微电子机械系统(MEMS)在光通信中的应用及其研究动态

近年来微电子机械系统（ＭＥＭＳ）成为光通信技术的新热点之一。本文叙述了ＭＥＭＳ技术的特点，论述了ＭＥＭＳ在光通信中的应用，并介绍了国内外的研究情况。     

光子晶体在光通信中的应用

妻亨首先介绍了新型材料光子晶体的基本特点,然后探讨了含有光子晶体的光器件在光通信系统中的各种应用。     

集成光学在光通信系统中的应用

本文从总体上介绍了当前和未来光通信系统应用的集成光学器件，重点介绍了LiNbO3光调制器及其它传输器件。     

微电机械系统在光通信中的应用:现状和未来

随着波分复用(WDM)网络的发展，光纤通信系统现已发展成一种复杂的多波长通信系统。由于光通信容量的愈益增加，人们寄希望于创新技术去实现光通信系统的巨大潜力，而微电机械系统(MEMS)则是解决WDM网络中关键技术的最有竞争力的候选技术。其应用包括大尺寸光开关结构(如光交叉连接器件、光插／分多路传输器)和传输网络用各种类型的有源和无源光学组件(如可调谐激光器和滤波器、色散补偿装置、放大增益匀衡器、偏振控制器及其他器件)。本文讨论了光通信用MEMS技术的开发现状、希望、面临的挑战及未来发展前景。重点讨论了基于MEMS的光交叉连接器。     

全光通信中的光开关技术

光开关是实现全光交换的核心器件,光开关的研究已成为全光通信领域研究的焦点。本文首先对光开关的原理进行归纳,总结光开关的应用范围。对传统机械式光开关、微电子机械式光开关、热光开关进行了进一步地划分,分析了它们的结构形式和性能特点。设计了光开关性能评价指标体系,对常见的4种光开关进行了定性与定量对比,指出不同类型光开关的优点和不足之处。最后依据全光通信网的发展趋势,指出大容量、高速、透明、低损耗是光开关的重点发展方向。     

微机电一体化与纳米技术

文中介绍了当前国际上微型机械、微型机械电子学的发展现状与趋势。提出了进行以微米、纳米技术为基础的微机电一体化新技术研究的建议。     

光通信网络中的光开关技术

对光开关的类型、特性及研究现状进行了讨论,并重点对MEMS光开关及其工艺技术进行了分析,指出MEMS是未来光开关技术的一个重要发展方向。     

光通信技术发展的新趋势

光通信技术作为近几十年才开始发展的新型通信方式,由于起步较晚,光通信的发展并非突飞猛进。甚至可以说是一波三折,但总体而言,光通信技术取得了一定成就,如在光器件、光协议网络等就有一定的技术。本文从光通信技术的含义入手,对光通信技术的现状进行了简要的分析,在分析的基础上对光通信技术发展的未来趋势做了大胆的展望。     

二维光子晶体在光通信中的应用研究

介绍了新型材料光子晶体的基本原理和光学性质。由于二维光子晶体具有制备简单和性能优异的特点，所以光子晶体的很多应用都用二维光子晶体来实现。我们探讨了二维光子晶体在光通信中的应用。     

无线光通信技术及其应用

光通信分为有线光通信和无线光通信两种。其中，有线光通信即光纤通信．已成为广域网、城域网的主要传输方式之一；无线光通信又称自由空间光通信（FSO．Free Space Optical communication）。近年来，随着“最后一公里”对高带宽、低成本接入技术的迫切需求，FSO在视距传输、宽带接入中有了新的发展机遇，同时由于光通信器件制造技术的飞速发展，无线光通信设备的制造成本大幅下降，FSO得到越来越多的应用。虽然目前FSO的使用无需通过政府的频率许可（目前无线电频率划分至300GHz，而光波远远超过该频率），但对于无线电管理部门来说，了解这种全新的通信技术的特征和发展趋势是大有裨益的。[编者按]     

Deep-space optical communications

A major problem in deep-space communication systems is that of obtaining high data rates (of the order of 107 bits per second). This article proposes some design concepts that indicate the probable feasibility of achieving wide-band communications by means of the laser. The example selected here is a hypothetical mission to Venus, chosen because of its great brightness and, hence, high background-noise level. Since no earth satellite relay is assumed, the communication channel includes the atmosphere. The down-link is the one considered because of its high-information-rate requirement.     

中国光通信产业发展现状

产业现状我国的光通信起步较早,70年代初就开始了大气传输光通信的研究,77年,研制出第一根石英光纤.80年代初,中国电信决定建设以光纤为主的干线传输网,首先建设的是1985年宁汉PDH140 Mbit/s光缆通信系统.八五期间干线建设以140 Mbit/s PDH系统为主,全国共建光纤通信干线40万公里,是“七五“期间总数的38.5倍.2000年光缆干线总长度达到1 20万公里,其中中国电信约占70%份额,其余约30%份额由中国联通、网通等公司拥有,共建成一级干线23条,在全国形成“八横八纵“的光缆骨干网实体结构,大多数干线直接采用2.5 Gbit/s系统,它覆盖全国省会以上的城市和70%的地市,全国通信网的传输光纤化比例已高达80%以上,沿海地区很多省光纤已到乡,许多大城市光纤已经通达大楼和住宅小区. 　　……     

Solitons in optical communications

In this paper we have calculated the effects of loss on the propagation of soliton solutions of the nonlinear Schrodinger equation. Since we are interested in the application of these results to optical communications, it is necessary to go beyond perturbative results. This is due to the fact that propagation distances in optical fibers are significantly greater than the decay length of the energy in the pulses. Some conclusions are drawn about the application of solitons in long-distance communications.     

Atmospheric optical communications systems

The increasing sophistication of optical (and infrared) components and techniques, combined with rapidly expanding communication requirements, suggests that optical systems operating partly or entirely within the atmosphere may soon represent desirable solutions to real communications problems. The design of such systems will be strongly influenced by considerations of atmospheric turbulence, molecular absorption, and aerosol scattering. The most promising alternatives are heterodyne systems operating at the 10.6 µ wavelength, and direct-detection systems at near-infrared or visible wavelengths. Feasible links include horizontal, ground-to-satellite, and satellite-to-ground (or aircraft) geometries. System requirements and atmospheric effects are reviewed. Components, signaling, and diversity techniques which will partially overcome atmospheric limitations are discussed. Specific representative systems designs are presented.     

Stretched-pulse optical fiber communications

We compare numerically long-distance propagation of two types of nonlinear pulses: a stretched pulse in a fiber with alternating normal and anomalous dispersion and a soliton in a fiber with uniformly anomalous dispersion. Numerical evaluation of timing jitter and Q factor reveals that stretched pulses can be propagated over longer distances than solitons with the same (averaged) fiber dispersion in the presence of weak fixed-frequency filtering. We also examine pulse-to-pulse interactions between stretched pulses and the influence of fluctuations of the fiber dispersion.     

Modulators for optical communications

This paper reviews the field of high-speed small-aperture modulators for applications in optical communications, with emphasis on electrooptic modulation. The capabilities and limitations of electrooptic modulators are discussed based on a review of the physical origin of the electrooptic effect. Thermal and photoconduction phenomena, which may severely limit the operation of practical devices, are emphasized. The modulation power and bandwidth limitations using various schemes of electrooptic interaction are derived and compared. It is shown that lumped modulators are capable of efficient modulation for bandwidths up to about 1 GHz for visible wavelengths and are also attractive for their simplicity. For broader bandwidth capability the traveling wave or zigzag types of interaction become more efficient but with added complexity. Finally, acoustooptic and magnatooptic modulators are briefly discussed and compared with electrooptic modulators.     

Capacity of wireless optical communications

We consider the ergodic capacity and capacity-versus-outage probability of direct-detection optical communication through a turbulent atmosphere using multiple transmit and receive apertures. We assume shot-noise-limited operation in which detector outputs are doubly stochastic Poisson processes whose rates are proportional to the sum of the transmitted powers, scaled by lognormal random fades, plus a background noise. In the high and low signal-to-background ratio regimes, we show that the ergodic capacity of this fading channel equals or exceeds that for a channel with deterministic path gains. Furthermore, knowledge of these path gains is not necessary to achieve capacity when the signal-to-background ratio is high. In the low signal-to-background ratio regime, path-gain knowledge provides minimal capacity improvement when using a moderate number of transmit apertures. We also develop expressions for the capacity-versus-outage probability in the high and low signal-to-background ratio regimes, by means of a moment-matching approximation to the distribution for the sum of lognormal random variables. Monte Carlo simulations show that these capacity-versus-outage approximations are quite accurate for moderate numbers of apertures.     

Space applications of optical communications

Optical communication in Space is now a reality. In this paper we present the recent developments that were undertaken in Europe for this application. We first describe the different missions where optical communications are useful: link between two geostationary satellites (geo-geo), Data Relay Mission (leo-geo) and High Data Rate Satellite Constellation Network. Then we detail the different candidate laser technologies from the most straightforward technologies that have been developed for optical fiber applications (λ=1.55 µm) and 0.8 µm technology based on Silicon detector to the recent developments based on high power fiber amplifiers. In the last chapter we describe thesilex (Semi conductor Intersatellite Link Experiment) program which performs optical communication betweenspot4 Earth observation satellite (cnes) andartemis (esa). The excellent results based on 0.8 µm laser diode technology are considered to be a major milestone in optical intersatellite communication