Showing papers on "Optical Transport Network published in 2012"

A Survey on Optical Interconnects for Data Centers

Abstract: Data centers are experiencing an exponential increase in the amount of network traffic that they have to sustain due to cloud computing and several emerging web applications. To face this network load, large data centers are required with thousands of servers interconnected with high bandwidth switches. Current data center networks, based on electronic packet switches, consume excessive power to handle the increased communication bandwidth of emerging applications. Optical interconnects have gained attention recently as a promising solution offering high throughput, low latency and reduced energy consumption compared to current networks based on commodity switches. This paper presents a thorough survey on optical interconnects for next generation data center networks. Furthermore, the paper provides a qualitative categorization and comparison of the proposed schemes based on their main features such as connectivity and scalability. Finally, the paper discusses the cost and the power consumption of these schemes that are of primary importance in the future data center networks.

Advanced Optical Wireless Communication Systems

Abstract: Optical wireless communications is a dynamic area of research and development. Combining fundamental theory with a broad overview, this book is an ideal reference for anyone working in the field, as well as a valuable guide for self-study. It begins by describing important issues in optical wireless theory, including coding and modulation techniques for optical wireless, wireless optical CDMA communication systems, equalization and Markov chains in cloud channels and optical MIMO systems, as well as explaining key issues in information theory for optical wireless channels. The next section describes unique channels that could be found in optical wireless applications, such as NLOS UV atmospheric scattering channels, underwater communication links and a combination of hybrid RF/optical wireless systems. The final section describes applications of optical wireless technology, such as quantum encryption, visible light communication, IR links and sensor networks, with step-by-step guidelines to help reduce design time and cost.

Optical Networking Beyond WDM

Abstract: Wavelength-division multiplexing (WDM) has been the workhorse of data networks, accommodating exponential traffic growth for two decades. Recently, however, progress in WDM capacity research has markedly slowed down as experiments are closely approaching fundamental Shannon limits of nonlinear fiber transmission. Space-division multiplexing (SDM) is expected to further scale network capacities, using parallel strands of single-mode fiber, uncoupled or coupled cores of multicore fiber, or even individual modes of few-mode fiber in combination with multiple-input-multiple-output (MIMO) digital signal processing. At the beginning of a new era in optical communications, we review initial research in SDM technologies and address some of the key challenges ahead.

Network operator requirements for the next generation of optical access networks

Abstract: This article describes FSAN operator perspectives on the drivers and system requirements for fiber access beyond 10-Gigabit-class PON systems (i.e., NG-PON2 in FSAN terminology). Additionally, a review of potential solutions in scope for NG-PON2 is given in the context of these operator drivers and requirements.

Ultra-stable long distance optical frequency distribution using the Internet fiber network

Abstract: We report an optical link of 540 km for ultrastable frequency distribution over the Internet fiber network. The stable frequency optical signal is processed enabling uninterrupted propagation on both directions. The robustness and the performance of the link are enhanced by a cost effective fully automated optoelectronic station. This device is able to coherently regenerate the return optical signal with a heterodyne optical phase locking of a low noise laser diode. Moreover the incoming signal polarization variation are tracked and processed in order to maintain beat note amplitudes within the operation range. Stable fibered optical interferometer enables optical detection of the link round trip phase signal. The phase-noise compensated link shows a fractional frequency instability in 10 Hz bandwidth of 5x10-15 at one second measurement time and 2x10-19 at 30 000 s. This work is a significant step towards a sustainable wide area ultrastable optical frequency distribution and comparison network.

System and method for performing in-service optical fiber network certification

Abstract: A system and method for performing an in-service optical time domain reflectometry test, an in-service insertion loss test, and an in-service optical frequency domain reflectometry test using a same wavelength as the network communications for point-to-point or point-to-multipoint optical fiber networks while maintaining continuity of network communications are disclosed.

Optical traffic grooming in OFDM-based elastic optical networks [Invited]

Abstract: Orthogonal frequency-division multiplexing (OFDM) is a multi-carrier modulation technology that transmits a high-speed data stream using multiple spectrally overlapped lower-speed subcarriers. Optical OFDM (O-OFDM) technology is a promising candidate for future high-speed optical transmission. Based on O-OFDM, a novel elastic optical network architecture with immense flexibility and scalability in spectrum allocation and data rate accommodation can be built to support diverse services and the rapid growth of Internet traffic. This architecture can provide various services directly at the optical layer in a spectrum-efficient way through bandwidth-elastic optical paths. However, carrying various data rate services using a single type of bandwidth-variable transponder might not be cost-efficient. Electrical traffic grooming is a traditional approach for sub-wavelength service accommodation in wavelength division multiplexing networks. However, it places additional electrical switching and optical-electrical-optical conversion requirements on the network, which may lead to higher cost and energy consumption. In contrast, grooming traffic optically is an attractive option for elastic optical networks. In this paper, we propose a novel optical grooming approach to aggregate and distribute traffic directly at the optical layer in OFDM-based elastic optical networks. We study routing and spectrum allocation algorithms of optical grooming to show the benefits of this approach. Our results demonstrate that significant transmitter and spectrum savings can be achieved by the optical grooming versus the non-grooming scenario, and a trade-off between optimizing the number of transmitters and optimizing spectrum usage should be considered during network planning.

Spectrum allocation policy modeling for elastic optical networks

Abstract: Today, optical transmission technologies are able to support 400Gbps over a single optical channel. However, this capacity cannot fit in the current fixed frequency grid optical spectrum. On the other hand, high rate optical channels have to co-exist with different ranges of line rates in order to serve heterogeneous bandwidth requests from variety of internet applications. Today's fixed rate and rigid frequency grid optical transmission systems cause over provisioning, where usually more spectral resources are provided than necessary.

A Power Consumption Analysis for IP-Over-WDM Core Network Architectures

Abstract: As Internet traffic is estimated to substantially grow in the near future, one of the most challenging issues will concern the reduction of its power requirement. For the core/transport section of the Internet, various network architectures can be considered, typically multi-layer architectures composed of an optical wavelength division multiplexing (WDM) transport layer under the classical electronic IP layer. Thus, we consider in this paper four architectures: basic IP over WDM with no optical switching, IP over synchronous digital hierarchy (SDH) over WDM, and IP over WDM with transparent or translucent switching. Energy efficiency in these architectures is expected to be enabled by optical switching technologies, mainly due to the significant reduction in the number of required optical/electronic/optical conversions. However, since optical signals are subject to relevant physical layer impairments when traversing core network devices, signal regeneration is often required, which has to be accomplished either at the electronic layer by routers/digital cross connects (DXCs) or directly at the optical layer through 3R-regenerators. Therefore, it is important to know which network architecture may provide the highest energy efficiency. In this paper we perform a comprehensive comparison between the four above-mentioned optical core network architectures, by performing energy assessment of the devices used at the transport layer of a telecom network and by developing an integer linear programming formulation for an energy-minimized and impairment-aware design of each of the considered architectures. We find that optical technology can enable power savings up to 60% with respect to classical IP-over-WDM architectures with no optical switching, but the best “optical” architecture is not univocal, and it is influenced by some crucial network parameters (connectivity, geographical extension, etc.).

Software defined optical network

Abstract: Software define network, which has good potential for packet-switched IP network, is currently not available on circuit-switched transport network. This paper introduces the concept of software define optical network that applies SDN-like features to optical transport network, and reviews key enabling technologies at various layers, such as variable transponder, flexible switching node, control applications, and open interface with circuit extension.

Cognitive optical networks: key drivers, enabling techniques, and adaptive bandwidth services

Abstract: To support efficient delivery of packet and circuit services simultaneously in future optical networks, software will play more and more important roles, not only in control and management plane, but also in transport plane. This article discusses a new concept of cognitive optical networks utilizing intelligent software (e.g., digital signal processing in the optical transport plane and GMPLS in the optical control plane) as well as flexible optics (e.g., colorless, directionless, contentionless, gridless ROADM, and optical OFDM). The software-defined CON architecture with advanced capabilities such as quality of transmission awareness and client service awareness is capable of provisioning adaptive bandwidth services at wavelength and sub-wavelength levels, making future optical networks more cognitive and reconfigurable.

400G WDM Transmission on the 50 GHz Grid for Future Optical Networks

Abstract: We review the recent technology advancements related to the transmission of 400Gb/s, wavelength-division-multiplexed channels for optical networks based on the standard 50 GHz grid We discuss the enabling modulation, coding, and line system technologies, as well as the existing challenges Specifically, these technologies include time-domain hybrid 32-64 quadrature amplitude modulation, nearly ideal digital Nyquist pulse shaping, improved channel bandwidth management methods such as end-to-end carrier frequency control and distributed compensation of filtering effects arising from reconfigurable optical add/drop multiplexers, distributed Raman amplification, and powerful forward error correction We demonstrate 400G transmission on the standard 50 GHz grid over meaningful transmission reach for regional and metropolitan applications However, further studies are needed to fully understand the potential for meeting the requirements of long-haul transmission applications

Tunable optical frequency comb enabled scalable and cost-effective multiuser orthogonal frequency-division multiple access passive optical network with source-free optical network units.

Abstract: We propose and experimentally demonstrate a multiuser orthogonal frequency-division multiple access passive optical network (OFDMA-PON) with source-free optical network units (ONUs), enabled by tunable optical frequency comb generation technology. By cascading a phase modulator (PM) and an intensity modulator and dynamically controlling the peak-to-peak voltage of a PM driven signal, a tunable optical frequency comb source can be generated. It is utilized to assist the configuration of a multiple source-free ONUs enhanced OFDMA-PON where simultaneous and interference-free multiuser upstream transmission over a single wavelength can be efficiently supported. The proposed multiuser OFDMA-PON is scalable and cost effective, and its feasibility is successfully verified by experiment.

Spectrum-efficient and agile CO-OFDM optical transport networks: architecture, design, and operation

Abstract: Traditional ITU-T fixed frequency grid-based optical transport networks suffer several drawbacks such as low fiber spectral efficiency, difficulty in supporting large-bandwidth super-channels, and inflexibility in network bandwidth reconfiguration and modification. To overcome these drawbacks, a new-generation optical transport network based on the concepts of agile spectrum operation and elastic bandwidth allocation has been recently proposed and is receiving increasing attention. This new-generation network is called coherent optical orthogonal frequency-division multiplexing (CO-OFDM) optical transport network. It employs the promising CO-OFDM transmission technique and the new-generation bandwidth-variable ROADMs that use the coherent detection capability of the CO-OFDM transmission for optical channel filtering. The CO-OFDM optical transport network is characterized by arbitrarily assigning center frequency and bandwidth of an optical channel, thereby providing flexibility in network design and operation and achieving efficient fiber spectrum utilization. Despite the increasing attention and considerable progress, there are still many outstanding issues regarding the implementation of CO-OFDM optical transport networks. This article reviews the literature on the architectures of the CO-OFDM optical transport network and discusses key issues, particularly involving network control plane, lightpath routing and spectrum assignment, impact of channel modulation format and optical reach, subwavelength traffic grooming, network survivability, and network reconfiguration.

Demonstration of a 40Gb/s time and Wavelength Division Multiplexed passive optical network prototype system

Abstract: We demonstrate a TWDM-PON prototype system with 40Gb/s downstream and 10Gb/s upstream bandwidth. It supports 20km distance with a 1:512 split ratio. It also coexists with commercially deployed G-PON and XG-PON systems.

All-Optical Signal Processing for UltraHigh Speed Optical Systems and Networks

Abstract: With high-bandwidth and on-demand applications continuing to emerge, next-generation core optical networks will likely require significant improvements in reconfigurability and ultra-fast operations Optical signal processing overcomes the electronic bandwidth limitations with the advantages in terms of transparency and scalability We review recent progresses in all-optical signal processing potentially for ultrahigh speed systems and networks Starting from a brief overview of optical signal processing in high-speed optical systems and networks, we highlight a few key network functionalities, including optical logic operations, reconfigurable add/drop multiplexing, optical regeneration, wavelength conversion, format conversion, and phase-sensitive amplification Different techniques are investigated and discussed, employing a wide range of devices and various nonlinearities Some of experimental results are presented in both single polarization systems and polarization-division multiplexing systems

An OFDMA-based optical access network architecture exhibiting ultra-high capacity and wireline-wireless convergence

Abstract: This article presents ACCORDANCE, a novel optical access network architecture based on OFDMA technology and applied on a PON topology. In compliance with next generation optical access requirements, this architecture aims to outperform existing PON solutions in terms of total capacity, bandwidth allocation flexibility, number of users, and network reach. Moreover, it provides the opportunity for convergence with wireless technologies and a smooth migration path from legacy access solutions like TDMA-PONs and DSL.

Network-embedded self-tuning cavity for WDM-PON transmitter.

Abstract: A network-embedded self-tuning cavity is proved in wavelength division multiplexed passive optical network transmission over 32 channels. The external source-less topology takes advantage of a reflective element at the remote node and a reflective semiconductor optical amplifier at the optical network unit to establish a distribution-fiber based cavity. The bit error rate performance of up to 5-km cavities is presented with two optical network units simultaneously operating and with downstream signal co presence. The experimental analysis at 1.25 Gb/s provides an evaluation of polarization dependences when exploiting low polarization dependent gain reflective semiconductor optical amplifiers with 25-km and 50-km standard single mode fiber transmission.

System and method for optical layer management in optical modules and remote control of optical modules

Abstract: A system and method for managing the optical layer network data communications of an optical fiber data network by an optical transceiver module is disclosed The management of the optical layer network data communications comprising data link layer functions or layer 2 functions in an OSI model Benefits include reduction in reduced cost of network deployments from consolidation of network equipment, such as switches, and reduction in power consumed as well as enabling point-to-multipoint network connections from previously only point-to-point network connection

Push-pull technique for defragmentation in flexible optical networks

Abstract: An efficient defragmentation technique based on optical channel re-tuning is proposed for flexible optical networks. Effective defragmentation with no traffic disruption is achieved without additional spare transponders or re-equalization operations.

100-Gb/s optical transport network and beyond employing digital signal processing

Abstract: We overview the requirements and the enabling technologies for optical transmission systems up to 100 Gb/s and beyond Polarization- division multiplexed quadrature phase shift keying with digital coherent detection, and fast recovery in optical channel rerouting are key technologies for 100-Gb/s long-haul systems and beyond We review test results of a realtime 80-channel wavelength-division multiplexing transmission over 420 km of field-installed fiber Finally, we focus on digital nonlinear compensation and pilot tone phase noise compensation as technologies for systems beyond 100 Gb/s

From static to software-defined optical networks

Abstract: Software-defined optical transceivers, a fully programmable optical express layer, and control plane-assisted network automation are key constituents of a new generation of optical core networks. This paper explains enabling technologies, reviews emerging applications, and discusses new questions arising for network design and modeling. It also examines the integration of the optical wavelength with the OTN and MPLS layers.

Total cost of ownership of WDM and switching architectures for next-generation 100Gb/s networks

Abstract: The bandwidth efficiency and relative costs for 100 Gb/s WDM transport and switching architectures are compared in North American and pan-European long-haul networks. The first architecture uses muxponders and ROADMs for end-to-end wavelength transport with no digital sub-wavelength grooming. The other two utilize digital OTN switching, as either a standalone OTN switch or a converged integrated WDM/switch system, to efficiently groom services onto WDM wavelengths. Results show the integrated WDM/switch architecture utilizes the fewest WDM wavelengths and client service interfaces, and an integrated WDM/switch architecture using photonic integrated circuit technology provides the lowest operational costs.

Next-Generation Optically-Interconnected High-Performance Data Centers

Abstract: The communication requirements imposed by the unabated growth in both the size and computational density of modern data centers will soon outpace the fundamental capabilities of conventional electronic interconnection networks. Optical interconnects represent a potentially disruptive technology that can simultaneously satisfy the throughput, latency, and energy demands of these next-generation systems. In this paper, we propose an end-to-end photonic networking platform for future optically-interconnected data center networks. A reconfigurable hybrid photonic network building block and a protocol-agnostic optical network interface comprise the key elements of our proposed system. A modular optical switch fabric prototyping platform is designed and implemented to support a wide variety of potential photonic technologies. We successfully demonstrate nanosecond-scale optical packet-switching at 1-Tb/s per port (40-Gb/s ×25λs) through our prototype, configured as a 4×4 switch, and confirm error-free transmission across all wavelengths. In order to flexibly allocate appropriate bandwidth for heterogeneous applications, we further implement and evaluate a novel wavelength-reconfigurable optical packet- and circuit-switch by utilizing our optical switch platform. Finally, we detail our implementation of an optical network interface card (O-NIC) designed to bridge the gap between the well-established protocol layers utilized in current networks and the physical layer of the proposed photonic networks and demonstrate its functionality by the streaming of high-definition video through the end-to-end optical network.

Cost evaluation for flexible-grid optical networks

Abstract: We have compared the total cost of an innovative elastic network with respect to the conventional WDM ones operating in realistic network scenarios. The results give an insight of the cost benefits that can be obtained with an elastic OFDM-based network for the operation of future optical transport networks with different protection schemes.

Systems and methods for channel additions over multiple cascaded optical nodes

Abstract: A method, an optical node, and an optical network include a power controller configured to bring channels in-service in parallel over multiple cascaded optical nodes quickly, efficiently, and in a non-service affecting manner. The method, node, and network utilize multiple states of a control loop that maintains a stable response in downstream optical nodes as channels are added in parallel. Further, the power controller is configured to operate independently alleviating dependencies on other power controllers and removing the need for coordination between power controllers. The method, node, and network provide efficient turn up of dense wave division multiplexing (DWDM) services which is critical to optical layer functionality including optical layer restoration.

Traffic trends: Drivers and measures of cost-effective and energy-efficient technologies and architectures for backbone optical networks

Abstract: We examine trends and characteristics of the traffic, systems, and architectures of backbone optical networks to illustrate baselines, future requirements, and possible metrics to gauge the relative performance of capabilities and concepts being researched today.

Optical Packet & Circuit Integrated Network for Future Networks

Abstract: This paper presents recent progress made in the development of an optical packet and circuit integrated network. From the viewpoint of end users, this is a single network that provides both high-speed, inexpensive services and deterministic-delay, low-data-loss services according to the users' usage scenario. From the viewpoint of network service providers, this network provides large switching capacity with low energy requirements, high flexibility, and efficient resource utilization with a simple control mechanism. The network we describe here will contribute to diversification of services, enhanced functional flexibility, and efficient energy consumption, which are included in the twelve design goals of Future Networks announced by ITU-T (International Telecommunication Union - Telecommunication Standardization Sector). We examine the waveband-based network architecture of the optical packet and circuit integrated network. Use of multi-wavelength optical packet increases the switch throughput while minimizing energy consumption. A rank accounting method provides a solution to the problem of inter-domain signaling for end-to-end lightpath establishment. Moving boundary control for packet and circuit services makes for efficient resource utilization. We also describe related advanced technologies such as waveband switching, elastic lightpaths, automatic locator numbering assignment, and biologically-inspired control of optical integrated network.

Systems and methods for policy-based intelligent provisioning of optical transport bandwidth

Abstract: Policy-based, on-demand provisioning of optical transport bandwidth is disclosed. In one of many possible embodiments, a system is provided for policy-based, on-demand provisioning of optical transport bandwidth. The system includes a layer-specific operation support subsystem (OSS) configured to manage network elements that form a sub-network over an optical transport network. The optical transport network provides bandwidth-on-demand provisioning capabilities. The layer-specific OSS includes one or more predefined bandwidth provisioning policies. The layer-specific OSS is configured to selectively request on-demand provisioning of bandwidth on the sub-network based on the predefined bandwidth provisioning policies.

Price-points for components of multi-core fiber communication systems in backbone optical networks

Abstract: The communication capacity limit of conventional optical fiber is being approached, and spatial multiplexing on strands of optical fiber is being pursued because of its potential to significantly increase the capacity of optical transmission systems and networks. Here, we estimate price-points under several scenarios for some of the critical enabling components of potential ultra-high-capacity optical fiber transmission systems based on multi-core fibers. For the input parameters and scenarios considered-including the case when the existing conduit is exhausted, we find the modeled price-point of multi-core fiber to be in the range 0-15% higher than the price of fiber ribbon cable. We also illustrate how larger increases in the value (price-point) of future network elements can occur if the efficiencies of installation are substantially improved.