下一代光接入网络上安全的多虚拟专网构建机制

简要介绍了下一代光接入网络上构建安全的虚拟专网存在的挑战以及网络编码的特性, 重点研究基于网络编码构建安全多虚拟专网的机制。依据提出的机制, 多个安全的虚拟专网可以在无源光网络的下一代光接入网络的主要实现形式上独立构建。最后分析了提出的虚拟专网机制, 提高了下行数据传输吞吐量。     

Stream traffic management over an ATM passive optical network

Several alternatives based either on wired or wireless infrastructures are considered for the provision of broadband services in the local loop. In the field of wired solutions, Passive Optical Networks (PON) look very promising due to their bandwidth capacity. Also called APONs (ATM over PON), PON systems are designed in order to satisfy end-to-end ATM connections. Because it is based on a point-to-multipoint optical tree configuration, a PON access system requires a MAC protocol for the upstream traffic. Two approaches may be adopted for the design of an APON MAC protocol. The first approach considers a MAC protocol based on a work-conserving discipline combined with a stand-alone traffic shaper between the head of the optical tree and an ATM switch. The second approach consists in an integrated mechanism able to reduce Cell Delay Variation (CDV) of CBR/VBR connections by means of non-work conserving disciplines at the MAC layer. After having described the main characteristics of APON systems, we propose a new APON MAC protocol with integrated shaping well suited to real time traffic management. The performances of our protocol are investigated by means of both computer simulations and analytical modeling. By extension of our analytical study, a Call Admission Control procedure is proposed for real time VBR connections.     

An Efficient Resource Allocation Mechanism for LTE–GEPON Converged Networks

Optical–wireless convergence is becoming popular as one of the most efficient access network designs that provides quality of service (QoS) guaranteed, uninterrupted, and ubiquitous access to end users. The integration of passive optical networks (PONs) with next-generation wireless access networks is not only a promising integration option but also a cost-effective way of backhauling the next generation wireless access networks. The QoS performance of the PON–wireless converged network can be improved by taking the advantages of the features in both network segments for bandwidth resources management. In this paper, we propose a novel resource allocation mechanism for long term evolution–Gigabit Ethernet PON (LTE–GEPON) converged networks that improves the QoS performance of the converged network. The proposed resource allocation mechanism takes the advantage of the ability to forecast near future packet arrivals in the converged networks. Moreover, it also strategically leverages the inherited features and the frame structures of both the LTE network and GEPON, to manage the available bandwidth resources more efficiently. Using extensive simulations, we show that our proposed resource allocation mechanism improves the delay and jitter performance in the converged network while guarantying the QoS for various next generation broadband services provisioned for both wireless and wired end users. Moreover, we also analyze the dependency between different parameters and the performance of our proposed resource allocations scheme.     

Shared-per-wavelength asynchronous optical packet switching: A comparative analysis

This paper compares four different architectures for sharing wavelength converters in asynchronous optical packet switches with variable-length packets. The first two architectures are the well-known shared-per-node (SPN) and shared-per-link (SPL) architectures, while the other two are the shared-per-input-wavelength (SPIW) architecture, recently proposed as an optical switch architecture in synchronous context only, which is extended here to the asynchronous scenario, and an original scheme called shared-per-output-wavelength (SPOW) architecture that we propose in the current article. We introduce novel analytical models to evaluate packet loss probabilities for SPIW and SPOW architectures in asynchronous context based on Markov chains and fixed-point iterations for the particular scenario of Poisson input traffic and exponentially distributed packet lengths. The models also account for unbalanced traffic whose impact is thoroughly studied. These models are validated by comparison with simulations which demonstrate that they are remarkably accurate. In terms of performance, the SPOW scheme provides blocking performance very close to the SPN scheme while maintaining almost the same complexity of the space switch, and employing less expensive wavelength converters. On the other hand, the SPIW scheme allows less complexity in terms of number of optical gates required, while it substantially outperforms the widely accepted SPL scheme. The authors therefore believe that the SPIW and SPOW schemes are promising alternatives to the conventional SPN and SPL schemes for the implementation of next-generation optical packet switching systems.     

Particle swarm optimization-based DRWA for wavelength continuous WDM optical networks using a novel fitness function

Greater demand of bandwidth and network usage flexibility from customers along with new automated means for network resource management has led to the concept of dynamic resource provisioning in WDM optical networks where unlike the traditional static channel assignment process, network resources can be assigned dynamically. This paper examines a novel particle swarm optimization (PSO)-based scheme to solve dynamic routing and wavelength assignment (dynamic RWA) process needed to provision optical channels for wavelength continuous Wavelength Division Multiplexed (WDM) optical network without any wavelength conversion capability. The proposed PSO scheme employs a novel fitness function which is used during quantization of solutions represented by respective particles of the swarm. The proposed fitness function takes into account the normalized path length of the chosen route and the normalized number of free wavelengths available over the whole route, enabling the PSO-based scheme to be self-tuning by minimizing the need to have a dynamic algorithmic parameter ‘α’ needed for better performance in terms of blocking probability of the connection requests. Simulation results show better performance of the proposed PSO scheme employing novel fitness function for solving dynamic RWA problem, not only in terms of connection blocking probability but also route computation time as compared to other evolutionary schemes like genetic algorithms.     

High Efficiency of PON Network Monitoring and Management

This paper presents a transmission surveillance and protection-based approach for failures/faults over the passive optical network (PON) with an excellent combination of Smart Access Network _ Testing, Analyzing and Database (SANTAD) and Smart Drop Protection Scheme (SDPS). SANTAD is an optical monitoring and management system tool that focused on optical testing and line’s status monitoring in PON with some excellence features added, while SDPS is implemented in the drop region to provide self-protection capabilities against fiber cuts. A tapper circuit is designed to allow the optical time domain reflectometer (OTDR) testing signal to bypass the optical splitter for distant monitoring when emitted in downstream direction. With the assistance of fourth window region at 1,625 nm and de(multiplexing) capabilities of wavelength selective coupler, the status of each fiber link can be displayed onto computer screen. Access Control System (ACS) is function to control the OTDR troubleshooting signals and activate the SDPS restoration scheme according to the type of failure in the drop region of PON. The implementation of the excellent combination in PON shows its contributions on obtains the high accuracy in detecting any occurrence of failures/faults and recovery the failure links within 15 s.     

基于分布式路径计算单元的多域光网络组密钥管理方案

针对分布式路径计算单元（PCE）架构下多域光网络的通信特点和密钥管理需求，提出一种该架构下的组密钥管理方案。首先使用超图理论对分布式PCE架构下的多域光网络密钥关系进行建模得到两层式密钥超图；然后在自治域层采用基于自认证公钥密码体制和成员过滤技术的密钥管理方法，在PCE层采用基于椭圆曲线密码体制的组密钥协商方法；最后完成密钥的产生、分发、更新和动态管理，较好地解决了成员的私钥保密性问题和第三方节点的冒充问题，减少了密钥更新时的计算开销。性能分析显示，该方案具有前向安全性、后向安全性、密钥保密性和抗合谋攻击等特点，与典型的分散式方案相比，在密钥存储量、加解密次数和通信开销等方面取得了较优的性能。     

Hybrid analog/digital wavelength-time optical CDMA systems in radio-over-fiber transmissions

This study presents a hybrid analog/digital (A/D) mechanism of two-dimensional (2-D) structure of wavelength-hopping and time-spreading coding optical code-division multiple-access (OCDMA) system for future generation communication and network technologies. The 2-D method increases the maximum permissible number of simultaneous base stations (BSs) and security using a finite bandwidth of optical broad-band light source (BLS). In the proposed system, we can employ low-cost BLS which can mitigate the sampling rate of optical switch (OSW) and has the advantage of power saving. The performance enhancement is using the time-spreading method by a Mach-Zehnder modulator (MZM) with switch function to suppress the phase-induced intensity noise (PIIN) effect of the wavelength domain and the receiver structure is equipped with balanced detectors in order to suppress the multiple-access interference (MAI). In addition, the hybrid OCDMA network is equipped using a dual input MZM for the choice which time analog or digital signals to be transmitted and the advantage of these two kinds of signals can transmit by the same coder/decoder (codec) mechanism and recover by different type filters in the receiver end. The numerical evaluation results demonstrate that, for analog and digital signals under PIIN- and MAI-limited conditions, the proposed system outperforms a conventional multi-wavelength and time-spreading OCDMA scheme. Hence, enhancing the confidentiality of the asynchronous networks of codeword assignments and integratable hardware designs for the scheme with a MZM, an optical switch (OSW), arrayed-waveguide grating (AWG) and fiber Bragg gratings (FBGs) in hybrid A/D 2-D OCDMA system is proposed.     

等效导频功率最大化的FBMC/OQAM系统导频结构设计

由于FBMC/OQAM系统不需要循环前缀CP、具有极高的频谱使用效率和良好的带外抑制等优点,满足了5G通信技术的需求,成为5G的备选波形。根据FBMC/OQAM系统的特点,本文将导频的一阶邻域对导频的干扰和导频之和作为新的伪导频,提出一种基于等效导频功率最大化的导频结构,通过提高等效导频的功率来减小噪声和其他干扰对信道估计性能的影响。仿真表明,本文提出的新的导频结构较传统的导频结构,更能提高信道估计的性能。     

A subcarrier modulation based optical wireless communication system employing transmission diversity

In this paper, we propose an optical wireless communication service for indoor environment. To seamlessly cover the target area and keep the received signal power strength at an acceptable level, we send the signal from multiple diffused optical emitters and achieve possible transmit diversity. With the proposed diversity scheme, the effective coverage range of the proposed system can be significantly enlarged with a guaranteed BER performance. Simulation results show a 13.4 m² area can be effectively covered by two optical emitters with optical emitter spacing of 3 m and average transmit optical power of 28 dBm.     

Accurate optical flow computation under non-uniform brightness variations

In this paper, we present a very accurate algorithm for computing optical flow with non-uniform brightness variations. The proposed algorithm is based on a generalized dynamic image model (GDIM) in conjunction with a regularization framework to cope with the problem of non-uniform brightness variations. To alleviate flow constraint errors due to image aliasing and noise, we employ a reweighted least-squares method to suppress unreliable flow constraints, thus leading to robust estimation of optical flow. In addition, a dynamic smoothness adjustment scheme is proposed to efficiently suppress the smoothness constraint in the vicinity of the motion and brightness variation discontinuities, thereby preserving motion boundaries. We also employ a constraint refinement scheme, which aims at reducing the approximation errors in the first-order differential flow equation, to refine the optical flow estimation especially for large image motions. To efficiently minimize the resulting energy function for optical flow computation, we utilize an incomplete Cholesky preconditioned conjugate gradient algorithm to solve the large linear system. Experimental results on some synthetic and real image sequences show that the proposed algorithm compares favorably to most existing techniques reported in literature in terms of accuracy in optical flow computation with 100% density.     

新能源电厂的可重构高透明度光通信技术

随着新能源技术的迅猛发展,使得数据光通信呈现出一种爆炸式增长态势,因此其安全性、可靠性、管理方式等都成为在电力光通信网管理工作中急需考虑的问题,并需要优化相应的新能源电厂光通信并网的管理方式。本文提出了一种高透明度、可重构性的波长转换方案,并提出了最优驱动条件。通过理论推导、仿真模拟和实验分析,验证了该驱动条件可以使波长转换具有最高转换效率和误比特率性能,同时验证了该波长方案可以动态可控地调整转换波长的频率,对转换信号几乎没有波形损伤等优点。     

Two-stage report generation in long-reach EPON for enhanced delay performance

Long-reach passive optical networks (LR-PONs), as a part of the next generation PON technologies, aim at combining the capacity of metro and access networks so that the telecommunication network topology is simplified and the operational cost is reduced. However, in order to eliminate the delay performance degradation introduced by long propagation distance, LR-PONs call for bandwidth distribution schemes that are different than the existing schemes for conventional PONs. In this paper, we propose a new bandwidth distribution approach which employs a two-stage buffering mechanism at the ONUs and adopts the reduced delay advantage of multi-thread polling. REPORT generator at an ONU generates the requests by using an adaptive burst assembly process. According to the proposed scheme, ONUs maintain time threshold and size threshold values for the upstream input queues. Upon receipt of a GATE message, each ONU runs an adaptive burst assembly procedure to set the appropriate time and size thresholds and determines the bandwidth request of the REPORT message. We evaluate our proposed bandwidth distribution scheme by simulations for the ONU-OLT distances of 20 km and 100 km. The simulation results confirm that consolidation of multi-thread polling and two-stage buffering enhances the delay performance of long-reach EPON (LR-EPON). Furthermore, under heavy loads, the proposed scheme leads to high utilization of the upstream channel.     

相干光学系统图像复原的各向异性扩散方法

相干光学系统中图像噪声污染严重,提出一种基于各向异性扩散的图像复原模型,该模型的扩散系数从理论上满足Charbonnier等人提出的构造扩散系数准则,同时结合对数变换对相干光学图像进行复原去噪处理。实验结果表明,同SRAD、Lee、Frost、Non-local Means算法和基于小波的BLS-GSM、BM3D等方法相比,该算法可以更有效地进行边缘平滑,而且还能够较好地解决图像边缘和细节失真的问题,不论从PSNR,还是从视觉评价效果来看,该算法都具有一定的优越性。     

三值光学计算机模拟器的设计与实现

三值光学计算机(ternary optical computer, TOC)作为一种新体系结构的计算机,具有处理器位数众多且易扩展、位功能可重构、位可分组使用等特点,在海量或复杂数据的快速处理方面有很大潜力,但它的应用开发探索尚处于初期。为了扩展其应用范围,提出了一种基于三值光学计算机体系架构的模拟器TOCSim设计方案。该方案通过软件形式模拟TOC的运行过程,并在普通PC机上实现其雏形。TOCSim主要模拟TOC处理器的重构策略、处理器位的分配策略、中间结果解码以及运算效果模拟等过程。通过本模拟器的模拟效果图与TOC原型机上的运行结果光图进行对比,表明该模拟器的设计方案是正确的、可行的。     

Priority-aware optical shared protection: An offline evaluation study

The availability of an optical connection is considered to be a critical service differentiator in WDM optical networks. In this regard, the design of a protection scheme that improves the availability of high priority optical connections and makes efficient use of optical resources is a major challenge faced by optical network operators. In a previous study, we proposed the so-called priority-aware shared protection survivability scheme as a potential solution to this design issue.In this paper, we complement our previous study. More specifically, we develop an offline study whose main purpose is to assess the efficiency of the priority-aware shared protection scheme. Through this study, we show that the priority-aware shared protection strategy as opposed to existing protection strategies is able to achieve the best tradeoff between optical resource usage and optical connections’ availability satisfaction.     

Priority-enabled optical shared protection: An online efficiency evaluation study

The availability of an optical connection is considered to be a critical service differentiator in WDM optical networks. In this regard, the design of a protection scheme that is able to improve the availability of high priority connections while making efficient use of optical resources is a major concern for optical network operators. In a previous work, we proposed the so-called priority-aware shared protection as a potential survivability scheme for next generation WDM networks to deal with the previously exhibited concern.

This paper develops an online study whose main purpose is to assess the efficiency of the aforementioned protection scheme. Through this study, we show that the priority-aware shared protection strategy is able to achieve both the best efficiency in terms of resource usage and in terms of availability satisfaction rate compared to existing protection solutions.     

A flexible optical switch architecture for efficient transmission of optical bursts

In this paper, we propose a new optical switch architecture for optical WDM networks. Flexibility and efficiency in terms of controlling and utilizing optical power are key features of the architecture. The architecture uses switching components which have increased flexibility of how optical power received on an input port is managed when switching optical signals. Like the traditional optical switches, optical power can be directed towards one output port only. Further, unlike the traditional switches, on need basis, the power can be split on a desired sub-set of output ports, thus reducing power wastage on unwanted ports. Such split power can be directed fully towards a single output port as and when it is needed. This flexible and efficient power management makes the architecture a potential candidate for optical networks with its usage in several dimensions. The dimensions include (1) switching methods such as circuit level switching and bursty level switching, (2) network types such as core, metro, and access networks, (3) support for technologies such as Light-trails and Light-trees, and (4) support for functionalities such as survivability and multicasting with new features. Importantly, there is potential that the architecture enhances adaptability based on the needs, and it supports co-existence and seamless integration of different environments.In this paper, our focus is on investigating bursty level switching using the proposed switch architecture. We use the flexibility of the switch and adopt a new switching method for data bursts. This switching method is efficient for switching bursts while introducing new challenges. Unlike the traditional switching method, it switches bursts arriving on an input link with zero (or very small) time gaps to different output links in certain scenarios. Further, it also switches bursts from different input links to the same output link when they arrive with zero (or very small) time interval. Adopting such switching approaches has potential benefits in terms of delay-load performance and blocking performance. While the bursts are switched from the same input link to different output links in this approach, it creates some unwanted signals. We investigate scenarios in which the unwanted signals create any problems and this poses some challenges. To address such challenges, we develop a transmission protocol. We investigate the performance of our solutions using simulation studies and verify the two significant gains: (1) networks’ capability to sustain traffic loads up to the maximum level in terms of the delay-load performance, which is similar to the performance seen for hypothetical ideal switches with zero switching time, and (2) improved blocking performance.     

A simulation study of optical burst switching and access protocols for WDM ring networks

We consider a wavelength division multiplexing metro ring architecture with optical burst switching. The ring consists of N nodes, and each node owns a home wavelength on which it transmits its bursts. The ring operates under the fixed transmitter tunable receiver scheme. Control information is transmitted on a separate control channel. Five different burst switching access protocols are proposed, and their performance and fairness is evaluated by simulation.     

基于PON技术的矿井监控通信系统

介绍了一种最新的适合矿井通信的光纤通信技术———无源光网络PON(PassiveOpticalNet work)。在详细分析了PON的基本原理、关键技术及未来发展后,比较了两种PON技术———APON(ATMPON)和EPON(EthernetPON),并设计了PON在矿井中的应用结构模型。