Showing papers presented at "International Conference on Transparent Optical Networks in 2011"

Higher-order modulation instability in nonlinear fiber optics

Abstract: We report theoretical, numerical, and experimental studies of higher-order modulation instability in the focusing nonlinear Schrodinger equation. This higher-order instability arises from the nonlinear superposition of elementary instabilities, associated with initial single breather evolution followed by a regime of complex, yet deterministic, pulse splitting. We analytically describe the process using the Darboux transformation and compare with experiments in optical fiber. We show how a suitably low frequency modulation on a continuous wave field induces higher-order modulation instability splitting with the pulse characteristics at different phases of evolution related by a simple scaling relationship. We anticipate that similar processes are likely to be observed in many other systems including plasmas, Bose-Einstein condensates, and deep water waves.

An introduction to Augmented Reality with applications in aeronautical maintenance

Abstract: Augmented Reality is a breakthrough technology that could considerably ease execution of complex operations. Augmented Reality mixes virtual and actual reality, making available to the user new tools to ensure efficiency in the transfer of knowledge for several processes and in several environments. Various solutions based on Augmented Reality have been proposed by the research community: particularly in maintenance operations Augmented Reality tools have offered new perspectives and have promised dramatic improvements. On the other side Augmented Reality is an extremely demanding technology and, at the present day, it is still affected by serious flaws that undermine its implementations in the industrial context. This paper presents examples of Augmented Reality applications and shows the feasibility of Augmented Reality solutions in maintenance tasks, underlining advantages it could introduce. At the same time the principal flaws of Augmented Reality are commented and possible lines of investigation are suggested.

Architecture on demand for transparent optical networks

Abstract: We present the Architecture on Demand (AoD) concept whereby transparent optical cross-connects (OXC) do not have an associated static architecture but can adapt their architecture to suit to the switching and processing requirements of input traffic. The proposed AoD-OXC is implemented with a 96×96 3D-MEMS optical switch functioning as an optical backplane that interconnects architecture-building modules that provide the required services such as arbitrary spectrum switching, time-domain sub-wavelength switching and optical multicasting. This approach will enable unprecedented levels of flexibility and modularity for the introduction of new services and applications in transparent optical networks.

The potential role of Bismide alloys in future photonic devices

Abstract: In a similar manner to the dilute nitrides, the incorporation of Bismuth in semiconductors such as GaAs is predicted to lead to a band-anti-crossing effect (in the valence band) causing a large band gap bowing. In addition, the large size of Bismuth atoms gives rise to a large spin-orbit splitting. This opens-up interesting new possibilities for efficient photonic devices, such as near- and mid-infrared lasers which are more thermally stable and less susceptible to losses compared to conventional InP-based devices. Since Bismuth principally influences the valence band, while nitrogen influences the conduction band, combining Bismuth and Nitrogen in III–V alloys offers huge potential for engineering the conduction and valence band offsets, the band gap and spin-orbit splitting, with wide scope for the design of photonic devices.

Off-line algorithms for Routing, Modulation Level, and Spectrum Assignment in elastic optical networks

Abstract: Optical network architectures with elastic bandwidth provisioning are a very promising approach for next generation optical networks. Such elastic optical networks will enable efficient resource utilization and flexible sub-wavelength and super-channel connection provisioning to support heterogeneous and immense bandwidth demands. In this paper, we focus on the problem of Routing, Modulation Level, and Spectrum Allocation/Assignment (RMLSA) which emerges in such networks. We both formulate RMLSA as an Integer Linear Programming (ILP) problem and propose an effective heuristic method called Adaptive Frequency Assignment - Division and Collision Avoidance (AFA-DCA) to be used if the solution of ILP is not attainable.

Proposal of small-aperture guided-mode resonance filter

Abstract: A guided-mode-resonance filter (GMRF) consisting of a thin film waveguide and a surface periodic relief has been widely studied for application to a laser mirror as well as to an optical wavelength filter, because of its great advantage in mass production in comparison to multilayer dielectric mirrors. However, GMRF needs some considerably large coupling area to provide high coupling efficiency, meaning that the direct coupling to an optical fiber or a semiconductor laser end is difficult. Therefore, the miniaturization of GMRF is very attractive in practical applications. In this paper, we propose a new concept of the integration of a cavity resonator consisting of a pair of distributed Bragg reflectors to miniaturize a GMRF aperture down to several micrometers matching to the electric-field size of an optical fiber or a semiconductor laser.

Energy-efficient lightpath provisioning in a static WDM network with dedicated path protection

Abstract: The interest in the energy consumption of communication networks has risen in the recent years. In an effort to tackle this problem, several approaches have been presented to reduce the power consumed by the entire network infrastructure, including optical transport. Most of the solutions studied and proposed in the literature, however, pay little or no attention to the power consumed to ensure the resiliency of the overall network.

Maximizing time-dependent spectrum sharing between neighbouring channels in CO-OFDM optical networks

Abstract: For CO-OFDM-based networks, we develop an efficient wavelength indexing algorithm to maximally share optical spectrum between neighbouring channels through properly arranging lightpaths that have good match of spectrum usage as neighbours in the optical spectrum. Simulation studies indicated that the proposed algorithm can achieve much better optical spectrum efficiency than the conventional wavelength assignment algorithms such as random and first-fit algorithms, no matter under a single-link or an irregular mesh-network case.

Exploring the potentials of optical-wireless communication using white LEDs

Abstract: This paper reviews the main experimental results achieved by our research group in the area of high-speed wireless visible light communication (VLC). Depending on the modulation complexity and receiver sensitivity, various links operating at rates in the range of 10 – 800 Mbit/s have been demonstrated using off-the-shelf optical components.

Energy-efficient content distribution over telecom network infrastructure

Abstract: Energy consumption of content-delivery networks employing optical infrastructure is improved if some backbone nodes can also host content. In a typical scenario, up to 18% energy is saved using this approach vs. monolithic datacenter architecture.

Cognitive Heterogeneous Reconfigurable Optical Networks (CHRON): Enabling technologies and techniques

Abstract: We present the approach of cognition applied to heterogeneous optical networks developed in the framework of the EU project CHRON: Cognitive Heterogeneous Reconfigurable Optical Network. We introduce and discuss in particular the technologies and techniques that will enable a cognitive optical network to observe, act, learn and optimizes its performance, taking into account its high degree of heterogeneity with respect to quality of service, transmission and switching techniques.

How to save energy in Passive Optical Networks

Abstract: In this paper an overview of the energy consumption of current Passive Optical Network (PON) devices is first provided. Then where and how to save energy in PONs is discussed: current and novel approaches are presented and hints on how to improve PON energy efficiency are provided.

Laser ablation and thin film deposition

Abstract: Laser ablation is the process of removing material from a solid surface by irradiating it with a laser beam At low laser flux, the material is heated by the absorbed laser energy and evaporates or sublimates At high laser flux, the material is typically converted to a plasma Usually, laser ablation refers to removing material with a pulsed laser, that's why is also called pulsed laser deposition (PLD) This review describes some of the recent investigations in oxide's thin film deposition technology which have led to improved understanding and control of film grown The first part is concerned with the development of laser ablation method offering control of the energy of depositing species, which describe the link between film deposition parameters and film structures The second part is focused on parameters described quality of the film

Fast and robust CD and DGD estimation based on data-aided channel estimation

Abstract: In this paper data-aided (DA) frequency domain (FD) channel estimation in a 2×2 multi-input-multi-output (MIMO) system is investigated. Using orthogonal training sequences, fast and robust CD and DGD estimation is demonstrated for a 112 Gbit/s PDM-QPSK system over a wide range of combined linear channel impairments.

Enabling the future optical Internet with OpenFlow: A paradigm shift in providing intelligent optical network services

Abstract: This paper proposes an optical networking paradigm suitable for future Internet services enabled by OpenFlow. The OpenFlow technology supports the programmability of network functions and protocols by separating the data plane and the control plane, which are currently vertically integrated in routers and switches. OpenFlow facilitates fundamental changes in the behaviour of networks and their associated protocols. This paper introduces an OpenFlow optical network architecture enabled by optical flow, optical flow switching elements and programmable OpenFlow controllers. The proposed solution allows intelligent, user controlled and programmable optical network service provisioning with the capability to operate any user defined network protocol and scenario.

Logarithmic step-size based digital backward propagation in N-channel 112Gbit/s/ch DP-QPSK transmission

Abstract: We propose and numerically investigate logarithmic step-size distribution for implementing efficient digital backward propagation (DBP) algorithm using split-step Fourier method (SSFM). DBP is implemented in N-channel 112Gbit/s/ch dual-polarization quadrature-phase-shift-keying (DP-QPSK) transmission over 2000km standard single mode fiber (SMF) with no in-line optical dispersion compensation. This algorithm is compared with constant step-size modified DBP (M-SSFM) algorithm in terms of efficiency, complexity and computational time. Furthermore, we investigate the same-capacity and same-bandwidth-efficiency transmission systems with 28GBaud and 56GBaud per-channel rates. The logarithmic step-size based DBP algorithm depicts efficient mitigation of chromatic dispersion (CD) and non-linear (NL) impairments. Benefit of the logarithmic step-size is the reduced complexity and computational time for higher baud rates.

Access services availability and traffic forecast in PON deployment

Abstract: In this paper, offered and new broadband services for residential customers are considered in Passive Optical Networks (PONs). The user bit rates together with QoS requirements are evaluated for the availability of the services in the PONs, according to the number of users and the network bit rates deployed. Traffic forecast is also estimated for the next future access services evolution and for the dimensioning of the optical access networks, taking into account the required bit rates and the number of users involved.

Fiber-wireless sensor networks (Fi-WSNs) for smart grids

Abstract: Apart from reducing their own energy consumption and greenhouse gas emissions, access networks may be also adopted in economic sectors other than communications in order to enhance the efficiency of energy use and achieve an increased overall CO 2 reduction across different sectors. In this paper, we explore the opportunities of deploying fiber-wireless (FiWi) broadband access networks enhanced with fiber optic and wireless sensors to realize a smart grid communications infrastructure that effectively helps reduce the demand peakiness of today's power grids by means of centralized inter-home scheduling for electricity time-of-use pricing.

Performance evaluation of integrated OTN/DWDM networks with single-stage multiplexing of optical channel data units

Abstract: Optical transport networks are evolving towards the support of dynamic setup/tear-down of services, demanding efficient accommodation of heterogeneous bandwidth requirements while minimizing capital and operational expenditures. Integrated OTN/DWDM networks can attain this objective by optimizing the utilization of traffic grooming and optical bypass at transit nodes. Moreover, the multiplexing of mixed lower order optical channel data units into a higher order data unit in a single stage enables to avoid bandwidth fragmentation, improving the wavelength channel utilization in these networks. This paper evaluates the blocking performance of an integrated OTN/DWDM network for different node and input traffic setups.

Auto tracking system for free space optical communications

Abstract: This paper proposes a transceiver system for automatic tracking and dynamic routing for free space optical (FSO) communication. The proposed transceiver architecture has M transmitters and M receivers in a M × M configuration that can dynamically orient themselves at different angles to establish a link between two transceivers. A request to setup a lightpath is blocked if a free wavelength is not available at a transmitter or a receiver in a node along the route. The number of resources remaining the same, in comparison to a fixed FSO, the methods we propose for routing and recovery that exploit the M × M transceiver architecture achieve reduced blocking probability as well as increased percentage of recovery of affected traffic after a link failure.

Comparison of peak power reduction techniques in optical OFDM systems based on FFT and FHT

Abstract: In this paper, we present different peak-to-average power ratio (PAPR) reduction techniques, for optical orthogonal frequency division multiplexing (O-OFDM) systems based on both the fast Fourier transform (FFT) and the fast Hartley transform (FHT). We analyze the performance of selective mapping (SLM), interleaving and partial transmit sequence (PTS) techniques for transmitting real-valued OFDM signals. In O-OFDM systems based on FFT, a direct implementation of PTS and interleaving techniques destroy the Hermitian symmetry. In FHT-based O-OFDM, all the proposed techniques are implemented and compared, showing that PTS provides the highest PAPR reduction. Furthermore, we demonstrate that the proposed solutions considerably improve the bit error rate (BER), by reducing the clipping noise in intensity-modulated direct-detection O-OFDM systems.

Software-defined optical transmission

Abstract: Progress in electronic data processing enables software-defined optical (SDO) transmission. Modulation formats and symbol rates are set by software-controlled field programmable gate arrays (FPGA). We demonstrate a real-time SDO transmitter for 8 modulation formats, which can be swapped in 5 ns. Single-polarization 64QAM symbol generation at 28 GBd allows transmitting 168 Gbit/s real-time data. We further present a 101.5 Gbit/s single-polarization OFDM transmitter based on real-time FPGA processing, where we modulate 58 subcarriers with 16QAM data. For terabit OFDM reception, optical pre-processing is required to demultiplex high-bitrate signals down to lower-bitrate tributaries, which then can be processed digitally. We discuss a 10.8 Tbit/s receiver employing an all-optical fast Fourier transform to demultiplex 75 optical subcarriers modulated with 16QAM-formated symbols at a rate of 16 GBd.

Adaptive Multi-Gate polling with Void filling for long-reach passive optical networks

Abstract: In this paper, we introduce a new dynamic bandwidth allocation (DBA) algorithm for long-reach passive optical networks (LR-PON) based on the multi-threads (MT) polling algorithm. For the proposed new DBA algorithm, named as the Adaptive Multi-GAte polling with Void filling (AMGAV), the number of threads changes according to the traffic load of a PON in contrast to the static number of threads used in the MT polling algorithm. This makes the algorithm adaptive to load variations and it improves the delay performance for both higher and lower load scenarios. Moreover, the AMGAV algorithm requires no extra effort to enforce separation between threads which makes it simpler to implement than the MT polling algorithm. In the process, we also propose a novel bandwidth reporting scheme which does not have to keep track of the number of threads. Finally, through extensive simulations, we prove that for LR-PON, the AMGAV algorithm provides a better delay performance than the MT polling algorithm for a network load up to 90%, and a comparable performance at higher loads while improving the channel utilization.

Design of transparent optical networks considering physical impairments, CAPEX and energy consumption

Abstract: We propose a methodology which applies a multi-objective Evolutionary Algorithm, the NSGAII, in order to design transparent optical networks, aiming to minimize simultaneously the total cost to build the network, the blocking probability and the energy consumption during operation. The optimizer provides a set of non-dominated solutions and, after that, the designer can decide which solution is more suitable for a specific case. We believe these three different important aspects must be taken into account during the design process. However, just some few papers tackle energy consumption from a physical network design perspective. Besides, to the best of our knowledge, none of the previous presented proposals consider all these issues simultaneously.

Tight binding analysis of the electronic structure of dilute bismide and nitride alloys of GaAs

Abstract: We use a nearest-neighbour sp3s* tight-binding Hamiltonian to investigate the electronic structure of GaAs-based dilute bismide and bismide-nitride alloys. We show that the observed strong variation of the band gap (E g ) and spin-orbit splitting energy (Δ SO ) with Bi composition in GaBi x As 1−x is due primarily to a band-anticrossing interaction between the extended states of the host matrix valence band maximum and highly localised Bi-related defect states lying in the valence band, with the change in E g also having a significant contribution from a conventional alloy reduction in the conduction band edge energy. We calculate a crossover to an E g < Δ SO regime at approximately 10.5% Bi composition in bulk GaBi x As 1−x , in agreement with recent experimental studies of GaBi x As 1−x epilayers grown on GaAs. Finally, we present calculations which show that the effects of N and of Bi are largely independent of each other in random GaBi x N y As 1−x−y alloys, of relevance for future high efficiency photonic devices.

Evolution of FTTH networks based on radio-over-fibre

Abstract: In this paper we review and compare the current gigabit passive optical networks (GPON) fibre to the home (FTTH) based solution, and discuss an evolution scenario to future next generation PONs (XGPONs) and wavelength division multiplexing PONs (WDM-PONs) from an operator point-of-view, i.e., taking into account standardization, wavelength planning, optical line terminal as well as optical network terminal equipment and transmission convergence layer. We also compare proposed solutions for the provision of quintuple play services over orthogonal frequency division multiplexing (OFDM) in several aspects such as equipment requirements, capacity to the end user and limitations

Cost-efficient remote PON monitoring based on OTDR measurement and OTM functionality

Abstract: We present a method to monitor single- and cascaded-splitter TDM-PON systems based on combined techniques of Optical Time-Domain Reflectometry (OTDR) and Optical Transceiver Monitoring (OTM). The method is non-invasive to data traffic flow and requires no additional functionality (hardware or software) at the Optical Network Terminals (ONT). The description of the Fiber Plant Manager (FPM) overall architecture and components is followed by measurement results proving the concept on a 25-km 1∶32 PON testbed.

Energy-efficient IP over WDM networks with data centres

Abstract: The presence of data centres in IP over WDM networks can create a hot node scenario leading to a significant increase in the power consumption of data centre nodes. In this paper, we investigate the power consumption associated with transporting data between data centres and end-users in IP over WDM networks. We study two problems. Firstly, we optimize the location of the data centres in the IP over WDM network so as to minimize the power consumption. Secondly, we investigate introducing renewable energy to IP over WDM networks with data centres and evaluate the problem of whether to locate data centres next to renewable energy or to transmit renewable energy to data centres. The results show that optimizing the data centre locations in the presence of renewable energy sources can save up to 71% of the power consumption.

A perspective on optical-wireless converged NG-FTTH networks using directly modulated lasers

Abstract: OFDM-based next generation fiber to the home (NG-FTTH) networks using directly modulated lasers (DMLs) have been proposed as a solution to deliver quintuple play services addressing cost-effective optical-wireless convergence. In this article, we highlight the principles and discuss the main technical challenges of the optical infrastructure of these networks. A first experimental assessment of transmission of coexisting baseband and ultra-wideband signals along distances typical of NG-FTTH networks using DMLs is presented.

Self- coherent optical OFDM: An interesting alternative to direct or coherent detection

Abstract: Recently, coherent optical orthogonal frequency division multiplexing (CO-OFDM) has been considered for the next generation 400-Gb/s long haul data transmission. For long haul transmission systems coherent detection is beneficial compared to direct detection as it provides higher sensitivity. Though CO-OFDM offers a virtually unlimited tolerance against linear impairments, phase noise represents major challenge that must be compensated for. Thus, phase noise compensation (PNC) technique must be applied in the digital signal processing (DSP), which is already limited in speed and processing capabilities. Conversely, self coherent optical (SCO-) OFDM is an interesting alternative which does not require any PNC in the DSP. Furthermore, no local oscillator (LO) is required at the receiver. In this paper, an overview of the recently seen self coherent techniques will be given. Generally, self coherent detection is realized by sending an optical carrier along with the data signal like in direct detection systems. At the receiver, however, the optical carrier is extracted from the signal with the use of filters with very narrow bandwidth and used as an LO using heterodyne or homodyne detection. The performance of such a system depends on the filter bandwidth that is used to extract the carrier.