Integrated Components and Solutions for High-Speed Short-Reach Data Transmission

We are delighted to introduce a Special Issue on Optical Interconnects for the IET Optoelectronics magazine. This issue presents the current status as well as some of the outstanding progress that has been witnessed in the rapidly evolving area of optical interconnects. Today, data centres (DC) and high-performance computers are struggling with limited interconnect capacity and increased power consumption while trying to meet overwhelming bandwidth demands. As photonics technologies have been rapidly maturing, optical interconnects have come into the spotlight as the means to cope with the emerging bandwidth, energy, and capacity needs. As such, a wealth of photonic interconnect solutions across the DC hierarchy has unfolded, covering from electro-optic boards to transceiver development, on-chip and on-board switches and interconnects as well as novel noninvasive monitoring methods for light controlling for compensating thermal crosstalk, fabrication tolerances and unstable environmental conditions. At the same time, the increased penetration of optical interconnects in short-reach communications, such as board and chip levels, has triggered new challenges in photonics technologies calling for new innovations with respect to integration techniques and packaging methods. This Special Issue of IET includes integrated circuits, assembly techniques, systems-level architectures, and controlling methods related to short reach ‘chip-to-chip’, ‘in-the-box’, and ‘box-to-box’ communications. Specific areas covered by this special issue include: Silicon photonic transceiver technologies and flat DC topologies; High-speed electro-optic hosting boards and fast, energy-efficient electronics; DC switches and co-packaged optic (CPO) technologies; and Noninvasive controlling techniques for complex photonic integrated circuits. The four papers in this special section promote high-performance optical interconnect architectures and key technologies to tackle the rising bandwidth demands of DCs. They cover (a) co-packaged DC optics, (b) silicon technology transceiver modules and high-speed hosting boards for multisocket server board (MSB) interconnects and (c) automated controlling architecture for complex photonic systems; Items (b) and (c) draw from impressive achievements accomplished through the recently completed European H2020 Project ICT-STREAMS. This report written by C. Mickenberg tries to shed light on motivating factors behind co-packaged optics (CPO), the trade-offs involved and their potential impact on data centre network architectures. The article reviews the evolution of DC switch application-specific integrated circuit (ASICs) and DC optics, provides a future road map and finally discusses the potential impact of CPO on the network architecture. This topic is covered by two articles. The first, written by M. Morallis-Pegios, proposes using silicon photonics to advance interconnect throughput, socket connectivity and energy efficiency in MSB layouts by enabling a flat-topology wavelength division multiplexing (WDM) point-to-point optical MSB interconnect scheme. WDM silicon photonic transceivers coassembled with their electronic circuits achieving a 50-Gb/s line rate and 400-Gb/s aggregate data transmission are demonstrated. The article also proposes silicon photonic Arrayed Waveguide Grating Router (AWGRs) that can offer collision-less time-of-flight connectivity for up to 16 nodes. The second article covering that area is written by T. Lamprecht and reports on the development of electro-optic hosting boards for on-board transceiver subassemblies which is required to eventually form the Tb/s multi-socket onboard communication. The article also discusses the electrical interface as well as photonic board requirements, including the manufacturing technique and the assembly concept that was followed to deliver terabyte per second multichip optical communication. This article, written by F. Zanetto, introduces a novel dithering technique for real-time control of multiple cascaded photonic integrated devices, proposing a calibration-free strategy to support the development and real-life diffusion of increasingly complex photonic systems. The article elaborates on the implementation of a calibration-free automated control loop exploiting integral controllers to close a real-time feedback and stabilise the optimum working point of the employed photonic devices. The effectiveness of the proposed architectural approach is experimentally validated with the error-free routing and transmission of a 30-Gbit/s optical signal traversing a cascade of micro-ring resonator filters. All of the articles selected for this Special Issue present a wide variety of key topics and significant results addressing optical interconnects in high-performance data communication systems, including new progress on architectures, systems and packaging techniques as well as novel optimised controlling methods. As guest editors, we would like to thank all of the authors for their high-quality submissions that significantly contribute to the optical interconnect field. We would also like to thank the reviewers for their valuable and constructive technical comments that greatly enhance the Special Issue, because their feedback and comments ensure the high quality of the IET Optoelectronics Journal. We hope that this IET Special Issue will provide a useful reference of the state-of-the-art in optical interconnects to readers, and we anticipate such technological perspectives will stimulate new advancements and technological outcomes that will in turn enrich the growing field of optical interconnects. This work was supported by the E.C. through the H2020-ICT-STREAMS research project (688172).

Globally, the long-haul transmission of ultra-high bandwidth data is enabled through coherent communications. Driven by the rapid pace of growth in interconnectivity over the last decade, long-haul data transmission has reached capacities on the order of tens to hundreds of terabits per second, over fiber reaches which may span thousands of kilometers. Data center communications operate in regimes featuring shorter reaches and higher cost sensitivity. While integrated microresonator frequency combs are poised to revolutionize light sources used for high-speed data transmission over fiber, recent progress has focused largely on coherent detection schemes. Furthermore, though state-of-the-art intensity modulators are advancing in speed, it has not been demonstrated in the literature if microresonator-based comb lines can accommodate higher intensity modulated direction data (IMDD) line rates in tandem with these advancements. In this manuscript, we demonstrate the use of microresonator frequency combs pumped with a single laser for the transmission of high-speed IMDD data. We demonstrate error-free transmission of 30 Gbs-1 per comb non-return-to-zero data over fiber lengths of 6 km, as well as bit error rates under the forward error correction limit for propagation through 20 km of optical fiber. 60 Gbs-1 and 42 Gbs-1 pulse modulation amplitude 4 (PAM4) data modulated on each frequency comb line is further quantified to have a bit error rate under the forward error correction limit for fiber reaches of up to 6 km and 20 km respectively. The results showcase CMOS-compatible microresonator frequency comb modulated using IMDD formats as a promising technology for high-speed transmission in the data center transceiver industry.

High-speed card-to-card optical interconnects are highly demanded in high-performance computing and data centers. Compared with other solutions, free-space optical interconnects have the capability of providing both reconfigurability and flexibility. In this paper we propose and experimentally demonstrate a free-space based reconfigurable optical interconnect architecture and it is capable of connecting cards located both inside the same rack as well as in different racks. Results show that 3xiO Gb/s data transmission is achieved with a worst-case receiver sensitivity better than -9.38 dBm.

One of the important design goals of electronic quotation system is to carry out high-speed data transmission while controlling the consumption of server-side computation resources and network bandwidth resources. Different from other exchange markets (e.g. stock market), bulk-commodity exchange market is characterized by fewer varieties of future contracts and more focus on single future contract. As inadequate attention has been paid to the market characteristics during the design stage for most existing bulk quotation systems, these systems are faced with such problems as huge uneconomic resource consumption and significant data transmission delay, and the design goals are difficult to realize. As novel quotation system architecture, HSQuotes employs separated channel, broadcast long-connection model and compressed HTTP short-connection model as well as other technologies to perform classified data storage and high-speed transmission. HSQuotes has been successfully applied to dozens of bulk-commodity exchange markets including steel, chemical industry, port trade and stock index futures, etc., and exhibits the characteristics of reliability, stability and high efficiency.

Short-reach optical interconnects among massive serves in data centers have attracted extensive research recently. Increasing capacity, cost and power efficiency as well as wavelength switching between data center network nodes are still key challenges for current optical interconnects. In this work, we experimentally demonstrate the real-time inter-mode optical wavelength switching technique, for high-speed wavelength flexible data center interconnects. A 10 Gbit/s 1 550 nm single mode vertical cavity surface emitting laser (VCSEL) is optically injected and used to control a 10 Gbit/s multimode VCSEL carrier at 850 nm. Results show that a clearly open eye diagram is achieved at back-to-back analysis, implying a successful wavelength switch and error-free operation at 10 Gbit/s. A fully optical wavelength conversion of a multimode VCSEL operation at 850 nm using a single mode VCSEL subject to external optical injection at 1 550 nm is reported. This work opens new perspectives towards the development of a cost effective high-speed real-time inter-band wavelength switching technique between servers and network devices operating at different transmission windows at network nodes, for current and future optical interconnects.

Bandwidth hungry applications such as real-time video processing are currently straining data center networking infrastructure. This is expected to become a more serious challenge in the near future. Optics enables massive data transmission rates: in telecom settings researchers have demonstrated rates in excess of 100 Tb/s in a single mode fiber; however, the data center presents a different set of challenges. Low cost, low power dissipation, low latency, small physical size, and the ability to integrate with mainstream silicon electronics are more important than the ability to transmit signals over long distances, the traditional telecoms focus. A clearer understanding of the requirements and technology challenges of the new applications which are changing the face of the Internet and the data center, should facilitate development of optical interconnection networks that will solve these challenges. By linking the end-to-end research areas we seek to identify critical technology gaps and enable the design of forward-looking, efficient, cost-effective, higher bandwidth data centers that can take optimal advantage of advances in multicore processors.KeywordsCloud ComputingData CenterInterconnection NetworkHigh BandwidthRing ResonatorThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

As the infrastructure of cloud computing and big data, data centers have been deployed widely. Then, how to make full use of the computing and storage resources in data centers will be the focus. Data center networks are considered important solution for the problem above, which include intra-data center and inter-data center networks. Both of them will depend on the optical networking due to its advantages, such as high bandwidth, low latency, and low energy consumption. Data center interconnected by flexi-grid optical networks is a promising scenario to allocate spectral resources for applications in a dynamic, tunable and efficient control manner. Compared with inter-data center, optical interconnect in intra-data center networks is a more pressing need and promising scenario to accommodate these applications in a dynamic, flexible and efficient manner. OpenFlow based Software Defined Networking (SDN) is considered as a good technology, which is very suitable for data center networks. This paper mainly focuses on the data center optical networks based on software defined networking (SDN), which can control the heterogeneous networks with unified resource interface. Architecture and experimental demonstration of OpenFlow-based optical interconnects in intra-data center Networks and OpenFlow-based flexi-grid optical networks for inter-data center are presented in the paper respectively. Some future works are listed finally.

The exponential increase of Internet traffic due to cloud computing and other emerging web applications has created the need for more powerful data centres. These warehouse-scale data centres consist of thousands of racks interconnected with commodity switches and consume vast amount of energy. To face the requirements of the future data centres, new interconnection schemes have to be adopted to provide high throughput and reduced power consumption. Several optical interconnects for future data centre networks have recently appeared that provide high throughput, low latency and reduced power consumption. This paper discusses the need for a shift of the data centres networks to the optical domain to reduce the power consumption and meet the bandwidth requirements. Additionally, this paper presents some indicative optical interconnects for high performance data centres that have appeared recently in the research literature. Finally, it presents a qualitative categorization and comparison of these schemes based on their main features such as performance, connectivity and scalability.

Energy-saving superconducting power delivery from renewable energy source to a 100-MW-class data center

With the rapid development of national economy, our demand for power resources has also increased rapidly. The traditional power grid can not be achieved operational status of equipment for effective monitoring and control, we will not be able to ensure the quality and quality of electricity service. Cloudbased build smart grid information platform enables gathering the parameter of grid operation state, greatly increasing the economic efficiency of power enterprises. Firstly, cloud computing and smart grid briefly described, and then pointed out that cloud computing applications in the smart grid information platform, and specialized of cloud-based smart grid information platform, in order for the power grid enterprises to enhance their level of service and provide effective reference. KEYWORD: cloud computing; smart power grids; information platform; Application 4th International Conference on Mechanical Materials and Manufacturing Engineering (MMME 2016) © 2016. The authors Published by Atlantis Press 202 3 THE MAIN PROBLEM IS STILL THE SMART GRID INFORMATION PLATFORM FACING The transition to a cloud computing data center. Our data center because of the different regions and the degree of information presents different characteristics, some data centers already have a basic cloud computing capabilities, but most data centers still remain in the initial level, to ensure the normal operation of the existing data center power under the premise, gradual transition to cloud computing data center in order to meet future requirements of the development of smart grid. Restricting data transmission problem. State Grid Corporation between provincial branches and there are a lot of data needs to be transmitted, will bring massive data transmission efficiency decreases, taking into account the load balancing device between the cloud node, thus building a wide area network channels to resolve data transmission problem. Security of data transmission. Data Center for Cloud Computing power companies to build internal private cloud, capable of self-maintenance and management, system wide area network data transmission services, according to the third security zone defined security partition, and install proprietary equipment production area and external public network isolation . 4 CLOUD COMPUTING APPLICATIONS IN THE SMART GRID INFORMATION POLICY PLATFORM Integrate and optimize the management of heterogeneous resources. Among the smart grid systems, data resources, information systems between various platforms and mutually dispersed, severe heterogeneity, thus leading to the integration of the quality of information sharing to increase difficulty, unable to effectively improve network management efficiency for the power distribution system electrical work quality management and marketing operations system maintenance upgrade will not be able to effectively meet demand (Jie Yang, 2014). Cloud computing technology enables the power system to effectively integrate the various business data and computing resources on the basis of information for business collaboration platform built on effective, able to satisfy the huge demand for smart grid information resource sharing. Cloud computing network virtualization and application virtualization technology, the server virtualization technology and other resources to achieve each service abstraction, and then realize the difference between the system and the software effectively eliminated by the appropriate method to achieve the effective integration of information resources, and then to optimize the management, greatly improving the efficiency of heterogeneous resources management applications. Distributed storage and management of large volume of data. After application of smart grid information platform construction, customer service requests varied, huge data volume information brought it to the storage and management of data provides a great challenge. Cloud computing technology in general face amount of data each smart grid system and unit collected using forms distributed storage of data to achieve the effective storage, greatly to ensure the security and reliability of data storage. GFS effective use of technology with each node, the master server is responsible for the effective management of the whole file system, the file system and complete the work of the metadata stored in the data block is the main server for data storage block sliced, and by saving three or more redundant backup storage. At the same time, client access and complete access to the main block server information. Fast Power System Parallel Computation and Treatment. Smart grids and information platform for the large volume of data to provide stable operation of the power grid data base, but more critical is the analysis and design of each system operating data, planning and decision-making, and even failures and transient stability, state estimation and intelligent a variety of computing and content analysis and decision-making process, its huge computing needs, general computing system can not reach its goal (Wang, Mengxue, 2015). Cloud computing technology through parallel computing technology has greatly enhanced parallel processing capability of the power system, which provides parallel programming model makes more simple and efficient parallel algorithms. MapReduce as Google made an important parallel programming model, and its role in large data sets in parallel computing plays a very prominent. Parallel processing job results by the client to achieve effective user submitted, via decomposition automated master role, the corresponding task scheduling to working nodes and nodes work completed by the specific calculations and perform the appropriate task. 5 SMART GRID INFORMATION PLATFORM CLOUD COMPUTING ANALYSIS Cloud Computing Smart Grid Information Platform Architecture. Smart grid technology information platform architecture cloud computing include the following several levels and aspects (Yan Cui, 2015): First, that the platform infrastructure layer is the integration of the various hardware resources and related management capabilities of virtualized using virtual technology to achieve the corresponding hardware devices such as computers and network storage devices abstraction, and then complete the automation and optimization of resource data and load management; secondly, the main platform for the integration of the various layers of software

High-speed and high-density interconnections between racks and modules in the high-performance computing systems and data centers are currently being developed. The transmission range of conventional electrical interconnections is limited due to the bandwidth of electrical channels. VCSEL-based optical interconnection technologies are a promising solution for overcoming bandwidth bottlenecks in large scale computing systems [1-3]. Although it is anticipated that the next challenge for optical interconnections is to move to a serial data-rate of 40Gb/s, there are few 40Gb/s class VCSELs at present. Overdriving is a method that boosts high-frequency response to overcome the VCSEL speed limit [4,5]. To develop high-density optical interconnections, a low-power over-driving IC is a key technology. In addition, the optical modulation amplitude (OMA) must be increased to enable long-distance transmission in large scale computing systems as a data center. To achieve this large modulation amplitude, we must overcome the jitter issue caused by the intrinsic group delay of VCSELs. In this paper, we present a 40Gb/s driver IC for over-driving a 25Gb/s VCSEL using a new 2-tap pre-emphasis circuit with tunable group-delay compensation. This circuit compensates for the complex group delay of VCSELs. With this circuit, we achieve 40Gb/s low-jitter operation with 2.3dBm OMA and reduce the power consumption to as low as 312mW/ch.

The rapid scaling of microprocessor technologies has led to unprecedented advancements in processing speed and transistor density. However, as device dimensions shrink below the nanometre scale, traditional electrical on-chip interconnects face critical limitations including increased signal delay, power consumption, and reduced bandwidth. These challenges have emerged as major bottlenecks in the performance and energy efficiency of modern microprocessors, especially in multi-core and many-core architectures. To overcome these limitations, optical interconnects have gained significant attention as a high-performance alternative for on-chip and chip-to-chip communication. Optical interconnects offer key advantages such as higher data rates, lower latency, reduced power dissipation, and immunity to electromagnetic interference. The integration of optical components like waveguides, modulators, photodetectors, and silicon photonics within the chip architecture has the potential to revolutionize interconnect design by addressing the shortcomings of conventional electrical wiring. This paper explores the evolution of on-chip interconnects, comparing the performance, scalability, and integration challenges of electrical and optical solutions in scaled microprocessors. It also discusses emerging hybrid interconnect architectures that combine the strengths of both technologies. A comparison is made between electrical and optical interconnects for different design criteria, based on projections about the future of optical devices. Around a tenth of the length of the chip's edge is the crucial dimension beyond which optical connectivity becomes preferable to electrical interconnect at the 22 nm technological node.

With the deepening of human exploration of space, the amount of data we get from exploring space is increasing. Due to the performance improvement of various space payloads, it is a great test for space high-speed data transmission system. Space mission has great particularity. Different from ground equipment, the complex space environment greatly limits the device performance, so it is difficult to achieve stable and high-speed data transmission. This paper verifies the high-speed data transmission of 2.4Gbps in the experimental design of a certain type of satellite. This paper introduces the design method and simulation results in detail, and puts forward the prospect of space high data transmission system.

Data rates are continuing to increase for box-to-box, rack-to-rack, board-to-board, and chip-to-chip interconnects for terabit switches and routers, multiprocessor computers and high-end servers. The increase in individual line rates and bandwidth drives the need to replace copper interconnects with optical interconnects. Fiber optics are advantageous for these applications because they allow for longer link lengths, increased bandwidth, smaller cables and connectors, less susceptibility to electromagnetic interference, and potentially lower power dissipation, depending on the data rate and link length. Towards this direction, this thesis aims to design and demonstrate low-cost, low-latency, high throughput, rack-to-rack optical interconnect architectures for exascale (i.e., performing 10^18 floating point operations per second) high-performance computing (HPC) systems and data centers. In particular, a novel, cost-effective, optical interconnect architecture for ultrafast optical switching, based on semiconductor optical amplifiers (SOAs), is studied. The proposed design of a fast N×N all-optical, wavelength-space crossbar switch for optical interconnects uses a minimum number of ON/OFF gates. This thesis compares and proves the superiority of the proposed architecture with respect to its originally-proposed counterpart, both theoretically and experimentally. Additionally, in order to increase the capacity and to minimize the impact of transmission effects (especially self-gain modulation (SGM), cross-gain modulation (XGM), self-phase modulation (SPM), cross-phase modulation (XPM), and polarization dependent gain (PDG)), we investigate the performance of conventional binary intensity modulation (IM), in conjunction with direct detection, as well as of advanced, more resilient, spectrally-efficient modulation formats (e.g., Differential Phase Shift Keying (DPSK), Orthogonal Frequency Division Multiplexing (OFDM), Polarization Division Multiplexed Quadrature Phase Shift Keying (PDM-QPSK), Single (SP)- and PDM- 16-ary Quadrature Amplitude Modulation (16QAM) in conjunction with coherent detection). Finally, as a seperate research activity, we study the performance of point-to-point links based on vertical-cavity surface-emitting lasers (VCSELs) and single- or multi- mode fibers, in conjuction with IM/DD, four-level Pulse Amplitude Modulation (4-PAM), and OFDM, to enable state-of-the-art, high-capacity, low-cost optical interconnects.

Though TDM (and recently WDM) are generally adopted to increase the total throughput in optical communication systems, SDM must be more effective in most optical interconnection systems. This is because SDM has more advantage in cost and power consumption than TDM, when the transmission distance is rather short, i.e. less than a few hundred meters. VCSEL and smart pixel arrays are very important for constructing optical interconnection systems because they can emit, switch and process a number of broadband optical signals simultaneously. This paper reviews VCSELs and VCSEL-based smart pixels, and discusses the issues for their application to optical interconnections. VCSELs and smart pixels are applicable to three types of parallel optical interconnections: 1) parallel optical fiber link-the optical signals from the SEL array are transmitted through a fiber ribbon for distances less than a few hundred meters; 2) free-space optical interconnects-high-density optical signals from a two-dimensional SEL array are distributed into several ports for distance shorter than one meter; 3) reconfigurable optical interconnects nterconnect patterns among processors are changed dynamically by means of free-space photonic switching networks.