Photonic integration enabling new multiplexing concepts in optical board-to-board and rack-to-rack interconnects

New broadband applications are causing the datacenters to proliferate, raising the bar for higher interconnection speeds. So far, optical board-to-board and rack-to-rack interconnects relied primarily on low-cost commodity optical components assembled in a single package. Although this concept proved successful in the first generations of optical-interconnect modules, scalability is a daunting issue as signaling rates extend beyond 25 Gb/s. In this paper we present our work towards the development of two technology platforms for migration beyond Infiniband enhanced data rate (EDR), introducing new concepts in board-to-board and rack-to-rack interconnects. The first platform is developed in the framework of MIRAGE European project and relies on proven VCSEL technology, exploiting the inherent cost, yield, reliability and power consumption advantages of VCSELs. Wavelength multiplexing, PAM-4 modulation and multi-core fiber (MCF) multiplexing are introduced by combining VCSELs with integrated Si and glass photonics as well as BiCMOS electronics. An in-plane MCF-to-SOI interface is demonstrated, allowing coupling from the MCF cores to 340x400 nm Si waveguides. Development of a low-power VCSEL driver with integrated feed-forward equalizer is reported, allowing PAM-4 modulation of a bandwidth-limited VCSEL beyond 25 Gbaud. The second platform, developed within the frames of the European project PHOXTROT, considers the use of modulation formats of increased complexity in the context of optical interconnects. Powered by the evolution of DSP technology and towards an integration path between inter and intra datacenter traffic, this platform investigates optical interconnection system concepts capable to support 16QAM 40GBd data traffic, exploiting the advancements of silicon and polymer technologies

Design and experimental verification of a transimpedance amplifier for 64-Gb/s PAM-4 optical links

The use of four-level pulse-amplitude modulation (PAM-4) has emerged as a solution to increase the serial rate in short-range optical links, offering twice the data throughput but requiring similar bandwidth as on-off keying. However, the receiver design should take into account the increased susceptibility of PAM-4 to noise, intersymbol interference, and nonlinearity. This papers explores these challenges, and details the design of a transimpedance amplifier (TIA) for 64-Gb/s PAM-4 optical links. The TIA was implemented in 0.13-mu m SiGe BiCMOS, and has a power consumption of 180 mW. It contains a digital gain controller, which allows switching between four gain modes, to tradeoff sensitivity against linearity. Bit error rate (BER) measurements show that the dynamic range is significantly extended: Optical modulation amplitudes between -7 dBm and at least -0.2 dBm yield a BER lower than 10(-3)

Quaternary TDM-PAM and its implications for TDMA equipment

The migration towards a 20 Gb/s quaternary TDM-PAM passive optical network with chirped and non-linear optical transmitters is experimentally studied. We show that a loss budget of 27.3 dB is compatible together with a packet power ratio of 10 dB between loud and soft ONUPeer ReviewedPostprint (published version

High-speed electronics for short-link communication

High-speed electronic integrated circuits are essential to the development of new fiber-optic communication systems. Close integration and co-design of photonic and electronic devices are becoming more and more a necessity to realize the best performance trade-offs. This paper presents our most recent results and a brief introduction to our research in recently started EU projects

Integrating optical switching in SDN cloud datacenters: the NEPHELE project

<p>Invited presentation at the Special ECOC 2017 Symposium in Lyngby, Denmark</p

Optical switching in datacenter networks: Why and how?

<p>European Conference on Optical Communication (ECOC2015), Sunday Workshop on "Optical technologies for the exascale cloud datacenter era", September 27, 2015, Valencia, Spain. Presentation of Paraskevas Bakopoulos with title “Optical switching in datacenter networks: Why and how?”,</p