1、 Web ProForum Tutorials http:/www.iec.org Copyright The International Engineering Consortium 1/23 Fiber-Optic Technology Definition Fiber-optic communications is based on the principle that light in a glass medium can carry more information over longer distances than electrical signals can carry in
2、a copper or coaxial medium.The purity of todays glass fiber,combined with improved system electronics,enables fiber to transmit digitized light signals well beyond 100 km(60 miles)without amplification.With few transmission losses,low interference,and high bandwidth potential,optical fiber is an alm
3、ost ideal transmission medium.Overview The advantages provided by optical fiber systems are the result of a continuous stream of product innovations and process improvements.As the requirements and emerging opportunities of optical fiber systems are better understood,fiber is improved to address the
4、m.This tutorial provides an extensive overview of the history,construction,operation,and benefits of optical fiber,with particular emphasis on outside vapor deposition(OVD)process.Topics 1.From Theory to Practical Application:A Quick History 2.How Fiber Works 3.Outside Vapor Deposition(OVD)Process 4
5、.OVD Benefits 5.Fiber Geometry:A Key Factor in Splicing and System Performance 6.How to Choose Optical Fiber Self-Test Correct Answers Web ProForum Tutorials http:/www.iec.org Copyright The International Engineering Consortium 2/23 Glossary 1.From Theory to Practical Application:A Quick History An i
6、mportant principle in physics became the theoretical foundation for optical fiber communications:light in a glass medium can carry more information over longer distances than electrical signals can carry in a copper or coaxial medium.The first challenge undertaken by scientists was to develop a glas
7、s so pure that one percent of the light would be retained at the end of one kilometer(km),the existing unrepeatered transmission distance for copper-based telephone systems.In terms of attenuation,this one-percent of light retention translated to 20 decibels per kilometer(dB/km)of glass material.Gla
8、ss researchers all over the world worked on the challenge in the 1960s,but the breakthrough came in 1970,when Corning scientists Drs.Robert Maurer,Donald Keck,and Peter Schultz created a fiber with a measured attenuation of less than 20 dB per km.It was the purest glass ever made.The three scientist
9、s work is recognized as the discovery that led the way to the commercialization of optical fiber technology.Since then,the technology has advanced tremendously in terms of performance,quality,consistency,and applications.Working closely with customers has made it possible for scientists to understan
10、d what modifications are required,to improve the product accordingly through design and manufacturing,and to develop industry-wide standards for fiber.The commitment to optical fiber technology has spanned more than 30 years and continues today with the endeavor to determine how fiber is currently u
11、sed and how it can meet the challenges of future applications.As a result of research and development efforts to improve fiber,a high level of glass purity has been achieved.Today,fibers optical performance is approaching the theoretical limits of silica-based glass materials.This purity,combined wi
12、th improved system electronics,enables fiber to transmit digitized light signals well beyond 100 km(more than 60 miles)without amplification.When compared with early attenuation levels of 20 dB per km,todays achievable levels of less than 0.35 dB per km at 1310 nanometers(nm)and 0.25 dB per km at 15
13、50 nm,testify to the incredible drive for improvement.Web ProForum Tutorials http:/www.iec.org Copyright The International Engineering Consortium 3/23 2.How Fiber Works The operation of an optical fiber is based on the principle of total internal reflection.Light reflects(bounces back)or refracts(al
14、ters its direction while penetrating a different medium),depending on the angle at which it strikes a surface.One way of thinking about this concept is to envision a person looking at a lake.By looking down at a steep angle,the person will see fish,rocks,vegetation,or whatever is below the surface o
15、f the water(in a somewhat distorted location due to refraction),assuming that the water is relatively clear and calm.However,by casting a glance farther out,thus making the angle of sight less steep,the individual is likely to see a reflection of trees or other objects on an opposite shore.Because a
16、ir and water have different indices of refraction,the angle at which a person looks into or across the water influences the image seen.This principle is at the heart of how optical fiber works.Lightwaves are guided through the core of the optical fiber in much the same way that radio frequency(RF)signals are guided through coaxial cable.The lightwaves are guided to the other end of the fiber by being reflected within the core.Controlling the angle at which the light waves are transmitted makes i