and electronic components based on electro-optic polymers and InP materials.

FhG-HHI has been participating in POLYSYS with its polymer group and detector group, both from HHI’s Photonic Components Department. HHI has designed complex passive optical structures (i.e. multi-mode interference couplers-MMI couplers and Bragg-gratings) on the electro-optic polymer platform provided by GigOptix and has been developed the required techniques for the hybrid integration of active InP-based elements with the polymer optical boards. HHI has also developed arrays of ultra-high speed InP-based photodiodes and photo receivers and took actively part in the system integration and packaging of the receiver modules.

Development of efficient III-V-to-polymer integration processes

A major objective of POLYSYS was the hybrid integration of InP-based active components (DFB lasers, gain chips and photodetectors) with the electro-optic polymer platform. Hybrid integration was realized using the butt-coupling technique. This approach holds the promise for real yield management in the manufacturing and assembling process of the components enabling the development of planar optical devices of higher functionalities at substantially lower costs.

Photo of the packaged 2x100 Gb/s transmitter prototype of POLYSYS - © P. Groumas, V. Katopodis, J. H. Choi,  H. G. Bach, J. Y. Dupuy, A. Konczykowska, Z. Zhang, P. Harati, E. Miller, A. Beretta, L. Gounaridis, F. Jorge, V. Nodjiadjim, A. Dede, A. Vannucci, G. Cangini, R. Dinu, N. Keil, N. Grote, H. Avramopoulos, and Ch. Kouloumentas, “Multi-100 GbE and 400 GbE Interfaces for Intra-Data Center Networks Based on Arrayed Transceivers with Serial 100 Gb/s Operation,” accepted for publication in the special issue of IEEE/OSA Journal of Lightwave Technology on optical Interconnects (March/April 2015), DOI: 10.1109/JLT.2014.2363107

Based on this technique, POLYSYS integrated for the first time active components with polymer modulators allowing for integrated transmitter modules with the highest potential for high-speed operation. POLYSYS aimed at collimator-free coupling of DFB lasers or gain chips to the polymer platform forming the 100 Gb/s, the 4x100 Gb/s and the tunable 100 Gb/s transmitter modules.

Devices and applications

Ultra-high speed photonic and electronic components developed under POLYSYS were ultimately integrated to form devices for datacom applications. The incorporation of thousands of servers in modern data centers has created the necessity to transfer massive amounts of data between racks efficiently and at low cost. Connectivity is thus a key factor and it is today well understood that electrical cables cannot accommodate this bandwidth explosion. The "infiltration" of photonics in data centers is already evident, as active optical cables are used to carry tens of Gb/s through hundreds of meters.

However, the migration from 10 or 40 Gb/s to 100 Gb/s products that is taking place today, and the preparation for the next migration to the 400 Gb/s products requires novel types of optical transceivers. POLYSYS relied on the potential of polymer modulators and InP receivers and electronics for supporting devices that can operate directly at 100 Gb/s without the complexity of advanced modulation formats or polarization diversity. The transmitter and receiver modules were co-packaged to demonstrate the full functionality of a transceiver that can be used in single-lane 100 Gb/s or four-lane 400 Gb/s systems. The project concluded in 9/2013 with a successful demonstration of a 100 Gb/s and a 2x100 Gb/s transmission system over dispersion uncompensated optical links in excess of 1,6 km, using a wavelength tunable 100 Gb/s transmitter, a 2x100 Gb/s arrayed transmitter and a 4x100 Gb/s arrayed receiver.

Final meeting in March 2014 in Athens - Project partners: Lefteris Gounaridis (NTUA), Ziyang Zhang (HHI), George von Buren (GigOptix), Hercules Avramopoulos (NTUA), Antonello Vannucci (LINKRA), Jung-Han Choi (HHI) und Vasilis Katopodis (NTUA)  (from left to right) © FhG-HHI

The achievement of the challenging objectives of POLYSYS brings Europe at the forefront of 100G technology and  at the forefront of the research for next generation 400 Gb/s solutions. “POLYSYS made it to open the door to the 100 Gbaud era for datacom applications” predicts Dr. Christos Kouloumentas, National Technical University of Athens. Through the exploitation of the project results, POLYSYS partners will be in the position to offer a technology solution with all performance and simplicity and reliability credentials for efficient intra-data center networking. The European Commission has decided to highlight POLYSYS as a project success story and is now presenting it in the Photonics newsletter of the Digital Agenda for Europe.

Article written by Dr. Christel Budzinski with kind support from Fraunhofer Heinrich Hertz Institute  

Christos Kouloumentas
Institute of Communication & Computer Systems/
National Technical University of Athens (ICCS/NTUA)

Hercules Avramopoulos
Institute of Communication & Computer Systems/
National Technical University of Athens (ICCS/NTUA)

Norbert Keil
Head of Polymer OEIC Group
Photonic Components Dept.
Tel  +49 30 31002 590
Fax +49 30 31002 558
Fraunhofer Heinrich Hertz Institute
Einsteinufer 37, 10587 Berlin, Germany