Optical layer survivability: a services perspective

This article provides a perspective on optical layer protection and restoration based on the services offered by carriers using the optical layer. This is different from other viewpoints that provide a taxonomy of protection techniques in a more abstract fashion for the purposes of standardization. The latter viewpoints are mostly based on the classification adopted in the SONET/SDH standards. In contrast, taking a services-based view provides a way to distinguish between protection schemes based on implementation costs and the associated services enabled by the protection scheme     

光网逻辑层的生存性技术(本期优秀论文)

提出了生存性技术的基本分类原则和光网络生存性的分层视图,在此范畴内,分析比较了包括纯链路、纯路径、Meta-Mesh、p-cycles、SBPP、SLSP在内的逻辑层生存性技术,最后总结出逻辑层生存性技术所具有的灵活性和容量利用高效率的特征.     

基于分层虚拓扑的跨粒度层增强生存性的方法

在多粒度光网络中,为了满足可变的业务带宽请求,降低高带宽请求业务的阻塞率,减少低带宽请求业务接入时造成的网络资源浪费,提出了一种基于分层虚拓扑的跨粒度层增强生存性的方法.该方法首先根据波长粒度和波带粒度设计了一种分层虚拓扑,然后根据业务请求带宽在各粒度层上或跨粒度层计算工作路径和保护路径.分析结果表明,该方法可有效提高...     

Selective survivability with disjoint nodes and disjoint lightpaths for layer 1 VPN

This paper deals with the problem of survivable routing and wavelength assignment in layer 1 virtual private networks (VPNs). The main idea is routing the selected lightpaths by the layer 1 VPN customer, in a link-disjoint manner. The customer may freely identify some sites or some connections, and have their related lightpaths routed through link-disjoint paths through the provider’s network. This selective survivability idea creates a new perspective for survivable routing, by giving the customer the flexibility of selecting important elements (nodes or connections) in its network. This study is different from previous studies which aim to solve the survivable routing problem for the whole VPN topology. The proposed scheme is two-fold: disjoint node based, and disjoint lightpath based. In disjoint node scheme, all lightpaths incident to a node are routed mutually through link-disjoint paths. In disjoint lightpath scheme, a lightpath is routed in a link-disjoint manner from all other ligthpaths of the VPN. We present a simple heuristic algorithm for selective survivability routing. We study the performance of this algorithm in terms of resources allocated by the selective survivability routing scheme compared to shortest path routing with no survivability. The numerical examples show that the amount of used resources by the selective survivability scheme is only slightly more than the amount used in shortest path routing, and this increase is linear. The extra resources used by the new scheme are justified by better survivability of the VPN topology in case of physical link failures, and the simplicity of the implementation.     

Optical single layer lift-off process

The lithography of the metal wiring layers is becoming the most confining technology in the era of VLSI (very large-scale integration), as more and more circuits have to be wired on the chip itself. The two competing technologies are subtractive etch (wet or dry), and additive metal lift-off. As lift-off needs no etching, it inherently offers cost and density advantages. It, however, requires an undercut photoresist profile. These undercuts can be achieved with an image-reversal process. The paper describes such a reversal process, especially tuned for lift-off applications. The result is a simple single-layer lift-off technology with excellent image quality.     

Feedback control applied to survivability: a host-based autonomic defense system

We address the problem of information system survivability, or dynamically preserving intended functionality & computational performance, in the face of malicious intrusive activity. A feedback control approach is proposed which enables tradeoffs between the failure cost of a compromised information system and the maintenance cost of ongoing defensive countermeasures. Online implementation features an inexpensive computation architecture consisting of a sensor-driven recursive estimator followed by an estimate-driven response selector. Offline design features a systematic empirical procedure utilizing a suite of mathematical modeling and numerical optimization tools. The engineering challenge is to generate domain models and decision strategies offline via tractable methods, while achieving online effectiveness. We illustrate the approach with experimentation results for a prototype autonomic defense system which protects its host, a Linux-based web-server, against an automated Internet worm attack. The overall approach applies to other types of computer attacks, network-level security and other domains which could benefit from automatic decision-making based on a sequence of sensor measurements.     

Optical interference effect of a thick absorbing LT-GaAs layer on a Bragg reflector

Near-infrared reflectance spectra of 5 μm thick low-temperature (LT) GaAs films on GaAs/AlAs Bragg reflectors (BRs) have been studied by model calculations as a function of the linear absorption coefficient of the films α_f. With increasing α_f, the reflectance of the stop band decrease monotonously. In contrast, the interference modulation due to the LT-GaAs layer on the BR inside of the stop band increases with increasing α_f until 1×10³ cm⁻¹ and decreases for larger α_f. This unusual behavior of the Fabry–Perot features in the stop band is explained by the attenuation of the light in the film as well as by the interference in the case of destructive superposition between the partial waves, which are strongly reflected at the film/BR interface, and those partial waves, which are much more weakly reflected at the air/film interface.     

Optical layer multicast: rationale, building blocks, and challenges

Optical layer multicast refers to the support of point-to-multipoint connections directly at the physical layer by employing passive devices capable of splitting the power of an input signal among several outputs. Optical multicast technology enables a broad set of applications and opens new directions to network design. We examine the underlying principles and essential components for a practical optical multicast service. We also present a set of key research challenges along with a survey of the literature.     

New results using membrane-supported circuits: a Ka-band poweramplifier and survivability testing

This paper describes recent results which pertain to the integration and reliability testing of micromachined, membrane-supported transmission line circuits. These circuits employ a 1.4-μm-thick dielectric membrane to support thin-film conducting lines above an air substrate. With regard to integration, the development of a Ka-band solid state power amplifier (SSPA) is presented. The design includes a membrane-supported Wilkinson power divider/combiner with 0.2 dB loss, along with a commercially available monolithic microwave/millimeter wave integrated circuit (MMIC) amplifier stage. Also reported are tests which investigated the survivability of membrane lines under space qualification conditions. No failures occurred as a result of thermal cycling and vibration testing at levels which reached 39.6 grms     

Differential modulation for two-way wireless communications: a perspective of differential network coding at the physical layer

This work considers two-way relay channels (TWRC), where two terminals transmit simultaneously to each other with the help of a relay node. For single antenna systems, we propose several new transmission schemes for both amplify-and-forward (AF) protocol and decode-and-forward (DF) protocol where the channel state information is not required. These new schemes are the counterpart of the traditional noncoherent detection or differential detection in point-to-point communications. Differential modulation design for TWRC is challenging because the received signal is a mixture of the signals from both source terminals. We derive maximum likelihood (ML) detectors for both AF and DF protocols, where the latter can be considered as performing differential network coding at the physical layer. As the exact ML detector is prohibitively complex, we propose several suboptimal alternatives including decision feedback detectors and prediction-based detectors. All these strategies work well as evidenced by the simulation results. The proposed protocols are especially useful when the required average data rate is high. In addition, we extend the protocols to the multiple-antenna case and provide the design criterion of the differential unitary space time modulation (DUSTM) for TWRC.     

Optical transitions in a quantized cylindrical layer in the presence of a homogeneous electric field

Variations in the charge carrier energy spectrum in the presence of a transverse electric field in a cylindrical semiconductor layer are considered using the one-electron approximation. The explicit dependences of the Stark shift on an external field and on nanoradial sample dimensions are obtained. The absorption factors are calculated and the selection rules are obtained for both interband and intraband-intersubband optical transitions in the presence of an external electric field.     

Sprint long distance network survivability: today and tomorrow

The high reliability exhibited by the Sprint long distance network is the result of many interrelated factors. The network utilizes robust architectures, systems, and equipment to provide a reliable transport infrastructure. Redundant equipment, conservative synchronization, protected power, and other factors combine to form a dependable foundation. New architectures and systems are under development to meet the changing demands of customers. This article summarizes Sprint's current network reliability, and emerging demands and technology, and presents possible directions for the future Sprint network. Sprint selected the SONET four-fiber bidirectional line switched ring (4F BLSR) architecture for the vast majority of its transport network architecture. A 4F BLSR architecture requires four fibers, or four optical wavelengths of wave division multiplexing (WDM), to accommodate a work and protect path in each direction around a ring of network elements or add-drop multiplexers (ADMs)     

光网络组播的生存性

简要回顾了光层组播的概念,讨论了如何对组播树实施保护恢复的生存性机制,提出了几种不同的资源共享策略,并介绍了一些目前研究组播生存性问题常用的理论方法。     

Digital television: a perspective

Commercial television was standardized originally mainly for entertainment, sports, and news, using over-the-air broadcasts. While a few upward compatible changes have been added over the years, the standard has remained essentially unchanged. Moreover, no other standard has had so many products and services built around it and withstood such a period of rapid technological change. Digital television promises to disturb the current equilibrium in consumer television and in the broader media industries. It is forcing a convergence with the simultaneous expansion of personal computing into the home and the commercialization of research networks. Digitizing television in a cost-effective manner and integrating it with computers, telecommunication networks, and consumer products will produce a large array of new products and services. The paper describes digital television, factors affecting it, its potential, and some major issues in its evolution     

ISDN: a customer perspective

Early projected benefits of the integrated services digital network (ISDN) are evaluated from a customer premises equipment (CPE) perspective. It is argued that economic conditions continue to affect ISDN investment in the USA. Worldwide customer acceptance of ISDN is contrasted with earlier projections and shown to be running at about 25% of earlier projections. IBM's current ISDN product set is discussed briefly. Even though the rollout of services has not yet achieved expectations, IBM believes the potential for ISDN use by customers is significant     

100Gbit/s波分复用系统光层保护方式探讨

文章首先介绍了100Gbit/s波分复用系统中几种常用的光层保护方式,探讨了其技术本质及优劣势,然后结合现网案例进行系统性能模拟分析,最后给出了100Gbit/s波分复用系统保护方式选择的建议。     

基于切片分组网（SPN）的彩光技术及组网方案

随着5G的规模部署,对传输网络提出更大带宽、更低时延的要求。作为面向5G的综合业务承载平台,切片分组网（SPN）统一承载无线业务、家庭宽带业务和政企专线业务等,业务量的激增迫使SPN汇聚层和核心层急需大带宽长距传输技术。对SPN彩光技术及组网方案进行研究,包括业务需求、技术方案、组网方案、产业及标准进展等,并进行实验室和现网测试,验证SPN彩光组网功能和性能。     

Optical network packet error rate due to physical layer coding

A physical layer coding scheme is designed to make optimal use of the available physical link, providing functionality to higher components in the network stack. This paper presents results of an exploration of the errors observed when an optical gigabit Ethernet link is subject to attenuation. The results show that some data symbols suffer from a far higher probability of error than others. This effect is caused by an interaction between the physical layer and the 8B/10B block coding scheme. The authors illustrate how the application of a scrambler, performing data whitening, restores content-independent uniformity of packet loss. They also note the implications of their work for other (N, K) block-coded systems and discuss how this effect will manifest itself in a scrambler-based system. A conjecture is made that there is a need to build converged systems with the combinations of physical, data link, and network layers optimized to interact correctly. In the meantime, what will become increasingly necessary is both an identification of the potential for failure and the need to plan around it.