Computing the single-link performance measurement for elastic optical OFDM

Elastic optical networks based on orthogonal frequency-division multiplexing (OFDM) have emerged as the preferred technology for future optical networks because of their good spectral efficiency and flexibility. In OFDM optical networks, multiple subcarriers can be allocated to accommodate both subwavelength and superwavelength traffic. In this work, we developed an algorithm based on the superposition concept in electrical networks using the Kaufman/Delbrouck recursion model to accurately compute the revenue loss in the OFDM-based single link. The algorithm is applicable when there are many call types requesting diverse numbers of contiguous subcarriers offered to a link with numerous subcarriers.     

Design considerations for transceiver-limited elastic optical networks

The continuous increase of data traffic for present-day applications necessitates the development of Elastic Optical Networks (EONs). Significant advancements in efficient Routing and Spectrum Assignment (RSA) algorithms for EONs have been noticed in the recent past. These existing algorithms did not mention constraints on the number of transceivers per node in a network. However, for the planning of a realistic network, it is necessary to estimate the number of transceivers required at each node for the efficient operation of a network. Therefore, transceiver constraints should be taken into account while designing the RSA algorithms. In this paper, we present the impact of putting a limit to the number of transmitters and receivers available at each node of an EON. Moreover, the cost of a network heavily depends on the number of transceivers that each node in the network may offer. Hence, estimating the required number of transceivers per node in a network is vital to approximate the design cost of a network. Here, we present an Integer Linear Programming (ILP) formulation that includes the transceiver constraints and also develop a transceiver-aware heuristic algorithm for routing and spectrum assignment in EONs. Simulation results help us provide a proper design tool to estimate the number of transceivers per node in elastic optical networks.

     

On the performance of advanced integrated microring filters for switching applications in next-generation elastic optical networks

We investigate the use of integrated advanced microring resonator-based sum-difference all-pass optical filters for switching applications in circuit-switched elastic optical networks. A practical design taking into account optical losses accordingly to typical reported values for strip waveguides in silicon-on-insulator technology is considered. By incorporating tuning elements (i.e., standard phase shifters), three different synthetized elliptic filters are emulated in the same physical structure showing the potential in terms of bandwidth configurability of the architecture. Practical filter design rules for standard silicon-on-insulator single-mode strip waveguides are also discussed. Beside possible advantages in terms of reduced fabrication costs, simulations performed on Nyquist PM-QPSK signals with different channel capacities over 50, 37.5 and 25 GHz frequency slots suggest that the proposed structure can achieve similar or better performance than commercial spectrum selective switch filters.     

Flexible high-order QAM transmitters for elastic optical networks

In order to adapt to the dynamics in the future optical networks, we propose and experimentally demonstrate two flexible high-order quadrature amplitude modulation (QAM) transmitter schemes: (a) a flexible transmitter using a tandem in-phase/quadrature modulators for generating 16QAM, 32QAM, 64QAM signals; and (b) a scheme based on monolithically integrated quad-Mach–Zehnder in-phase/quadrature with binary driving electronics for synthesizing minimum phase-shift keying (MSK), quadrature phase-shift-keying (QPSK), 8-ary phase-shift keying (8PSK), and 16QAM. These schemes provide different approaches to configure a flexible high-order QAM transmitter, either using cascaded off-the-shelf modulators or via highly integrated monolithic modulator. These flexible and reconfigurable transmitter schemes exhibit different characteristics in terms of system performance, which provides the network operators different flexible transmitter solutions suitable for different application scenarios in elastic optical networks.     

The energy minimization algorithm for elastic optical networks

Photonic Network Communications - In this paper, a novel energy-aware grooming-based algorithm, named energy minimization algorithm (EMA), is proposed that aims at providing the quality of service...     

支持流量疏导弹性光网络的共享保护策略

针对支持流量疏导的EON(弹性光网络),提出了一种改进的共享保护策略。改进策略针对不同粒度级别(如光隧道级和低速子载波级)的路径进行分级的共享保护,以保证对网络中隧道级路径进行隧道级保护。仿真结果表明,文章所提保护算法比传统的共享保护算法在阻塞率及资源利用率方面都有明显改善,其中业务阻塞率最大降低了0.47;在保护带G为16个频隙的情况下,资源利用率可节约10.95%。     

Adaptive multilevel modulation for grooming in elastic cloud optical networks

In order to mitigate the mismatch of granularities between fixed grid and client traffic, the elastic optical network (EON) was proposed by using orthogonal frequency division multiplexing. In EONs, the bandwidth variable transponder adjusts the number of bits per symbol, so that an optical signal generates by using just enough sub-carriers each with appropriate modulation level. Owing to the advantage of line-rate adaption above, the application of cloud computing has witnessed rapid growth in EONs. However, bandwidth variable transponders consume more power compared with ordinary ones, which will lead to a power-thirsty EON if no effective measure is taken. As a result, the green grooming was proposed for EONs. Unfortunately, the adaptive multilevel modulation was neglected in the current works focusing on green grooming. Thus, in this paper, we design a novel modulation adaptive grooming with guaranteeing transmission performances in green EONs. The distance-adaptive spectrum resource allocation is applied to the green grooming algorithm previously designed by us for EONs. The simulation results show that the adaptive multilevel modulation plays an important role on saving spectrum and power consumption for the green grooming in EONs, because the spectral bandwidth can be saved by increasing the number of bits per symbol to transmit the same data rate.     

Novel node upgradation strategy for migration to elastic optical networks

For migration from dense wavelength division multiplexing (DWDM) networks to elastic optical networks (EON),it is required to upgrade the traditional reconfigurable optical add-drop multiplexer (ROADM) to the new-generation ROADM that supports flexible grids.However,for a large-scale optical network,it is generally impossible to upgrade the ROADM nodes all in once; rather,they would be upgraded gradually.For this,it is critical to study different strategies for selecting the ROADM nodes to be upgraded.Also,for the interconnection between different generations of ROADM,the sub-band virtual concatenation (VCAT) technique was employed to enable an optical channel to be established via traversing different types of nodes.An integer liner programming (ILP) model and an efficient heuristic algorithm were developed to jointly select the ROADM nodes to upgraded and assign spectrum resources.Simulation studies show that the proposed strategy for the upgraded node selection is efficient to perform close to the ILP model in terms of the maximum number of FS used in the whole network.     

Virtual infrastructure mapping in software-defined elastic optical networks

Software-defined networking (SDN) enables efficient and scalable network virtualization, which allows infrastructure resources such as computing and networking resources to be abstracted and outsourced as a service. The SDN technologies can be extended to the optical transport networks to achieve an intelligent and flexible resource management, thus achieving high-capacity, low-cost, and long-reach optical transport networks. In this paper, we introduce an architecture for software-defined elastic optical networks and study the virtual infrastructure (VI) mapping problem with the objective of minimizing the blocking probability. We propose a set of efficient heuristic algorithms, among which the Network followed by Compute Load Balancing (NCLB) algorithm is a novel attempt to solve the VI mapping problem by provisioning the networking resource first followed by allocating the computing resource. Furthermore, we propose a modified version of NCLB, called Network Depth-based NCLB (ND-NCLB), which confines the VI mapping assignment in a small-range sub-network to further optimize the physical network resource consumption. Through comprehensive simulations in various scenarios, we demonstrate that the proposed ND-NCLB algorithm achieves the best performance in terms of blocking probability compared to the other algorithms in this work.     

Improved dynamic routing algorithms in elastic optical networks

The considered Routing, Modulation Level and Spectrum Allocation (RMLSA) problem covers path length minimization while still meeting the spectrum continuity constraints, non-overlapping spectra constraints, spectrum contiguity constraints, and choice of modulation level. In this problem, the relationship between spectrum connection and bit rate of the incoming request has been taken into account. In this paper, two algorithms have been proposed. The first one is based on a set of shortest paths whose lengths are determined by the number of links in the network. The second one is a modified version of Dijkstra’s algorithm. Modification of this algorithm is based on introduction of weights of the network links depending on the utilization of the links and the introduction of a aggregated spectrum of the path that is being selected. Extensive research has shown that algorithms reject the lower traffic volume as compared to well-known algorithms proposed in literature.     

Green grooming in spectrum-sliced elastic optical path networks

With the continuous expansion in network scale and the rapid growth of Internet traffic, a high-capacity and power-efficient transport system is required. The Spectrum-Sliced Elastic Optical Path Network (SLICE) based on Orthogonal Frequency Division Multiplexing has been considered as a promising solution due to flexible spectrum provisioning. In a SLICE, compared with traditional components, the bandwidth variable transponder and cross-connects have higher power costs. So it is necessary to make a green footprint in this new networking framework. In this paper, we make a comprehensive study of green grooming in SLICEs, with the objective to save both spectrum and power consumptions. An Integer Linear Programming formulation with various SLICE constraints is presented for the optimization problem above. Under the large-scale network scenario, we also propose the auxiliary graph model which reflects spectrum/power usage, grooming policies implemented by adjusting link costs according to a comprehensive power consumption model, as well as a threshold-based spectrum reservation scheme. As a result, an efficient heuristic called green grooming algorithm is designed. The extensive simulation results demonstrate that our heuristic obtains near-optimal results and achieves a better performance in terms of spectrum and power efficiencies compared with benchmarks, under various topology structures.     

Optical performance monitoring for the next generation optical communication networks

Today’s optical networks function are in a fairly static fashion and are built to operate within well-defined specifications. This scenario is quite challenging for next generation high-capacity systems, since network paths are not static and channel-degrading effects can change with temperature, component drift, aging, fiber plant maintenance and many other factors. Moreover, we are far from being able to simply “plug-and-play” an optical node into an existing network in such a way that the network itself can allocate resources to ensure error-free transmission. Optical performance monitoring could potentially enable higher stability, reconfigurability, and flexibility in a self-managed optical network. This paper will describe the specific fiber impairments that future intelligent optical network might want to monitor as well as some promising techniques.     

Characterisation of nonlinearity performance for coherent optical OFDM signals under influence of PMD

The first experiment of polarisation-mode dispersion (PMD) impact on fibre nonlinearity in coherent optical OFDM (CO-OFDM) systems is reported. The optimal Q value at 10.7 Gbit/s has been improved by 1 dB after introduction of differential group delay (DGD) of 900 ps.     

基于相干光OFDM的WDM系统传输性能分析

首先对相干光OFDMWDM系统理论模型和基本原理进行了研究,然后基于Opt i syst em仿真软件,对相干光OFDMWDM传输系统进行了仿真分析,并研究了该系统的传输性能,发现基于相干检测的光OFDM技术和WDM技术结合,可以有效抑制光纤色散和非线性影响,提高系统的性能。将此系统与传统的NRZ WDM光传输系统进行比较,发现系统性能较NRZ系统有很大的提高。     

Upgrade-aware virtual infrastructure mapping in software-defined elastic optical networks

An emerging use case in software-defined networking is to provide efficient mapping of multiple virtual infrastructures (VIs) simultaneously over the same physical substrate (PS) which can increase the resource utilization of the PS, thus improving its provider’s revenue. In this paper, for the first time, we investigate a practical and yet theoretically challenging issue related to dynamic VI mapping in software-defined elastic optical networks while considering the presence of possible upgrade of the VIs and the optical layer constraints, which has not been addressed in any of the existing studies. More specifically, we investigate the following aspects: (1) Which revenue models are appropriate? (2) How to map a new VI request or to upgrade an existing VI to maximize the PS providers revenue? In particular, we study two different revenue models in terms of the incremental pricing policy and the binding pricing policy and propose a number of efficient heuristics to solve the upgrade-aware VI mapping (U-VIM) problem. We also perform comprehensive performance evaluation in different scenario, and the results show that plan-ahead is a desirable strategy when conducting VI mapping in the presence of VI upgrade.     

一种基于能量感知的弹性光网络RSA算法

弹性光网络具有高频谱效率和灵活性等优点,是光网络发展的主要方向。路由和频谱分配是弹性光网络的核心技术之一。文章提出了一种改进的基于能量感知的弹性光网络RSA(路由和频谱分配)算法,在进行选路和频谱分配时,同时考虑了网络中的能耗和可用频谱资源情况。理论分析和仿真结果表明,与传统RSA算法相比,改进算法可以提高能量效率,降低业务阻塞率。     

Hop distance–based bandwidth allocation technique for elastic optical networks

Elastic optical networks (EON) have emerged as a solution to the growing needs of the future internet, by allowing for greater flexibility, spectrum efficiency, and scalability, when compared to WDM solutions. EONs achieve those improvements through finer spectrum allocation granularity. However, due to the continuity and contiguity constrains, distant connections that are routed through multiple hops suffer from increased bandwidth blocking probability (BBP), while more direct connections are easier to form. This paper proposes HopWindows, a novel method that strategically allocates bandwidth to connections based on their hop distance. This new algorithm applies masks that control the range of frequency slots (FSs) allocated to each n‐hop connection. Furthermore, a new network metric is introduced, the normalized bandwidth blocking probability (normalized BBP). Utilization of this metric ensures increased fairness to distant connections. Extended simulation results are presented which indicate that the proposed HopWindows method achieves a superior performance over the well‐known FirstFit algorithm. The proposed algorithm may achieve a decrease in bandwidth blocking probability of up to 50%.     

基于Exponentiated Weibull 湍流模型的OFDM光链路性能分析

研究了Exponentiated Weibull 大气湍流下OFDM光链路误码性能,分别考虑大气湍流的单独影响及大气湍流和指向误差对误码率的联合影响,利用MeijerG函数推导出多载波条件下总平均误码率的闭合表达式。根据总平均误码率闭合表达式进行了仿真,分析了在不同大气湍流强度、QAM调制阶数、抖动标准差和波束宽度条件下,链路误码率随发射功率变化的关系。通过仿真分析证明仅在大气湍流影响下发射功率的增加对误码率的改善优于在大气湍流与指向误差的联合影响下;不同调制阶数,增大发射功率对链路误码性能的改善近乎相同;随着湍流强度、抖动标准差和波束宽度的增加,误码率增加。