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

Silicon Photonic Flex-LIONS for Bandwidth-Reconfigurable Optical Interconnects

This paper reports the first experimental demonstration of silicon photonic (SiPh) Flex-LIONS, a bandwidth-reconfigurable SiPh switching fabric based on wavelength routing in arrayed waveguide grating routers (AWGRs) and space switching. Compared with the state-of-the-art bandwidth-reconfigurable switching fabrics, Flex-LIONS architecture exhibits 21× less number of switching elements and 2.9× lower on-chip loss for 64 ports, which indicates significant improvements in scalability and energy efficiency. System experimental results carried out with an 8-port SiPh Flex-LIONS prototype demonstrate error-free one-to-eight multicast interconnection at 25 Gb/s and bandwidth reconfiguration from 25 Gb/s to 100 Gb/s between selected input and output ports. Besides, benchmarking simulation results show that Flex-LIONS can provide a 1.33× reduction in packet latency and >1.5× improvements in energy efficiency when replacing the core layer switches of Fat-Tree topologies with Flex-LIONS. Finally, we discuss the possibility of scaling Flex-LIONS up to N = 1024 ports (N = M × W) by arranging M^2 W-port Flex-LIONS in a Thin-CLOS architecture using W wavelengths

Enabling Technologies for Optical Data Center Networks: Spatial Division Multiplexing

With the continuously growing popularity of cloud services, the traffic volume inside the\ua0data\ua0centers is dramatically increasing. As a result, a scalable and efficient infrastructure\ua0for\ua0data\ua0center\ua0networks\ua0(DCNs) is required. The current\ua0optical\ua0DCNs using either individual fibers or fiber ribbons are costly, bulky, hard to manage, and not scalable.\ua0Spatial\ua0division\ua0multiplexing\ua0(SDM) based on multicore or multimode (few-mode) fibers is recognized as a promising technology to increase the\ua0spatial\ua0efficiency\ua0for\ua0optical\ua0DCNs, which opens a new way towards high capacity and scalability. This tutorial provides an overview of the components, transmission options, and interconnect architectures\ua0for\ua0SDM-based DCNs, as well as potential technical challenges and future directions. It also covers the co-existence of SDM and other\ua0multiplexing\ua0techniques, such as wavelength-division\ua0multiplexing\ua0and flexible spectrum\ua0multiplexing, in\ua0optical\ua0DCNs

Roadmap of optical communications

© 2016 IOP Publishing Ltd. Lightwave communications is a necessity for the information age. Optical links provide enormous bandwidth, and the optical fiber is the only medium that can meet the modern society's needs for transporting massive amounts of data over long distances. Applications range from global high-capacity networks, which constitute the backbone of the internet, to the massively parallel interconnects that provide data connectivity inside datacenters and supercomputers. Optical communications is a diverse and rapidly changing field, where experts in photonics, communications, electronics, and signal processing work side by side to meet the ever-increasing demands for higher capacity, lower cost, and lower energy consumption, while adapting the system design to novel services and technologies. Due to the interdisciplinary nature of this rich research field, Journal of Optics has invited 16 researchers, each a world-leading expert in their respective subfields, to contribute a section to this invited review article, summarizing their views on state-of-the-art and future developments in optical communications

Next Generation Silicon Photonic Transceiver: From Device Innovation to System Analysis

Silicon photonics is recognized as a disruptive technology that has the potential to reshape many application areas, for example, data center communication, telecommunications, high-performance computing, and sensing. The key capability that silicon photonics offers is to leverage CMOS-style design, fabrication, and test infrastructure to build compact, energy-efficient, and high-performance integrated photonic systems-on- chip at low cost. As the need to squeeze more data into a given bandwidth and a given footprint increases, silicon photonics becomes more and more promising. This work develops and demonstrates novel devices, methodologies, and architectures to resolve the challenges facing the next-generation silicon photonic transceivers. The first part of this thesis focuses on the topology optimization of passive silicon photonic devices. Specifically, a novel device optimization methodology - particle swarm optimization in conjunction with 3D finite-difference time-domain (FDTD), has been proposed and proven to be an effective way to design a wide range of passive silicon photonic devices. We demonstrate a polarization rotator and a 90◦ optical hybrid for polarization-diversity and phase-diversity communications - two important schemes to increase the communication capacity by increasing the spectral efficiency. The second part of this thesis focuses on the design and characterization of the next- generation silicon photonic transceivers. We demonstrate a polarization-insensitive WDM receiver with an aggregate data rate of 160 Gb/s. This receiver adopts a novel architecture which effectively reduces the polarization-dependent loss. In addition, we demonstrate a III-V/silicon hybrid external cavity laser with a tuning range larger than 60 nm in the C-band on a silicon-on-insulator platform. A III-V semiconductor gain chip is hybridized into the silicon chip by edge-coupling to the silicon chip. The demonstrated packaging method requires only passive alignment and is thus suitable for high-volume production. We also demonstrate all silicon-photonics-based transmission of 34 Gbaud (272 Gb/s) dual-polarization 16-QAM using our integrated laser and silicon photonic coherent transceiver. The results show no additional penalty compared to commercially available narrow linewidth tunable lasers. The last part of this thesis focuses on the chip-scale optical interconnect and presents two different types of reconfigurable memory interconnects for multi-core many-memory computing systems. These reconfigurable interconnects can effectively alleviate the memory access issues, such as non-uniform memory access, and Network-on-Chip (NoC) hot-spots that plague the many-memory computing systems by dynamically directing the available memory bandwidth to the required memory interface

Multi-FSR Silicon Photonic Flex-LIONS Module for Bandwidth-Reconfigurable All-to-All Optical Interconnects

This article proposes and experimentally demonstrates the first bandwidth-reconfigurable all-to-all optical interconnects using a multi-Free-Spectral-Ranges (FSR) integrated 8 × 8 SiPh Flex-LIONS module. The multi-FSR operation utilizes the first FSR (FSR1) to steer the bandwidth between selected node pairs and the zeroth FSR (FSR0) to guarantee a minimum diameter all-to-all topology among the interconnected nodes after reconfiguration. Successful Flex-LIONS design, fabrication, packaging, and system testing demonstrate error-free all-to-all interconnects for both FSR0 and FSR1 with a 5.3-dB power penalty induced by AWGR intra-band crosstalk under the worst-case polarization scenario. After reconfiguration in FSR1, the bandwidth between the selected pair of nodes is increased from 50 to 125 Gb/s while maintaining a 25 Gb/s/λ all-to-all interconnectivity in FSR0