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Optical Communications and Networking, IEEE/OSA Journal of

Issue 9 • Date September 2011

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Displaying Results 1 - 17 of 17
  • IEEE/OSA Journal of Optical Communications and Networking - front cover

    Publication Year: 2011 , Page(s): C1
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  • Table of contents 3

    Publication Year: 2011 , Page(s): iii
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  • New Strategies for Connection Protection in Mixed-Line-Rate Optical WDM Networks

    Publication Year: 2011 , Page(s): 641 - 650
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (504 KB) |  | HTML iconHTML  

    Today's optical wavelength division multiplexing backbone networks need to support traffic demands with very diverse capacity requirements. Recent studies have shown how to design an optical transport network that supports mixed line rates (MLR), where the wavelength channels of the optical paths (i.e., lightpaths) can have a variety of capacities (10/40/100 Gbps). Some preliminary work on the design of MLR optical networks has already appeared, but survivability, which is a key concern in optical network design, is a nascent topic in MLR networks. This study investigates the problem of protection in MLR optical networks: in particular, we study how to design a cost-effective transparent MLR network that provides dedicated protection at the lightpath level. We propose three mechanisms: MLR-at-p-lightpath protection (MLR-p), MLR-at-lightpath protection (MLR-l), and MLR-with-backup-flow-grooming protection (MLR-g). The design problem is solved by two different approaches: (1) a two-step approach that formulates part of the problem as an integer linear program and (2) a heuristic approach. Our results show that, by appropriate assignment of rates to lightpaths, MLR networks can provide protection for diverse traffic demands with much lower transponder cost compared to single-line-rate networks. View full abstract»

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  • Offline Routing and Regenerator Placement and Dimensioning for Translucent OBS Networks

    Publication Year: 2011 , Page(s): 651 - 666
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (817 KB) |  | HTML iconHTML  

    The deployment of translucent optical networks is considered the most promising short term solution to decrease costs and energy consumption in optical backbone networks. In fact, translucent wavelength switched optical networks (WSONs) have recently received great attention from the research community due to their technological maturity. However, the inflexibility and coarse granularity of WSONs is (re-)fostering research interest in sub-wavelength switching technologies such as optical burst switching (OBS). In OBS, however, the majority of research works neglect the impact of physical layer impairments by considering either fully transparent (i.e., with optical 3R regeneration) or opaque (i.e., with electrical 3R regeneration) networks. For this very reason, in this paper we present a translucent OBS (T-OBS) network architecture which aims at bridging the gap between the transparent and opaque solutions. In the T-OBS network the problem of routing and regenerator placement and dimensioning (RRPD) emerges. Joint RRPD is a complex problem and, in order to approach it, we propose to decompose it into the routing and RPD subproblems. As a consequence, we provide a mixed integer linear programming formulation of the routing problem and several heuristic strategies for the RPD problem. Illustrative numerical results prove the effectiveness of these methods at minimizing the number of electrical 3R regenerators deployed in the network. Considering a broad range of network topologies, we show that the proposed RPD heuristics ensure a proper quality of transmission performance whilst at the same time providing a cost-effective T-OBS network architecture. View full abstract»

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  • Scalable Passive Optical Network Architecture for Reliable Service Delivery

    Publication Year: 2011 , Page(s): 667 - 673
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (622 KB) |  | HTML iconHTML  

    A scalable and reliable architecture for both a wavelength division multiplexing passive optical network and a hybrid wavelength and time division multiplexing passive optical network with self-healing capability is presented and evaluated. Our protection scheme is compatible with a cascaded arrayed waveguide grating that can accommodate an ultra-large number of end users. A simple interconnection pattern between two adjacent optical network units (ONUs) is applied in order to provide protection for distributed fibers between a remote node and the ONUs. Therefore, the investment cost on a per-user basis can be significantly reduced. Meanwhile, the performance evaluation shows that our approach can achieve high connection availability while maintaining the support of long reach and high splitting ratio. View full abstract»

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  • Dual-Operability and Bandwidth Partitioning Enabled by an ONU With Tandem-Modulator

    Publication Year: 2011 , Page(s): 674 - 682
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1139 KB) |  | HTML iconHTML  

    An upgrade at the physical layer regarding unbundling and dynamic bandwidth provisioning of a wavelength division multiplexed access network is presented. The capability of a reflective modulator to act as a photodetector is exploited and allows a tandem configuration to be used at the optical network unit (ONU) for flexible switching of the detection and modulation branch. Consequently, a mechanism for service operator selection and for dynamic bandwidth partitioning up to twice the nominal data rate is provided. The scheme is experimentally evaluated for different kinds of modulators and shows, together with a full-duplex transmission at 10 Gb/s, additional operation modes, featuring unidirectional downstream and upstream burst-mode transmission with up to 20 Gb/s for ONUs based on a combination of a semiconductor optical amplifier and a reflective electro-absorption modulator. View full abstract»

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  • Distributed SNIR Optimization Based on the Verhulst Model in Optical Code Path Routed Networks With Physical Constraints

    Publication Year: 2011 , Page(s): 683 - 691
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (674 KB) |  | HTML iconHTML  

    In this work, the performance of a distributed power control algorithm (DPCA), based on the Verhulst model for signal-to-noise plus interference ratio (SNIR) optimization in optical code path (OCP) routed networks, was investigated. These networks rest on 2-D codes (time/wavelength) to establish the OCP. The DPCA can be effectively implemented in each node because it uses only local parameters. The SNIR model considers multiple-access interference, amplified spontaneous emission at cascaded amplified spans, group velocity dispersion, and polarization mode dispersion. Numerical results have shown SNIR convergence at power penalties of 7.94 and 11.51 dB for 2.5 and 10 Gbps, respectively. These results could be utilized for adjustment of either the transmitted power to a transmitter node or the gain to dynamic intermediary amplifiers. View full abstract»

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  • Effect of ASE Noise on the Power Consumption of MVMC and Benes Optical Packet Switches

    Publication Year: 2011 , Page(s): 692 - 703
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (757 KB) |  | HTML iconHTML  

    In this paper we compare the average energy consumption per bit of matrix-vector multiplier crossbar (MVMC) and Benes optical packet switches realized in semiconductor optical amplifier (SOA) technology. Sophisticated analytical models are introduced to evaluate the power consumption versus the offered traffic, the main switch parameters, and the used device characteristics. We also study the impact that the amplifier spontaneous emission (ASE) noise generated by a transmission system has on the power consumption of the MVMC and Benes switches due to the gain saturation of the SOAs used to realize the switching fabric. We show that for large size, a Benes switch is more effective in power consumption than an MVMC switch under conditions of low ASE noise and when the power consumption of turned off SOAs is taken into account. As a matter of example for 64 × 64 switches supporting 64 wavelengths and offered traffic equal to 0.8, the average energy consumption values are 6.24×10-1 nJ/bit and 4.87×10-1 nJ/bit for MVMC and Benes switches, respectively. View full abstract»

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  • An All-Optical Carrier Recovery Scheme for Access Networks With Simple ASK Modulation

    Publication Year: 2011 , Page(s): 704 - 712
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (918 KB) |  | HTML iconHTML  

    We theoretically investigate and experimentally demonstrate a scheme for all-optical carrier recovery in loopback access networks that avoids orthogonal or complex modulation formats for the downstream or upstream signals. The applied technique is based on a passive resonating circuit that is capable of recovering the optical carrier of the amplitude-shift-keyed downstream signal for remodulation with a reflective modulator as upstream transmitter enabling full-duplex 10 Gb/s operation. The scheme is compared with alternative pattern suppression techniques based on optical gain saturation and electro-optical feed-forward injection for the stringent requirements of next-generation access networks, namely, an extended loss budget and high upstream data rates. Operation at downstream modulation depths of ~3 dB is reported with the feed-forward approach, while higher modulation depths of up to 9 dB are demonstrated with the all-optical carrier recovery technique, for which the dependence on longer sequences of consecutive identical bits is investigated. Finally, the feasibility of the all-optical downstream cancelation technique for optical access networks is evaluated in a wavelength division multiplexed passive optical network, showing full-duplex transmission with margins of at least 9 dB. View full abstract»

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  • Dynamic Provisioning and Stability of p-Cycles in WDM Networks

    Publication Year: 2011 , Page(s): 713 - 724
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1016 KB) |  | HTML iconHTML  

    p-Cycles correspond to an efficient pre-configured and pre-cross-connected Please check `pre-cross connected' throughout. Should this be `pre-cross-connected'? protection scheme which can achieve ring-like recovery speed while retaining the capacity efficiency of mesh-based schemes. While most studies have focused on static traffic, we study here the stability and efficient reconfiguration of p-cycles in the context of dynamic traffic. We design two new highly scalable mathematical models and algorithms for dynamic p-cycles. We consider two objectives, the classical one with the minimization of the spare bandwidth requirements and the objective of minimizing the number of optical bypasses to be newly established or reset while reusing as much as possible the previously established optical bypasses. We use integer linear programming formulations relying on decomposition techniques. The results confirm that not only are the proposed models and algorithms highly scalable but, in addition, they show that p-cycles are highly stable protection schemes. View full abstract»

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  • Optimized Routing and Buffer Design for Optical Transport Networks Based on Virtual Concatenation

    Publication Year: 2011 , Page(s): 725 - 738
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1743 KB) |  | HTML iconHTML  

    The emergence of new telematic applications and services is creating significant growth in the traffic carried over the optical transport network (OTN). One potential cost-effective approach for satisfying these demands consists in applying inverse-multiplexing techniques, such as virtual concatenation (VCAT). In this context, efficient load balancing can be achieved by exploiting multipath routing at the cost of introducing differential delay in the concatenated circuits. This effect can be compensated through appropriate delay compensation techniques (e.g., electrical buffering), which can act either in a centralized way with the buffering at the end nodes, or by distributing the differential delay throughout the intermediate nodes. In order to properly solve the routing and differential delay compensation distribution problem in the OTN, we propose two novel methods: a dual-step integer linear programming (ILP) model and a tabu search multi-stage heuristic. These strategies are compared with our two former proposals consisting of a single-step ILP model and an iterative search heuristic. The four solutions are further expanded to consider the possibility of using homogeneous or heterogeneous VCAT. The performance of these optimization methods is examined in two network topologies assuming that 100 Gb/s Ethernet streams are carried over 40 Gb/s channels (homogeneous case) or over a mixed combination of 40 Gb/s and 10 Gb/s channels (heterogeneous case) in the OTN. The results obtained show that, as expected, the smallest buffering requirements are obtained by both ILP models, with the dual-step version exhibiting also a significant reduction in the number of optical-to-electrical and electrical-to-optical operations used for intermediate compensation. In addition, the novel tabu search framework is able to surpass our former heuristic by simultaneously leveraging minimum link capacities and reducing the buffer sizes. View full abstract»

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  • Best Effort SRLG Failure Protection for Optical WDM Networks

    Publication Year: 2011 , Page(s): 739 - 749
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (475 KB) |  | HTML iconHTML  

    With the increase in the size and number of shared risk link groups (SRLGs) in optical wavelength-division multiplexing (WDM) networks, the capacity efficiency of shared-path protection becomes much poorer due to the SRLG-disjoint constraint, and thus the blocking probability becomes much higher. Furthermore, due to severe traps caused by SRLGs, it becomes more difficult to find an SRLG-disjoint backup path with trap avoidance within reasonable computational complexity. As a result, in a mesh WDM network with a large number of SRLGs or a large SRLG size, 100% SRLG failure protection is no longer a practical protection scheme. To solve this problem, we present a new protection scheme called best effort SRLG failure protection, in which we try to provide an SRLG-disjoint backup path by choosing the backup path sharing the least number of SRLGs with the working path; this is to make the impact of SRLG failures as low as possible and accept as many as possible connection requests. As a result, the proposed best effort SRLG failure protection scheme manages to make a trade-off between blocking probability and survivability. 100% SRLG failure protection becomes a special case of best effort SRLG failure protection when the working path and backup path share zero SRLG. Due to the NP-completeness of this problem, we propose a heuristic to find the optimal result of the best effort SRLG-disjoint backup path under dynamic traffic. We formulate the connection survivability against SRLG failures and analyze the possibility of backup sharing under best effort SRLG failure protection. Analytical and extensive simulation results with various network topology and SRLG parameters demonstrate that, compared with 100% SRLG failure protection, the proposed best effort SRLG failure protection scheme offers much better capacity efficiency and much lower blocking probability while keeping survivability as high as possible. This can be explained by the fact that by slightly loosing the SRL- - G-disjoint constraint, shared-path protection will become more capacity efficient and more efficient in overcoming traps. View full abstract»

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  • Node Isolation Probability for Serial Ultraviolet UV-C Multi-hop Networks

    Publication Year: 2011 , Page(s): 750 - 757
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (475 KB) |  | HTML iconHTML  

    Non-line-of-sight optical wireless transmission, operated in the unlicensed ultraviolet UV-C band, has been recently suggested as an alternative means of communication. However, due to limited coverage, relayed UV-C networks need to be deployed in order to supply communication services at large distances. In this paper, we consider a serial multi-hop UV-C network where the nodes are distributed at fixed positions on a given service interval. We adopt a suitable path loss model and derive analytical expressions for the node isolation probability assuming on-off keying and pulse position modulation formats. Moreover, we investigate the node density required to achieve connectivity for several geometrical transceiver configurations. The numerical results of this paper are of significant value for telecom researchers working toward a flexible UV-C network deployment in practice. View full abstract»

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  • Impairment Mitigation for a 60 GHz OFDM Radio-Over-Fiber System Through an Adaptive Modulation Technique

    Publication Year: 2011 , Page(s): 758 - 766
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1064 KB) |  | HTML iconHTML  

    We investigate several existing impairments in an orthogonal frequency-division-multiplexed radio-over-fiber (OFDM-ROF) system delivering a 60 GHz optical millimeter wave with double optical sidebands and a suppressed central carrier. It is found through theoretical analysis and numerical simulation that intersubcarrier interference and frequency-selective fading are the dominant factors degrading the OFDM-ROF system performance. With that in mind, we propose and experimentally demonstrate what we believe to be a novel scheme to mitigate system impairments in an OFDM-ROF link by using the adaptive modulation technique in which different subcarriers may have different modulation formats according to their signal-to-noise ratio over the ROF channel. View full abstract»

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  • Anycast Routing for Survivable Optical Grids: Scalable Solution Methods and the Impact of Relocation

    Publication Year: 2011 , Page(s): 767 - 779
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (643 KB) |  | HTML iconHTML  

    In this paper, we address the issue of resiliency against single link network failures in optical grids and show how the anycast routing principle, which is typical of grids, can be exploited in providing efficient shared path protection. We investigate two different integer linear program models for the full anycast routing problem, deciding on the primary and backup server locations as well as on the lightpaths toward them. The first model is a classical integer linear programming (ILP) model, which lacks scalability. The second model is a large-scale optimization model which can be efficiently solved using column generation techniques. We also design two new heuristics: the first one is an improvement of a previously proposed one which, although providing near optimal solutions, lacks scalability, while the second one is highly scalable, at the expense of reduced accuracy. Numerical results are presented for three mesh networks with varying node degrees. They allow an illustration of the scalability of the newly proposed approaches. Apart from highlighting the difference in performance (i.e., scalability and optimality) among the algorithms, our case studies demonstrate the bandwidth savings that can be achieved by exploiting relocation rather than using a backup path to the original (failure-free) destination site. Numerical results for varying network topologies, as well as different numbers of server sites show that relocation allows bandwidth savings in the range of 7-21%. View full abstract»

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    Publication Year: 2011 , Page(s): v
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  • [Cover 3]

    Publication Year: 2011 , Page(s): C3
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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.

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Meet Our Editors

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