An availability requirement for fiber optic transport systems in distribution feeder applications

This paper contains a discussion of Bellcore's proposed channel availability requirement for fiber optic transport systems used in distribution feeder applications. A representative model of the distribution network is first constructed which includes a high capacity fiber optic system running to a distribution hub. An overall availability requirement, consistent with present availability requirements, is applied to this model. The allocation to the fiber system is determined by truncation of the current interoffice channel availability requirement which is prorated with distance. Further allocation of downtime to the electronic hardware reliability failures yields an objective that can be directly compared with the results of electronic hardware reliability models. This requirement is now included in Bellcore's proposed “Generic Reliability Assurance Requirements for Fiber Optic Transport Systems.”     

Feed forward rings

Military and other critical (life-threatening/life-saving) systems require performance evaluations from a survivability, reliability, maintainability, and availability (SRMA) perspective. Applying SRMA concepts to commercial token passing ring local area networks (LANs) (e.g., IEEE-802.5, FDDI, SAE-9B) has uncovered several design issues that could impact the utility of these networks in a critical system. This article discloses a new architecture for token passing rings, called “feed forward rings” (FFR), which provides a significant improvement in system survivability, can eliminate “jabber mode” induced ring failures, and provides for passive optical bridging between rings.

The basic “feed forward” concept is that LANs, based on token passing protocols and utilizing multiple, physically separated, fiber optic rings, should have the serial data stream on each ring flowing in the same direction of rotation. This article provides qualitative observations on the performance of current commercial rings and discusses the advantages of several FFR topologies. Implementation issues related to FFRs are also discussed. It is recommended that FFR alternatives to counterrotating rings (CRR) with separated cables be considered for inclusion in LAN standards.     

Network survivability analysis

Advances in fiber optic and local area network (LAN) technologies are providing system designers with many new options for interconnecting computer equipment. A recurring problem for military system designers, who are end-users of a LAN standard, is implementing LANs so that the survivability, reliability, maintainability, and availability (SRMA) of a system is maximized. LAN standards working groups are currently making design decisions about topologies, components, and protocols that directly affect the SRMA of the end-user's system. This article focuses on a new analytic technique, called “network survivability analysis,” that provides the mathematical tools needed to compare the survivability of arbitrary network topologies. For background, several network metrics are described and their limitations for LAN standards development identified. Network survivability is defined, and several token-passing ring case examples are analyzed. The primary strength of network survivability analysis is that it can be used to provide a quantitative comparison among LAN topologies without knowledge of the end-user's equipment, systems, or environments.     

闭环光纤陀螺数字信号处理系统设计

针对光纤陀螺信号处理要求实时性高、算法较为复杂的特点,提出了一种以Xilinx公司的现场可编程门阵列XC6SLX16为基础的闭环光纤陀螺信号处理方案。根据光纤陀螺高精度和匹配性要求,对闭环信号处理系统关键的模数转换器和数模转换器的选择进行了理论分析,并对系统的硬件和软件进行了设计。对试验样机的测试结果表明,该系统能准确快速地实现光纤陀螺信号检测,体积小、功耗低、可靠性高,对光纤陀螺的工程化具有实际的参考意义。     

Implication of very wide fiber bandwidth for network architecture

The basic premise of this article is that at some point in the future all the transmission facilities of the public (telephone) network will be fiberoptic, i.e., end-to-end fiber connectivity will be provided to each subscriber. With the advent of coherent transmission systems the available bandwidth will become enormous, and thus the question we address is: given the availability of “infinite” bandwidth to every subscriber in the relatively near future, what does this imply for the network architecture? In particular, which switching technology is best suited to providing all foreseeable voice, data, and video services? Having discussed advantages and disadvantages of architectures based on different switching technologies, we conclude that an architecture based on circuit-switched, fixed-bandwidth channels for the transport of user information is the most appropriate for a network in which there are no constraints on the transmission bandwidth. The standard channel capacity should be determined by the service having the greatest bandwidth requirement.     

Reliability of 1.3-μm InGaAsP/InP laser diodes

Degradation mechanisms and methods for reliability improvement in 1.3-μm quaternary lasers for use in submarine fiber optic cable communications are reviewed. The reliable diode requires an optimized structure, such as a thin active layer and a narrow stripe width, to achieve a low threshold current I_th, high characteristic temperature T_o, and high maximum temperature for CW operation, T^CW_max. Accelerated long-term life test data predict an MTTF of ∼10⁷ h at room temperature for state-of-the-art optimized lasers with T_o ∼ 80 K, T^CW_max∼ 100°C, I_th ∼ 20 mA, and 5-mW optical power, which barely meets the system requirement. Based on the present rate of reliability improvement, a useful life of ∼10⁹ h is forecast by 1986.     

评估环圈光纤机械可靠性的模型

为评估应用于光纤陀螺和光纤电流传感器等传感领域的光纤环圈的机械可靠性,排除光纤涂覆和环圈灌胶等因素,必须评估所用光纤在弯曲状态下的机械可靠性.在已被广泛接受的均匀拉伸应力状态下通信光纤的机械可靠性模型基础上,根据这种环圈光纤在弯曲状态下的一般应力分布,对于绕环张力和弯曲应力同时存在的情形,建立了评估这种环圈光纤的机械可靠性的一种模型.该模型通过采用弯曲状态下光纤表面的最大弯曲应力值,和由于一般情况下弯曲中轴内侧的压缩应力远小于外侧拉伸应力的这一事实而忽略内侧的压缩应力,从而简化了弯曲应力的不均匀分布;同时通过该模型中所含的多个参量的选择给出了最为保守的结果.利用该模型进行的数值计算预测了采用不同直径的光纤分别绕制的不同环圈直径的环圈光纤在不同服役条件下的机械可靠性.结果表明,除了光纤半径和疲劳因子等这些光纤自身的固有因素外,绕环张力、环圈半径和筛选张力等工艺参量对环圈光纤的机械可靠性也是有重要影响.     

CiADS固态功率源的可用性设计与分析

ADS加速器面临的一大技术挑战是高可用性要求,进行固态功率源可用性设计是为ADS加速器的可用性设计与分析做准备。首先对CiADS的可用性要求进行了分配,固态功率源的分配结果为0.999;然后对固态功率源进行了初步可用性设计,分析的结果无法满足要求;最后对固态功率源进行了冗余设计,使用Reliasoft软件建立了固态功率源的可靠性框图,分析结果显示:满足一定的维修条件下,当其他元件的平均故障间隔时间（MTBF）达到171 702 h,25/28冗余设计可以满足0.999的可用性要求。One of the challenging technologies of ADS is the high availability requirement. The availability design of the solid-state amplifier is the preparation for ADS. Firstly the availability requirement of CiADS is proposed as 0.8. The distribution result of the solid-state amplifier is 0.999 according to this requirement. Then the availability result shows the preliminary design of solid-state amplifiers can not reach the availability requirement. At last the power loss is considered to build the k/N redundancy model of the main amplifier and the mean time between failure (MTBF) is calculated for various redundancy models. The reliability block diagram of the solid-state amplifier is set up by Reliasoft and the simulation results show that the 25/28 redundancy model can meet the requirement 0.999 when MTBF of other components reaches 171 702 hours with the certain maintenance.     

基于半导体纳米线和金属脊的混合表面等离子体波导模式特性分析

波长可开关光纤激光器可以选择多波长光纤激光器中的一个或多个波长输出,支持光网络中多个波长的动态分配,适应现代光纤通信系统信道数越来越多的波分复用和密集波分复用的发展方向.本文提出并实现了一种自激发多波长可开关掺铒光纤激光器.该激光器通过一个980 nm泵浦进行抽运,使用掺铒光纤作为增益介质,产生1 550 nm光谱,并通过一个环形结构返回,从而实现自激发的过程,降低了实验成本.实验使用一个含有两段保偏光纤的Sagnac环作为滤波器.通过调整Sagnac环形滤波器内偏振控制器的角度,改变Sagnac环形滤波器的腔内增益,可以让光纤光栅反射出来的波长选择性通过,从而实现波长的开关功能.实验证明,通过调整Sagnac滤波器的腔内增益而让多波长选择性通过,是一种有效的实现波长可开关功能的方法.     

多路音频信号的数字化光纤传输系统

在信息传输的各个领域中，光纤作为传输信号媒介的应用得以迅速发展。光纤的音频多路数字化传输也是光纤领域目前开发的热点课题之一，它充分利用光纤本身所具有的各种特点，使音频信号的传输更有效、更可靠。本文利用串行信号的时分复用技术，完成了多路音频数字化信号的光纤传输。提出信号传输中,数据信号和控制信号的复用及解复用解决方法。     

Bringing fiber optics to america: The cable television experience

Fiber optic technology is now being deployed on a large scale by cable television companies. Fiber brings unique benefits to cable system design in terms of improved reliability, reduced operating costs, and upgrades of channel capacity. The increased deployment of fiber will also enable cable companies to offer new services to take advantage of the increased functionality of the resulting network design. A survey of cable companies' deployment of fiber is presented.     

束参数瞬态测量在复杂环境中的电磁干扰及兼容设计技术

强流电子束束参数瞬态测量系统在直线感应加速器的复杂电磁环境中会受到强电磁的干扰,主要包括:干扰特性、干扰机理、数学描述、抑制措施、防范措施等,这些干扰既针对电路又针对系统,从而对束参数瞬态测量系统测量的稳定性以及测量数据的有效性都有很大的影响。介绍时间分辨测量系统的原理,分析了瞬态脉冲干扰的成因和抑制方法,给出了束参数测量系统的实验布局和特点,进一步探讨电子器件电性能受瞬态脉冲干扰后的抑制措施,其目的是为了达到减少或消除干扰,破坏干扰信号的传输条件,从而提高整个系统的抗干扰能力及可靠性。通过采用光纤传输控制信号可以很好地传输窄脉冲,减少信号延时抖动,以达到高速信号的可靠稳定传输;利用紧凑嵌入式方法,提高了抗电磁干扰的能力,可以更好保护测量系统电子器件,提高整个系统的抗干扰能力。     

Genetic algorithm-support vector regression for high reliability SHM system based on FBG sensor network

Structural Health Monitoring (SHM) based on fiber Bragg grating (FBG) sensor network has attracted considerable attention in recent years. However, FBG sensor network is embedded or glued in the structure simply with series or parallel. In this case, if optic fiber sensors or fiber nodes fail, the fiber sensors cannot be sensed behind the failure point. Therefore, for improving the survivability of the FBG-based sensor system in the SHM, it is necessary to build high reliability FBG sensor network for the SHM engineering application. In this study, a model reconstruction soft computing recognition algorithm based on genetic algorithm-support vector regression (GA-SVR) is proposed to achieve the reliability of the FBG-based sensor system. Furthermore, an 8-point FBG sensor system is experimented in an aircraft wing box. The external loading damage position prediction is an important subject for SHM system; as an example, different failure modes are selected to demonstrate the SHM system's survivability of the FBG-based sensor network. Simultaneously, the results are compared with the non-reconstruct model based on GA-SVR in each failure mode. Results show that the proposed model reconstruction algorithm based on GA-SVR can still keep the predicting precision when partial sensors failure in the SHM system; thus a highly reliable sensor network for the SHM system is facilitated without introducing extra component and noise.     

Coherent noise, scale invariance and intermittency in large systems

We introduce a new class of models in which a large number of “agents” organize under the influence of an externally imposed coherent noise. The model shows reorganization events whose size distribution closely follows a power law over many decades, even in the case where the agents do not interact with each other. In addition, the system displays “aftershock” events in which large disturbances are followed by a string of others at times which are distributed according to a t⁻¹ law. We also find that the lifetimes of the agents in the system possess a power-law distribution. We explain all these results using an approximate analytic treatment of the dynamics and discuss a number of variations on the basic model relevant to the study of particular physical systems.     

High-speed bridges for fiber optic local area networks

Progress in optical fiber communications allows ever-increasing channel capacity for local area networks (LANs). However, there are still many problems to solve with respect to bridges interconnecting these LANs, which constitute a system bottleneck. To eliminate the bridge bottleneck in the interconnection of fiber optic LANs, a high-speed bridge using optical technology is proposed. The proposed optical bridge uses bistable optical devices, such as interference filters, as essential components of its design. As these devices can be easily fabricated, the implementation of this optical bridge is feasible.     

Three-dimensional diffuse optical imaging of hand joints: System description and phantom studies

In this paper we describe a three-dimensional (3D) continuous wave (CW) diffuse optical tomography (DOT) system and present 3D volumetric reconstruction studies using this DOT system with simple phantom models that simulate hand joints. The CCD-based DOT system consists of 64×64 source/detector fiber optic channels, which are arranged in four layers, forming a cylindrical fiber optic/tissue interface. Phantom experiments are used to evaluate system performance with respective to axial spatial resolution, optical contrast and target position for detection of osteoarthritis where cartilage is the primary target region of interest. These phantom studies suggest that we are able to quantitatively resolve a 2 mm thick “cartilage” and qualitatively resolve a 1 mm thick “cartilage” using our 3D reconstruction approach. Our results also show that optical contrast of 3:1–7:1 between the “disease cartilage” and normal cartilage can be quantitatively recovered. Finally, the target position along axial direction on image reconstruction is studied. All the images are obtained using our 3D finite-element-based reconstruction algorithm.     

Transmit power and bits/channel use adaption in competitive cognitive radio networks

In this paper, we propose an optimization framework to determine the distribution of power and bits/channel use to secondary users in a competitive cognitive radio networks. The objectives of the optimization framework are to minimize total transmission power, maximize total bits/channel use and also to maintain quality of service. An upper bound on probability of bit error and lower bound on bits/channel use requirement of secondary users are considered as quality of service. The optimization problem is also constrained by total power budget across channels for a user. Simulating the framework in a centralized manner shows that more transmit power is required to allocate in a channel with higher noise power. However, allocation of bits/channel use is directly proportional to signal to interference plus noise power ratio. The proposed framework is more capable of supporting high bits/channel use requirement than existing resource allocation framework. We also develop the game theoretic user based distributed approach of the proposed framework. We see that user based distributed solution also follows centralized solution.     

多失效模式光电系统可靠性建模分析方法北大核心CSCD

系统可靠性建模分析是开展可靠性分配、预计、故障树分析及可靠性优化设计的基础。介绍了一种光电系统可靠性建模分析方法,针对光电系统中部分分系统具有多种失效模式且各失效模式均服从指数分布的特点,依据齐次马尔科夫理论,采用马尔科夫状态转移图方法建立了产品的可靠性模型,并给出解析表达式、数值计算方法和Monte Carlo仿真方法。最后,将其应用于某机载光电系统供电回路的实例分析中。采用两种计算方法及Monte Carlo仿真方法分别进行计算,并将结果进行对比分析,证明了该方法的正确性及可行性。     

Worldwide activities in fiber optics: Part II—systems and field trials

This report is essentially in two parts. The first is a summary of systems and field trials in North America, Japan, and Europe, based on a paper entitled “A Survey of World Wide Optical Waveguide Systems” by R. L. Gallawa, T. E. Midwinter, and S. Shimada, at the 1979 IEEE/USA Topical Meeting on Optical Fiber Communications, March 64, 1979, in Washington, D.C.

The second part is a complete listing of the technical characteristics of over 100 operational and experimental fiber optic systems compiled by Information Gatekeepers, Inc., 167 Corey Road, Brookline, MA 02146.