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Showing papers in "Photonic Network Communications in 2013"


Journal ArticleDOI
TL;DR: This work presents a column (more precisely, path) generation-based method for the RSA problem that is capable of finding reasonable sets of lightpaths, avoiding large sets of precomputed paths, and leading to high-quality solutions.
Abstract: Finding optimal routes and spectrum allocation in flexgrid optical networks, known as the RSA problem, is an important design problem in transport communication networks. The problem is $$\mathcal{NP }$$ NP -hard, and its intractability becomes profound when network instances with several tens of nodes and several hundreds of demands are to be solved to optimum. In order to deal with such instances, large-scale optimization methods need to be considered. In this work, we present a column (more precisely, path) generation-based method for the RSA problem. The method is capable of finding reasonable sets of lightpaths, avoiding large sets of precomputed paths, and leading to high-quality solutions. Numerical results illustrating effectiveness of the proposed method for obtaining solutions for large RSA problem instances are presented.

57 citations


Journal ArticleDOI
TL;DR: This paper proposes a novel dynamic RSA algorithm by means of ant colony optimization (ACO) that achieves lower blocking probability, complexity, and higher adaptability to more line rates mixture.
Abstract: Optical networks with flexible bandwidth provisioning are a very promising networking architecture. It enables efficient resource utilization and supports heterogeneous bandwidth demands. In this paper, we focus on the dynamic routing and spectrum allocation (RSA) problem which emerges in such networks and propose a novel dynamic RSA algorithm by means of ant colony optimization (ACO). In our proposed algorithm, ants are launched to modify the routing table according to the length and the spectrum fragmentation information along the path. A simulation study is performed considering five algorithms in terms of blocking probability: WDM-based RWA approach, KSP-based RSA approach, Slot-based RSA algorithm, and our proposed ACO-based RSA approach. We then compare the deterioration degree of blocking probability by adding more types of line rate. Simulation results indicate that our proposed ACO-based RSA approach achieves lower blocking probability, complexity, and higher adaptability to more line rates mixture.

25 citations


Journal ArticleDOI
TL;DR: This paper introduces an LED layout scheme in which the LEDs tilt toward the room corners, and the effects of changing LED direction on system performance, including illuminance, received power, and SNR are analyzed.
Abstract: Visible light communication (VLC) is expected to be the next generation of indoor wireless communication. A VLC system uses many LED chips, and its performance is greatly affected by the direction of light-emitting diodes (LEDs). Normally, the LEDs are directed vertically downward to the floor. In this paper, we introduce an LED layout scheme in which the LEDs tilt toward the room corners. The effects of changing LED direction on system performance, including illuminance, received power, and SNR, are analyzed. The analysis is then verified by the simulations.

21 citations


Journal ArticleDOI
TL;DR: The use of a novel approach based on a differential evolution (DE) algorithm to the RWA problem in wavelength-routed dense division multiplexing (DWDM) optical networks shows that the DE-RWA outperform those algorithms.
Abstract: The routing and wavelength assignment (RWA) problem, known to be an NP-complete problem, seeks to optimally establish routes and adequate wavelengths for the requested connections according to an objective function. This paper presents the use of a novel approach based on a differential evolution (DE) algorithm to the RWA problem in wavelength-routed dense division multiplexing (DWDM) optical networks. The proposed DE-RWA algorithm is modeled to optimize not only the network wavelength requirement ( $$ NWR $$ N W R , which is the minimum number of wavelengths needed to fulfill traffic demand) but also the average path length ( $$ APL $$ A P L ). We present the impact of the control parameters of the DE algorithm on the improvement of system's performance. Additionally, we present two strategies to improve the efficiency of the algorithm, knowing as the disjoint cut-set paths (DCS-P) algorithm and the use of a random mutation ( $$ random -M$$ r a n d o m - M ) parameter for DE. The proposed approach is evaluated for test bench optical networks with up to 40 nodes. Experiments show that the DE-RWA algorithm obtains results that equal the $$ NWR $$ N W R lower bound for networks with and without wavelength conversion capability, whereas reduce the $$ APL $$ A P L . The performance of the DE-based approach is compared against results obtained with the particle swarm optimization (PSO) and genetic algorithm (GA) models, showing that the DE-RWA outperform those algorithms. The presented DE-RWA model is simple to implement and could also be extended by adding other features such as impairment-aware, energy efficient, survivability among others in optical networks.

18 citations


Journal ArticleDOI
TL;DR: A novel algorithm for dynamic source aggregation of connections is proposed and a novel node architecture is introduced enabling the realization of the proposed source aggregation in a cost-effective way, demonstrating considerable improvement in the network spectrum utilization.
Abstract: Elastic optical network technologies arise as promising solutions for future high-speed optical transmission, since they can provide superior flexibility and scalability in spectrum allocation toward the seamless support of diverse services along with the rapid growth of Internet traffic. In elastic optical networks, heterogeneous traffic demands are typically supported by a single type of bandwidth-variable transmitters, which is not always spectrum and cost-efficient. In light of this, the aggregation of same source but different destination subwavelength connections has been recently introduced for elastic optical networks, aiming to obtain both transmitter and spectrum usage savings. In this paper, we propose a novel algorithm for dynamic source aggregation of connections. Moreover, we introduce a novel node architecture enabling the realization of the proposed source aggregation in a cost-effective way. The obtained results demonstrate considerable improvement in the network spectrum utilization, as well as a significant reduction in the number of necessary transmitters per node.

16 citations


Journal ArticleDOI
TL;DR: The proposed PON architecture is found that the proposed DBA schemes efficiently manage bandwidth even when the occurred traffic load is quite different from the reserved bandwidth, and is appropriate in supporting diverse services in future high-speed optical access network.
Abstract: In this paper, we propose a novel passive optical network (PON) architecture that has multiple optical line terminals (OLTs) Unlike existing PONs where all ONUs are connected to a single OLT, the proposed multi-OLT PON allows subscribers to choose their own service providers from among multiple OLTs Service companies and subscribers can make service level agreements (SLA) on the amount of bandwidth that each OLT or ONU requires A new control protocol and bandwidth allocation algorithms appropriate in this new PON environments are suggested For the downstream, a scheme to share the bandwidth among multiple OLTs is studied to maximize the total transmitted packets while guaranteeing each OLT's SLA A modified Limited Dynamic Bandwidth Allocation named mLimited scheme is also proposed for upstream transmission toward multiple OLTs, which maximizes the total upstream throughput while minimizing the delay of each ONU Performances of the proposed PON architecture and algorithms are analyzed A PON system with two OLTs and 16 ONUs is used in the analysis Self-similar traffic reflecting current packet distribution is used in the packet generation The results show that the proposed DBA schemes efficiently manage bandwidth even when the occurred traffic load is quite different from the reserved bandwidth It is found that the proposed PON architecture is appropriate in supporting diverse services in future high-speed optical access network

13 citations


Journal ArticleDOI
Huanlin Liu1, Xue Xiang1, Yong Chen1, Fang Qiang1, Sheng Huang1 
TL;DR: Simulation results show that the proposed algorithm can groom traffic efficiently with low blocking probability and high network throughput constraint by limiting number of node transceivers and grooming ports.
Abstract: With the growth of multi-granularity multicast applications, there comes into being a huge gap between the bandwidth of a wavelength provided and a multicast traffic required in the wavelength division multiplexing (WDM) networks. The dynamic multicast traffic-grooming is an effective way for WDM networks to improve the wavelength utilization and decrease the traffic blocking probability. A novel switching node architecture with the multicast switching matrix and traffic-grooming fabric is studied in the paper. Then, an efficient dynamic multicast traffic-grooming algorithm is proposed for the architecture. According to the ratio of network available grooming port number to network transceiver number, the proposed algorithm estimates whether the traffic-grooming port is a scarce resource for input traffic and chooses the appropriate grooming strategy. If the traffic-grooming port is scarce, the minimized use grooming port strategy is designed for the coming traffic. On the contrary, the minimized use node transceiver strategy is applied for the coming traffic. Simulation results show that the proposed algorithm can groom traffic efficiently with low blocking probability and high network throughput constraint by limiting number of node transceivers and grooming ports.

11 citations


Journal ArticleDOI
TL;DR: It is shown that the bit-loading algorithm is a very efficient PAPR reduction technique by reducing it at about 1.2 dB over 100 Km of transmission and that the optimum method for suppressing the OBI is the TD + bit-loading.
Abstract: The peak-to-average power ratio (PAPR) and optical beat interference (OBI) effects are examined thoroughly in orthogonal frequency-division multiplexing access (OFDMA)-passive optical networks (PONs) at a signal bit rate up to $$\sim 20\,\mathrm{{Gb}}/{\hbox {s}}$$ ~ 20 Gb / s per channel using cost-effective intensity-modulation and direct-detection (IM/DD). Single-channel OOFDM and upstream multichannel OFDM-PONs are investigated for up to six users. A number of techniques for mitigating the PAPR and OBI effects are presented and evaluated including adaptive-loading algorithms such as bit/power-loading, clipping for PAPR reduction, and thermal detuning (TD) for the OBI suppression. It is shown that the bit-loading algorithm is a very efficient PAPR reduction technique by reducing it at about 1.2 dB over 100 Km of transmission. It is also revealed that the optimum method for suppressing the OBI is the TD + bit-loading. For a targeted BER of $$1 \times 10 ^{-3}$$ 1 × 10 - 3 , the minimum allowed channel spacing is 11 GHz when employing six users.

10 citations


Journal ArticleDOI
TL;DR: A signal-to-noise-and-distortion ratio (SNDR) considering fiber dispersion with respect to an input signal power and an EDFA gain in both noise-dominant and third order intermodulation (IM3)-dominant cases is investigated.
Abstract: The performances of radio on fiber (RoF) systems with a dual-electrode Mach-Zehnder modulator and an erbium-doped fiber amplifier (EDFA) are optimized by numerical equations including the third order intermodulation (IM3) as well as amplified spontaneous emission (ASE) noise. We investigate a signal-to-noise-and-distortion ratio (SNDR) considering fiber dispersion with respect to an input signal power and an EDFA gain in both noise-dominant and third order intermodulation (IM3)-dominant cases. We also verify that the numerical analysis results are well matched with those of a commercial simulator, VPItransmissionMaker. In the analysis results, the optimum input signal power for the maximum SNDR of a RoF system with EDFA was reduced over 8 dB compared with that without EDFA. The dramatic reduction of IM3 power at a receiver was resulted from this decrement of input signal power. Thus, the maximum SNDR of the system with EDFA was obtained over 17 dB at 40 km fiber compared with that of the system without EDFA. In addition, the results showed that the SNDR was efficiently improved by EDFA in the noise-dominant case, while the SNDR improvement was negligible by EDFA in the IM3 dominant case.

8 citations


Journal ArticleDOI
Yue Chen1, Nan Hua1, Xin Wan1, Hanyi Zhang1, Xiaoping Zheng1 
TL;DR: This work proposes both link-state (LS) and distance vector (DV) schemes for dynamic lightpath provisioning in optical WDM mesh networks with asymmetric nodes and proposes the information diffusion-based routing (IDBR), which can achieve the lowest blocking probability with the lowest computational complexity.
Abstract: The wavelength selective switch-based reconfigurable optical add/drop multiplexers is a promising switching equipment for future reconfigurable wavelength-division multiplexing (WDM) mesh networks. However, its asymmetric switching property complicates the optimal routing and wavelength assignment problem. In an asymmetric switching scenario, using the classic Dijkstra's algorithm can lead to invalid paths traversing unconnected ports of an asymmetric node. To solve this problem, we propose both link-state (LS) and distance vector (DV) schemes for dynamic lightpath provisioning in optical WDM mesh networks with asymmetric nodes. The proposed LS schemes include the asymmetric switching-aware (ASA) Dijkstra's algorithm, the $$K$$ -shortest path-based algorithm, and the entire path searching (EPS) algorithm. Simulation results show that the ASA-Dijkstra's algorithm will bring notable improvement of the blocking performance with low computational complexity, while the EPS algorithm has much higher complexity and is not suitable to be employed in large-scale networks. On the other hand, our proposed DV solution, i.e., the information diffusion-based routing (IDBR), can achieve the lowest blocking probability with the lowest computational complexity. Moreover, IDBR does not require the distribution of local asymmetric switching information like the LS schemes, thus having a high level of topology confidentiality.

8 citations


Journal ArticleDOI
TL;DR: The results show that the two schemes improve the throughput of optical OBS networks and enhance the hop-count fairness.
Abstract: In this paper, we propose and evaluate two schemes for improving bandwidth utilization in optical burst-switched (OBS) networks employing timer-based burst assembly routines. The first scheme adjusts the size of the search space for a free wavelength in optical switches using a balancing formula that promotes throughput and hop-count fairness. The formula achieves controllable increase in the size of the search space either when the size of the burst increases or when the hop count of the traveling burst increases. The second scheme proactively discards bursts at the source network access station using a dropping probability matrix that satisfies certain horizontal and vertical constraints. The matrix assigns smaller dropping probabilities to bursts with larger sizes and longer lightpaths. The results of extensive performance tests to evaluate the two schemes and compare them with previous schemes for improving fairness and throughput are presented and discussed. The results show that the two schemes improve the throughput of optical OBS networks and enhance the hop-count fairness.

Journal ArticleDOI
TL;DR: This paper proposes a heuristic based on two existing queueing models: one with quantization and one with impatience, which translates the optical buffer problem into two well-known queueing problems, with accurate performance expressions available in the literature.
Abstract: Optical switching (optical packet switching, optical burst switching, and others) provides alternatives to the current switching in backbone networks. To switch optically, also packet buffering is to be done optically, by means of fiber delay lines (FDLs). Characteristic of the resulting optical buffer is the quantization of possible delays: Only delays equal to the length of one of the FDLs can be realized. An important design challenge is the optimization of the delay line lengths for minimal packet loss. To this end, we propose a heuristic based on two existing queueing models: one with quantization and one with impatience. Combined, these models yield an accurate performance modeling heuristic. A key advantage of this heuristic is that it translates the optical buffer problem into two well-known queueing problems, with accurate performance expressions available in the literature. This paper presents the heuristic in detail, together with several figures, comparing the heuristic's output to existing approaches, validating its high accuracy.

Journal ArticleDOI
TL;DR: This paper introduces the software-based emulation testbed of a programmable optical router, which is here developed and applied to test optical switching fabrics and proves the effectiveness of the proposed tool to emulate an optical router at different levels of granularity.
Abstract: A programmable optical router is a key enabler for dynamic service provisioning in Future Internet scenarios. It is equipped with optical switching hardware to forward information at hundreds of Gigabits/s rates and above, controlled and managed through modular and flexible procedures according to emerging standards. The possibility to test such costly optical architectures in terms of logical and physical performance, without implementing complex and expensive testbeds, is crucial to speed-up the development process of high-performance routers. To this purpose, this paper introduces the software-based emulation testbed of a programmable optical router, which is here developed and applied to test optical switching fabrics. Accurate characterization of the optical devices and physical layer aspects is implemented with the Click software router environment. Power loss and optical signal-to-noise-ratio evaluation are provided through accurate software representation of the physical characteristics of the optical devices employed. The scalability of the proposed emulation testbed is also assessed on standard PC hardware. All the obtained results prove the effectiveness of the proposed tool to emulate an optical router at different levels of granularity.

Journal ArticleDOI
TL;DR: The correct operation of this algorithm is confirmed by a set of simulations using OMNet++ framework, and the outcome results show that EMDBA performance is satisfactory in terms of delay and service differentiation.
Abstract: This work presents a new approach on dynamic bandwidth allocation (DBA) for Ethernet Passive Optical Networks (EPONs). A brief introduction to the DBA area and major term definitions are given. The related research and standardization efforts are presented. Justification that EPONs can be used on the aggregation network is provided, based on their evolution and related research proposals. Focus is given to the Long Reach-Passive Optical Networks (LR-PONs) and their limitations which show the need for a non-polling, midterm DBA scheme for next-generation EPONs. The challenges arising, because of this new approach, are discussed along with possible solutions. Finally, this work proposes the EMDBA algorithm which is able to overcome the discussed issues. The correct operation of this algorithm is confirmed by a set of simulations using OMNet++ framework, and the outcome results show that EMDBA performance is satisfactory in terms of delay and service differentiation.

Journal ArticleDOI
TL;DR: A dynamic lightpath establishment scheme considering four-wave mixing (FWM) in multifiber wavelength-division multiplexed (WDM) all-optical networks is proposed and the effectiveness of the proposed scheme is shown through simulation experiments.
Abstract: This paper proposes a dynamic lightpath establishment scheme considering four-wave mixing (FWM) in multifiber wavelength-division multiplexed (WDM) all-optical networks. The FWM is one of the most important physical impairments to be resolved in WDM networks because the FWM induces nonlinear inter-channel crosstalk and decays the performance of WDM networks. In WDM networks, data are transmitted via lightpaths. When the effect of FWM crosstalk is large, it is highly possible that data transmission fails even if lightpaths are correctly established. The proposed scheme aims to avoid not only the blocking of lightpath establishment but also the accumulation of FWM crosstalk by means of ingenious selection of routes, wavelengths, and fibers for lightpath establishment. In the proposed scheme, a route and a wavelength are selected for each lightpath based on wavelength availability and wavelength placement of established lightpaths. Furthermore, fibers on the route are selected based on estimated FWM power. In this paper, we show the effectiveness of the proposed scheme through simulation experiments.

Journal ArticleDOI
TL;DR: A novel eco-sustainable routing and wavelength assignment algorithm, based on shortest path routing with an adaptive link weighting function relying on an extension of the OSPF-TE protocol to convey carbon footprint information, has been proposed to decrease the network ecological impact while balancing the traffic load and maintaining acceptable connection-blocking rate.
Abstract: It is quite easy to foresee that in the next years, the future generation ultra-high speed network infrastructures and equipments will be no longer constrained only by their pure transport capacity, but also by their energy consumption costs and environmental effects. In particular, large network infrastructures are now widely recognized to play a fundamental role in the emission of greenhouse gases in the atmosphere, significantly affecting the environmental sustainability of new evolutions in network architectures as well as technological developments in communication devices. In this paper, a novel eco-sustainable routing and wavelength assignment algorithm, based on shortest path routing with an adaptive link weighting function relying on an extension of the OSPF-TE protocol to convey carbon footprint information, has been proposed to decrease the network ecological impact while balancing the traffic load and maintaining acceptable connection-blocking rate. The trade-off between load balancing and carbon footprint is also analyzed to evaluate the effectiveness of the proposed strategy within the context of a real world network.

Journal ArticleDOI
TL;DR: This paper investigates the capacity planning problem against double-link failures considering wavelength—continuity constraint and proposes two efficient approaches: the New Static Preplanned Path Protection (NSPPP) and the New Dynamic Rerouting (NDR).
Abstract: Survivability is always a key concern in WDM optical transport networks as failures may result in large amount of traffic disruption and significant degradation of network performance. In this paper, we investigate the capacity planning problem against double-link failures considering wavelength--continuity constraint. Our objective is to minimize the resource consumption when guaranteeing connection request 100 % survivability. We propose two efficient approaches: (1) the New Static Preplanned Path Protection (NSPPP); (2) the New Dynamic Rerouting (NDR). In NSPPP, we present a new backup resource sharing rule to compress the spare capacity. In NDR, only the working path of connection request is necessary to be given, and the rerouting path can be dynamically found on the network after double-link failures. Compared to previous algorithms, our proposed two capacity planning approaches can efficiently solve double-link failures problem of WDM networks, also obtain higher resource utilization ratio and lower network resource.

Journal ArticleDOI
TL;DR: It is shown here that LRC produces lower blocking probability and distributes losses more uniformly among routes than do other existing scheduling policies.
Abstract: This paper presents a novel channel scheduling policy for optical burst switching networks called least reusable channel (LRC). LRC decides to which interval of the output channel (void) an incoming burst should be allocated on the basis of reuse of the remaining voids. LRC dynamically uses information available to make allocation decisions. It is shown here that LRC produces lower blocking probability and distributes losses more uniformly among routes than do other existing scheduling policies.

Journal ArticleDOI
TL;DR: The feasibility and performance analysis of DV architecture in reverse direction is described and the possible hardware model of the node switch have been discussed and a comparative study with DV on throughput, latency and latency distribution is presented.
Abstract: Multistage interconnection networks are employed in data centres to interchange information between the processors and memory elements. Data Vortex (DV) is a multistage minimum logic network which can be used in data centres. DV satisfies the requirements of the interconnection networks such as scalability and throughput. However, the latency is on higher side, and reduction in latency can lead to higher throughput. In the present paper, we describe the feasibility and performance analysis of DV architecture in reverse direction. The routing and the possible hardware model of the node switch have been discussed. We present the performance analysis of Reverse Data Vortex (RDV) architecture in terms of throughput, latency and latency distribution. A comparative study with DV on throughput, latency and latency distribution is also presented. The simulation result shows that the decrease in latency of RDV is about 50 % that of DV and this leads to an increase in injection rate of RDV to values more than two times that of DV.

Journal ArticleDOI
TL;DR: The results indicate that the proposed technique is very power efficient, and when the bit rate is constant, the network capacity can be expanded to accommodate a large number of simultaneous active users with low error rate.
Abstract: This paper presents a simple and efficient multiple access interference (MAI) cancelation technique in optical code division multiple access (OCDMA) system. The proposed technique is based on hybrid frequency shift keying (FSK) with an enhanced modified prime code as a signature sequence for coding techniques. Coherent FSK modulation along with incoherent demodulation using Arrayed-Waveguide Grating has been examined in the transceiver structure. In the proposed technique, a reference signal is constructed by using one of the addressed spreading sequences, and MAI cancelation is performed by subtracting the reference signal from the received signal of the desired user. The performance of the proposed FSK-OCDMA system is compared with the performance of the existing pulse position modulation (PPM)---OCDMA system. The simulation results reveal that the bit-error rate performance of the proposed technique is superior to the performance of the pulse position modulation (PPM) technique. Also, the results indicate that the proposed technique is very power efficient, and when the bit rate is constant, the network capacity can be expanded to accommodate a large number of simultaneous active users with low error rate. Moreover, the proposed technique simplifies the hardware of the receiver design.

Journal ArticleDOI
TL;DR: Simulations show that the SSBP method can get better BR and WER than the previous results demonstrated, and the performance to be evaluated includes wavelength efficiency ratio (WER), blocking ratio (BR), and executing time.
Abstract: For a delay-constrained multicast transmission request, the goal of delay-constrained survivable multicast routing problem is to provide the primary multicast tree and the tree protecting sparse resources. The shared segment-based protection (SSBP) method is used in this article to protect the delay-constrained multicast transmission. Two heuristic methods are proposed to find the delay-constrained primary tree and the backup segments with delay constraint. Experiments are conducted to evaluate the performance of the proposed methods, and the performance to be evaluated includes wavelength efficiency ratio (WER), blocking ratio (BR), and executing time. Simulations show that the SSBP method can get better BR and WER than the previous results demonstrated Din and Jiang (Comput Commun 35(10):1172---1184, 2012).

Journal ArticleDOI
TL;DR: This paper proposes an elastic ONU-class-based idle time elimination algorithm (EOCA), which is elastic in the sense that the lower-class transmission is first considered, and then if insufficient lower- class transmissions exist to eliminate the idle time, the OLT pre-allocates the higher-class transmissions in the following cycle to test whether or not the idleTime is eliminated.
Abstract: To fully exploit the upstream bandwidth in Ethernet passive optical networks (EPONs), dynamic bandwidth allocation (DBA) algorithms need to collect the report messages from all the optical network units (ONUs), incurring an idle time comprising the DBA computation time and the round trip time. Some studies have addressed the problem by using the data transmissions of some or all ONUs (ONU-based) to eliminate the idle time. To satisfy the stringent quality of service (QoS) requirements, for example, to improve the packet delay and jitter for delay sensitive applications without degrading QoS support for other types of applications, some studies have proposed to separate the transmission of higher-class and lower-class traffic within one scheduling cycle. Existing studies on the separable scheduling scenario use the class-based concept, that is, use either the higher-class transmission or the lower-class transmission to eliminate the idle time. By contrast, in this paper, an elastic ONU-class-based idle time elimination algorithm (EOCA) is proposed in which the idle time is eliminated using both the higher-class and lower-class transmissions. The proposed mechanism is elastic in the sense that the lower-class transmission is first considered, and then if insufficient lower-class transmissions exist to eliminate the idle time, the OLT pre-allocates the higher-class transmissions in the following cycle to test whether or not the idle time is eliminated. If the idle time is still not eliminated, the OLT reallocates the bandwidth corresponding to the uneliminated idle time to either the last ONU (uneven method) or all of the ONUs (even method) such that the ONU(s) can early transmit any lower-class packets which arrive during the waiting time. Compared to existing class-based or ONU-based idle time elimination algorithms, the proposed EOCA algorithm performs better. The validity of the proposed EOCA algorithm is demonstrated via detailed simulation experiments.

Journal ArticleDOI
TL;DR: The benefit of node clustering in optical networks, regarding routing with physical layer impairment awareness, is investigated under the CANON network architecture where regenerators are conveniently placed and routing is confined among a small subset of nodes.
Abstract: Physical layer impairment aware routing algorithms have been proposed for optical transparent networks in order to calculate the feasibility of dynamically establishing an optical path when no regeneration is used. The benefit of node clustering in optical networks, regarding routing with physical layer impairment awareness, is investigated under the CANON network architecture where regenerators are conveniently placed and routing is confined among a small subset of nodes. The CANON architecture exhibits enhanced blocking performance, high resource utilisation and adequate physical performance; hence, it can serve Quality of Service.

Journal ArticleDOI
TL;DR: The experimental results presented in this paper clarify that the BS-ROADM can multiplex and demultiplex the wavelengths successfully without limiting the pass-through wavelengths, providing the wavelength transparent networks.
Abstract: Bidirectional stackable ROADMs (BS-ROADMs) with 3-port optical add/drop multiplexers (OADMs) have been presented for minimizing the lightpath interference during reconfiguration of the ROADMs. The BS-ROADM is constructed by connecting some modules with different wavelengths, and it is reconfigured by adding new modules required in it. The reconfigurations of the BS-ROADMs are done for upgrading the in-service networks to support newly appeared traffic demand. The experimental results presented in this paper clarify that the BS-ROADM can multiplex and demultiplex the wavelengths successfully without limiting the pass-through wavelengths, providing the wavelength transparent networks. The reconfiguration of an in-service BS-ROADM can be made without influencing any lightpath in the network, and this type of BS-ROADMs is used for premium users. However, while adding a new module in comparatively low-cost BS-ROADMs in-service, the transmission break of some lightpaths might be taken place. The investigated transmission break time was limited within recovery time specified in the service level agreement for best-effort transmission, which has strong cost-effectiveness rather than high QoS. This upgradability of the BS-ROADMs adds more flexibility in coarse wavelength division multiplexing networks in terms of scalability and reconfigurability.

Journal ArticleDOI
TL;DR: A novel self-surviving architecture for next-generation orthogonal frequency division multiplexing (OFDM) passive optical network (PON) supporting colorless optical network units that can protect distribution and feeder fiber simultaneously is proposed.
Abstract: In this paper, we propose a novel self-surviving architecture for next-generation orthogonal frequency division multiplexing (OFDM) passive optical network (PON) supporting colorless optical network units. The proposed scheme can protect distribution and feeder fiber simultaneously. Two different frequency bands are used in this proposed system for paratactic OFDM-PON. The disrupt signals can be restored via the fiber links of the neighboring OFDM-PON without special protecting fibers. We analytically and experimentally study the receiver sensitivity to downstream 10 Gb/s OFDM signals and upstream 2.5 Gb/s NRZ signals. The proposed architecture is designed mainly for next-generation PON systems.

Journal ArticleDOI
TL;DR: The optimality is theoretically proved, the computational complexity is shown to be more efficient than existing approaches, and the discussed extensions are shown to have performance comparable to standard PCEP approach.
Abstract: The path computation element (PCE) enables optimal path computation in single-domain (G)MPLS networks. To overcome the lack of traffic engineering (TE) information in multi-domain networks and to preserve both computation optimality and domain confidentiality, the backward-recursive PCE-based computation (BRPC) procedure has been standardized. BRPC procedure is based on PCE protocol (PCEP) and enables synchronized computation of TE label-switched paths with the requested level of reliability and quality of service requirements (i.e., guaranteed bandwidth). In this paper, the problem of computing $$K$$ K -survivable optimal multi-domain paths by resorting to BRPC procedure is analyzed. Extensions to PCEP protocol are discussed to achieve path optimality when domain information is kept confidential. The optimality is theoretically proved, and the computational complexity is shown to be more efficient than existing approaches. The discussed extensions are experimentally validated in an MPLS network test bed based on commercial equipments and are shown to have performance comparable to standard PCEP approach.

Journal ArticleDOI
TL;DR: This paper investigates the quality-of-service (QoS)-driven multicast routing problem in a sparse-splitting optical network and proposes a heuristic algorithm to construct a feasible light-tree that satisfies the required QoS parameters in large-scale networks.
Abstract: This paper investigates the quality-of-service (QoS)-driven multicast routing problem in a sparse-splitting optical network. The main objective is to minimize the total cost of wavelength channels utilized by the light-tree while satisfying required QoS parameters. In this paper, both the optical-layer constraints (e.g., optical signal power) and application-layer requirements (e.g., end-to-end delay and inter-destination delay variation) are considered as the QoS parameters. First, integer linear programming (ILP) formulations to solve the optimal multicast routing problem with the given QoS parameters are presented. Solving the ILP formulations for large-scale networks can easily overwhelm the capabilities of state-of-the-art computing facilities, and hence, a heuristic algorithm is proposed to construct a feasible light-tree that satisfies the required QoS parameters in large-scale networks. Simulation results demonstrate the performance of the proposed heuristic algorithm in terms of the cost of utilized wavelength channels.

Journal ArticleDOI
TL;DR: The performance of a hybrid WDM/OCDM technology is investigated under impairments of Multiple Access Interference and architectures comprising Sparse-Partial Optical Code Converters with Sparse -Partial Wavelength Converters provide better performance.
Abstract: The performance of a hybrid WDM/OCDM technology is investigated under impairments of Multiple Access Interference. We employed analytical models of Optical Orthogonal Codes to evaluate the switching network resources, such as the number of optical codes carried on each wavelength. Moreover, we propose and analyze a few optical code and wavelength conversion switching architectures, in order to scale the number of codes and wavelength converters and obtain a minimum burst blocking probability. The results demonstrate that architectures comprising Sparse-Partial Optical Code Converters with Sparse-Partial Wavelength Converters provide better performance. The network resources utilization are improved with number of converters, hence reaching a better cost benefit.

Journal ArticleDOI
Raed Mesleh1
TL;DR: Results demonstrate that the effect of distortion due to clipping is eliminated or significantly reduced based on the considered number of LEDs.
Abstract: A method to reduce signal clipping distortion in indoor optical wireless communication systems based on orthogonal frequency division multiplexing (OFDM) modulation is presented in this paper. Compensating the resulting clipping distortion due to LED operational constrains is achieved through the use of iterative signal clipping (ISC) and multiple light emitting diodes (LED) at the transmitter. ISC technique is based on iterative clipping of the time domain OFDM signal and transmission from a multiple LED transmitter. Transmit LEDs are synchronized, located close to each other, and placed to emit light in the same direction. Hence, the channel path gains from each LED to the receiver photo diode are similar. The received signals from the different LEDs add coherently at the receiver. Reported results demonstrate that the effect of distortion due to clipping is eliminated or significantly reduced based on the considered number of LEDs.

Journal ArticleDOI
TL;DR: An analytical model is proposed based on a non-homogeneous Markovian analysis to minimize the packet loss probability by ranking packets to achieve an optimal balance between latency and residual lifetime in the general class of scheduling schemes.
Abstract: Signal loss and noise accumulation can cause fading in optical buffers implemented by fiber delay lines (FDLs). Optical packets that excessively recirculate through FDLs are easily dropped from their routing paths. Therefore, analytical models and packet scheduling schemes require additional considerations for FDL buffers. This work proposes an analytical model for all-optical packet switching networks with finite FDL buffers and a general class of scheduling schemes including many basic scheduling schemes. We intend to minimize the packet loss probability by ranking packets to achieve an optimal balance between latency and residual lifetime in the general class of scheduling schemes. The analytical model is based on a non-homogeneous Markovian analysis to study the effects of various scheduling schemes on packet loss probability and average latency. Analytical results show how various network parameters affect the optimal balance, and illustrate how properly balancing latency and residual distance can significantly improve network performance.