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Optical Communications and Networking, IEEE/OSA Journal of

Issue 8 • Date Aug. 2012

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Displaying Results 1 - 11 of 11
  • [Front cover]

    Page(s): c1
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  • [Inside front cover]

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  • Table of contents

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  • Multicast overlay for high-bandwidth applications over optical WDM networks

    Page(s): 571 - 585
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (466 KB) |  | HTML iconHTML  

    Multicast communication in wavelength division multiplexed (WDM) networks is traditionally supported by the assumption that the optical crossconnects are multicast capable, i.e., they are capable of switching an incoming signal to more than one output interface. A naïve method of supporting this functionality in a multicast-incapable (MI) environment is by creating a virtual topology consisting of lightpaths from the multicast source to each destination of the multicast session. For large sets of multicast requests, however, the network bandwidth consumed by such a scheme may become unacceptable due to the unicasting nature of the lightpaths. We refer to this method as achieving multicast via WDM unicast (MVWU). To support users' multicast requests (from higher electronic layers) in MI networks, we propose two overlay solutions: drop at member node (DMN) and drop at any node (DAN). In these solutions, we achieve multicasting by creating a set of lightpath routes (possibly multiple hops) in the overlay layer from the source node of a request to each destination member. In the DMN case, we allow a lightpath route to originate/terminate only at source and destination members of a request, whereas in the DAN model we impose no such restrictions. We first consider a static traffic model, wherein the set of multicast requests is known ahead of time, and present integer linear programs (ILPs) to solve these problems (MVWU, DMN, and DAN) with the goal of minimizing the total number of wavelengths required to service the set. We also present an efficient heuristic and compare its performance to the ILP for a small network, and run simulations over real-world, large-scale networks. Moreover, we present lower bounds to calculate the minimum number of wavelengths required by the DMN and DAN models. Finally, we evaluate the performance of the heuristic (minimization of the number of wavelengths) under a dynamic traffic scenario and also evaluate the blocking performanc- for a fixed number of wavelengths. View full abstract»

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  • Design of QoS-aware energy-efficient fiber-wireless access networks

    Page(s): 586 - 594
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (372 KB) |  | HTML iconHTML  

    Energy-efficient network design has recently become a very important topic because of the energy cost increases in service providers' infrastructures. This is of particular importance in access networks because of the growing demand for digital traffic by end users. Here we address the challenge of reducing the energy consumption of fiber-wireless (FiWi) access networks, which use both optical and radio frequency technologies to provide high bandwidth and ubiquity for end-user applications, while keeping delay under a threshold. Our goal is to find optimal sleep mode schedulings that allow energy consumption to be reduced while keeping packet delay acceptable. For this purpose a mathematical formalization and an algorithm are developed. The results show that the proposed approach is able to reduce the average packet delay, with negligible energy cost increases, in many scenarios, besides being computationally efficient and scalable. The proposed approach may, therefore, serve as a basis for planning and design of quality-of-service-aware energy-efficient FiWi access networks. View full abstract»

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  • Weighted undepleted pump model for broadband counter-pumped Raman fiber amplifiers

    Page(s): 595 - 602
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (557 KB) |  | HTML iconHTML  

    We develop a low complexity computational model for the gain profile and amplified spontaneous emission noise for broadband counter-pumped Raman fiber amplifiers. The proposed model is based on two adjustment parameters used to account for the interactions between the pumps. The obtained results show a good agreement between experimental measurements and detailed numerical simulations, for different combinations of pump wavelengths and pump powers, with a processing time several times lower than the time taken by a detailed numerical model. View full abstract»

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  • Dynamic routing and spectrum assignment in spectrum-flexible transparent optical networks

    Page(s): 603 - 613
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1160 KB) |  | HTML iconHTML  

    The continual growth of Internet traffic necessitates a high-capacity transmission platform and also highlights the importance of a multi-granularity transport network due to the flexible bitrates of Internet traffic. To meet these challenges, a spectrum-flexible optical network based on orthogonal frequency-division multiplexing (OFDM) transmission technologies has been proposed as a promising solution because of its large transport capacity and bandwidth flexibility. In spectrum-flexible optical networks, we focus on the complete dynamic routing and spectrum assignment (RSA) problem, which integrates the signal format selection subproblem, the routing subproblem, and the spectrum assignment subproblem. In the complete RSA problem, we jointly consider the spectrum continuity constraints, the transmission distance constraints, and the relationship between the traffic bitrate and the signal bandwidth. A nonlinear programing model is presented to state the complete RSA problem. To solve the problem, we introduce a decomposition approach that divides the nonlinear problem into three steps: selecting the modulation format, solving the linear basic RSA problem, and checking the transmission distances. Based on the decomposition, we propose two heuristic approaches: modulation level fixed and adaptive RSA approaches for the complete RSA problem. Through analysis of the approaches, we prove that, in theory, the modulation level adaptive RSA approach can find the optimal solution to the complete RSA problem. The two approaches are implemented and compared in simulations. The results prove that the modulation level adaptive approaches achieve a lower capacity blocking probability than the modulation level fixed approaches. View full abstract»

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  • ALC burst-mode optical fiber amplifiers for 10 Gb/s-class long-reach PONs

    Page(s): 614 - 621
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (679 KB) |  | HTML iconHTML  

    This paper proposes a burst-mode optical fiber amplifier (OFA) that consists of a combination of an automatic gain controlled praseodymium-doped fiber amplifier (AGC-PDFA), a fast automatic level controlled circuit (ALC), and a PDFA with just forward pumping. The second PDFA is used as a booster to achieve high gain, over 20 dB. The combination of AGC and ALC techniques suppresses optical surge generation against strong burst signal inputs and also prevents overloading of the burst-mode receivers; it provides OFA-based passive optical network (PON) repeaters with wide input dynamic range and solves the near-far problem in upstream transmission in long-reach PONs. We experimentally compare the operating range of the proposed burst-mode PDFA with that of a conventional burst-mode PDFA. Experiments show that the proposed PDFA achieves a much wider operating area than a conventional PDFA; a wide dynamic range in an access span of 17.5 dB, which is equivalent to the input dynamic range of the burst-mode receiver used in 10 gigabit Ethernet PON (10G-EPON), is obtained with an allowable loss margin of 14 dB in a trunk span. A maximum link budget of 55 dB is achievable. View full abstract»

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  • Optical switching for dynamic distribution of wireless-over-fiber signals in active optical networks

    Page(s): 622 - 627
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1039 KB) |  | HTML iconHTML  

    In this paper, we report on an experimental validation of dynamic distribution of wireless-over-fiber by employing optical switching using semiconductor optical amplifiers; we also provide a channel distribution scheme and a generic topology for such an optical switch. The experiment consists of a four wavelength-division-multiplexed channel system operating on a WiMax frequency band and employing an orthogonal-frequency-division-multiplexing modulation at 625 Mbits/s per channel, transmission of the data over 20 km of optical fiber, and active switching in a 1 × 16 active optical switch. The results show a negligible power penalty on each channel for both the best and the worst case in terms of inter-channel crosstalk. The presented system is highly scalable both in terms of port count and throughput, a desirable feature in highly branched access networks, and is modulation- and frequency-band independent. View full abstract»

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  • M-burst: A framework of SRLG failure localization in all-optical networks

    Page(s): 628 - 638
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (551 KB) |  | HTML iconHTML  

    Fast and unambiguous failure localization for shared risk link groups (SRLGs) with multiple links is essential for building a fully survivable and functional transparent all-optical mesh network. Monitoring trails (m-trails) have been proposed as an effective approach to achieve this goal. However, each m-trail traverses through each link by constantly taking a wavelength channel, causing a significant amount of resource consumption. In this paper, a novel framework of all-optical monitoring for SRLG failure localization is proposed. We investigate the feasibility of periodically launching optical bursts along each m-trail instead of assigning it a dedicated supervisory lightpath to probe the set of fiber segments along the m-trail, aiming to achieve a graceful compromise between resource consumption and failure localization latency. This paper defines the proposed framework and highlights the relevant issues regarding its feasibility. We provide theoretical justifications of the scheme. Asa proof of concept, we formulate the optimal burst scheduling problem via an integer linear program (ILP) and implement the method in networks of all possible SRLGs with up to d = 3 links. A heuristic method is also proposed and implemented for multiple-link SRLG failure localization, keeping all the assumptions the same as in the ILP method. Numerical results for small networks show that the scheme is able to localize single-link and multiple-link SRLG failures unambiguously with a very small amount of failure localization latency. View full abstract»

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  • CAPEX study for a multilayer IP/MPLS-over-flexgrid optical network

    Page(s): 639 - 650
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (431 KB) |  | HTML iconHTML  

    The ever-increasing Internet Protocol (IP) traffic volume has finally brought to light the high inefficiency of current wavelength-routed over rigid-grid optical networks in matching the client layer requirements. Such an issue results in the deployment of large-size, expensive, and power-consuming IP/Multi-Protocol Label Switching (MPLS) layers to perform the required grooming/aggregation functionality. To deal with this problem, the emerging flexgrid technology, allowing for reduced-size frequency grids (usually referred to as frequency slots), has recently attracted much attention among network operators, component and equipment suppliers, and the research community. In this paper, we tackle the multilayer IP/MPLS-over-flexgrid optimization problem. To this end, an integer linear programing formulation and a greedy randomized adaptive search procedure (GRASP) metaheuristic are provided. Using GRASP, we analyze the cost implications that a set of frequency slot widths have on the capital expenditure investments required to deploy such a multilayer network. For the sake of a compelling analysis, exhaustive numerical experiments are carried out considering a set of realistic network topologies, network equipment costs, and traffic instances. Results show that investments in optical equipment capable of operating under slot widths of 12.5 GHz, or even 25 GHz, are more appropriate, given the expected traffic evolution. View full abstract»

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Aims & Scope

IEEE/OSA Journal of Optical Communications and Networking covers advances in the state-of-the-art of optical communications and networks.

Full Aims & Scope

Meet Our Editors

Editors-in-Chief
Patrick Iannone
  Alcatel-Lucent Bell Labs
Ori Gerstel
   Cisco Systems, Inc.