光纤通信技术,英文版,chapter4
光通信英语作文
光通信英语作文In the realm of telecommunications, optical communication has emerged as a pivotal technology, revolutionizing the way information is transmitted across vast distances. This essay delves into the evolution of optical communication, its current state, and its profound impact on various sectors of society.IntroductionThe advent of optical communication can be traced back to the invention of the laser in the 1960s, which paved the way for the transmission of information through light. Over the decades, this technology has undergone significant advancements, transforming the landscape of global communication.Historical EvolutionThe journey of optical communication began with the use of optical fibers, which are thin strands of glass capable of transmitting light signals over long distances with minimal loss. The 1970s saw the first deployment of optical fibers in telecommunications, marking a shift from copper wires to a medium that could carry more data with greater efficiency.As technology progressed, the 1980s brought about the development of dense wavelength division multiplexing (DWDM),allowing multiple signals to be transmitted on a single optical fiber by using different wavelengths of light. This innovation significantly increased the capacity of optical communication networks.Current State of Optical CommunicationToday, optical communication is the backbone of the internet and global telecommunications. The technology has evolved to include advanced modulation techniques, such as quadrature amplitude modulation (QAM), which further enhance the data carrying capacity of optical fibers.The integration of optical communication with other technologies, like satellite links and undersea cables, has facilitated the creation of a global network that connects continents. This has led to the rise of cloud computing and the ability to access information and services from anywhere in the world.Technological AdvancementsRecent advancements in optical communication technology include the development of photonic integrated circuits, which combine multiple optical components onto a single chip, and the exploration of quantum communication, which promises unprecedented levels of security.The ongoing research in the field is also focusing on solving the challenges of signal distortion and attenuation in optical fibers, with new materials and designs beingdeveloped to improve the performance of optical communication systems.Impact on SocietyThe impact of optical communication on society is vast and multifaceted. It has facilitated the growth of thedigital economy, enabled high-speed internet access in remote areas, and supported the rise of online education, telemedicine, and e-commerce.Moreover, the high bandwidth and low latency of optical communication networks are critical for emerging technologies such as the Internet of Things (IoT), autonomous vehicles, and smart cities, which require real-time data transmission.Challenges and Future ProspectsDespite its many advantages, optical communication faces challenges such as the high cost of deployment, particularly in developing regions, and the need for skilled technicians to maintain and upgrade the infrastructure.Looking ahead, the future of optical communication is likely to involve further miniaturization of components, increased integration with other technologies, and the development of more efficient and cost-effective systems. The potential for quantum communication to revolutionize data security also holds great promise for the future.ConclusionIn conclusion, optical communication has come a long way since its inception and has become an indispensable part of modern society. Its ability to transmit vast amounts of data quickly and reliably has underpinned the digital revolution and continues to shape the way we live and work. As technology advances, optical communication is set to play an even more significant role in connecting the world and enabling new possibilities.References1. Agrawal, G. P. (2012). Fiber-Optic Communication Systems. Wiley.2. Saleh, B. E. A., & Teich, M. C. (2019). Fundamentals of Photonics. Wiley.3. Zhang, J., & Miao, G. (2020). Recent Progress in High-Capacity Optical Communication Systems. IEEE Communications Magazine, 58(2), 25-31.4. Smith, P. W. (2018). The Role of Optical Fibers in the Evolution of Telecommunications. IEEE Access, 6, 25762-25769.(Note: This essay is a fictional piece created for the purpose of this task and does not contain actual references.)。
solution4
(b) With R1 = 0.9 and R2 = 0.32, 1 1 gth = 0.05 cm ln 0.9(0.32) + 10 cm-1 = 34.9 cm-1 (c) From Eq. (4-37) ηext = ηi (gth - α )/gth ;
thus for case (a): ηext = 0.65(55.6 - 10)/55.6 = 0.53 For case (b): ηext = 0.65(34.9 - 10)/34.9 = 0.46 4-10. Using Eq. (4-4) to find Eg and Eq. (4-3) to find λ, we have for x = 0.03, 1.24 1.24 λ= E = = 1.462 µm 1.424 + 1.266(0.3) + 0.266(0.3)2 g From Eq. (4-38) dP(mW) ηext = 0.8065 λ(µm) dI(mA) Taking dI/dP = 0.5 mW/mA, we have ηext = 0.8065 (1.462)(0.5) = 0.590 4-11. (a) From the given values, D = 0.74, so that ΓT = 0.216 Then n 2 eff = 10.75 and W = 3.45, yielding ΓL = 0.856 (b) The total confinement factor then is Γ = 0.185 4-12. From Eq. (4-46) the mode spacing is λ2 ∆λ = 2Ln = (0.80 µm)2 = 0.22 nm 2(400 µm)(3.6)
通信工程专业英语 Unit 4：Common-Channel Signaling
把同位语从句可译为与主句并列的一个分句。
基于信令网的（高）速度和方便性，网管信号（传送） 方便.
Specialized English for Communication Engineering
Importantly, it obviates the need for most of the per circuit signaling equipment which is necessary when channel-associated signaling is used. for most of…equipment: 作定语修饰“the need”； which:引导定语从句,修饰“the percircuit signalling equipment”； “when”引导时间状语从句。 重要的是，共路信令省略了大部分的噪声抑制电路信令设备，这 些设备是当使用随路信令时是必需的。
小
专业英语翻译的标准 忠实（True） 通顺（Smooth） 专业英语的翻译方法 照译 转译 省译 赠补 Common-Channel Signaling
结
Specialized English for Communication Engineering
Specialized English for Communication Engineering
This was not possible with the earlier channel-associated signaling system, which were tailored to match the transmission and switching systems with which they worked, and whose message repertoires were extremely limited.
Fiber_4
Review
Why single-mode fiber?
Avoid intermodal dispersion Reduce pulse spreading Increase bit rate
How single-mode fiber?
V 2.405
Where single-mode fiber?
Loss increases with
Increasing MFD
Therefore, increasing wavelength
Decreasing bending radius (same as multimode)
Macrobending loss specified in data sheets
Single-mode fiber principles Attenuation Dispersion and bandwidth Data sheets
Slide 23
2010年3月1日星期 一10时2分44秒
Dispersion and Bandwidth
Chromatic dispersion
Slide 16
2010年3月1日星期 一10时2分44秒
Cutoff Wavelength
Condition for single-mode operation
d 2 2 V n1 n2
2.405
Condition in terms of wavelength
d
2.405 1.306 d NA C
Slide 18
2010年3月1日星期 一10时2分44秒
Single-mode Fiber: Outline
光通信技术外文翻译
外文文献阅读及翻译译文及原稿译文题目以太网无源光网络原稿题目 Passive optical network based on Ethernet 姓名吴腾学号 31202130班级通信1204以太网无源光网络格伦·克雷默北京邮电大学出版社2007以太网无源光网络（Ethernet Passive Optical Network ， EPON）是一种新型的光纤接入网技术，它采用点到多点结构、无源光纤传输，在以太网之上提供多种业务。
它在物理层采用了PON技术，在链路层使用以太网协议，利用PON的拓扑结构实现了以太网的接入。
因此，它综合了PON 技术和以太网技术的优点：低成本；高带宽；扩展性强，灵活快速的服务重组；与现有以太网的兼容性；方便的管理等等。
由于EPON的众多优点，它越来越受到人们的青睐，即将成为宽带接入网一种最有效的通信方法。
为了保证EPON网络能够稳定、高效、准确的运行，为EPON提供一个有效的网络管理系统显得尤为重要。
在网络管理领域，随着基于TCP/IP体系的网络管理技术的不断发展，SNMP已经成为事实上的标准。
基于SNMP的EPON网络管理系统是指采用SNMP管理协议框架，对EPONSNMP的介绍SNMP（简单网络管理协议）是一种基于TCP/IP的网络管理协议，它使用UDP作为传输层协议，能管理支持代理进程的网络设备。
SNMP主要包括SMI（管理信息结构）、MIB（管理信息库）和SNMP协议几部分。
SMI 给出了管理对象定义的一般框架。
MIB是设备所维护的全部被管理对象的结构集合。
SNMP协议包括SNMP操作、SNMP信息的格式以及如何在应用程序和设备SNMP采用代理/管理站模型进行网络管理。
SNMP有5种消息类型，分别为Get-Request、Get-Response、Get-Next-Request、Set-Request和Trap。
代理和管理站之间通过这几种消息报文进行相互通信，以获取网络设备的各种信息，从而控制网络设备的正常运行。
Fiber-Optic Communications Technology光纤通信技术
Content Overview & Introduction (1) Overview & Introduction (2) Fiber Optics (1) Fiber Optics (2) Fiber Optics (3) Fiber Optics (4) Fiber Optics (5) Fiber Optics (6) & Review Optical Transmitters (1) Optical Transmitters (2) Receivers (1) Receivers (2) Amplifiers Passive Components (1) Passive Components (2) & Prospects Review & Questions
Order 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
Time Mar 6 Mar 13 Mar 20 Mar 27 Apr 3 Apr 10 Apr 17 Apr 24 May 2 May 8 May 15 May 22 May 29 Jun 5 Jun 19 Jun 26
1.1 Why Fiber-Optic Communications?
The capacity limit
– Shannon-Hartley theorem:
– Bndwidth: the range of frequencies within which the signals can be tranmitted without substantial attenuation
Textbook:
– Djafar K. Mynbaev and Lowell L. Scheiner, Fiber-Optic Communications Technology, 1st Edition, 科学出版社(英 文影印版)，2002.
通信专业英语之光纤通信
Translation of Text 1-2
第8课 光纤通信 广义地说，把信息从一点传送到另一点就称 为通信。当信息跨越一段距离被传送时，就需要 一个通信系统。在通信系统中，信息传送是通过 把信息叠加在电磁波上或对电磁波进行调制来实 现的，电磁波起着载送信号的作用。
Translation of Text 2-1
Translation of Text 1-1
Lesson 8 Optical Fiber Communications
Communication may be broadly defined as the transfer of information from one point to another. When the information is to be conveyed over any distance a communication system is usually required. Within a communication system the information transfer is frequently achieved by superimposing or modulating the information on to an electromagnetic wave which acts as a carrier for the information signal.
Typical optical fiber communications system is shown in Fig.13-1. In this case the information source provides an electrical signal to a transmitter comprising an electrical stage which drives an optical source to give modulation of the lightwave carrier. The optical source which provides the electrical-optical conversion may be either a semiconductor laser or light emitting diode (LED).
光纤通信简介专业英语
Optical Fiber Communication-introduction ForewordThe use of light to send messages is not new .Fires were used for signaling in biblical times, smoke signals have been used for thousands of years and flashing lights have been used to communicate between warships at sea since the days of Lord Nelson.The idea of using glass fiber to carry an optical communication signal originated with Alexander Graham Bell. However this idea had to wait some 80 years for better glasses and low-cost electronics for it to become useful in practical situations.The predominant use of optical technology is for transmission of data at high speed. Optical fibers replace electric wire in communications systems and nothing much else changes. Perhaps this is not quite fair. The very speed and quality of optical communications systems has itself predicated the development of a new type of electronic communications itself designed to be run on optical connections. ATM (Asynchronous Transfer Mode) and SDH (Synchronous Digital Hierarchy) technologies are good examples of the new type of systems.It is important to realize that optical communications is not likeelectronic communications. While it seems that light travels in a fiber much like electricity does in a wire this is very misleading. Light is an electromagnetic wave and optical fiber is a waveguide. Everything to do with transport of the signal even to simple things like coupling (joining) two fibers into one is very different from what happens in the electronic world. The two fields (electronics and optics) while closely related employ different principles in different ways.Some people look ahead to “true”optical networks. These will be networks where routing is done optically from one end-user to another without the signal ever becoming electronic. Indeed some experimental local area (LAN) and metropolitan area (MAN) networks like this have been built. In 1998 optically routed nodal wide area networks are imminently feasible and the necessary components to build them are available. However, no such networks have been deployed operationally yet.In 1998 the “happening”area in optical communications was Wavelength Division Multiplexing (WDM). This is the ability to send many (perhaps up to 1000) independent optical channels on a single fiber. The first fully commercial WDM products appeared on the market in 1996. WDM is a major step toward fully optical networking.1. Transmitting Light on a FiberAn optical fiber is a very thin strand of silica glass in geometry quite like a human hair. In reality it is a very narrow, very long glass cylinder with special characteristics. When light enters one end of the fiber, it travels (confined within the fiber) until it leaves the fiber at the other end. Two critical factors stand out:Very little light is lost in its journey along the fiber.Fiber can bend around corners and the light will stay within it and be guided around the corners.An optical fiber consists of two parts: the core and the cladding. The core is a narrow cylindrical strand of glass and the cladding is a tubular jacket surrounding it. The core has a (slightly) higher refractive index than the cladding. This means that the boundary (interface) between the core and the cladding acts as a perfect mirror. Light traveling along the core is confined by the mirror to stay within it-even when the fiber bends around a corner.When light is transmitted on a fiber, the most important consideration is “what kind of light?”The electromagnetic radiation that we call light exists at many wavelengths. These wavelengths go from invisible infrared through all the colours of the visible spectrum to invisible ultraviolet. Because of the attenuation characteristics of fiber, we are only interested in infrared “light”for communication applications. This light is usuallyinvisible, since the wavelengths used are usually longer than the visible limit of around 750 nanometers ( nm ) .If a short pulse of light from a source such as a laser or an LED is sent down a narrow fiber, it will be changed (degraded) by its passage down the fiber. It will emerge (depending on the distance) much weaker, lengthened in time (“smeared out”), and distorted in other ways.2. Optical Transmission System ConceptsThe basic components of an optical communication system are optical transmitter and receiver,Fiber jumpers,Optical,fiber splice tray Optical fiber.A serial bit stream in electrical from is presented to a modulator, which encodes the data appropriately for fiber transmission.A light source (laser or Light Emitting Diode—LED) is driven by the modulator and the light focused into the fiber. The light travels down the fiber (during which time it may experience dispersion and loss of strength).At the receiver end the light is fed to a detector and converted to electrical form. The signal is then amplified and fed to another detector, which isolates the individual state changes and their timing. It then decodes the sequence of state changes and reconstructs the original bit stream.The timed bit stream so received may then be fed to a using device. Optical communication has many well-known advantages.Weight and SizeFiber cable is significantly smaller and lighter than electrical cables to do the same job. In the wide area environment a large coaxial cable system can easily involve a cable of several inches in diameter and weighing many pounds per foot. A fiber cable to do the same job could be less than one half an inch in diameter and weigh a few ounces per foot. This means that the cost of laying the cable is dramatically reduced. Material CostFiber cable costs significantly less than copper cable for the same transmission capacity.Information CapacityThe idea rate of system in 1998 was generally 150 or 620Mbps on a single (unidirectional) fiber. This is because these systems were installed in past years. The usual rate for new systems is 2.4Gbps or even 10Gbps. This is very high in digital transmission terms.In telephone transmission terms the very best coaxial cable systems give about 2,000 analog voice circuits. A 150Mbps fiber connection gives just over 2,000 digital telephone (64kbps) connections. But the 150Mbpsfiber is at a very early stage in the development of fiber optical systems. The coaxial cable system with which it is being compared is much more costly and has been developed to its fullest extent.Fiber technology is still in its infancy. Using just a single channel per fiber, researchers have trial systems in operation that communicate at speeds of 100Gbps.By sending many (“wavelength division multiplexed ”) channels on a single fiber, we can increase this capacity a hundred and perhaps a thousand times. Recently researchers at NEC reported a successful experiment where 132 optical channels of 20Gbps each were carried over 120km. This is 2.64 terabits per second! This is enough capacity to carry about 30 million uncompressed telephone calls (at 64kbps per channel). Thirty million calls is about the maximum number of calls in progress in the world at any particular moment in time. That is to say, we could carry the world’s peak telephone traffic over one pair of fibers. Most practical fiber systems don’t attempt to do this because it costs less to put multiple fibers in a cable than to use sophisticated multiplexing technology.No Electrical ConnectionThis is an obvious point but nevertheless a very important one . Electrical connections have problems. In electrical systems there is always the possibility of “ground loops” causing a serious problem,especially in theLAN or computer channel environment . When you communicate electrically you often have to connect the grounds to one another or at least go to a lot of trouble to avoid making this connection. One little known problem is that there is often a voltage potential difference between “ground”at different locations. The author has observed as much as 3 volts difference in ground potential between adjacent buildings (this was a freak situation). It is normal to observe 1or 2 volt differences over distance of a kilometer or so.With shielded cable there can be a problem if you earth the shields at both ends of the connection. Optical connection is very safe. Electrical connections always have to be protected from high voltages because of the danger to people touching the wire . In some tropical regions of the world, lightning poses a severe hazard even to buried telephone cables! Of cause, optical fiber isn’t subject to lightning problems but it must be remembered that sometimes optical cables carry wires within them for strengthening or to power repeaters . These wires can be a target for lightning.No Electromagnetic InterferenceBecause the connection is not electrical, you can neither pick up nor create electrical interference (the major source of noise). This is one reason that optical communication has so few errors. There are very few source of things that can distort or interfere with the signal. In a buildingthis means that fiber cables can be placed almost anywhere electrical cables would have problems, (foe example near a lift motor or in a cable duct with heavy power cables). In an industrial plant such as a steel mill, this gives much greater flexibility in cabling than previously available.In the wide area networking environment there is much greater flexibility in route selection. Cables may be located near water or power lines without risk to people or equipment.Distances between RegeneratorsAs a signal travels along a communication line it loses strength (is attenuated) and picks up noise. The traditional way to regenerate the signal, restoring its power and removing the noise, is to use either a repeater or an amplifier. Indeed it is the use of repeaters to remove noise that gives digital transmission its high quality.In long-line optical transmission cables now in use by the telephone companies, the repeater spacing is typically 40 kilometers. This compares with 12 km for the previous coaxial cable electrical technology. The number of required repeaters and their spacing is a major factor in system cost.Open Ended CapacityThe maximum theoretical capacity of installed fiber is very great (almostinfinite). This means that additional capacity can be had on existing fibers as new technology becomes available. All that must be done is change the equipment at either end and change or upgrade the regenerators.Better SecurityIt is possible to tap fiber optical cable. But it is very difficult to do and the additional loss caused by the tap is relatively easy to detect.There is an interruption to service while the tap is interested and this can alert operational staff to the situation. In addition, there are fewer access points where an intruder can gain the kind of access to a fiber cable necessary to insert a tap.3. Wavelength Division MultiplexingWavelength Division Multiplexing (WDM) is the basic technology of optical networking. It is a technique for using a fiber (or optical device) to carry many separate and independent optical channels. The principle is identical to that used when we tune our television receiver to one of many TV channels. Each channel is transmitted at a different radio frequency and we select between them using a “tuner” which is just a resonant circuit within the TV set. Of course wavelength in the optical world is just the way we choose to refer to frequency and optical WDM isquite identical to radio FDM.There are many varieties of WDM. A simple form can be constructed using 1310nm as one wavelength and 1550 as the other or 850 and 1310. This type of WDM can be built using relatively simple and inexpensive components and some applications have been in operation for a number of years using this principle.Wavelength selective couplers are used both to mix (multiplex) and to separate (de-multiplex) the signals. The distinguishing characteristic here is the very wide separation of wavelengths used (different bands rather than different wavelengths in the same band).Th ere are many variations around on this very simple theme. Some systems use a signal fiber bidirectionally while others use separate fibers for each direction . Other systems use different wavelength bands from those illustrated in the figure (1310and 1550 for example). The most common systems run at very low data rates. Common application areas are in video transport for security monitoring and in plant process control.Dense WDM however is another thing.Dense WDM refers to the close spacing of channels.Sadly，＂dense＂is a qualitative measure and just what dense means is largely in the mind of the description.Others use the term to distinguish systems where the wavelength spacing is 1nm per channel or less.Each optical channel is allocated its own wavelength —or rather range of wavelengths.A typical optical channel might be 1nm wide. This channel is really a wavelength range within which the signal must stay. It is normally much wider than the signal itself. The width of a channel depends on many things such as the modulated line width of the transmitter,its stability and the tolerances of the other components in the system. In practical terms the transmitter is always a laser.It must have a line width which (after modulation) fits easily within its allocated band. It must not go outside the allocated band so it should have chirp and drift characteristics that ensure this. Depending on the width of the allocated band,these characteristics don't need to be the most perfect obtainable.However they do have to be such that the signal stays where it is supposed to be. The receiver is relatively straightforward and is generally the same as a non-WDM receiver .This is because the signal has been de-multiplexed before it arrives at the detector.光纤通信简介前言使用光来传送信息并不新鲜。
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2004~2005 Jin’s Fiber Optic Communications
How a singlemode fiber conducts one beam
Gaussian beam
I (r ) I (0) exp( 2r w )
2 2 0
How can we compare difference beams? We have to introduce some measure by convention, known as the mode-field diameter(MFD), is equal to 2w0.
The MFD is important characteristic of a singlemode fiber. When you need to connect two fibers, if these two fibers have different mode-field diameters, you will have extra insertion loss. This insertion loss can be calculated by the following formula:
Chapter5 Singlemode fibers--basics
Fiber Optic Communications
5.1 How a singlemode fiber works
There are many differences between multimode and singlemode fibers. These differences start with the principle of action and run through all the fiber characteristics.
The principle of action
Making a fiber that supports only one mode
V
2 a
(n n2 )
2 1 2
1
2
2 a
N . A. 2.408
Manufacturers use all these means to achieve their goal. The core diameter of a singlemode fiber is around 10um and less, the range of operating wavelengths typically starts at 1300nm, and the relative index is less than 0.4%.
chromatic dispersion: material dispersion and waveguide dispersion
1. Material dispersion (材料色散）
Pulse spreading caused by material dispersion
tmat Dmat ( ) L
Effective refractive index, neff is the combination of the core and cladding refractive indexes, this is another significant characteristic of a singlemode fiber. The MFD and Operating Wavelength the shorter the wavelength, the less the MFD typical graphs of MFD as a function of wavelength are shown in figure 5.4.
例题
Calculate the limitation in transmission length caused by fiber loss if A=0.2dB/km, Pin=0.029mW, and Pout=0.001mW, where A is fiber attenuation, Pin is light power launched into the fiber, and Pout is power coupled to a photodiode.
1) How many modes can be supported for a graded－index fiber if d is 50 um, NA is 0.225, and the operating wavelength is 1310 nm? (2%) 2) What is the number of modes for a step-index optical fiber whose d = 8.3 um, n1core= 1.4514, n2clad=1.4468, and the operation wavelength is 1550 nm? (2%) 3) For a fixed guided mode, the operating wavelength should be larger or shorter than the cutoff wavelength? Why? (2%) 4) To guarantee a single mode guiding , the operating wavelength should be larger or shorter than the cutoff wavelength? Why? (2%)
Fig. 2-23: Mode-field diameter
MFD is the crosssectional dimension 2w0, where the beam’s intensity drops to 1/e2=1.135
Fig. 2-23: Mode-field diameter
Core, cladding, and mode-field diameter
In multimode fibers, we need to know the core diameter because all the light is confined within the core. In singlemode fibers, however, this statement is not true, as fig5.3 , the essential portion of the light( typically, about 20%) is carried by the cladding. So manufacturers do not even specify the core diameter at all.
Single mode fiber attenuation
Multimode fiber
These graph show the similarities and differences between singlemode and multimode fibers. The key difference is in the lower level of attenuation introduced by singlemode fiber
Pulse fraction delivered by λ0 component
Pulse fraction delivered by
λ0 --νλ/2
Pulse fraction delivered by λ0 +νλ/2
output pulse
Keep clearly in mind that material dispersion equals zero at a specific wavelength—around 1300nm. This phenomenon stems from the dispersive properties of silica. Another point to stress is that for lamd<1300nm, D(lamd) is negative. This means that light at a wavelength, say, of 1000nm travels more slowly than light at a wavelength of 1100nm, as we discussed above.
Here we discuss the step-index fiber. Manufacturers use the mode-field diameter, MFD, rather than the core diameter as a parameter that describes singlemode fibers. This is in contrast to multimode fiber, where the geometric sizes of both the core and the cladding are given in the data sheets
LosscouplingMFD (dB) 10 log[4 ( MFD1 MFD2 MFD2 MFD1 ) ]
2
Cutoff wavelength
From the formulas
V
2 a
(n n2 )
2 1 2
1
2
2 a
N . A. 2.408
we can see the cutoff wavelength
5.3 Dispersion and bandwidth
The major mechanism that causes dispersion in a singlemode fiber is chromatic dispersion. Another form of dispersion is polarization-mode dispersion.(偏振模色散）