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Fiber Optics and Modern Communications Backbones

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[Princeton University]

 - The Building Blocks of the Optical Communication System

Fiber optical communication enables telelcommunications networks to provide high bandwidth high speed data connections across countries and the globe. As a result of these advantages, fiber optic communications systems are widely employed for applications ranging from major telecommunications backbone infrastructure to Ethernet systems, broadband distribution, and general data networking.

A fiber-optic cable is made up of incredibly thin strands of glass or plastic known as optical fibers; one cable can have as few as two strands or as many as several hundred. Each strand is less than a tenth as thick as a human hair and can carry something like 25,000 telephone calls, so an entire fiber-optic cable can easily carry several million calls. Fiber optic data transmission systems send information over fiber by turning electronic signals into light.  

Fiber optic communication is a method of transmitting information from one place to another by sending pulses of light through an optical fiber. Optical communication relies on optical fibers to carry signals to their destinations. A modulator/demodulator, a transmitter/receiver, a light signal and a transparent channel are the building blocks of the optical communications system.  

Modern fiber optic communication systems generally include an optical transmitter to convert an electrical signal into an optical signal to send through the optical fiber, a cable containing bundles of multiple optical fibers that is routed through underground conduits and buildings, multiple kinds of amplifiers, and an optical receiver to recover the signal as an electrical signal. The information transmitted is typically digital information generated by computers, telephone systems and cable television companies.


(Dr. Charles Kao at work in his laboratory at Harlow, England in 1966.)

Dr. Charles Kuen Kao - The Father of Fiber Optic Communications 

Dr. Charles Kuen Kao is known as the “father of fiber optic communications” for his discovery in the 1960s of certain physical properties of glass, which laid the groundwork for high-speed data communication in the Information Age. Before Kao's pioneering work, glass fibers were widely believed to be unsuitable as a conductor of information because of excessively high signal loss from light scattering. Kao realized that, by carefully purifying the glass, bundles of thin fibers could be manufactured that would be capable of carrying huge amounts of information over long distances with minimal signal attenuation and that such fibers could replace copper wires for telecommunication. He shared the 2009 Nobel Prize in Physics with Canadian physicist Willard S. Boyle (1924-2011) and American scientist George E. Smith (1930-), coinventors of the charge-coupled device, which is used to convert optical information to an electrical signal. Fiber optics and charge-coupled devices made possible the broadband communications on which contemporary medical informatics and electronic publishing depend, as well as specific imaging devices in ophthalmologic equipment and microscopes.     


- The Advantages of Optical Fiber

The biggest advantage of optical fiber is the fact it is the most cost effective means of transporting information. FIber can transport more information longer distances  in less time than any other communications medium. The bandwidth and distance capability of fiber means that fewer cables are needed, fewer repeaters, less power and less maintenance. 

In addition, fiber is unaffected by the interference of electromagnetic radiation which makes it possible to transmit information and data with less noise and less error. Fiber is lighter than copper wires which makes it popular for aircraft and automotive applications. These advantages open up the doors for many other advantages that make the use of optical fiber the most logical choice in data transmission. These advantages have led to fiber becoming the transport medium of choice for practically all data, voice and video communications.  


- Fiber Optic Backbone

Fiber optic communication systems are widely employed for applications ranging from major telecommunications backbone infrastructure to Ethernet systems, broadband distribution, and general data networking. Optical fiber is used by many telecommunications companies to transmit telephone signals, Internet communication, and cable television signals. Fiber optic communication enables telelcommunications networks to provide high bandwidth high speed data connections across countries and the globe. 

Using fiber optic cable, fiber optic communication has enabled telecommunications links to be made over much greater distances and with much lower levels of loss in the transmission medium and possibly most important of all, it has enabled much higher data rates to be accommodated.

The Internet generates massive amounts of computer-to-computer traffic, and insuring all that traffic can be delivered anywhere in the world requires the aggregation of a vast array of high-speed networks collectively known as the internet backbone.  

Like any other network, the internet consists of access links that move traffic to high-bandwidth routers that move traffic from its source over the best available path toward its destination. This core is made up of individual high-speed fiber-optic networks that peer with each other to create the internet backbone.


- The Internet Backbone

The individual core networks are privately owned by Tier 1 internet service providers (ISP), giant carriers whose networks are tied together. These providers include AT&T, CenturyLink, Cogent Communications, Deutsche Telekom, Global Telecom and Technology (GTT), NTT Communications, Sprint, Tata Communications, Telecom Italia Sparkle, Telia Carrier, Verizon, etc. mesh their high-speed fiber-optic networks together to create the Internet backbone, which moves traffic efficiently among geographic regions. 

By joining these long-haul networks together, Tier 1 ISPs create a single worldwide network that gives all of them access to the entire internet routing table so they can efficiently deliver traffic to its destination through a hierarchy of progressively more local ISPs. 

In addition to being physically connected, these backbone providers are held together by a shared network protocol, TCP/IP. They are actually two protocols, transport control protocol and internet protocol that set up connections between computers, insuring that the connections are reliable and formating messages into packets.

The Internet backbone is made up of the fastest routers, which can deliver 100Gbps trunk speeds. These routers are made by vendors including Cisco, Extreme, Huawei, Juniper, and Nokia, and use the border gateway protocol (BGP) to route traffic among themselves.

- Internet Exchange Points (IXP) Tie The Backbone Together

Backbone ISPs connect their networks at peering points, neutrally owned locations with high-speed switches and routers that move traffic among the peers. These are often owned by third parties, sometimes non-profits, that facilitate unifying the backbone. 

Participating Tier 1 ISPs help fund the IXPs, but don’t charge each other for transporting traffic from the other Tier 1 ISPs in a relationship known as settlement-free peering. Such agreements eliminate potential financial disputes that might have the result of slowing down internet performance.



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