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Routing and wavelength assignment with protection is an important problem in telecommunications. Given an optical network and incoming connection requests, a commonly studied variant of the problem aims to grant a maximum number of requests by assigning lightpaths with minimum network resource usage, while ensuring the provided services remain functional in the case of a single-link failure through dedicated protection paths. We consider a version where alternative lightpaths for requests are assumed to be given as a precomputed set and show that it is NP-hard. We formulate the problem as an Integer Programming (IP) model and also use it as a foundation to develop a Quadratic Unconstrained Binary Optimization (QUBO) model. We present necessary and sufficient conditions on objective function parameters to prioritize request granting objective over wavelength-link usage for both models, and a sufficient condition ensuring the exactness of the QUBO model. Moreover, we implement a problem-specific branch-and-cut algorithm for the IP model and employ a new quantum-inspired technology, Digital Annealer (DA), for the QUBO model. We conduct computational experiments on a large suite of nontrivial instances to assess the efficiency and efficacy of all of these approaches as well as two problem-specific heuristics. Although the objective penalty coefficient values that guarantee the exactness of the QUBO model were outside the acceptable range for DA, it always yielded feasible solutions even with smaller values in practice. The results show that the emerging technology DA outperforms the considered techniques coupled with GUROBI in finding mostly significantly better or as good solutions in two minutes compared to two-hour run time, whereas problem-specific heuristics fail to be competitive. [ABSTRACT FROM AUTHOR]

A method for defects extraction for a mercury cadmium telluride (MCT) multilayer lowbandgap heterostructure is presented. The N+/T/p/T/P+/n+ epitaxial layer was deposited on a GaAs substrate by a metal-organic chemical vapour deposition (MOCVD). The absorber was optimized for a cut-off wavelength of λc= 6 µm at 230 K. Deep-level transient spectroscopy (DLTS) measurements were conducted for the isolated junctions of the N+/T/p/T/P+/n+ heterostructure. Three localised point defects were extracted within the ptype active layer. Two of them were identified as electron traps and one as a hole trap, respectively. [ABSTRACT FROM AUTHOR]

Heterogeneous IoT-enabled networks generally accommodate both jitter tolerant and intolerant traffic. Optical Burst Switched (OBS) backbone networks handle the resultant volumes of such traffic by transmitting it in huge size chunks called bursts. Because of the lack of or limited buffering capabilities within the core network, burst contentions may frequently occur and thus affect overall supportable quality of service (QoS). Burst contention(s) in the core network is generally characterized by frequent burst losses as well as differential delays especially when traffic levels surge. Burst contention can be resolved in the core network by way of partial buffering using fiber delay lines (FDLs), wavelength conversion using wavelength converters (WCs) or deflection routing. In this paper, we assume that burst contention is resolved by way of deflecting contending bursts to other less congested paths even though this may lead to differential delays incurred by bursts as they traverse the network. This will contribute to undesirable jitter that may ultimately compromise overall QoS. Noting that jitter is mostly caused by deflection routing which itself is a result of poor wavelength and routing assigning, the paper proposes a controlled deflection routing (CDR) and wavelength assignment based scheme that allows the deflection of bursts to alternate paths only after controller buffer preset thresholds are surpassed. In this way, bursts (or burst fragments) intended for a common destination are always most likely to be routed on the same or least cost path end-to-end. We describe the scheme as well as compare its performance to other existing approaches. Overall, both analytical and simulation results show that the proposed scheme does lower both congestion (on deflection routes) as well as jitter, thus also improving throughput as well as avoiding congestion on deflection paths. [ABSTRACT FROM AUTHOR]

The routing and wavelength assignment (RWA) schemes play an important role in all computer networks. The performance of a computer network and resource utilization largely depend on the RWA. The demand for higher bandwidth is increasing with each passing day, so more efficient RWA schemes need to be devolved to cater the increasing requirements. RWA becomes more challenging for dynamic traffic as the nature and flow of data are not known in advance. In this paper, a dynamic RWA scheme has been proposed for establishing a path in optical networks. The proposed scheme is based upon dynamic conversion sensing algorithm. It can be applied on a number of different network topologies. The proposed scheme is dynamic in nature, which is significantly useful for dynamic traffic grooming. The proposed scheme has been applied on 14 nodes National Science Foundation Network (NFSNet). Simulation results have shown that the blocking probability of this scheme is very low as compared to the existing schemes. So, the proposed dynamic RWA scheme enhances the network efficiency. It is useful for congestion hit networks. The reduced blocking probability in wavelength division multiplexing optical networks leads to better resource utilization and enhanced performance. [ABSTRACT FROM AUTHOR]

Physical layer impairments (PLIs) is a matter of great concern in optical networks to achieve the optimum performance. In order to mitigate the PLI, a better routing and wavelength assignment (RWA) technique is required in optical wavelength division multiplexing (WDM) networks. In this paper, a dynamic ant colony routing algorithm with the consideration of various PLIs has been presented. This work also presents a Q-factor estimation model that includes impairments such as amplified spontaneous emission (ASE) noise, four-wave mixing (FWM), and cross phase modulation (XPM). The simulation results also prove that the proposed ant colony optimization (ACO) based algorithm significantly reduces the blocking probability as compared to dynamic load based shortest path algorithm (LB-SPA). [ABSTRACT FROM AUTHOR]

Congestion-level forecasting is essential for optical links to function properly with networking management schemes. Effective dynamical routing and wavelengths assigning (EDRWA) difficulties under the presumptions of perfect and non-ideal structural levels represent some of the foremost challenging optimization challenges faced in constructing 3rd-generation optical links. Such two issues are each NP-complete by design. They are challenging since the search space contains several nearby optima. Heuristics-dependent methods cannot effectively handle such challenges because of the irregular nature of searching space. The route and spectral assigning problems under various demanding scenarios are solved in this study using a genetic method optimization method for creating reliable optical cores. In contexts with stochastic unpredictable needs, this enhances network efficiency. The model outcomes show how successful genetic algorithms are at optimizing dedicated optical spectrum allocation in the face of uncertainty. [ABSTRACT FROM AUTHOR]

The intense absorbance and scattering of incident light at the surface plasmon resonance wavelength of gold nanoparticles (AuNPs) is of paramount importance in its various and diverse applications. Being governed by their morphologies and surface chemistry, the optical property of AuNPs can be tuned to suit variety of applications by careful and systematic engineering of the particle surface. Among other variables, the nature of the ligands or capping agents employed and their concentrations play vital roles. Three different alkanethiols, namely 1-dodecanethiol (DDT), 1-decanethiol (DT) and 1-hexanethiol (HT) were investigated as capping agents in different concentration of gold/thiol ([Au]/[Thiol]) ratios of 7:1, 5:1, 3:1, 1:1, 1:3 and 1:5. First, the AuNPs with average particle sizes of 2 nm and characterised by 1H NMR, UV–visible, and TEM. The 1H NMR confirmed the capping of gold nanoparticles by the thiol. The TEM image confirmed the monodispersity of the nanoparticles with average size distributions of 2.4 nm, and plasmon absorption wavelength peaks at 505 nm was confirmed by the UV. There were variations in the values of the plasmonic peaks with the nature and concentrations of the capping agents. [ABSTRACT FROM AUTHOR]

Diffractive optical elements (DOEs) fundamentally provide the possibility to simultaneously utilize multiple orders for different imaging functions within a system. However, to take advantage of this property, it is necessary to tailor the assignment of specific wavelengths or wavelength ranges with high diffraction efficiency to specific diffraction orders. To achieve this wavelength-selective assignment to different orders, simple diffractive profile shapes are not suitable; instead, multilayer DOEs are required. In this study, we conducted theoretical, scalar investigations on the diffraction efficiency of triple-layer double-relief DOEs for the purpose of tailored wavelength selectivity. Specific materials such as nanocomposites, layer materials, and high-refractive-index liquids with strong dispersion were included, in addition to inorganic glasses, to enable wide design freedom for wavelength selectivity across multiple orders. To simultaneously account for both positive and negative orders, specific material combinations featuring intersecting or touching dispersion curves were utilized. For various material combinations, we calculated significantly different efficiency profiles for multiple orders by varying the relief depths. Further, we discuss the possibility of fine-tuning the efficiency profiles by using high-index liquids as an intermediate layer between two solid profiles, whose dispersion properties can be varied continuously or at least in small steps. [ABSTRACT FROM AUTHOR]

The routing and wavelength assignment problem is crucial because it increases the efficiency of wavelength-routed all-optical networks built on the Wavelength Division Multiplexing approach. Given the physical network topology, the problem aims to establish routes for the connection requests and assign to each of them, a wavelength in accordance with the wavelength continuity and distinct wavelength constraints. In order to fulfill all requests, it is important to use the fewest possible wavelengths. This work proposes a novel method for determining the wavelength by employing acyclic coloring to determine the routing. [ABSTRACT FROM AUTHOR]

Wavelength division multiplexing (WDM) is one of the dominating technologies with high-capacity back bone networks. The cost associated with the high-capacity networks given more importance. The major issue is allocating and managing the available resources. To achieve this most efficient algorithms has to be used. We are considering the routing of lightpath and wavelength assignment problem, called as the routing and wavelength assignment (RWA) problem. The optimization of wavelength fragmentation in the WDM network is very much important in resource utilization. Wavelength fragmentation is one of the most important challenges in the area of the WDM network. Where it leads to some serious issues for the operators, such as the rejection of new requests. We are using integer linear program (ILP), here the problem is based on the node link formation. It is based on the multilayer concept and the original WDM network consists of several layers. We propose an efficient heuristic approach to solve this problem of finding the shortest path and assigning a wavelength without wavelength conversion. The model achieves better performance with fragmentation aware wavelength allocation strategy that minimizes fragmentation. [ABSTRACT FROM AUTHOR]

This paper introduces a practical comprehensive approach to optimize the cost of installed Optical Transport Network (OTN) interfaces, as well as the required number of wavelengths in the substrate Wavelength Division Multiplexing (WDM) optical network. The approach assumes grooming variable-bit-rate traffic demands on multi-rate OTN interfaces. We propose an Integer Linear Programming (ILP) formulation to address the combined problem of OTN interface deployment, virtual-network formation, traffic grooming on the established distinct-capacity virtual paths, and virtual network embedding on the WDM physical substrate. The presented model focuses on mitigating the capital expenditure required to deploy OTN interfaces, usually the most costly element in the network, as well as minimizing the required number of wavelengths in the Routing and Wavelength Assignment (RWA) problem, contributing to the overall reduction in network costs and ensuring open capacity for future expansions. As the RWA problem is NP-hard and involves significant computational costs, we also propose a multi-step heuristic approach to tackle larger network instances more efficiently. In this approach, the optimization steps for the OTN design and the RWA solutions are conducted independently. For the OTN-layer planning, the optimum ILP formulation (OTN-ILP) is maintained, so that the optimum solution for the cost of installed interfaces on the OTN layer is guaranteed. The RWA problem is proposed through either an ILP formulation (RWA-ILP) or a heuristic approach. The RWA-ILP model can find the same or slightly superior number of wavelengths compared to the optimum solution of the Integrated ILP formulation, but it can provide results in reasonable times only for small networks. On the other hand, the heuristic RWA is able to run any network size, but it requires more wavelengths compared to the RWA-ILP model. • An approach to optimize the cost of installed Optical Transport Network (OTN). • A formulation to address the OTN interface deployment and virtualization. • The model focuses on mitigating the capital expenditure required to deploy OTN. • The paper proposes a heuristic approach to tackle larger network instances. [ABSTRACT FROM AUTHOR]

In a telecommunication network, routing and wavelength assignment (RWA) is the problem of finding lightpaths for incoming connection requests. When facing a dynamic traffic, greedy assignment of lightpaths to incoming requests based on predefined deterministic policies leads to a fragmented network that cannot make use of its full capacity because of stranded bandwidth. At this point, service providers try to recover the capacity via a defragmentation process. We study this setting from two perspectives: (i) while granting the connection requests via the RWA problem and (ii) during the defragmentation process by lightpath rerouting. For both problems, we present the first two-stage stochastic integer programming model incorporating incoming request uncertainty to maximize the expected grade of service. We develop a decomposition-based solution approach, which uses various relaxations of the problem and a newly developed problem-specific cut family. Simulation of two-stage policies for a variety of instances in a rolling-horizon framework of 52 stages shows that our stochastic models provide high-quality solutions when compared with traditionally used deterministic ones. Specifically, the proposed provisioning policies yield improvements of up to 19% in overall grade of service and 20% in spectrum saving, while the stochastic lightpath rerouting policies grant up to 36% more requests, using up to just 4% more bandwidth spectrum. Summary of Contribution: For handling the intrinsic uncertainty of demand in the telecommunications industry, this paper proposes novel stochastic models and solution methodology for two fundamental problems in telecommunications at operational level: (i) routing and wavelength assignment (RWA) and (ii) lightpath rerouting problem. Despite the vast literature on the RWA problem, stochastic optimization has not been considered as a viable solution for resource allocation in optical networks. We propose two-stage stochastic programming models for both problems and design efficient decomposition-based solution methods that use various relaxations of the models and a new family of cutting planes. Our extensive and rigorous numerical experiments show the significant merit of incorporating uncertainty into decision making, as well as the effectiveness of the decomposition framework and our newly designed family of cuts in enhancing the solvability of both models. This work opens new avenues to explore where the powerful stochastic programming literature can be leveraged to make operational decisions in telecommunications problems, a field that currently relies mostly on deterministic and heuristic solution methods. [ABSTRACT FROM AUTHOR]

Optical networks are changing as new advanced technologies emerge. With each passing year, their sizes and capabilities expand. The standard architecture for network control and management cannot handle all of these complexities. The proliferation of cloud services and the massive volume of traffic provided by content delivery networks are driving the present fast increase in Internet traffic. This obviously exacerbates congestion concerns in communication networks, with a focus on the core and backbone components in particular. Software-defined networking (SDN) is evolving into a consolidated network management system that comprises a variety of strategies aiming at network management that are based primarily on one basic principle: decoupling control plane decisions from data plane activities. An essential resource allocation strategy in an all-optical network is routing and wavelength assignment. A novel SDN-based approach is proposed to address the problem of old methods mixed with new architecture in optical networks. The network resources were optimized for optimal scheduling using a binary hybrid topology particle swarm optimization method. In terms of recovery time, blockage rate, and resource consumption, simulation results demonstrate that the suggested technique outperforms previous classical methods. [ABSTRACT FROM AUTHOR]

The wavelength-routed optical network on chip (WRONoC) is a promising solution for signal transmission in modern System-on-Chip (SoC) designs. Previous works do not simultaneously handle all the following four main issues for WRONoCs: 1) correlations between the topological structure and physical layout; 2) tradeoffs between the maximum insertion loss and the number of wavelengths; 3) runtime scalability of wavelength assignment scheme; and 4) a fully automated flow to generate predictable designs. As a result, their insertion loss estimation is inaccurate, their wavelength assignment is inefficient, and thus, only suboptimal results are obtained. To remedy these disadvantages, we present a fully automated topological structure and a physical layout co-design flow with improved wavelength assignment schemes to minimize the maximum insertion loss and the laser power simultaneously with a significant speedup. The experimental results show that our co-design flow significantly outperforms state-of-the-art works in the maximum insertion loss, laser power, and runtimes. [ABSTRACT FROM AUTHOR]

With the overwhelming use of the Internet, the wavelength division multiplexing (WDM) optical networks have become the major mode of communication for wide applications. Hence, the routing and wavelength assignment (RWA) for a given traffic in WDM networks is the chief challenge in optical networks. This paper presents the RWA problem in WDM networks using the hybrid algorithm of flower pollination (FP) and simulated annealing (SA) algorithm (FA+SA) with and without wavelength conversion capability at the nodes of the network. Comparative analysis with techniques presented in literature is also carried out, i. e. differential evolution algorithm (DEA), firefly algorithm (FA), particle swarm optimization with less number of informers (Psolbest), SA and genetic algorithm (GA). The results prove that hybrid algorithm of FP and SA is potentially more efficient than algorithms present in literature for the light path establishment in an optical network. [ABSTRACT FROM AUTHOR]

The folded hypercube is one of the hypercube variants and is of great significance in the study of interconnection networks. In a folded hypercube, information can be broadcast using efficient distributed algorithms. In the context of parallel computing, folded hypercube has been studied as a possible network topology as an alternative to the hypercube. The routing and wavelength assignment (RWA) problem is significant, since it improves the performance of wavelength-routed all-optical networks constructed using wavelength division multiplexing approach. Given the physical network topology, the aim of the RWA problem is to establish routes for the connection requests and assign the fewest possible wavelengths in accordance with the wavelength continuity and distinct wavelength constraints. This paper discusses the RWA problem in a linear array for the folded hypercube communication pattern by using the congestion technique. • Study of the routing and wavelength assignment problem. • Guest graph is the folded hypercube communication pattern. • Host graph is a linear array wavelength division multiplexing optical network. • Congestion calculation by an embedding scheme and maximum induced subgraph problem. • Estimation of optimal number of wavelengths using congestion technique. [ABSTRACT FROM AUTHOR]

We recorded infrared (IR) spectra in the CH- and OH-stretching regions of size-selected clusters of methanol (M) with one water molecule (W), represented as MnW, n = 1-4, in a pulsed supersonic jet using the photoionization/IR-depletion technique. Vacuum ultraviolet emission at 118nmserved as the source of ionization in a time-of-flight mass spectrometer to detect clustersMnWas protonated forms Mn-1WH+. The variations in intensities ofMn-1WH+ were monitored as thewavelength of the IR laser light was tuned across the range 2700-3800 cm-1. IR spectra of size-selected clusters were obtained on processing of the observed action spectra of the related cluster-ions according to a mechanism that takes into account the production and loss of each cluster due to IR photodissociation. Spectra of methanol-water clusters in the OH region show significant variations as the number of methanol molecules increases, whereas those in the CH region are similar for all clusters. Scaled harmonic vibrational wavenumbers and relative IR intensities predicted with the M06-2X/aug-cc-pVTZ method for the methanol-water clusters are consistent with our experimental results. For dimers, absorption bands of a structureWMwith H2O as a hydrogen-bond donor were observed at 3570, 3682, and 3722 cm-1, whereas weak bands of MW with methanol as a hydrogen-bond donor were observed at 3611 and 3753 cm-1. For M2W, the free OH band of H2O was observed at 3721 cm-1, whereas a broad feature was deconvoluted to three bands near 3425, 3472, and 3536 cm-1, corresponding to the three hydrogen-bonded OH-stretching modes in a cyclic structure. For M3W, the free OH shifted to 3715 cm-1, and the hydrogen-bonded OH-stretching bands became much broader, with a weak feature near 3179 cm-1 corresponding to the symmetric OH-stretching mode of a cyclic structure. For M4W, the observed spectrum agrees unsatisfactorily with predictions for the most stable cyclic structure, indicating significant contributions from branched isomers, which is distinctly different from M5 of which the cyclic form dominates. [ABSTRACT FROM AUTHOR]

A new architectural paradigm, named, optical-computing-enabled network, is proposed as a potential evolution of the currently used optical-bypass framework. The main idea is to leverage the optical computing capabilities performed on transitional lightpaths at intermediate nodes and such proposal reverses the conventional wisdom in optical-bypass network, that is, separating in-transit lightpaths in avoidance of unwanted interference. In optical-computing-enabled network, the optical nodes are therefore upgraded from conventional functions of add-drop and cross-connect to include optical computing/processing capabilities. This is enabled by exploiting the superposition of in-transit lightpaths for computing purposes to achieve greater capacity efficiency. While traditional network design and planning algorithms have been well-developed for optical-bypass framework in which the routing and resource allocation is dedicated to each optical channel (lightpath), more complicated problems arise in optical-computing-enabled architecture as a consequence of intricate interaction between optical channels and hence resulting into the establishment of the so-called integrated/computed lightpaths. This necessitates for a different framework of network design and planning to maximize the impact of optical computing opportunities. In highlighting this critical point, a detailed case study exploiting the optical aggregation operation to re-design the optical core network is investigated in this paper. Optical aggregation enables the combination of lower-speed and/or lower-order format channels into a single higher-rate and/or higher-order format one for saving spectrum resources and such new perspective give rises to major challenges involving aggregation assignments. Specifically, the determination of demands for aggregation, the nodes at which the optical aggregation takes place and the wavelength selection for aggregated lightpaths constitute a critical issue to be tackled. Numerical results obtained from extensive simulations on the COST239 network are presented to quantify the efficacy of optical-computing-enabled approach versus the conventional optical-bypass-enabled one. [Display omitted] • Optical-computing-enabled network as an evolution of optical-bypass architecture. • In-network optical computing paves the way for era of optical-layer intelligence. • A vision on the integration of optical computing and communications infrastructure. • A new research problem, that is, routing, wavelength and aggregation assigment. • A call for optical network design and planning 2.0 framework. [ABSTRACT FROM AUTHOR]

Wireless traffic will significantly increase in next-generation networks. Therefore, there is a need for novel optical network front-/mid-/backhaul (x-haul) architectures that can deliver ultra-high bandwidth and ultra-low-latency services to wireless and edge cloud systems, as well as support various cloud radio access network (C-RAN) architectures. Designing and evaluating such architectures requires large-scale experimental platforms. In this article, we present the design and implementation of a unique, remotely accessible, disaggregated, and programmable optical network as the key component of the city-scale PAWR COSMOS advanced wireless testbed. We discuss the design and implementation of a dedicated multi-functional Ryu software-defined networking (SDN) controller for the testbed's optical network wavelength channel assignment and topology reconfiguration. We present an example use of the SDN controller for monitoring and automated measurement of the wavelength-dependent amplifier gain in deployed reconfigurable optical add/drop mul-tiplexer (ROADM) units. We also demonstrate a pilot experiment focusing on a wireless handover scheme for C-RAN architectures in the COSMOS testbed, where high traffic volume can be supported by dynamic wavelength allocation via optical switching in the fronthaul. The field-deployed testbed and SDN controller can be used by the research community to push the envelope in the area of optical networks for beyond 5G and 6G. [ABSTRACT FROM AUTHOR]

This non-conventional paper represents the first attempt to uncover a possible vulnerability in some proposals for optical network designs and performance comparisons. While optical network designs and planning lie at the heart of achieving fiber capacity efficiency and/or operational efficiency, its combinatorial nature makes it computationally hard to reach optimal solutions for realistic scenarios. As a consequence, the well-established way that have been taken for granted by not-so-small number of research papers is that an optimization model based on mixed integer linear programming (MILP) formulation is first proposed and then due to the intractability of such combinatorial optimization model, a heuristic algorithm is offered as an approximation. The solution-quality comparison between the MILP and heuristic is then carried out on small-scale instances including topologies and traffic tests to verify the efficacy of the proposed heuristic. Next such allegedly verified heuristic are used for optical network designs of realistic scenarios. This approach may nevertheless leave a critical vulnerability as there is no guarantee that one performs well in small tests will generalize adequately for large-scale cases, a common pitfall widely referred as the peril of extrapolation and/or overfitting. Besides, it is not uncommon that in some research works, for benchmarking purpose, the comparison between a new design proposal whose performance is obtained from on one heuristic and a reference design based on another heuristic is carried out. As the consequence of lacking solution quality check, such performance comparison relied merely on heuristic solutions may be equally vulnerable, resulting to possibly unreliable conclusions. In this work, we pinpoint those issues and provide a realistic case study to highlight and demonstrate the impact of such vulnerabilities. [ABSTRACT FROM AUTHOR]

Channel bonding is a recently proposed technique to provide higher aggregated line rates in NG-PONs by allowing ONUs to operate simultaneously in multiple wavelengths. On the other hand, the Dynamic Bandwidth Allocation (DBA) algorithm allocates to each ONU the grant time interval on each upstream frame that the ONU can use to transmit its data in the upstream direction. Channel bonding imposes a new challenge in the DBA algorithm as the grant time interval allocated to a ONU must be the same in all its channel-bonded wavelengths. In this work, we propose a new DBA algorithm for NG-PONs supporting data services which is a combination of a proportional fairness strategy and a max-min fairness strategy and guarantees the constraints imposed by channel bonding. We illustrate the merits of the new algorithm with two cases based on simulation. The results show that channel bonding can provide better QoS performance to data services even in cases where it is not strictly required. [ABSTRACT FROM AUTHOR]

Lightpaths in translucent optical networks have to undergo regeneration at certain nodes designated as regeneration sites to maintain its quality of transmission. Regenerating an optical signal necessitates optical-electronic-optical conversion and is thus a costly affair due to use of regeneration resources. Thus minimizing the cost of regeneration in such networks is vital. Minimizing cost of regeneration leads to two different problems; 1) the problem of minimizing the total cost of regeneration for the connections served and 2) the problem of minimizing the cost of regeneration at regeneration sites while serving the connections. The previous works on lightpath establishment in such networks have mostly addressed the first problem. In this paper we study the second problem i.e. the problem of minimizing the cost of regeneration at regeneration sites during dynamic establishment of lightpaths. As the problem is NP-Complete, we propose an Integer Linear Program for small networks and then propose two heuristic routing approaches for large networks. Time complexity analysis shows that our heuristic algorithms run in polynomial time. Extensive simulation experiments reveal that our approaches are not only efficient to address the problem but can also provide better blocking performance when regeneration resources are scarcely deployed at regeneration sites.

Silicon photonic interconnects on chip is an emerging technology for future ultra-scale and data-intensive computing chips, e.g., many-core processors, owing to its high transmission speed and low latency. However, in the Wavelength Division Multiplexing (WDM)-based architecture, the communication reliability can be significantly affected by the signal losses and crosstalk, due to the inherent characteristic of photonic devices. This paper studies the influence on reliability of managing application mapping and wavelength assignment separately. To deal with this issue, we propose a reliability-aware joint design method coordinating application mapping and wavelength assignment schemes. For a given application core graph and a network architecture, the design method can obtain a result of application mapping and wavelength assignment with improved reliability, compared to the separate scheme. According to the evaluation of Optical Signal-to-Noise Ratio (OSNR), the proposed method enables more reliable communication under given applications.

All Optical Burst Switched (OBS transport networks are often characterized by frequent occurrences of both contention and wavelength congestion. Their occurring often leads to degradations in overall network performance in handling moderate to high traffic levels, and all this leading to increases in data burst losses. Deflection routing contention resolution is quite popular in combating both types of congestions and ultimately leading to improvements in overall network throughput. However, it is necessary that network throughput always balance with effective utilization. In this paper, we propose a prioritized (indexed) cooperative based routing and wavelength assignment (PIC-RWA) scheme that reduce both contention and wavelength congestions. Performance results indicate that it significantly improves overall network performance in terms of improved effective resources utilization. [ABSTRACT FROM AUTHOR]

Integrating quantum key distribution (QKD) into the optical network through wavelength division multiplex (WDM) is promising for establishing large-scale QKD networks. However, the existing wavelength assignment schemes for WDM-QKD network all require to reserve a dedicate waveband for quantum signals, which influences the provisioning of data services, especially when the resource is tight. In this article, considering the quantum key pool (QKP) technology in the current QKD network, we propose a flexible key-size-driven wavelength assignment (KSD-WA) scheme to recycle the wavelength fragment to transmit quantum signals. Additionally, considering the noise impacts and the limited reconfiguration operations, we propose a heuristic algorithm to optimize the fragment selection with the objective of maximizing the secure key rate in the dynamic scenario. We also design a deep reinforcement learning (DeepRL) based algorithm to automatically learn the optimization policy under different environments. The simulation results verify that comparing with the conventional fixed-band (FB) scheme, the KSD-WA scheme assisted by the proposed optimization algorithms can provide adequate keys for encryption without affecting the provisioning of coexisting data services, which improves the compatibility of QKD with the real-life optical networks. [ABSTRACT FROM AUTHOR]

For the last few decades, fiber optic cables not only replaced copper cables but also made drastic evolution in the technology to overcome the optoelectronic bandwidth mismatch. Light trail concept is such an attempt to minimize the optoelectronic bandwidth gap between actual WDM bandwidth and end user access bandwidth. A light trail is an optical bus that connects two nodes of an all optical WDM network. In this paper, we studied the concept of split light trail and proposed an algorithm namely Static Multi-Hop Split Light Trail Assignment (SMSLTA), which aims to minimize blocking probability, the number of static split light trails assigned and also the number of network resources used, at the same time maximizing the network throughput. Our proposed algorithm works competently with the existing algorithms and generates better performance in polynomial time complexity. [ABSTRACT FROM AUTHOR]

In this paper, link fault tolerant algorithms (LFTAs) are employed for optimization of blocking performance in optical burst switching (OBS) networks for dynamic establishment of wavelength-routed lightpaths. This paper presents two algorithms: link fault tolerance algorithm for least congestion (LFTALC) and link fault tolerance algorithm for optimized blocking (LFTAOB). In former algorithm, the path with least congestion is selected and in the latter algorithm the path with least blocking probability is selected and then both the algorithms check for the availability of fault on the links present in the selected path. The findings indicate that methods of developing link based fault tolerant algorithms keep good performance and fairness among all the connections. The key advantage of these proposed algorithms as compared to routing and wavelength assignment algorithm is that these are very simple in nature and require less service disruption time. [ABSTRACT FROM AUTHOR]

The proposed traffic grooming methodology for long-reach-passive optical networks will decrease the latency in upstream. The scheduling and wavelength assignment for ethernet passive optical networks has been shown to perform much better in terms of delay. The dynamic traffic grooming algorithm based on intelligent water drop is proposed in which new depositions function has been introduced for efficient handling of bandwidth. Therefore, once equally distanced optical network units were scheduled on constant wavelengths, the void formation impact is reduced. The outcomes conjointly depict the result of the planned methodology on bandwidth utilization improvement and jitter by 1.46 and 408.66 µs improvements respectively, even overall latency is improved by 465.83 µs by value. These results depict the validity of the planned dynamic bandwidth allocation methodology for traffic grooming. [ABSTRACT FROM AUTHOR]

Dynamic routing and wavelength assignment problem in optical networks is a two-step problem that is influenced by the choice of a successful optimal path selection and wavelength assignment. Proper selection techniques reduce the number of wavelengths required in the network and thereby improves traffic grooming. Heuristic algorithms and integer linear programming models help in selection of route and wavelength separately. Hence, the computation time is large which makes the system slow. A cost function is computed which uses independent parameters in the network for the selection of route and wavelength for a call. The heuristic reduces computation time by combining the search of route and wavelength to be assigned. In addition, the network performance is analyzed with and without alternate routing along with proposed heuristics. The selection of proper route and wavelength finding technique is very essential since it improves the grooming factor of the network thereby allowing more traffic support by the network. Our objective is to investigate and propose a cost based heuristics for dynamic traffic routing and wavelength Assignment in WDM optical networks. For this we plan to develop cost functions and heuristics to compute the route and wavelength assignment strategy. Here, our objective is to reduce the computation time for selection of route and wavelength assignment strategy by weighted cost function. The function has to include network parameters for its processing. Our work provides an overview about DRWA by applying cost based heuristics in WDM networks. This paper explains the proposed cost function and its applications in line with selection of independent parameters. The details of other functions like cost function formulation, hop-based route assignment, available wavelength based route assignment, mathematical analysis of proposed cost function are also explained. Results and discussions based on the findings are presented. [ABSTRACT FROM AUTHOR]

The routing and wavelength assignment problem arises from the investigation of optimal wavelength allocation in an optical network that employs Wavelength Division Multiplexing (WDM). Consider an optical network that is represented by a connected, simple graph G. An all-to-all routing R in G is a set of paths connecting all pairs of vertices of G. The undirected optical index of G is the minimum integer k to guarantee the existence of a mapping ϕ : R → { 1 , 2 , ... , k } , such that ϕ (P) ≠ ϕ (P ′) if P and P ′ have common edge(s), over all possible routings R. A natural lower bound of the undirected optical index of G is the (undirected) edge-forwarding index, which is defined to be the minimum of the maximum edge-load over all possible all-to-all routings. In this paper, we first derive the exact value of the optical index of the complete m -ary trees, and then investigate the gap between undirected optical and edge-forwarding indices. [ABSTRACT FROM AUTHOR]

This newly research paper has a critical contribution in the investigation of the gain enhancement study of nanomaterial AlGaAs/GaAs type heterogeneous structure under the various number of GRINLs (Graded Refractive Index Nano Layers). Various spectral performance of modal type gain with photonic wavelengths under number of GRINLs for nanomaterial AlGaAs/GaAs type heterogeneous structures have been illustrated. The behaviours of changes in peak modal type gain and peak gain compression with several type of number of GRINLs have also been presented graphically. Moreover, the parameters like anti-guiding type factor and change in index of refraction versus charge carriers per cube cm have been calculated. The achieved modal type gain results correspondence to maximum modal type light gain of wavelengths (~830nm) for lasing phenomenon have an essential contribution in current days for the applications of EM radiations (SWIR and NIR) as well as this type wavelength range has been also useful in fibre optic telecommunications by the method of TIR with diminished losses and attenuations in db/km of light signals. [ABSTRACT FROM AUTHOR]

The problem of routing and wavelength assignment in optical networks consists in minimizing the number of wavelengths that are needed to route a set of demands, such that demands routed using lightpaths that share common links are assigned to different wavelengths. We present a biased random-key genetic algorithm for approximately solving the problem of routing and wavelength assignment of sliding scheduled lightpath demands in optical networks. In this problem variant, each demand is characterized not only by a source and a destination, but also by a duration and a time window in which it has to be met. Computational experiments show that the numerical results obtained by the proposed heuristic improved upon those obtained by a multistart constructive heuristic. In addition, the biased random-key genetic algorithm obtained much better results than an existing algorithm for the problem, finding solutions that use roughly 50% of the number of wavelengths determined by the latter. [ABSTRACT FROM AUTHOR]

The study aimed to validate the Clotrinear drop analytical method using modified wavelength using HPLC. A reliable and straightforward high-performance liquid chromatography method was used to confirm an ear drop in clotrin. Chromatography was performed on columnC18phenomena (4.6 * 250 mm * 5 mm) using mobile phase acetonitrile and diammonium hydrogen phosphate (buffer) (60:40 ). As a mobile process with a 1 ml/min flow rate, the detection was conducted at 210 nm, resulting in more reliable ear drop impurities. The statistical n analysis proves that the method for analyzing clotrimazole and lignocaine HCl in-ear drop is repeatable, sensitive, and more precise. [ABSTRACT FROM AUTHOR]

Optical network-on-chip (ONoC) is a new designing of multi-processor system-on-chip. On the one hand, global bus is a simple and common logical topology for ONoC. On the other hand, the parallel formulation of bitonic sorting has lower time complexity than the sequential implementation of bitonic sorting. Thus, it is meaningful to study the parallel implementation for bitonic sorting on bus ONoC. Different wavelengths are used to achieve the parallel processing for bitonic sorting on bus ONoC. The wavelength assignment scheme for n elements bitonic sorting is proposed such that the number of wavelengths required is just n/2. [ABSTRACT FROM AUTHOR]

All-optical networks have been largely investigated due to their high data transmission rates. The key to the high speeds in all-optical networks is to maintain the signal in optical form, to avoid the overhead of conversion to and from electrical form at the intermediate nodes. In the traditional WDM technology the spectrum of light that can be transmitted through the optical fiber has been divided into frequency intervals of fixed width with a gap of unused frequencies between them. In this context the term wavelength refers to each of these predefined frequency intervals. An alternative architecture emerging in very recent studies is to move towards a flexible model in which the usable frequency intervals are of variable width. Every lightpath is assigned a frequency interval which remains fixed through all the links it traverses. Two different lightpaths using the same link have to be assigned disjoint sub-spectra. This technology is termed flex-grid or flex-spectrum. The introduction of this technology requires the generalization of many optimization problems that have been studied for the fixed-grid technology. Moreover it implies new problems that are irrelevant or trivial in the current technology. In this work we focus on bandwidth utilization in path toplogy and consider two wavelength assignment, or in graph theoretic terms coloring, problems where the goal is to maximize the total profit. We obtain bandwidth maximization as a special case. [ABSTRACT FROM AUTHOR]

Optical switching networks (OSN) rely on both hardware components and signals for performing efficient switching operations achieving service level requirements of the end-user. In this manuscript, an incremental learning-based wavelength assignment is introduced to minimize asynchronous channel selection and dispersion-free switch-over in OSN. This method accounts on the wavelength dispersion characteristics of the light path for establishing and reconnecting communications between end-to-end devices. The learning process segregates favorable and conflict channels based on blocking probability and channel capacity assigned to the optical users. A conventional wavelength division multiplexing technique is employed for improving data transmission rates. This method is appropriate for evading blocking rates in optical networks to improve throughput rate and to leverage OSN performance. Machine learning (ML) paradigm is designed for OSN leverages the communication rate influenced by channel conflicts and utilization capacity. Therefore, the number of transmissions likely requires optimal switch-over with the knowledge of channel constraints to improve the performance of OSN. [ABSTRACT FROM AUTHOR]

One of the major problem faced by the optical networks is traffic grooming. The large size of data and the speedy transmission leads to traffic grooming. In this research paper, the wind driven optimization (WDO) technique has been used for optimizing the traffic grooming in the optical network. The paper describes the model of optical systems, WDM concepts, optimization and its components. Then, the issue of traffic grooming is discoursed in paper that includes information on its types, parameters, objective function, variables, and related constraints. The results achieved with the implementation of WDO algorithm proved to be cost effective. Two multiobjective indicators are used in the study. Results have been compared with multiobjective evolution algorithm based on decomposition (MOEA/D) and DEPT, i.e., differential evolution with Pareto tournaments in terms of multi-objective indicator hypervolume. Hypervolume is the effective quantative parameter that calculate the proximity of the calculated solution to the true pareto front. Multiobjective indicator set coverage values have also been evaluated using WDO and are compared with the setcoverage values obtained with the use of shortest path routing and first fit wavelength algorithm. Results obtained were quite promising in terms of hypervolume and setcoverage values both. Thus, WDO algorithm can be stated as optimizer as compared to existing techniques DEPT, MOEA/D and shortest path routing and first fit wavelength assignment method. [ABSTRACT FROM AUTHOR]

Multicast communication is the concurrent transmission of data from one source node to many destination nodes. It is widely deployed in high performance computing and communication networks. In this article, wide-sense nonblocking multicast communication is studied in wavelength division multiplexing networks namely modified linear array, unidirectional and bidirectional modified ring networks. The sufficient and necessary condition on the minimum wavelength number required for the network to be wide-sense nonblocking is derived for each of the above network topologies under longest link first routing technique which employs approximately half the number of hops when compared with networks without modification. An explicit wavelength allotment technique for multicast assignment is also given for each of the above network topologies. [ABSTRACT FROM AUTHOR]

The Fiber Installation Problem (FIP) in Wavelength Division Multiplexing (WDM) optical networks consists in routing a set of lightpaths (all-optical connections) such that the cost of the optical devices necessary to operate the network is minimized. Each of these devices is worth hundreds of thousands of dollars. In consequence, any improvement in the lightpath routing may save millions of dollars for the network operator. All the works in the literature for solving this problem are based on greedy heuristics and genetic algorithms. No information is known on how good are the solutions provided by these heuristics compared to the optimal solution. Besides, no proof that the problem is NP-Hard can be found. In this paper, we prove that FIP is NP-Hard and also present an Integer Linear Programming (ILP) formulation for the problem. In addition, we propose an implementation of the Iterated Local Search (ILS) metaheuristic to solve large instances of the problem. Computational experiments carried out on 21 realistic instances showed that the CPLEX solver running with our ILP formulation was able to solve 11 out of the 21 instances to optimality in less than two minutes. These results also showed that the ILS heuristic has an average optimality gap of 1% on the instances for which the optimal solution is known. For the other instances, the results showed that the proposed heuristic outperforms the best heuristic in the literature by 7%. [ABSTRACT FROM AUTHOR]