Fiber-Optics:
Communicating Faster at the Speed of Light
Abstract
The size of the Internet and demand for information continues to grow at an extremely fast pace.
To keep up with the pace new communication technologies are necessary. The old dial-up
connections and the present coaxial cable connections soon will not be fast enough. Fiber-optics
offers a possible solution to this problem, potentially offering blazing fast speeds and low cost.
Keywords
Fiber optics
Internet
Communications
Data
Network
Prepared by Carey Y. Zhang
Author Biography
Carey is a senior at USC’s Viterbi School of Engineering double majoring in Electrical
Engineering and Biomedical Engineering. After his planned graduation in May of 2013, he
expects to go on to graduate school and pursue a doctorate degree.
Contact Information
[email protected]
(315) 420-9512
Paper Submitted October 10, 2012
Prepared for
Marc Aubertin, Writing 340 Professor
USC Viterbi School of Engineering
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Introduction
In the modern world more than ever, people rely on a network to communicate long
distances quickly and efficiently. Originally, simple telegraph networks transmitting a series of
beeps in Morse code were enough to send data back and forth. Since the development of the
Internet in the 1990s, however, the amount of data that must be transferred at a time has grown
immensely. Instead of just transmitting beeps, systems must transmit entire documents, images,
and videos. The average time spent online has doubled from 7 hours a week in 1999 to nearly 14
hours in 2009 [1]. And it is still growing; web pages are continually getting bigger and bigger
and the increasing number of internet users is congesting the network with more and more traffic
(see Figure 1 below). As the size and scale of the web continues to grow and the density of its
content develops, the world needs a faster network with higher data rates to communicate
information quickly to the user. The telephone wires originally used in dial-up internet are
Figure 1: Increases in web page transfer sizes and total requests for web pages since Nov. 2010. The trend has been
continuously increasing. More complicated and media-rich web pages have augmented the size of pages dramatically
while the growing population of internet-users has increased global traffic to those pages. All of this increasing
demand is taxing the speed of networks, leading to the need for faster, more robust communication technologies [2].
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already considered slow and coaxial cables, while satisfactory to most users in the present, soon
may not be fast enough to service the world's users. A new technology is needed.
The Current State of the Internet
The main measure of the speed of information flow isn’t time, but data rate. Data rate is
the amount of information sent per second, and is measured in bits per second. Bits—and a
related larger unit, bytes—are the basic units of data in the digital world. All the media people
consume over the Internet can be measured in bits (b) or bytes (B). The average web page size in
2011 was about 784 kB and is projected to grow to nearly 2.4 MB in just five years [3]. The
growing popularity of cloud storage solutions is also driving the growth in the volume of data
being transmitted, as entire music collections and hard drives are being stored, uploaded, and
downloaded regularly.
Dial up modem technology, for example, was the initial technology used for the Internet
in the 90s. Based on the telegraph system it was capable of up to only 56 kbits/s [4]. For the
average page in 2011, it would have taken nearly two minutes to completely load the page, much
too slow by any standards.
Current cable internet is much faster than dial up. It merges the digital television signal
and the Internet signal into one line, transmitting not only requested internet traffic, but also
hundreds of high definition television signals. The internet portion of the cable is typically
between 10 and 20 Mbits/s with a standard package [5]. While those speeds may be enough for
typical use, transferring a large amount of data uploading and downloading still creates
noticeable lag. Large files can still take half an hour or more to download.
A technology capable of even higher data rates is needed to not only reduce the lag, but
also to keep up with the growing volume of information. Engineers and physicists are currently
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working together to keep up with the increasing demand. One of the most promising
technologies for solving this need is fiber optics. It is already available commercially and to
homes in providing television and Internet connections. That being said, the current state of the
technology is still a far cry from its future potential.
The Need for Fiber Optics
Fiber optics involves transmitting light signals instead of electrical signals to
communicate information. It takes advantage of the property of internal reflection to direct light
along a cable. Internal reflection
occurs when light within a
refractive material (like glass) hits
a boundary at a certain angle (see
Figure 2 at left) [6].
The phenomena was first
Figure 2: Any light moving through a transparent material gets reflected a
certain amount at the boundary between the material and air. In this diagram,
light from the glass (in blue) is partially reflected and partially transmitted to
the air above. Only when it hits the edge perfectly perpendicularly is nothing
reflected back into the glass. As the angle becomes more and more parallel
with the edge more and more of the light is reflected back inside. Past a
certain critical angle, all of the light is reflected back into the glass. This is
total internal reflection [6].
harnessed into a method of
communication in the 1880’s by
Alexander Graham Bell and his
photophone, which transferred the human voice about 200 meters [7]. However, it wasn’t until
Charles Kao’s Nobel Prize winning paper in 1966 that fiber optics took off [8]. He postulated
that light could be transmitted through optical fibers for hundreds of miles with minimal loss.
This was a large claim for at that time, fiber optics could only carry light a little more than a mile.
Kao theorized that the limited distance was due to impurities in the glass, scattering the light and
causing information loss [9].
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There are two main factors that give fiber optics an advantage over traditional cables. The
first is their standard operating frequency. The second is their ability to transmit over long
distances with low attenuation.
Higher Frequency means Higher Data Rates
Fiber optics uses signals in the visible region of the electromagnetic spectrum. The
electromagnetic spectrum is the continuum of waves ranging from high frequency x-rays to
visible light, infrared, and low frequency radio waves. Data is encoded onto the frequency of
these signals so the greater the frequency the greater the amount of data that can be encoded and,
by extension, the greater the data rate. The frequency is analogous to the width of a pipe. A
higher frequency means there is a wider pipe (larger bandwidth) and more information can flow
through at once. A lower frequency corresponds to a narrower pipe. As can be seen from Figure
3 (below), the frequency of visible light is in the hundreds of terahertz range (1014) [10]. The
Figure 3: The electromagnetic spectrum stretches from waves in the hundreds of hertz to frequencies in the terahertz
range and beyond. Visible light is on the side of the higher frequencies Because of the greater frequencies, visible light
has a larger bandwidth and greater potential for higher data rates [10].
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current coaxial cables, on the other hand, can only achieve rates up to the hundreds of megahertz
(108) [11]. If fiber optics were to reach their full potential using visible light, internet data rates
could increase by orders of magnitude from megabits per second to terabits.
Lower Attenuation means Lower Cost
Another advantage of fiber optics is its relatively low attenuation compared to
conventional coaxial cables [12]. Lower attenuation means that a signal transmitted through the
cable doesn’t lose its energy or fidelity as much over long distances. The signal can be
transmitted a greater distance before having to be repeated or regenerated so that fewer
regenerators are needed in general. This reduces the cost of infrastructure, which may eventually
lead to a lower cost trickling down to everyday users.
The Current State of Fiber Optics
Current state-of-the-art optical fibers have been able to achieve a whopping 10.2 Tbits/s.
That’s over 10 trillion bits per second [13]. Fast enough to copy over an entire computer’s hard
drive in less than one second. But that’s not even the limit of what optical fibers can achieve.
Theoretical estimates put the capacity of fiber optics at around 330 Tbits/s [14]. Enough to copy
over thirty times as much data in less than one second. With all this potential, it’s no wonder that
engineers and scientists are developing fiber optics technology as the means to higher data rates.
As mentioned earlier, some companies have already moved towards using optical fibers
as the main backbone in their infrastructure. Verizon, for example, has its FiOS program offering
fiber optics at speeds up to 300 Mbits/s [15]. Google Fiber, recently announced in summer 2012,
promises 1000 Mbits/s to subscribers [16]. These speeds are blazingly fast; fast enough to
download a full movie in less than 10 seconds. Yet they can still be faster as the technology
continues to grow. Fiber optics is already starting to enter the mainstream Internet. As demand
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for data and online media continues to grow, the world has no choice but to turn to fiber optics as
the most viable method of creating faster data rates.
Besides data communications, optical fibers are also promising technologies in other
domains. Their low power consumption, for example, has led engineers to investigate its
possibility as a high-efficiency substitute to wires in overhead lights. Optical fibers also have
potential applications in various sensors, including those used in medical electronics and military
defense. Each of these applications alone could warrant further research and progress in the field
of fiber optics but altogether they make its expansion all but unavoidable.
Conclusion
The Internet has been continuously growing, both in demand and data. While current
communication technologies may be adequate in the present, the speed and cost of such
technologies can always be improved. Fiber optics is one of the most promising solutions to the
growing demand on data. Not only does it have the potential to offer data rates millions of times
faster than existing speeds, but it also has the possibility of achieving it at a lower cost, making
this great speed accessible to all the consumers that need it.
References
[1] L. Whitney. “Average Net User Now Online 13 Hours per Week.” CNET. Internet:
http://news.cnet.com/8301-1023_3-10421016-93.html, [Sept. 24, 2012].
This is a news article covering the increased time spent on the Internet over the past
fifteen years. It includes statistics that support my point that the Internet is growing
significantly, so I intend to reference that data in my paper.
[2] “Trends.” HttpArchive. Internet: http://httparchive.org/trends.php, [Oct. 6. 2012].
This website collects data on web page sizes, number of requests, and general usage of
pages on the Internet. I intend to use figures from this source to show the trend in
increasing file size of web pages and also the increasing demand (number of requests).
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[3] “Web Pages are Getting More Bloated and Here’s Why.” Pingdom. Internet:
http://royal.pingdom.com/2011/11/21/web-pages-getting-bloated-here-is-why/, [Sept. 24,
2012].
This article discusses the main reasons web pages are getting larger (picture size, scripts,
other media) and the significance of increasing page sizes. I intend to use its statistics on
how large sizes are projected to be in the coming years to support my argument that the
Internet is getting bigger and more data will need to be transported at a time.
[4] “Dial-up Technology.” Cisco. Internet: http://docwiki.cisco.com/wiki/Dial-up_Technology,
[Sept. 24, 2012].
Cisco’s documentation site describes the standards and specifications for dial-up modem.
It explains how the protocol works and also theoretical maximum rates. I intend to use
the maximum data rate of the dial-up connection to illustrate how fast internet
connections used to be.
[5] “Time Warner Cable Internet Plans.” Time Warner Cable. Internet:
http://www.timewarnercable.com/SoCal/learn/hso/internetplans.html, [Sept. 24, 2012].
This is the home web site for Time Warner Cable Internet. It has information on rates for
different Internet plans. I intend to use this to get information on the typical data rate
available to consumers currently and to reference that data rate in the comparison of data
rates.
[6] “Shedding Light on Total Internal Reflection.” VCCLite. Internet:
http://vcclite.com/tag/total-internal-reflection/, [Oct. 6. 2012].
This web site describes the phenomena of total internal reflection. Since total internal
reflection is the method by which light travels along a fiber optic cable, it must be
explained to properly understand fiber optics. I intend to use the information from this
article and also the figure it includes in my description of total internal reflection.
[7] “The Nineteenth Century.” Fiber-Optics.info. Internet: http://www.fiber-optics.info/history,
[Oct. 6, 2012].
This page gives a description of the start of fiber optics in the nineteenth century,
particularly how it was first used to direct light along a desired path. I intend to use this
page in describing the history of fiber optics.
[8] “The Twentieth Century.” Fiber-Optics.info. Internet: http://www.fiber-optics.info/history,
[Oct. 6, 2012].
The page talks about how fiber optics became a more viable method of communication in
the 1950’s and 1960’s, particularly after Kao’s paper was published. I intend to use this
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information to talk about the rapid changes in fiber optics in the twentieth century.
[9] K.C. Kao and G.A. Hockham. “Dielectric-Fibre Surface Waveguides for Optical
Frequencies.” Proc. IEE. Vol. 113, No. 7, pp. 1151–1158, 1966.
This paper was the landmark, Nobel-prize-winning paper that has laid the foundations for
long-distance fiber optics communications as we know it. It asserts that optical fibers
have the potential to transmit light for hundreds of kilometers with minimal decay despite
the relatively short ranges at the time of publication. I intend to talk about this paper, and
the assertions it makes, as setting off the boom in fiber optics technology.
[10] “The Electromagnetic Spectrum.” Hyperphysics. Internet: http://hyperphysics.phyastr.gsu.edu/hbase/ems1.html, [Oct. 6, 2012].
This page has a figure of the electromagnetic spectrum. I intend to use it in my discussion
of the range of frequencies and where visible light fits into the spectrum. Specifically, I
plan to use it to show that visible light is at a much higher frequency than the radio wave
frequency we use in standard communications.
[11] “Data-Over-Cable Service Interface Specifications DOCSIS 2.0.” CableLabs, pp. 94-96.
Available: http://www.cablelabs.com/specifications/CM-SP-RFIv2.0-C02-090422.pdf,
[Oct. 6, 2012].
This document explains the specifications for current coaxial-cable communications
protocols. In particular, it talks about the operating frequencies for these cables. I intend
to use it in the comparison with optical fiber operating frequencies to show that
frequencies with fiber optics are much higher.
[12] “How to Choose Optical Fiber.” Fiber-Optic Technology. Available:
http://www.imedea.uib.es/~salvador/coms_optiques/addicional/Corning/fiber_optic.pdf,
[Oct. 6, 2012].
The document describes the physical properties of optical fibers. In particular, it
discusses attenuation properties of fibers and how in a pure-enough fiber an optical signal
can be transmitted a much greater distance without needing to be repeated compared to a
coaxial cable. I intend to reference and relate this to lower cost of infrastructure in my
article.
[13] S. Bigo et al. “10.2 Tbit/s Transmission over 100km TeraLight Fiber with 1.28bit/s/Hz
Spectral Efficiency,” presented at Optical Fiber Communication Conference, Anaheim,
Mar. 2001.
The paper discusses how scientists were able to achieve 10.2 Tbit/s data rate in an optical
fiber. I intend to use this as an example of what state of the art fiber-optics in the presentday can achieve. I will compare this to theoretical limits.
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[14] P. Mitra, J. Stark. “Nonlinear Limits to the Information Capacity of Optical Fiber
Communications,” Nature 411, Jun. 28, 2011, pp. 1027-1030.
The paper calculates the theoretical limit in the data rate for fiber optics and explains its
nonlineariy. I intend to compare the theoretical limit to what present-day technologies
can achieve to show that there is still room for it to grow.
[15] “Verizon FiOS.” Verizon. Internet: http://www22.verizon.com/home/aboutfios/, [Oct. 8,
2012].
The page shows data rates achievable by using FiOS. I intend to use it as an example of
what level of fiber optics technology is currently available to consumers fairly accessibly
and to also show how companies have started adopting the technology.
[16] “Features.” Google Fiber. Internet: http://fiber.google.com/features/, [Oct. 8, 2012].
The page shows data rates achievable by using Google Fiber. I intend to use it as an
example of what level of fiber optics technology is currently available to consumers and
to show how more and more companies are adopting the technology. Since it is the
highest grade of Internet fiber optics available to consumers at the moment, I will also
compare it to what is possible to show that the technology can still be further developed.
[17] “Optical Fiber has Bright Future in S.C.” GSA Business. Internet:
http://www.gsabusiness.com/news/42257-optical-fiber-brings-bright-future-for-s-c?rss=0,
[Dec. 4, 2012].
This article details some alternative applications to fiber optics technology. I will use
these to talk about the large potential of the technology outside of communications and
invite the reader to investigate further.
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