Equalizer State Caching for Fast Data Recovery in Optically-Switched Data Center Networks

Optical switching offers the potential to significantly scale the capacity of data center networks (DCN) with a simultaneous reduction in switching time and power consumption. Previous research has shown that end-to-end switching time, which is the sum of the switch configuration time and the clock and data recovery (CDR) locking time, should be kept within a few nanoseconds for high network throughput. This challenge of low switching time has motivated research into fast optical switches, ultra-fast clock and amplitude recovery techniques. Concurrently, the data rate between server-to-server and server-to-switch interconnect is increasing drastically from the current 100 Gb/s (4×25 Gb/s) to 400 Gb/s and beyond, motivating the use of high order formats such as 50-GBaud four-level pulse-amplitude modulation (PAM-4) for signalling. Since PAM-4 is more sensitive to noise and distortion, digital equalizers are generally needed to compensate for impairments such as transceiver frequency rolloff, dispersion and optical filtering, adding additional time for equalizer adaptation and power consumption that are undesired for fast optical switching systems. Here we propose and investigate an equalizer state caching technique that reduces equalizer adaptation time and computation power consumption for fast optical switching systems, underpinning optically-switched DCNs using high baud rate and impairment-sensitive formats. Through a proof-of-concept experiment, we study the performance of the proposed equalizer state caching scheme in a three-node optical switching system using 56 GBaud PAM-4. Our experimental results show that the proposed scheme can tolerate up to 0.8-nm (100-GHz) instantaneous wavelength change with an adaptation delay of only 0.36 ns. Practical considerations such as clock phase misalignment, temperature-induced wavelength drift, and equalizer precision are also studied

Hybrid Optoelectronic Router for Future Optical Packet‐ Switched Networks

With the growing demand for bandwidth and the need to support new services, several challenges are awaiting future photonic networks. In particular, the performance of current network nodes dominated by electrical routers/switches is seen as a bottleneck that is accentuated by the pressing demand for reducing the network power consumption. With the concept of performing more node functions with optics/optoelectronics, optical packet switching (OPS) provides a promising solution. We have developed a hybrid optoelectronic router (HOPR) prototype that exhibits low power consumption and low latency together with high functionality. The router is enabled by key optical/optoelectronic devices and subsystem technologies that are combined with CMOS electronics in a novel architecture to leverage the strengths of both optics/optoelectronics and electronics. In this chapter, we review our recent HOPR prototype developed for realizing a new photonic intra data center (DC) network. After briefly explaining about the HOPR‐based DC network, we highlight the underlying technologies of the new prototype that enables label processing, switching, and buffering of asynchronous arbitrary‐length 100‐Gbps (25‐Gbps × 4λs) burst‐mode optical packets with enhanced power efficiency and reduced latency

LIGHTNESS: a function-virtualizable software defined data center network with all-optical circuit/packet switching

©2016 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.Modern high-performance data centers are responsible for delivering a huge variety of cloud applications to the end-users, which are increasingly pushing the limits of the currently deployed computing and network infrastructure. All-optical dynamic data center network (DCN) architectures are strong candidates to overcome those adversities, especially when they are combined with an intelligent software defined control plane. In this paper, we report the first harmonious integration of an optical flexible hardware framework operated by an agile software and virtualization platform. The LIGHTNESS deeply programmable all-optical circuit and packet switched data plane is able to perform unicast/multicast switch-over on-demand, while the powerful software defined networking (SDN) control plane enables the virtualization of computing and network resources creating a virtual data center and virtual network functions (VNF) on top of the data plane. We experimentally demonstrate realistic intra DCN with deterministic latencies for both unicast and multicast, showcasing monitoring, and database migration scenarios each of which is enabled by an associated network function virtualization element. Results demonstrate a fully functional complete unification of an advanced optical data plane with an SDN control plane, promising more efficient management of the next-generation data center compute and network resources.Peer ReviewedPostprint (author's final draft

Digital signal processing optical receivers for the mitigation of physical layer impairments in dynamic optical networks

IT IS generally believed by the research community that the introduction of complex network functions—such as routing—in the optical domain will allow a better network utilisation, lower cost and footprint, and a more efficiency in energy usage. The new optical components and sub-systems intended for dynamic optical networking introduce new kinds of physical layer impairments in the optical signal, and it is of paramount importance to overcome this problem if dynamic optical networks should become a reality. Thus, the aim of this thesis was to first identify and characterise the physical layer impairments of dynamic optical networks, and then digital signal processing techniques were developed to mitigate them. The initial focus of this work was the design and characterisation of digital optical receivers for dynamic core optical networks. Digital receiver techniques allow for complex algorithms to be implemented in the digital domain, which usually outperform their analogue counterparts in performance and flexibility. An AC-coupled digital receiver for core networks—consisting of a standard PIN photodiode and a digitiser that takes samples at twice the Nyquist rate—was characterised in terms of both bit-error rate and packet-error rate, and it is shown that the packet-error rate can be optimised by appropriately setting the preamble length. Also, a realistic model of a digital receiver that includes the quantisation impairments was developed. Finally, the influence of the network load and the traffic sparsity on the packet-error rate performance of the receiver was investigated. Digital receiver technologies can be equally applied to optical access networks, which share many traits with dynamic core networks. A dual-rate digital receiver, capable of detecting optical packets at 10 and 1.25 Gb/s, was developed and characterised. The receiver dynamic range was extended by means of DC-coupling and non-linear signal clipping, and it is shown that the receiver performance is limited by digitiser noise for low received power and non-linear clipping for high received power

Spacelab system analysis: A study of the Marshall Avionics System Testbed (MAST)

An analysis of the Marshall Avionics Systems Testbed (MAST) communications requirements is presented. The average offered load for typical nodes is estimated. Suitable local area networks are determined

A Multifunctional Integrated Circuit Router for Body Area Network Wearable Systems

A multifunctional router IC to be included in the nodes of a wearable body sensor network is described and evaluated. The router targets different application scenarios, especially those including tens of sensors, embedded into textile materials and with high data-rate communication demands. The router IC supports two different functionality sets, one for sensor nodes and another for the base node, both based on the same circuit module. The nodes are connected to each other by means of woven thick conductive yarns forming a mesh topology with the base node at the center. From the standpoint of the network, each sensor node is a four port router capable of handling packets from destination nodes to the base node, with sufficient redundant paths. The adopted hybrid circuit and packet switching scheme significantly improve network performance in terms of end-to-end delay, throughput and power consumption. The IC also implements a highly precise, sub-microsecond one-way time synchronization protocol which is used for time stamping the acquired data. The communication module was implemented in a 4-metal, 0.35 μm CMOS technology. The maximum data rate of the system is 35 Mbps while supporting up to 250 sensors, which exceeds current BAN applications scenarios.This work was supported in part by the Fundação para a Ciéncia e a Tecnologia (FCT) (Portuguese Foundation for Science and Technology) under Project PROLIMB PTDC/EEAELC/103683/2008 and through the Ph.D. Grant SFRH/BD/75324/2010, and in part by the CREaTION, FCT/MEC through national funds and co-funded by the FEDER-PT2020 partnership agreement under Project UIDB/EEA/50008/2020, Project CONQUEST (CMU/ECE/030/2017), Project COST CA15104, and ORCIP. (Corresponding author: Fardin Derogarian Miyandoab.)info:eu-repo/semantics/publishedVersio

Design of 10 Gb/s burst-mode receivers for high-split extended reach PONs

The continuous stream of new applications for the internet, increases the need for higher access speed in the currently deployed communication networks. Most networks in use today still consist of twisted copper wires, inherited from the telephone network. The disadvantages of reusing the existing telephone network are twofold. Firstly, the bandwidth of twisted copper wires is limited and secondly, a large number of switches and routers are needed throughout the network leading to an excessive power consumption. The hybrid fiber coax network that reuses the television distribution network is not free from these drawbacks. The bandwidth is also limited and power hungry amplifiers are needed to bridge the distance to and from the user. The future of broadband access lies in optical fiber networks. The optical fiber has a virtually unlimited bandwidth and the lower attenuation leads to less switches and amplifiers in the network, reducing the power consumption of the complete infrastructure. This dissertation describes the design of a 10 Gb/s burst-mode receiver for high-split extended reach passive optical networks (PONs). The designed receiver incorporates two very advanced features. Firstly, the burst-mode receiver locks its gain setting within 6 ns avoiding packet loss due to gain switching during data payload reception. Secondly, the burst-mode receiver detects both burst start and burst end, making it the first burst-mode receiver of its kind to operate without any time critical signal requirements from outside the burst-mode receiver. The presented work covers the chip-level architecture study and design of a 10 Gb/s burst-mode transimpedance amplifier and a 10 Gb/s post-amplifier, which are the two most critical components of a burst-mode receiver