Showing papers presented at "International Conference on Transparent Optical Networks in 2013"

SDN-based cloud computing networking

Abstract: Software Defined Networking (SDN) is a concept which provides the network operators and data centres to flexibly manage their networking equipment using software running on external servers. According to the SDN framework, the control and management of the networks, which is usually implemented in software, is decoupled from the data plane. On the other hand cloud computing materializes the vision of utility computing. Tenants can benefit from on-demand provisioning of networking, storage and compute resources according to a pay-per-use business model. In this work we present the networking issues in IaaS and networking and federation challenges that are currently addressed with existing technologies. We also present innovative software-define networking proposals, which are applied to some of the challenges and could be used in future deployments as efficient solutions. cloud computing networking and the potential contribution of software-defined networking along with some performance evaluation results are presented in this paper.

Towards ultra-dense wavelength-to-the-user: The approach of the COCONUT project

Abstract: This paper presents the high-level COCONUT architecture of an optical access network based on coherent technology, supporting ultra-dense Wavelength Division Multiplexing (WDM). The COCONUT network should allow for seamless evolution from present PON architectures, but also support new emerging applications such as mobile back-haul and front-haul. Coherent techniques will hence allow serving a higher number of users, thanks to ultra-dense WDM, and reaching higher power budget, thanks to higher sensitivity. These features should allow for economy of scale and network consolidation. Although coherent solutions are well-developed for core networks, the prohibitive cost of their optical and electronic parts makes them unsuitable for the massive deployment of access networks. To this aim, COCONUT will address realization of coherent transmitter/receivers exploiting low-cost components and simple electronics, so that the cost of typical line terminals would be affordable to the end-users. The paper presents an overview of the target results and key issues that are addressed by the COCONUT partners.

The impact of content popularity distribution on energy efficient caching

Abstract: This paper evaluates the effect of content popularity distribution on the power consumption of cache-based services in an IP over WDM network. We consider the Zipf, Bimodal, Pareto and Equal Popularity distributions for content popularity. The results reveal that using our MILP model, reductions in power consumption under the Zipf, Pareto, Bimodal and Equal Popularity distributions are up to 47%, 71%, 72% and 71%, respectively. We also study the impact of the sizes of media files and the impact of the power efficiency of caches on the network power consumption. The results confirm that under the Zipf and Equal Popularity distributions the power consumption rises as the average size of media files and cache power consumption increases. Under the Bimodal and Pareto distributions, the average cache size in the network is not affected by the increase in media file sizes.

A novel statistical model for turbulence-induced fading in free-space optical systems

Abstract: In this paper, we propose a new probability distribution function which accurately describes turbulence-induced fading under a wide range of turbulence conditions. The proposed model, termed Double GG distribution, is based on a doubly stochastic theory of scintillation and developed via the product of two Generalized Gamma (GG) distributions. The proposed Double GG distribution generalizes many existing turbulence channel models in a closed-form expression and provides an excellent fit to the published plane and spherical waves simulation data. We finally evaluate the performance of a free-space optical system over the Double GG turbulence channel and derive closed-form expressions for the bit error rate, assuming intensity modulation/ direct detection with on-off keying.

DISCUS: End-to-end network design for ubiquitous high speed broadband services

Abstract: Fibre-to-the-premises (FTTP) has been long sought as the ultimate solution to satisfy the demand for broadband access in the foreseeable future, and offer distance-independent data rate within access network reach. However, currently deployed FTTP networks have in most cases only replaced the transmission medium, without improving the overall architecture, resulting in deployments that are only cost efficient in densely populated areas (effectively increasing the digital divide). In addition, the large potential increase in access capacity cannot be matched by a similar increase in core capacity at competitive cost, effectively moving the bottleneck from access to core. DISCUS is a European Integrated Project that, building on optical-centric solutions such as Long-Reach Passive Optical access and flat optical core, aims to deliver a cost-effective architecture for ubiquitous broadband services. One of the key features of the project is the end-to-end approach, which promises to deliver a complete network design and a conclusive analysis of its economic viability.

Anycast end-to-end resilience for cloud services over virtual optical networks

Abstract: Optical networks are crucial to support increasingly demanding cloud services. Delivering the requested quality of service is key to successfully provisioning end-to-end services in clouds. Therefore, as for traditional optical network services, it is of utter importance to guarantee that clouds are resilient to any failure of either network infrastructure or data centers. A crucial concept in establishing cloud services is that of network virtualization: the physical infrastructure is logically partitioned in separate virtual networks. Also, combined control of the network and data center (IT) resources is exploited. To guarantee end-to-end resilience for cloud services in such a set-up, we need to simultaneously route the services and map the virtual network, while ensuring that an alternate routing is always available. Note that the anycast routing concept applies: assigning server resources requested by the customer to a particular (physical) data center can be done transparently. This paper investigates the design of scalable optimization models to perform the virtual network mapping resiliently (for single bidirectional link failures), thus supporting resilient anycast cloud virtual networks. We compare two resilience approaches: PIP-resilience maps each virtual link to two alternate physical routes, VNO-resilience provides alternate paths in the virtual topology (while enforcing physical link disjointness).

An evolutionary spectrum assignment algorithm for Elastic Optical Networks

Abstract: A fundamental issue in Elastic Optical Networks (EONs) relies on choosing a proper route and necessary number of contiguous frequency slots from end-to-end to accommodate the traffic demands. Spectrum assignment based on the traditional First-Fit assignment has been extensively employed in EON investigations due to its inherent simplicity and favorable capacity of leaving end-to-end free slots in the network. This paper proposes a possible structure of an evolutionary algorithm that can be used to search for an appropriate spectrum ordering of the First-Fit spectrum assignment to mitigate request blocking probability. We here analyse the path request blocking probability when just lack of resource is emphasized. However, the proposal is general enough to be used in other situations.

Super-resolution microscopy by dielectric microcylinders

Abstract: It is shown that super-resolution microscopy can be performed by using dielectric microcylinders. We used silica (n ~ 1.46) optical fibers, chemically etched down to ~ 7 μm diameter, placed on top of a commercial Blu-ray® disk. We clearly resolved one-dimensional arrays of 200 nm width stripes separated by 100 nm width grooves. Potential applications of this imaging technique include microfluidics and nanophotonics applications.

Dynamic bandwidth allocation with optimal wavelength switching in TWDM-PONs

Abstract: Time and wavelength division multiplexed passive optical networks (TWDM-PONs) have been widely considered as one of the next evolutionary steps of optical access networks. A variety of algorithms exists that explore the problem of scheduling and wavelength assignment in TWDM-PONs. These algorithms, however, allow unlimited switching of wavelengths. In reality, wavelength switching increases guard bands due to the tuning and the switching time of components, limiting channel utilization and increasing packet delays. We propose a novel dynamic bandwidth allocation (DBA) algorithm for TWDM-PON that minimizes the performance degradation due to excessive wavelength switching.

Spectral and energy efficiency considerations in mixed-line rate WDM networks with signal quality guarantee

Abstract: Mixed-Line Rate (MLR) is a cost efficient solution to cope with the rapidly increasing and heterogeneous Internet traffic. In a MLR-based scenario wavelength channels are organized in groups (i.e., sub-bands), each of which consisting of channels operating at the same rate, e.g., it is possible to have on the same fiber link subbands operating at 10 Gbps, 40 Gbps, and 100 Gbps. In order to increase spectral efficiency one can reduce not only the channel spacing within a sub-band but also the frequency spacing between sub-bands operating at different rates, i.e., the sub-band spacing. On the other hand smaller sub-band spacing may: (i) negatively impact the transparent optical reach of wavelength channels due to the higher inter-channel crosstalk levels, and consequently (ii) increase the network power consumption because of the need of more signal regeneration. This paper aims at assessing the trade-off between spectral efficiency and the power consumption in a WDM transport network, when a certain quality of transmission needs to be guaranteed at the receiving node. This is accomplished by evaluating a number of spectral efficient MLR solutions, where the number of wavelength channels allocated to each sub-band is varied while keeping the required Bit Error Rate (BER) level at the receiving node fixed. Results show that the width of each sub-band plays a central role in determining the power consumption of an end-to-end connection.

Energy saving in TWDM(A) PONs: Challenges and opportunities

Abstract: Time- and Wavelength-Division Multiplexed (Multiple Access) TWDM(A) PONs are currently under standardization by ITU-T. Energy efficient schemes proposed for TDM(A) PON can still be applied to TWDM(A) PON for the subset of Optical Network Units (ONUs) transmitting and receiving at the same wavelength. However, because of the presence of multiple transmitters and receivers at the Optical Line Terminal (OLT), novel challenges and opportunities arise for improving the OLT energy efficiency. This paper surveys schemes, currently proposed in the literature, for improving TWDM(A) PON energy efficiency. Then it overviews the main challenges in providing energy efficiency at both the ONU and OLT side. Finally, it provides hints on how to tailor schemes to maximize energy efficiency while complying with the target cost and Quality of Service (QoS) requirements of PONs and user applications.

Evolution of fabless generic photonic integration

Abstract: In this paper, the evolution and current status of generic photonic integration model, from a fabless user perspective, is reviewed. The manufacturers and technologies are described, alongside with photonic chips created by the authors following this model.

High-speed coherent WDM PON for next-generation access network

Abstract: The wavelength-division-multiplexed passive optical network (WDM PON) is very attractive for the future broadband access network due to its capability of providing practically unlimited bandwidth to each subscriber. However, for the massive commercial deployment, its competitiveness is yet to be improved. In particular, we need to increase its operating speed and maximum reach, and, at the same time, enhance its cost-effectiveness. For these objectives, we have developed the high-speed WDM PON operating at per-wavelength speed of > 10 Gb/s by using reflective semiconductor optical amplifiers (RSOAs) and the digital coherent detection technique. We also evaluated the maximum operable speed of the RSOA-based WDM PON by using the classical Shannon theorem. This paper reviews these progresses achieved at KAIST.

Optimization models for flexgrid elastic optical networks

Abstract: In the paper we present integer programming (IP) optimization models for flexgrid elastic optical networks (EON). We consider several different basic assumptions regarding flexibility of EON that lead to a variety of IP formulations differing in precision and complexity. As usual, detailed models aiming at precisely describing technological aspects of EON suffer from tractability issues resulting from their greater complexity and have to be reasonably simplified. To achieve this, we consider cases where the bandwidth is divided into predefined slots, cases where the bandwidth is continuous and can be divided between demands with no restrictions, cases where a list of predefined paths is available, and finally cases where all the paths are indirectly taken into account. We present both compact and non-compact formulations. The non-compact formulations are accompanied with brief description of the dedicated column generation algorithms.

Bandwidth variable transponders based on OFDM technology for elastic optical networks

Abstract: In this paper, the flexible features of bandwidth variable transponders based on OFDM technology are investigated. The limiting factors due to the subsystem components and the trade-off between cost-effectiveness, capacity and reach are taken into account for designing this fundamental building block of elastic optical networks. Advanced functionalities, including sliceability, are discussed. Performance is analysed by means of numerical simulations. Furthermore, the experimental results, achieved within the EOS platform (Experimental platform for Optical OFDM Systems) of the ADRENALINE testbed, are presented.

Cloud orchestration with SDN/OpenFlow in carrier transport networks

Abstract: Software Defined Networking offers network programmability through open Application Programming Interfaces (API) and OpenFlow is the most prominent SDN protocol today. However, it is still quite immature and some concepts and features are missing for application in carrier transport networks. In this paper the authors will give an overview of current activities and latest results of the OFELIA project for OpenFlow enabled lambda switching in ROADM-based optical networks. Then the authors highlight required functionality and propose a system architecture to offer cloud orchestration services over multi-carrier and multi-technology transport networks.

Optimization algorithms for data center location problem in Elastic Optical Networks

Abstract: Modern optical networks must meet many challenges following from the quick and permanent development of IT industry. The latest trend that focuses much attention is cloud computing - a concept that enables delivery of various IT services over the Internet. From the network perspective, the cloud computing implies a growth of the traffic volume and advent of new traffic patterns. In this work, we combine the cloud computing topic with a new concept of optical networks, namely, Elastic Optical Network (EON), which allows for efficient and scalable bandwidth provisioning. In more detail, we address the problem of data center location with lightpath provisioning in EONs. We focus on optimization algorithms for locating data centers with the objective to minimize the amount of spectrum required to serve anycast demands. We propose effective heuristic algorithms that utilize the well-known optimization technique called Column Generation. We present results of numerical experiments run on a real topology of an European backbone network. Our heuristics perform well comparing to optimal results provided by the CPLEX solver. Moreover, we report the increase of spectrum requirement in years 2012-2020 according to traffic demand patterns generated according to Cisco forecasts.

Energy-efficient high-speed InP-based 1.3 µm short-cavity VCSELs

Abstract: In this paper, the enhanced high-speed performance and energy-efficiency of 1.3 μm Short-Cavity VCSEL with buried-tunnel-junction is reported. Error-free data-transmission at 30 Gb/s up to 10 km and at 25 Gb/s up to 25 km is performed at room temperature over single mode fiber. Furthermore, low energy-to-data-distance ratios of 24 fJ/(bit·km) are achieved.

Bit error rate analysis along a slanted path link between UAVs and Ground Stations

Abstract: Free space optical (FSO) communications links is a promising solution for the provision of high data rate point to point communications. The FSO links due to their huge bandwidth and license free spectrum provide a viable communication solution between Unmanned Aerial Vehicles (UAVs) and fixed Ground Stations (GS). It is of great importance to characterize the quality of the optical channel with a proper model, taking into consideration the interesting challenges of the mobility and the slanted path of the optical beam in order to design a high performance communication link. In this paper we investigate the performance of a mobile link between a fixed GS and an UAV in terms of Bit Error Rate (BER) and average Signal to Noise Ratio (SNR). It deals with modelling the influence of the scintillation index and the received optical power with noise on link performance, separating the slanted path into small intervals assuming a Gaussian-beam wave. An extensive comparative analysis among different FSO configurations links considering the altitude of the UAV, the wavelength and the atmospheric conditions is provided. The results show that there is degradation at the BER over a slanted path compared to a horizontal path at the same conditions.

Energy saving in access networks: Gain or loss from the cost perspective?

Abstract: Energy consumption in telecommunication networks has become a significant problem during the last few years. Many energy efficient mechanisms have been proposed and evaluated with respect to their impact on the overall network performance (e.g., delay, blocking probability, quality of transmission). Most of these mechanisms are based on the sleep mode functionality, i.e., a “low power” state of network devices that can be utilized in low traffic conditions. On the other hand, a frequent switching between a working and a sleeping state may increase the probability of failures in a device, which in turn makes the operational cost related to fault reparation higher. This paper discusses how sleep mode-based energy saving mechanisms can impact the reliability performance of network equipment by pointing out several physical phenomena that may lead to an increase of the failure rate. In order to quantify such effects we propose a methodology that estimates to what extent energy savings can be maximized without exceeding the extra reparation cost caused by the degradation of the reliability performance of network equipment due to frequent switching on and off. We perform a number of simulative studies focused on an optical access segment and show that the cost saved by reducing the energy consumption (i.e., as the result of a power efficient mechanism) may be easily overcome by the extra expenses related to reparation of network equipment and service interruption for business users.

Dual stage carrier phase estimation for 16-QAM systems based on a modified QPSK-partitioning algorithm

Abstract: Coherent optical communications based on higher order modulation formats are severely affected by the phase noise of transmitter and receiver lasers. In this work, a novel yet simple scheme is presented for carrier phase estimation (CPE) of 16-ary Quadrature Amplitude Modulation (16- QAM) formats, based on a modified QPSK-partitioning algorithm. The proposed algorithm can tolerate a linewidth times symbol duration product (Δv · Ts) of the order of 10-4, with 1 dB penalty at a bit error rate (BER) of 10-3. Tolerance can be further improved by introducing a maximum likelihood estimation (MLE) stage (Δv · Ts ≈ 1.432×10-4). Comparison of the scheme with other proposed algorithms is shown. The obtained results indicate that the presented approach can be used with the commercially available state of the art lasers for 16-ary Quadrature Amplitude Modulation (16- QAM) transmission at 100 Gbps.

Energy efficiency analysis of next-generation passive optical network (NG-PON) technologies in a major city network

Abstract: Ever-increasing bandwidth demands associated with mobile backhaul, content-rich services and the convergence of residential and business access will drive the need for next-generation passive optical networks (NG-PONs) in the long term At the same time, there is a growing interest in reducing the energy consumption and the associated cost of the access network In this paper, we consider a deployment scenario in a major city to assess the energy efficiency of various PON solutions from a telecom operator's perspective We compare five next-generation technologies to a baseline GPON deployment offering similar bandwidths and Quality of Service (QoS) for best-effort high speed connectivity services We follow two approaches: first, we consider a fixed split ratio (1:64) in an existing Optical Distribution Network (ODN); next, we consider an upgraded ODN with an optimized split ratio for the specific bandwidth and QoS values For medium bandwidth demands, our results show that legacy PONs can be upgraded to 10G PON without any ODN modification For future applications that may require access rates up to 1 Gb/s, NG-PON2 technologies with higher split ratios and increased reach become more interesting systems, offering the potential for both increased energy efficiency and node consolidation

A column generation approach for large-scale RSA-based network planning

Abstract: In flexgrid-based optical networks, the problem of finding optimal route and spectrum allocation (RSA) for the demands in a traffic matrix becomes harder to solve than similar problems in fixed DWDM networks, mainly due to the finer spectrum granularity and the spectrum contiguity and continuity constraints. Additionally, the increasing traffic volumes and the size of real networks lead to network planning problem instances consisting of hundreds of thousands, or even millions, of (binary) variables. In this work, we present a column generation decomposition method to obtain feasible solutions for RSA-based network planning problems. Numerical results show the utility of this method for solving intractable instances.

Diffuse IR-optical wireless system demonstration for mobile patient monitoring in hospitals

Abstract: Patient monitoring in the hospitals is very critical and important for medical treatment during both cure and recovery. Modern hospitals usually implies the facility of mobile patient monitoring based on radio frequency technology, however the radio frequency can experience electromagnetic interference (EMI) with sophisticated medical equipment, which may cause health risk to the patient. We experimentally demonstrate a solution for mobile patient monitoring based on diffuse infra-red (IR) optical wireless technology. In order to avoid background ambient light interference generated by florescent lamps, bipolar signalling is successfully exploited. The data rate of 10 Mbit/s with NRZ-AMI (bipolar signalling) is achieved with BER <; 10-5.

PVA-based gel polymer electrolytes doped with (CH3)4NI/KI for application in dye-sensitized solar cells

Abstract: Gel polymer electrolytes (GPEs) consisting of polyvinyl alcohol (PVA) and double iodide salts have been prepared using ethylene carbonate (EC) and propylene carbonate (PC). Potassium iodide (KI) and tetramethylammonium iodide (TMAI) were used as mixed salts for making the electrolyte ion conducting. The highest room temperature (298K) conductivity of 12.91 mS·cm-1 is obtained for the GPE containing the double salts in the ratio of 70 wt.% KI:30 wt.% TMAI, whereas the single salt electrolytes, 100 wt.% KI:0 wt.% TMAI and 0 wt.% KI:100 wt.% TMAI have the conductivities of 12.48 and 3.94 mS·cm-1, respectively. Utilizing the highest conducting binary salts electrolyte as the electrolyte medium in dye-sensitized solar cells (DSSCs) produced the highest efficiency (η) of 3.45%.

UltraFlow access networks: A dual-mode solution for the access bottleneck

Abstract: Optical Flow Switching (OFS) is promised to be an efficient solution for large Internet data transfers. In this paper, we introduce UltraFlow Access, a novel optical access network architecture that offers dual-mode service to its end-users: IP and OFS. With UltraFlow Access, we design and implement a new control plane and a novel dual-mode network stack to ensure efficient connection setup, and reliable and optimal data transmission. Experimental testbed results demonstrate concurrent error-free transmission of 10 Gbps per-wavelength OFS and 1.25 Gbps conventional IP, delivered over the same infrastructure.

An elastic networks OMNeT++-based simulator

Abstract: An increasing number of studies about flexgrid-based elastic optical networks are currently being carried out by industry as well as academic research teams. As access to real test-beds is limited, there is a lack of effective tools that emulate realistic scenarios for testing algorithms and network architectures. In this paper, we present a simulation framework based on an active stateful Path Computation Element (PCE) with Global Concurrent Optimization (GCO) for flexgrid optical networks. The simulator is fully configurable and allows implementing and testing new algorithms and architectures easily and quickly.

Store, schedule and switch - A new data delivery model in the big data era

Abstract: The big data era is posing unprecedented challenges on the existing network infrastructure. In today's networks, data are transferred across the network as a combination of a series of packets, delivered one by one, without considering the data in their entirety with respective service level requirements. The so called elephant data, which may be less sensitive to transfer delay, compete precious network resources with mice data, in most cases from interactive and delay sensitive applications. Consequently, the Quality of Service (QoS) of interactive applications is hard to provision, and the utility of network is low. We propose a new data transfer model to complement the existing per-packet forwarding paradigm. In the new data transfer model, a service level requirement is assigned (by the data source) to each big data transfer request. Instead of transferring these data on per-packet bases immediately upon entering the network, the network stores the data until it find necessary, or enough network resource is available for that transfer. The scheduled data delivery is realized through the use of dynamic circuit switching. We also present some preliminary simulation results of SSS networks.

Flexible next-generation optical access

Abstract: We propose a fibre access network paradigm achieving low latency, high throughput and energy efficiency, by combining the best of PON and AON, optical and electrical forwarding, and the concepts of software defined networks, flexible grid, and cache assisted networking.

Resonant optical gyro: Monolithic vs. hybrid integration

Abstract: Since several decades, angular velocity sensors are considered crucial devices in a wide range of vehicles such as military and civil airplanes, military ships, submarines, satellites, space launchers, and long-range ballistic missiles. The interest towards miniaturized gyroscopes for aerospace and defense industry has given rise to an increasing research effort aiming at the scaling of optical gyros through integrated optical technologies. In particular, the resonant optical gyro (ROG) has been identified as the ideal candidate for a new generation photonic angular velocity sensor. Two technological approaches are available to implement the ROGs, i.e., the hybrid integration of optoelectronic components manufactured on different substrates or the monolithic integration of all components on a single chip. The two options are critically discussed and compared in this paper with a special attention on integrated gyroscopes (gyro-on-a-chip, GoC) in silica on silicon and indium phosphide that have been recently theoretically and experimentally studied, demonstrating promising results.