COSIGN:a complete SDN enabled all-optical architecture for data centre virtualisation with time and space multiplexing

We present a Data Centre Virtualisation architecture with an SDN-controlled all-optical data plane combining OCS and TSON. Orchestration dynamically translates and provisions Virtual Data Centres requests onto the optical layer. We describe an implementation and characterisation of the data plane

A fully SDN enabled all-optical architecture for data centre virtualisation with time and space multiplexing

© 2018 [2018 Optical Society of America.]. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modifications of the content of this paper are prohibited.Virtual Data Centre (VDC) solutions provide an environment that is able to quickly scale-up and where virtual machines and network resources can be quickly added on-demand through self-service procedures. VDC providers must support multiple simultaneous tenants with isolated networks on the same physical substrate. The provider must make efficient use of their available physical resources whilst providing high bandwidth and low-latency connections to tenants with a variety of VDC configurations. This paper utilises state of the art optical network elements to provide high bandwidth optical interconnections and develop an VDC architecture to slice the network and the compute resources dynamically, to efficiently divide the physical network between tenants. We present a Data Centre Virtualisation architecture with an SDN-controlled all-optical data plane combining Optical Circuit Switching (OCS) and Time Shared Optical Network (TSON). Developed network orchestration dynamically translates and provisions VDCs requests onto the optical physical layer. The experimental results show the provisioned bandwidth can be varied by adjusting the number of time slots allocated in the TDM network. These results lead to recommendations for provisioning TDM connections with different performance characteristics. Moreover, application level optical switch reconfiguration time is also evaluated to fully understand the impact on application performance in VDC provision. The experimental demonstration confirmed the developed VDC approach introduces negligible delay and complexity on the network side.Peer ReviewedPostprint (author's final draft

Ultralow-crosstalk, strictly non-blocking microring-based optical switch

We report on the first monolithically integrated microring-based optical switch in the switch-and-select architecture. The switch fabric delivers strictly non-blocking connectivity while completely canceling the first-order crosstalk. The 4×4 switching circuit consists of eight silicon microring-based spatial (de-)multiplexers interconnected by a Si/SiN dual-layer crossing-free central shuffle. Analysis of the on-state and off-state power transfer functions reveals the extinction ratios of individual ring resonators exceeding 25 dB, leading to switch crosstalk suppression of up to over 50 dB in the switch-and-select topology. Optical paths are assessed, showing losses as low as 0.1 dB per off-resonance ring and 0.5 dB per on-resonance ring. Photonic switching is actuated with integrated micro-heaters to give an ∼24  GHz passband. The fully packaged device is flip-chip bonded onto a printed circuit board breakout board with a UV-curved fiber array

Space-Division Multiplexing in Data Center Networks: On Multi-Core Fiber Solutions and Crosstalk-Suppressed Resource Allocation

The rapid growth of traffic inside data centers caused by the increasing adoption of cloud services necessitates a scalable and cost-efficient networking infrastructure. Space-division multiplexing (SDM) is considered as a promising solution to overcome the optical network capacity crunch and support cost-effective network capacity scaling. Multi-core fiber (MCF) is regarded as the most feasible and efficient way to realize SDM networks, and its deployment inside data centers seems very likely as the issue of inter-core crosstalk (XT) is not severe over short link spans (<1  km ) compared to that in long-haul transmission. However, XT can still have a considerable effect in MCF over short distances, which can limit the transmission reach and in turn the data center’s size. XT can be further reduced by bi-directional transmission of optical signals in adjacent MCF cores. This paper evaluates the benefits of MCF-based SDM solutions in terms of maximizing the capacity and spatial efficiency of data center networks. To this end, we present an analytical model for XT in bi-directional normal step-index and trench-assisted MCFs and propose corresponding XT-aware core prioritization schemes. We further develop XT-aware spectrum resource allocation strategies aimed at relieving the complexity of online XT computation. These strategies divide the available spectrum into disjoint bands and incrementally add them to the pool of accessible resources based on the network conditions. Several combinations of core mapping and spectrum resource allocation algorithms are investigated for eight types of homogeneous MCFs comprising 7–61 cores, three different multiplexing schemes, and three data center network topologies with two traffic scenarios. Extensive simulation results show that combining bi-directional transmission in dense core fibers with tailored resource allocation schemes significantly increases the network capacity. Moreover, a multiplexing scheme that combines SDM and WDM can achieve up to 33 times higher link spatial efficiency and up to 300 times greater capacity compared to a WDM solution

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

Design and analysis of beam steering multicore fiber optical switches

The design and performance characteristics of a beam steering optical switch for multicore fibers (MCFs) are reported. Port count, core count, transmission crosstalk or a combination thereof can be optimized for the required application. Decreasing port separation or increasing the maximum steering angle both increase port count, whilst a higher core count or larger mode field diameter increase port capacity or port count respectively at the expense of greater intercore crosstalk. Potential losses from system misalignments and fiber fabrication variations in the core pitch are also estimated. A 50 port switch is possible for a 25 μm core pitch 7 core hexagonal trench assisted MCF (TA-MCF) with a total mean statistical crosstalk on the central core of -25 dB after 1 km, assuming a operational wavelength of 1550 nm and maximum collimator actuator angle of 10 degrees. In contrast, a high capacity 25 μm core pitch 61 core hexagonal TA-MCF can still offer up to a 5 port switch for the same level of crosstalk. For longer link distances, -25 dB crosstalk after 100 km (metro network) is achievable for a 50 port switch using a 35 μm core pitch 7 core TA-MCF. Similar levels of crosstalk can be accomplished at 1000 km (core network) for a 41 port switch using a 35 μm core pitch 7 core TA-MCF

MCF-SMF Hybrid Low-Latency Circuit-Switched Optical Network for Disaggregated Data Centers

This paper proposes and experimentally evaluates a fully developed novel architecture with purpose built low latency communication protocols for next generation disaggregated data centers (DDCs). In order to accommodate for capacity and latency needs of disaggregated IT elements (i.e. CPU, memory), this architecture makes use of a low latency and high capacity circuit switched optical network for interconnecting various endpoints, that are equipped with multi-channel Silicon photonic based integrated transceivers. In a move to further decrease the perceived latency between various disaggregated IT elements, this paper proposes a) a novel network topology, which cuts down the latency over the optical network by 34% while enhancing system scalability and b) channel bonding over multicore fiber (MCF) switched links to reduce head to tail latency and in turn increase sustained memory bandwidth for disaggregated remote memory. Furthermore, to reduce power consumption and enhance space efficiency, the integration of novel multi core fiber (MCF) based transceivers, fibers and optical switches are proposed and experimentally validated at the physical layer for this topology. It is shown that the integration of MCF based subsystems in this topology can bring about an improvement in energy efficiency of the optical switching layer which is above 60%. Finally, the performance of this proposed architecture and topology is evaluated experimentally at the application layer where the perceived memory throughput for accessing remote and local resources is measured and compared using electrical circuit and packet switching. The results also highlight a multi fold increase in application perceived memory throughput over the proposed DDC topology by utilization and bonding of multiple optical channels to interconnect disaggregated IT elements that can be carried over MCF links

Beam-steering all-optical switch for multi-core fibers

We report on the development of the first multi-lane all-optical switch with directly integrated multi-core fibers. A 3-port single-sided beam-steering switch connecting 4-core fibers shows core-to-core losses below 2.2 dB with less than 1-dB variation