High-capacity undersea long-haul systems

This paper reviews technologies and techniques that have been used in deployed long-haul wavelength division multiplexing (WDM) systems and emerging technologies that could be used for the next generation of cost-reduced systems. The overview of current generation technologies starts with a discussion of modulation formats, focusing on the superior properties of the chirped return to zero on-off shift keying (CRZ-OOK) modulation format. The use of 10-Gb/s CRZ-OOK modulation format together with advanced fiber types, more powerful forward error correction (FEC), and broadband erbium-doped fiber amplifiers resulted in the deployment of dense WDM systems with capacities per fiber in terabits per second range and trans-Pacific reach. Demand for the systems with large design capacity led to further development of broadband optical amplifiers. Laboratory demonstrations successfully expanded transmission into the full C-band and later in the C and L transmission bands. The current market conditions dictate the need for reducing the first cost of an installed system rather than reaching record capacity per fiber. Reducing first cost can be achieved by reducing the amount of optical amplifiers in the cable by utilizing an excess performance margin provided by available RZ-OOK technology. Further improvements would be possible if more powerful FEC and modulation formats with better receiver sensitivity are used. For example, the RZ differential phase-shift keying (RZ-DPSK) modulation format with 3-dB better receiver sensitivity and better nonlinear tolerance to large amounts of accumulated dispersion is a very promising technology. This paper will review long-haul transmission results using RZ-DPSK and will compare the transmission properties of RZ-DPSK signals versus RZ-OOK signals. Due to superior receiver sensitivity, the RZ-DPSK modulation format can be an enabling technology for 40-Gb/s per channel transoceanic transmission.     

High-capacity transmission over polymer optical fiber

Polymer optical fiber (POF) is a promising transmission medium to provide broad-band telecommunication services within the customer's premises. POF offers several attractive features for data transmission such as broad bandwidth and low cost for in-house, access, and local-area-network (LAN) applications. This paper presents a review on optical transmission systems using POF and their enabling technologies. A summary is given of experimental data links with record capacity over record transmission distances. To conclude, we discuss trends for further development and research     

存储区域网络在电力通信中的应用

随着电力通信行业及光纤传输技术的快速发展,维持电力各项系统稳定运行的数据量也与日俱增,急需完成数据的存储、保护、备份和复制任务,并力争达到最优性价比。存储区域网络(storage area network,SAN)是一种提供在计算机与存储系统之间数据传输的高速网络,专注于企业级存储的各类需求。主要讨论SAN网络中裸光纤(dark fiber)或波分复用(wavelength division multiplexing,WDM)连接,同步光纤网(synchronous optical network,SONET)连接和IP网络连接3种适合电力通信系统的连接方式,比较其优缺点,并给出电力通信系统中适用的解决方案。     

长跨距无中继光纤传输系统的实验与分析

无中继光纤传输系统是指在光纤链路上不包括任何光电中继设备的传输系统。结合2.5 Gbit/s、10 Gbit/s、40 Gbit/s三种典型信道速率下的长跨距无中继传输系统实验,分析了实现大容量长跨距无中继传输的物理受限因素,探讨了应对的关键性技术,并通过实验证明了双向泵浦喇曼放大技术在无中继光纤传输系统中潜在的重要应用价值。     

Development of optical multidrop transmission lines and operation and maintenance technology for the full automation of power distribution lines

For the multimedia era, the authors plan to use optical fiber cables as the transmission media in integrated automatic distribution systems. This system provides a variety of advanced customer service functions and power distribution reliability features, such as remote metering, load control, and information service, including power consumption notification. The authors study an optical fiber multidrop network whose transmission path contains no active devices, using only optical fibers and optical couplers. The development of these passive optical networks must be accompanied by the development of useful components, maintenance methods, and operation procedures. The authors have developed ABF (air-blown fiber) composite power cables and optical branch boxes and have studied new optical network control procedures. They have also studied maintenance methods for optical multidrop networks, such as localization of obstacle points and charge-over switches for transmission paths. © 1997 Scripta Technica, Inc. Electr Eng Jpn 119(1): 24–34, 1997     

High bit-rate OTDM transmission over standard fiber using mid-spanspectral inversion and its limitations

An accurate modeling of very high bit-rate transmission systems over standard-fiber using mid-span spectral inversion (MSSI) is reported. As for the pulsewidth, comparison of simulations with experimental data in an 80-Gb/s transmission system over 106 km shows that second-order group velocity dispersion (GVD) is the limiting factor in this transmission scheme. Additionally, it is shown that even though first-order GVD can be compensated easily second-order GVD, is still remaining. It is pointed out that the performance of the system is very sensitive to the length of the different fiber spans     

光纤喇曼放大器的结构分析

光纤喇曼放大器以其灵活的增益谱、较高的光信噪比和较低的非线性特性,在近年来大容量、长距离光纤通信系统中获得广泛应用。文章在简述喇曼放大基本原理的基础上,针对其结构上的新特点,分析比较了3种典型喇曼放大系统的传输特性;指出通过在FRA中引入前向泵浦和色散管理技术,可以进一步提升喇曼放大系统的传输性能;并通过自行搭建的实验系统进一步验证了双向泵浦对FRA性能的改善。     

基于SAN技术的波分容灾系统传输时延研究

为了选择适合于容灾系统的传输技术,需要对容灾系统的传输时延进行研究。文章对比分析了基于SAN技术的容灾系统中的几种主流互联技术,以及选用波分技术的优势;采用理论分析和搭建实验平台验证的方法,建立光纤和波分系统的综合传输时延的模型,证明了模型的正确·l生,进一步得出了影响容灾系统传输时延的主要因素是光纤传输、传输器件时延的结论。     

Application of SPICE simulation to study WDM and SCM systems using EDFAs with chirping

The authors have proposed an equivalent electrical circuit model of erbium-doped fiber amplifiers (EDFAs), including the chirping effect for teaching or studying the distortions and performance of lightwave transmission systems. Through the aid of a SPICE circuit simulator, its validity is demonstrated by analyzing the cross modulations of an eight-channel wavelength division multiplexing system. The intermodulations in an amplitude modulation-subcarrier multiplexing (SCM) system are demonstrated. The channel-number dependence of the composite second-order distortion in a 42-channel SCM system is shown, and its applications to analyze other systems are also discussed.     

On the use of electrical precompensation of dispersion in optical single-sideband transmission systems

The use of electrical predistortion in optical single-sideband (OSSB) transmission systems is proposed to extend the tolerance to fiber dispersion impairment. Due to the spectral properties of OSSB signals, a simple electrical dispersive line can be used to mitigate the fiber dispersion, reducing the complexity of electrical predistortion methods proposed recently for optical modulations other than OSSB. Carrier-suppressed and carrier-unsuppressed optical modulations can be compensated by such technique, extending the range compared to previously reported works on fiber dispersion mitigation after direct detection using OSSB signals, where only carrier-unsuppressed modulations can be effectively compensated. The use of electrical precompensation is investigated for three signaling formats: Nonreturn to zero, return to zero, and alternate mark inversion (AMI). Due to distortion occurring in the sideband suppression process, signaling formats with reduced duty cycles present improved performance as a consequence of enhanced tolerance to intersymbol interference. Using such formats with electrical predistortion, the reach limitation arises not from fiber dispersion but from nonlinear impairments and optical noise accumulation. Using AMI and ideal electrical predistortion, distances greater than 1200 km of standard single mode fiber are achieved at 10 Gb/s with bit error ratio (BER) lower than 10/sup -12/, without using optical dispersion compensation. Introducing accurate models for the electrical dispersive lines, the transmission distance is reduced to 720 km for BER lower than 10/sup -12/.     

Reducing interchannel crosstalk in long-haul DWDM systems

Nonlinear interaction between signal channels may result in significant performance degradation in transoceanic dense wavelength-division-multiplexing (WDM) transmission systems operated at high bit rates. In this paper, we report that the nonlinear crosstalk for systems with high spectral efficiency can be suppressed if WDM channels are launched with orthogonal relative states of polarization. It is shown that for adjacent channels (that experience the strongest nonlinear interaction) the launched relative state of polarization is maintained over the large distance of low polarization-mode dispersion fiber typically used in undersea systems. Numerical studies, as well as experimental results, are presented for standard and dispersion slope-matched dispersion maps     

Modeling of transoceanic fiber-optic WDM communication systems

The rapid growth of long-haul wavelength-division multiplexing (WDM) fiber-optic telecommunications challenges lightwave system designers to increase the transmission capacity per fiber pair, while reducing the time to market. This makes it essential to have fast and accurate computer modeling tools to aid the systems design. There is a natural engineering tradeoff between simulation speed and accuracy; fast approximations tend to be inaccurate, while the exact treatment of the physical processes affecting transmission are nearly impossible to capture in a time-efficient algorithm. The proof of a successful tool development lies in the comparison of simulation results to transmission system measurements. In this paper, we discuss a new simulation technique based on careful evaluation of the key physical effects that produce system impairments. We show that this new approach can produce fast and accurate simulations of long-haul WDM transmission systems     

Demonstration of negative dispersion fibers for DWDM metropolitanarea networks

We present a detailed experimental and theoretical study, showing that a novel nonzero dispersion-shifted fiber with negative dispersion enhances the capabilities of metropolitan area optical systems, while at the same time, reducing the system cost by eliminating the need of dispersion compensation. The performance of this dispersion-optimized fiber was studied using different types of optical transmitters for both 1310- and 1550-nm wavelength windows and for both 2.5-and 10-Gb/s bit rates. It is shown that this new fiber extends the nonregenerated distance up to 300 km when directly modulated distributed feedback (DFB) laser transmitters at 2.5 Gb/s are used. The negative dispersion characteristics of the fiber also enhance the transmission performance in metropolitan area networks with transmitters that use electroabsorption (EA) modulator integrated distributed feedback (DFB) lasers, which are biased for positive chirp. In the case of 10 Gb/s, externally modulated signals (using either EA-DFBs or external modulated lasers using Mach-Zehnder modulators), we predict that the maximum reach that can be accomplished without dispersion compensation is more than 200 km for both 100- and 200-GHz channel spacing. To our knowledge, this is the first demonstration of the capabilities of a nonzero dispersion-shifted fiber with negative dispersion for metropolitan applications     

CY7C924在光纤通信中的应用

在当前的许多电子系统中,越来越多的数据传输应用中倾向于使用光纤通信技术。CY7C924作为一款高集成度、强灵活性、高可靠度的物理层通信接口芯片,可以方便的应用于光纤通信系统中。本文介绍了CY7C924的功能特性,描述了利用CY7C924分别结合现场可编程门阵列和单片机作为系统主机的光线通信系统应用,并给出了系统仿真结果。采用CY7C924的光纤通信方案预期可缩短系统开发周期。     

The 345-kV underground/underwater Long Island Sound cable project

A high-voltage underground/underwater cable system was installed to increase the transmission capacity from the mainland of New York to Long Island. The use of high-pressure fluid-filled (HPFF) pipe-type cable on the land portion represents the largest application of paper-propylene-paper (PPP) insulated cable in the United States. State-of-the-art technologies were implemented in the use of fiber optic cables for relay protection, temperature monitoring and leak detection systems, SF₆ gas-insulated substations, and underwater cable laying and embedment techniques. The design and installation of a 750 MVA, 43 km (26.6 miles), 345 kV underground/underwater electric transmission system are discussed     

一种实用的大容量电力电子系统高速光纤环网拓扑及其协议

基于串行光纤通信技术的分布式控制是大容量电力电子变流系统的一个发展方向。该文针对现有电力电子变流系统分布式控制方案存在的一些缺陷,提出一种软件控制可切换数据通道的高速光纤环形网络拓扑结构,并制定了简单可行的通信协议,简化了通信控制的软件编程和测试难度,提高了同步精度,同时也较大程度地减小了整个高速光纤环形控制网络的传输延时,扩展了基于高速光纤环网通信拓扑的分布式控制方案在复杂高性能电力电子变流系统中的应用范围。最后,该文给出了相应的数据传输、数据源切换以及反馈数据上传等方面的实验结果,验证了该种网络拓扑及协议的正确性、有效性和可行性。     

光纤复合架空地线施工质量与安全保障措施

随着我国电力通信系统的不断发展,迫切需要采用信息量大、抗干扰能力强的光纤通信系统,其中采用光纤复合架空地线(OPGW)是一种较好的方式。本文介绍OPGW施工质量和安全保障的有关措施。     

Numerical analysis of laser transmitter nonlinearity compensation technique for radio over fiber system

The task of reducing the noise and distortion generated by a laser transmitter has always been a challenge to improve the performance of radio over fiber systems. This paper presents a compensation system for nonlinear distortion of a laser transmitter supporting 5.2 GHz radio transmission over fiber employing a feed‐forward linearization technique. The nonlinearity of the laser diode is modeled using Volterra series analysis. The proposed linearization system is also simulated using commercial optical system software. The novel design has achieved 30 dB nonlinearity reduction considering 800 MHz modulation bandwidth. As an addition, this work also analyzes the effect of transmission length towards distortion reduction of the proposed system. Copyright © 2011 John Wiley & Sons, Ltd.     

Circuit quality degradation caused by optical fiber cable switching

With increased demands for optical fiber cable removal, a system which reduces circuit quality degradation due to optical fiber switching has been strongly required. The optical switching elements and optical fiber switching systems were studied aimed at shortening optical switching time, optical loss and other optical specifications. However, the circuit quality degradation cannot be evaluated by these specifications. For this reason, it is important to study the circuit quality degradation due to optical fiber switching, and the study must comprehend the transmission system performance after optical fiber switching. To analyze the circuit quality degradation during optical fiber switching, the standard analysis model and the optimum analysis parameters were defined. Using them, the frame hunting time after optical fiber switching was studied theoretically and its influence on a working transmission system was estimated. The circuit degradation was evaluated experimentally with regard to an actual transmission system, and experimental results agreed with the estimation. Moreover, by utilizing the results of these studies, it was found that the reduction of circuit quality degradation can be realized firmly and the effect of these studies was verified.     

FEC技术对线路保护通道的影响分析

长距离的光纤传输系统常常应用FEC技术增加光纤信号传输的中继距离,改善信道的传输质量,但FEC技术的应用对线路保护通道时延产生一定的影响.基于FEC技术原理,分析了FEC技术处理信号的过程和影响线路保护通道时延的因素,并结合目前线路保护装置对传输通道的时延要求进行计算,为线路保护通道的设计和运行维护提供参考.