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ELECTRONIC COMMUNICATIONS
A SYSTEMS APPROACH
CHAPTER
16
Fiber Optics
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
All Rights Reserved
Introduction
• Fiber-optic communications system:
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Fiber-optic transmission strand
Source of invisible infrared radiation
Photosensitive detector
Efficient optical connectors at light
source
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
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Introduction
• Advantages of Optical Communications
Extremely wide system bandwidth
Immunity to electrostatic interference
Elimination of crosstalk
Lower signal attenuation than other
systems
 Substantially lighter weight and smaller
size
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Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
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Introduction
• Advantages of Optical Communications
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Lower costs
Safety
Corrosion
Security
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
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The Nature of Light
• Refraction of light
 Reduction as light passes into denser
material; causes light wave to be bent.
• Speed reduction and refraction different
for each wavelength.
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
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The Nature of Light
• Visible light striking prism
 Refraction at both air/glass interfaces;
separates light into its various
frequencies (colors).
• Amount of bend by refraction depends
on refractive index of two materials
involved.
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
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The Nature of Light
• Infrared light waves
 Electromagnetic light waves below
frequencies in visible spectrum.
• Optical spectrum
 Frequencies from infrared on up.
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
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The Nature of Light
• Construction of the Fiber Strand
 Core
• Carries transmitted light.
 Cladding
• Material surrounding core.
 Plastic coating surrounds cladding to
provide protection.
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
All Rights Reserved
Optical Fibers
• Criteria for Choice of Fiber Type
 Signal losses, with respect to distance
 Ease of light coupling and
interconnection
 Bandwidth
• Multimode Step-Index Fiber
 Rarely used in telecommunications;
very high amounts of pulse dispersion;
minimal bandwidth capability.
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
All Rights Reserved
Optical Fibers
• Multimode Graded-Index Fiber
 Handle higher bandwidths and/or longer
lengths of transmission before pulse
dispersion effects destroy intelligibility
and introduce bit errors.
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
All Rights Reserved
Optical Fibers
• Single-Mode Fibers
 Accepts only low-order mode allowing
operation in high-data-rate, longdistance systems.
 Used with high-power, highly directional
modulated light sources (laser).
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
All Rights Reserved
Optical Fibers
• Fiber Classification
 Telecommunications Industry
Association
• See Table 16-2: Multimode Classifications
(by the Refractive Index Profile and
Composition)
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
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Table 16-2 Multimode Classifications (by the
Refractive Index Profile and Composition)
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
All Rights Reserved
Optical Fibers
• Fiber Classification
 Telecommunications Industry
Association
• See Table 16-3: Single-Mode
Classifications
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
All Rights Reserved
Table 16-3
Single-Mode Classifications
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
All Rights Reserved
Optical Fibers
• Fiber Classification
 International Electrotechnical
Commission
• See Table 16-4: Generalized
Comparisons of Single-Mode and
Multimode Fiber
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
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Table 16-4 Generalized Comparisons of SingleMode and Multimode Fiber
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
All Rights Reserved
Optical Fibers
• Fiber Classification
 Plastic Optical Fiber
• Used in short-range markets.
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
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Fiber Attenuation and Dispersion
• Attenuation
 Loss of power introduced by fiber.
 Results from combination of:
• Scattering, absorption, macrobending,
microbending.
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
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Fiber Attenuation and Dispersion
• Attenuation
• Dispersion
 Pulse broadening; light pulse spreads
out in time as it propagates along fiber
strand.
• See Table 16-5: Dispersion Values for
Common Optical Wavelengths for Class
IVa Fiber
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
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Table 16-5 Dispersion Values for Common Optical
Wavelengths for Class IVa Fiber
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
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Fiber Attenuation and Dispersion
• Dispersion
 Modal
• Predominantly in multimode fiber.
 Chromatic
• Single-mode and multimode fibers.
 Polarization mode
• Single-mode systems.
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
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Fiber Attenuation and Dispersion
• Dispersion Compensation
 Acts like equalizer, negative dispersion
canceling positive dispersion.
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
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Optical Components
• Diode laser (DL)
 Source for moderate-band to wideband
systems.
• DL
 Source for single-mode fiber; LEDs have
low input coupling efficiency.
• LED
 Cheaper; less-complex driving circuitry
than DL.
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
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Optical Components
• Both LEDs and DLs multilayer devices.
• Light emitted from ED result of
recombining of electrons and holes.
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
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Optical Components
• Modulating the Light Source
 Fiber-optic communication
• Digital pulse systems.
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
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Optical Components
• Intermediate Components
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Isolators
Attenuators
Branching devices
Splitters
Couplers
Wavelength division multiplexers
Optical-line amplifiers
Electronic Communications: A Systems Approach
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Optical Components
• Detectors
 Most applications: detector is p-i-n
diode.
 Avalanche photodiode also used.
 Responsivity
Electronic Communications: A Systems Approach
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Optical Components
• Detectors
 Dark current
 Response speed
 Spectral response
• See Table 16-7: A Comparison of
Detectors
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
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Table 16-7
A Comparison of Detectors
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
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Fiber Connections and Splices
• Optical fiber ultrapure glass; joined in
permanent fusion splice or with
connector.
• Fusion splicing
 Long-term method; two fibers fused or
welded together.
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
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Fiber Connections and Splices
• Mechanical splices
 Permanent/economical choice for fibersplicing applications.
• Fiber Connectorization
 See Table 16-8: General Fiber
Connector Requirements
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
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Table 16-8
General Fiber Connector Requirements
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
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System Design and Operational
Issues
• Long-haul system
 High channel density and bit rate, highly
reliable, incorporate redundant
equipment, extensive engineering
studies.
• Local-area networks (LANs)
 Lower channel capacity and minimal
redundance; prespecified and
preengineered as to length, bit-rate
capability, performance.
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
All Rights Reserved
System Design and Operational
Issues
• Dispersion
 Single-mode, long-haul, high-bit-rate
consideration.
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
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Cabling and Construction
• Exterior (Outdoor) Installations
 Fiber installed
• Poles, underground in ducts, utility
tunnels, direct burial; be aware of
exposure.
• Interior (Indoor) Installations
 Environment well controlled.
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
All Rights Reserved
Cabling and Construction
• Testing the Fiber Installation
 Optical time-domain reflectometer
(OTDR)
• Sends light pulse down fiber; measures
reflected light.
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
All Rights Reserved
Optical Networking
• Defining Optical Networking
 Synchronous optical network (SONET)
• Standard for long-haul optical transport
of telecommunications data.
• See Table 16-9: SONET Hierarchy Data
Rates
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
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Table 16-9
SONET Hierarchy Data Rates
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
All Rights Reserved
Optical Networking
• Defining Optical Networking
 Fiber to the home (FTTH)
• Cost-effective way to provide largebandwidth capabilities to home.
• See Table 16-10: Ethernet/Fiber
Numerics
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
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Table 16-10
Ethernet/Fiber Numerics
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
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Optical Networking
• Air Fiber
 Propagation of laser energy through
atmosphere, a line-of-sight technique
uses parabolic lens to focus laser energy
in narrow beam.
• Fiber Distributed Data Interface
 American National Standards Institute
(ANSI) developed Fiber Distributed Data
Interface (FDDI); utilizes two 100-Mbps
token-passing rings.
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
All Rights Reserved
Safety
• As light propagates through fiber,
factors will attenuate light if there is an
open or break.
• Beware of eye damage.
• Factors can increase optical power at
exposed fiber end.
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
All Rights Reserved
Safety
• Safety factors for both fiber optic
equipment and the mechanics.
• In all cases, be sure craft personnel
have proper training for the job!
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
All Rights Reserved
Troubleshooting
• You should be able to:
 Draw a fiber link showing all
components.
 Explain the use of the optical power
meter.
 Describe rise-time measurement.
 Troubleshoot fiber-optic data links.
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
All Rights Reserved