Showing papers presented at "International Conference on Transparent Optical Networks in 2008"

Optical layer monitoring in Passive Optical Networks (PONs): A review

Abstract: Motivations, challenges and requirements of optical layer monitoring in PONs are discussed. An exhaustive review of monitoring systems is given considering both time-division multiplexed PON (TDM-PON) and wavelength-division multiplexed PON (WDM-PON) cases.

Optical wireless communications for broadband access in home area networks

Abstract: As a part of the EU-FP7 R&D programme, the OMEGA project (hOME Gigabit Access) aims at bridging the gap between mobile broadband terminals and the wired backbone network in homes. To provide Gb/s connectivity a combination of various technologies is considered. Beside radio frequencies, the wireless links will use infrared and visible light. Combined with power-line communications this enables a home area network (HAN) that meets the vision of broadband home networking dasiawithout new wirespsila. A technology-independent MAC layer is foreseen to control such network and to provide services as well as connectivity to any device the user wishes to connect. Moreover, this MAC layer should allow the service to follow the user from device to device in any room of a building /apartment. The contribution presents ideas and approaches for broadband optical wireless (OW) communications using infrared Gb/s hotspots and 100 Mb/s information broadcasting by means of interior lighting based on white-light LEDs. Important issues concerning the physical layer are discussed.

Silicon oxynitride based photonics

Abstract: Silicon oxynitride is a very attractive material for integrated optics. Besides possessing excellent optical properties it can be deposited with refractive indices varying over a wide range by tuning the material composition. In this contribution we will summarize the key properties of this material class and discuss several application examples. Preliminary results on novel processes, which will lead to largely reduced hydrogen incorporation and enable reflow of SiON material, are being presented.

Dynamic impairment aware networking for transparent mesh optical networks: Activities of EU project DICONET

Abstract: In order to realize the core networks of the future utilizing the translucent or transparent optical networks the DICONET vision is presented in this article. Providing ultra high-speed end-to-end connectivity with quality of service and high reliability through the exploitation of optimized protocols and lightpath routing algorithms that will complement a flexible control and management plane is integrated in the proposed solution. Physical layer impairments and optical performance are monitored and incorporated in impairment aware lightpath routing algorithms. These algorithms will be integrated into a novel dynamic network planning tool that would consider dynamic traffic characteristics, a reconfigurable optical layer, varying physical impairment and component characteristics. The network planning tool along with extended control planes will make possible to realize the vision of optical transparency possible. This article presents the DICONET framework, which address dynamic cross-layer network planning and optimization while considering the development of a future transport network infrastructure.

OLT design approach for resilient extended PON with OBS dynamic bandwidth allocation sharing the OLT optical resources

Abstract: The scalable advanced dense access network architecture (SARDANA) is a proposal for the fiber-to-the- home (FTTH) future next-generation of access networks. It is based on a flexible Hybrid WDM/TDM architecture built with remote nodes (RNs) that connect PONs to a WDM ring, providing resiliency. The RNs have remotely pumped amplification permitting a long distance reach. The ONUs are colorless, seeded for uplink by the downstream light generated at the OLT. In this work, we propose a design for the optical line terminal (OLT) that shares its available optical resources, thus providing great traffic efficiency. The traffic is managed by a Dynamic Bandwidth Allocation protocol based on OBS that suits the employed modulation format.

Power consumption issues in future high-performance switches and routers

Abstract: The underlying demand for network capacity can only be satisfied by contemporaneously increasing the transmission bit rate and the switching capacity. An increase of data transmission and processing speed unavoidable leads to high requirements on power supply. Especially in the case of high-capacity electronic routers, the question of power consumption will be the major issue and probably the most important limiting factor as routers become larger in the future. Using optical switching fabrics could relax the limitations to some extent, but optical buffers occupy larger area and dissipate more power than electronic ones. In this paper, we address power consumption issues in future high-capacity switching elements. Different technologies and switching paradigms such as electronic packet/circuit switching or optical circuit/burst/packet switching are considered. In particular, we consider four different node architectures as candidates for future high-performance network elements. These architectures are described and examined with regard to power consumption.

High reliable optical wireless links for the last mile access

Abstract: In the last couple of years the need for higher data rates and more bandwidth has arisen. This development will continue in the next couple of decades and allegorizes a challenge for the future next generation networks. Taking this into account the end-user will need higher data rates, getting theoretical access to the full available bandwidth of the backbone delivered to the home. Free space optics (FSO) is an excellent supplement to conventional radio links and fiber optics, capable of handling point-to-point and point-to-multipoint connections. On the one hand-side FSO is a broadband wireless solution for the "last mile" connectivity in metropolitan networks, on the other hand-side FSO can be used to interlink locations within one local area network. In the last years different types of cost-effective systems were developed and realized at the Institute of Broadband Communication of Graz University of Technology (TU Graz). The first type was based on a modular concept using available standard components allowing demonstrations at a data rate of 2 times 10 Mbit/s for short distances up to 300 m at a specific power margin of 25 dB/km. Later the units were improved to allow a data rate of 100 Mbit/s, higher data rates are currently under development. The reliability and availability of a FSO-link is mainly determined by the local atmospheric conditions, in free space the transmitted light is reflected, refracted or absorbed by objects, rain, fog, wind or sun. All these parameters directly influence the quality of a FSO-link and indirectly affect the quality of an access network. Many FSO-installations (permanent and nomadic use) have been set-up in the area of Styria by TU Graz and cooperation partners. In this contribution we will show some practical installations for different events, including the latest permanent installation, which was started in the summer of 2007 together with the municipality of Dobl, a small suburb of Graz, and the ML11 GmbH, an IT-company. Within this cooperation the elementary school of Dobl was connected to the Internet via FSO. The FSO-units were successfully installed and the setup is now used to explore the influence of weather on the FSO-link in the area of Graz.

Multiple pulse amplitude and position modulation for the optical wireless channel

Abstract: The increasing demand for high speed optical wireless applications has strongly motivated recent research work towards improvement in the throughput of the optical channels. Numerous modulation schemes have been studied in this area. Multiple pulse position modulation (MPPM) has proved to be more power efficient than other modulation schemes such as on off keying (OOK), pulse amplitude modulation (PAM), and pulse position modulation (PPM). However, MPPM is not a strong candidate when the bandwidth efficiency is taken into account. To achieve optimum power and bandwidth efficiency, a new modulation scheme, multiple pulse amplitude and position modulation (MPAPM), is proposed. This paper analyses the proposed modulation scheme in terms of bandwidth requirements and power efficiency. The new scheme delivers an improvement in energy per unit bandwidth of 10 dB.

Intelligent and fast IRWA algorithm based on power series and Particle Swarm Optimization

Abstract: In all-optical networks signals are transmitted through physical layer with no regeneration. Therefore, physical impairments along lightpath can severely reduce network performance. For this reason, many efforts have been made to develop impairment aware routing and wavelength assignment algorithms (IRWA) in order to mitigate the impairments effects, improving the network performance. In this paper we propose and analyze the performance of an adaptive impairment aware routing algorithm based on a set of chosen input network parameters. The cost function of this routing algorithm is based on a power series expansion. The routing algorithm, called Power Series Routing (PSR), is trained by an optimization technique called Particle Swarm Optimization. We show that this IRWA algorithm can learn during the training stage and adapt itself to the network conditions.

FTTH deployment and its impact on network maintenance and repair costs

Abstract: The introduction of FTTH leads to high costs, especially in fiber deployment. In operations we face a high complexity and corresponding high cost of fiber splicing compared to copper welding. However, fiber based access networks are less vulnerable to degradation because of outside plant conditions, leading to lower failure rates. In order to correctly calculate the business case for a new FTTH network deployment, the capital expenditures need to be balanced with the expected gains in operational expenditures compared to the current (e.g. copper based) access network. In this paper we present a hierarchical approach for getting a clear and balanced view on the costs of an FTTH deployment. This includes a gradual increasing level of detail and a clear view on the trade-offs in each step, an integrated calculation model containing both CapEx and OpEx and the interaction between both. We focus on the modeling of the network maintenance (preventive repair) and repair process and highlight the key differentiators between the copper and the fiber based case.

Analysis of electronic buffers in optical packet/burst switched mesh networks

Abstract: We present in this paper the study of electronic buffering in an innovative architecture for optical packet/burst switched network (OPSN). This architecture comprises optical bufferless nodes with electronic packet queuing out of the optical layer, deflection routing to perform contention resolution and fully connected mesh topologies under uniform traffic distribution. We demonstrate, by means of simulation, that the studied architecture has a great improvement in performance when we introduce such electronic buffers, which are more efficient when used with the optimized mesh topologies.

Flexible simulators for oBS network architectures

Abstract: Since the OBS paradigm has become a potential candidate to cope with the needs of the future all optical networks, it has really caught the attention from both academia and industry worldwide. In this direction, OBS networks have been investigated under many different scenarios comprising numerous architectures and strategies. This heterogeneous context encourages the development of flexible simulation tools. These tools should permit both an easy integration of any possible new network protocol design and a rapid adaptation to different performance target goals. In this paper, we present two OBS network simulators, namely, a C-based simulator (ADOBS) and our novel Java-based simulator (JAVOBS). We compare their performances and we provide some exemplary results that point out remarkable flexibility that can be achieved with the JAVOBS simulator.

Optical signal processing using MMI elements

Abstract: In the past, multimode interference (MMI) devices mostly have been used as couplers, combiners and simple switches. Recently, there has been much research interest in making modifications to the basic MMI structure in order to achieve much greater functionality. Of particular interest has been the possibility of implementing a variety of all-optical signal processing functions. This paper reviews recent novel advances with these devices and examines some of the possible signal processing applications.

Security issues in optical networks physical layer

Abstract: Network management and maintenance in optical networks faces additional security challenges arose from increased transparency in optical network components and systems. A review on existing physical security breaches on these types of networks will be presented. From these some of the methodologies for location and detection will be described and characterized in terms of applicability. Special focus will be given to the ones that are more prone to Passive optical networks due to its proximity to the user, leading to increased attack diversity.

Development of the method of single expression (MSE) for analysis of plane wave oblique incidence on multilayer structures having complex permittivity and permeability

Abstract: An extension of the method of single expression (MSE) for analysis of plane electromagnetic wave oblique incidence on a wavelength-scale multilayer structure consisting of dielectric and magnetic layers is performed. Corresponding Helmholtzpsilas equations, boundary conditions and the expression for power flow density in complex media are derived in the terms of MSE for TE and TM electromagnetic waves. TE and TM waves incidence on multilayer structures comprising alternating quarter-wavelength dielectric or magnetic layers of high and low permittivity or permeability is analysed. The reflectance peculiarities on the angle of incident wave, distributions of electric and magnetic field amplitudes inside the considered structures are obtained. For a structure consisting of dielectric or magnetic layers the full transmission state is observed at Brewster angle for TM and TE waves, correspondingly.

Acoustic-induced modulation of photonic crystal fiber Bragg gratings

Abstract: Acoustic-induced modulation is achieved with a grating written in a H2-loaded 10-ring PCF. The effect caused by the acoustical wave changes the spectrum shape, but preserves the grating reflected power. The effect can be usefully applied in the modulation of a DFB laser.

Multiple sub-carrier optical wireless systems

Abstract: A comparative study of various multiple sub-carrier modulation (MSM) techniques suitable for optical wireless communication systems is presented. The key features of each modulation scheme are examined in the context of employability for multi-spectral optical wireless applications. A review of recent techniques for improving power efficiency of MSM systems is also presented. As a special case of MSM, the performance of orthogonal frequency division multiplexing (OFDM) scheme in an optical wireless channel is examined and several techniques to reduce the peak-to-average power ratio (PAPR), employed for the wireless radio domain, are studied for suitability of implementation in the multi-spectral indoor optical wireless environment.

Silicon-Organic Hybrid (SOH) devices for nonlinear optical signal processing

Abstract: Silicon-on-insulator (SOI) is a promising material system for dense on-chip integration of both silicon photonic and electronic devices. The high refractive index of silicon enables strong light confinement and compact lowloss devices at telecommunication wavelengths. In addition, on-chip nonlinear optical signal processing becomes feasible, because the third-order nonlinear susceptibility chi(3) of silicon is about 200 times that of glass, and because the tight light confinement enhances the nonlinear response. However, for many applications it would be desirable to have even stronger nonlinearities, and to exploit second-order chi(2)-nonlinearities which are negligibly small in mono-crystalline silicon. On the other hand, many organic materials are highly nonlinear, but have only a low refractive index. Silicon-organic hybrid (SOH) systems combine the strengths of both materials resulting in extremely large effective nonlinearities. We report on the design of a 100 Gbit/s / 1 V modulator based on an 80 mum long slow-light SOI photonic crystal slot waveguide filled with a chi(2)-nonlinear organic material. Further, we demonstrate demultiplexing of a 120 Gbit/s signal to 10 Gbit/s with four-wave mixing in a 6 mm long SOI slot waveguide, on which an organic highly chi(3)-nonlinear material was deposited with a molecular beam.

TDM-to-WDM conversion from 130 Gbit/s to 3 × 43 Gbit/s using XPM in a NOLM switch

Abstract: We report the first demonstration of OTDM-to-WDM conversion from 130 Gbit/s simultaneously to 3 times 43 Gbit/s WDM channels in a nonlinear optical loop mirror (NOLM). The scheme is exploiting the ultra-fast Kerr based XPM in a NOLM and gives full flexibility for selecting the output WDM channel wavelengths. For the success of the experiment we rely crucially on a new specially designed highly nonlinear fiber (HNLF) exhibiting low dispersion and low dispersion slope such that low walk-off operation across the C-band is possible. Error free performance is achieved with penalties ranging from 0.5 dB to 3.5 dB for all three WDM channels.

Micro/nano-scale optical network: A new challenge toward next generation

Abstract: This paper presents an overview of our work on the design, fabrication, and integration of micro/nano-scale optical devices, circuits, and networks. This is an extension of the macro/mega-scale optical networks down to the level of micro/nano-scale optical circuits and networks. The micro/nano-optical circuits and networks are designed to perform the functions of collecting, storing, transporting, processing, switching, routing, and distributing optical signals on boards or on chips. The integrated optical components include micro/nano-scale light sources, waveguides, detectors, switches, modulators, sensors, directional couplers, multi-mode interference devices, AWGs, ring-resonators, photonic crystal devices, plasmonic devices, and quantum devices, made of polymer, silicon and other semiconductor materials. The paper discusses scientific and engineering issues concerning the integration of micro/nano-scale photonic devices, circuits, and networks of ultra-small-scale dimensions to a very large scale integration density as applicable for datacom, telecom, transportation, aero/space/avionic, and bio/sensor systems.

A tabu search algorithm for attack-aware lightpath routing

Abstract: Attacks in Transparent Optical Networks present a serious security threat to successful network operation due to the high data rates involved and the vulnerabilities associated with transparency. Typical physical layer attacks can involve injecting high-powered jamming signals on legitimate data channels to exploit vulnerabilities in optical components such as crosstalk in switches and fibers, and gain competition in amplifiers. To assure a certain quality of service in the network, we propose a novel approach which considers such security threats during the network planning process. More specifically, we propose a tabu search heuristic aimed to perform lightpath routing in such a way as to minimize the possible dasiareachabilitypsila of a jamming attack with respect to gain competition and inter-channel crosstalk. In this way we limit the worst case scenario which can potentially be caused by such an attack. We tested the algorithm on the 14-node NSF network and compare with shortest path routing. The algorithm not only yields better attack protection, but reduces lightpath congestion and minimizes the upper bound on the number of wavelengths needed for wavelength assignment.

Driving technologies addressing the future dynamic transparent core networks

Abstract: Reconfigurable transparent networks are now a reality in the core layer thanks to the implementation of innovative transmission and wavelength routing sub-systems. Transparency on a large scale opens up new perspectives in terms of scalability and flexibility. There are numerous promising technologies to achieve that goal but it is likely that only few of them will really prevail in the field. For instance, the compliance with the already installed transmission infrastructures or the power consumption consideration may prevent a technology from appearing in a real optical network. This paper presents some of our current research directions that exhibit a high potential to meet the market requirements for the future dynamic transparent core networks.

On supporting radio over fiber and passive optical network systems with a common fiber plant: Compatibility aspects

Abstract: In view of the current prospects in wired and wireless access networks, it is becoming increasingly important to address potential convergence issues between both types of access networks. Therefore, this paper analyzes compatibility aspects of supporting radio signals over a passive optical infrastructure, which must be accounted for to enable the coexistence of fixed and radio access systems over a common fiber plant.

Connection provisioning with feasible shareability determination for availability-aware design of optical networks

Abstract: In this paper, we present two adaptive connection provisioning algorithms to offer better availability per connection under dynamic traffic with shared backup path protection. The proposed schemes monitor the status of the network in terms of resource consumption and average unavailability per connection and adapt the sharing degree for the links. We compare our heuristic and optimized sharing degree approach with a conventional connection provisioning approach under two different topologies. The simulation results show that our proposed approaches offer better availability to incoming connection requests. Results referring to resource overbuild guarantee that shared backup protection is not violated since resource overbuild is kept in a feasible range.

Inverse problem of scattering for inhomogeneous layered media

Abstract: New methods of the solution of inverse problems of electromagnetic scattering are considered for layered media with imbedded 3D inhomogeneous structures. The retrieval of the structure of media parameters is based on the solution of 3D integral equations of the perturbation theory that are reduced to convolution equations with respect to lateral co-ordinates using the plane wavespsila decomposition of Green functions. Possibilities of resultpsilas applications to media coherent scanning tomography are considered and results of numerical simulation are presented.

Physical layer security: All-optical cryptography in access networks

Abstract: The physical layer security of passive optical networks (PON) is investigated within a rigorous cryptoanalysis framework; we consider different threats and confidentiality attacks and propose different secure optical code division multiple access (OCDMA)-based architectures.

Reach extension of passive optical networks using semiconductor optical amplifiers

Abstract: Passive optical networks are being aggressively pursued as a means of delivering access network solutions. The cost benefits resulting from reducing the number of interfaces between nodes has enabled increasing deployment of passive optical network delivering fibre to the home and fibre to the kerb. However, in many cases, the need for high split ratios or extended reach requires some form of amplification to overcome the additional losses. Erbium doped amplifiers are not appropriate for passive optical networks since the operational wavelength typically include backhaul at 1.3 mum. Semiconductor based amplifiers offer a cost effective solution with a migration path towards integration. Implementation options include using the SOA as a pre-amplifier, booster or mid-span amplifier. This paper summarises the potential for SOAs from both a theoretical and practical perspective.

Management-augmented stateless PCE for Wavelength Routed Optical Networks

Abstract: Two stateless path computation element (PCE) implementations to be used in GMPLS-based wavelength routed optical networks (WRONs) are discussed (fully stateless PCE, F-SL-PCE, and contention avoidance stateless PCE, CA-SL-PCE). The proposed CA-SL-PCE implementation exploits static management information for avoiding resource contentions among subsequent lightpath requests, while preserving network scalability. Simulation results show the capability of CA-SL-PCE implementation in strongly reducing resource contentions, thus resulting in a significant reduction of the overall blocking probability.

Genetic algorithm channel control for indoor optical wireless communications

Abstract: A genetic algorithm controlled multispot transmitter is proposed as an alternative approach to optimising the power distribution for single element receivers in fully diffuse mobile indoor optical wireless communication systems. Results are presented that show by dynamically controlling the powers of individual diffusion spots, a consistent power distribution, with negligible impact to bandwidth and rms delay spread, can be created in multiple rooms, independent of the reflection characteristics and user movement patterns. The advantageous adaptability of the genetic algorithm approach removes the need for bespoke design and provides for a more cost effective system, capable of deployment in multiple locations whilst improving end user friendliness. Results have been presented based around the use of a single element receiver with a FOV = 55deg in conjunction with two algorithms that are shown to be capable of reducing the dynamic range, referenced against the peak received power, by up to 26% when empty and furthermore, maintaining to the within 7% of this optimised case, the power distribution when the user perturbs the channel through movement.

Supporting differentiated survivability services in WDM optical networks

Abstract: Optical networks are currently widely employed to support a variety of telecommunications and other applications. In order to provide the increased bandwidth needed by the existing and emerging applications, optical networks rely extensively on wavelength division multiplexing (WDM). In these networks, WDM is not only used to satisfy capacity requirements, but it can be also exploited to offer advanced features and functionalities such as service differentiation, varying QoS guarantees etc. This paper studies the use of WDM in core optical networks with focus on resilience issues. More specifically the use and suitability of WDM to support differentiated survivability requirements of traffic generated by different applications are investigated. The proposed approach combines various routing and wavelength assignment schemes with the aim to facilitate efficient resource sharing, thus leading into significant enhancement of the spare capacity utilization, as demonstrated by our evaluation results. At the same time, routing and wavelength assignment can be used to differentiate various classes of services based on their survivability requirements. Simulations have shown significant network performance improvement through the proposed approach compared to conventional solutions that do not include survivability differentiation between services.