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Fiber Optics: An Introduction
Carey Williamson
University of Calgary
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Introduction
 Optical
fiber makes possible the
transmission of digital data at several
gigabits per second (Gbps) over long
distances with very low error rates
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Optical Fiber
 Manufactured
from refined glass
 Very few impurities
 Very thin (e.g., 8-12 microns for core)
 Core is surrounded by cladding
Cladding
Core
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Fiber-based Transmission
 Bits
are represented as pulses of light
 Transmitted using lasers
 Light pulses, once transmitted into the
core, continue to travel down the fiber,
according to the physical principle of
total internal reflection
 Very little signal attenuation (loss)
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Fiber Optic Transmission
 Transmission
performed using laser
 Usually
a fixed wavelength
 Some are tunable to different wavelengths
 Receiver
uses photo-electric diode to
detect incoming signals
 Usually
a fixed wavelength
 Some are tunable to different wavelengths
 Optical-electrical
conversions required
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Fiber Optic Transmission
 Can
transmit using several different
wavelengths on the same fiber
(monomode versus multimode fiber)
 Called Wavelength Division
Multiplexing (WDM)
 Same principle as Frequency Division
Multiplexing (FDM)
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Fiber Optics: Facts
 Optical
fiber works best with
wavelengths of light around either 0.85,
1.3, or 1.5 microns
 Each band has a theoretical bandwidth
of approximately 25 TeraHz
 Current laser technology can achieve
several Gbps
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Fiber Optic Transmission
 Various
physical layer phenomena
serve to constrain the current
achievable bandwidth on optical fiber
 Dispersion:
modal, chromatic, material
 Absorption
 Attenuation
 Repeaters
or amplifiers are needed to
facilitate long range transmission
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Summary
 Optical
fiber offers immense bandwidth
 B-ISDN/ATM assumes fiber optic
based transmission at the physical layer
 International standard for fiber-based
transmission: SONET
(Synchronous Optical Network)
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