Optical Communications: Circuits, Systems and Devices
Chapter 1: Introduction
Optical Fiber Communication: Technology and Systems
Overview
lecturer: Dr. Ali Fotowat Ahmady
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Chapter 1 Introduction
Optical Fiber Communications
High Speed Electrical Links
• Necessary to equalize the growing disparity between on-chip computation
and chip-to-chip communication bandwidth
• Components
- High-bandwidth transceiver (TX, RX)
- Terminated channel
- Precise clock generation and recovery
TX
RX
Channel
Timing
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Limitations of Electrical Links (1 of 2)
• Maximum on-chip clock frequency that can be propagated without swing
attenuation
• Clock period limit  6 – 8 FO4 inverter delays
- 0.25 CMOS  750 – 1000ps  1 – 1.3GHz
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Limitations of Electrical Links (2 of 2)
• Limited bandwidth distance product of wires
B  1015 A l 2 Bits/s (LC lines)
• Proportional noise sources
- Reflections
- Cross-talk
• Power Consumption ~ 30mW/Gb/s
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Electromagnetic Spectrum
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Chapter 1 Introduction
Optical Fiber Communications
Benefits of Optical Links (1 of 2)
• Enormous capacity: 1.3 mm-1.55 mm allocates bandwidth of 37 THz!!
• Cables and equipment have small size and weight
- A large number of fibers fit easily into an optical cable
- Applications in special environments as in aircrafts, satellites,
ships
• Longer Distances (SMF)
- Less attenuation per distance: Optical fiber loss can be as low as
0.2dB/km Compared to loss of coaxial cables: 10-300dB/km)
- Almost zero frequency dependant loss
- Dispersion Limited (Chromatic ~5ps/nm/km)
• Lower Power
- Less attenuation
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Benefits of Optical Links (2 of 2)
• Less Noise
- No crosstalk between fibers
- No reflections
• Immunity to interference
- Nuclear power plants, hospitals, EMP resistive systems
(installations for defense)
• Electrical isolation
- Electrical hazardous environments
- Negligible crosstalk
• Signal security
- Banking, computer networks, military systems
• Silica fibers have abundant raw material
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Market Transition from Electrical to Optical
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Chapter 1 Introduction
Optical Fiber Communications
History of Optical Telecommunications (1 of 3)
• Roman times-glass drawn into fibers
• Venice Decorative Flowers made of glass fibers
• 1841- Daniel Colladon-Light guiding demonstrated in water jet
• 1870- Tyndall observes light guiding in a thin water jet
• 1880- Bell invents Photophone
• 1888- Hertz Confirms EM waves and relation to light
• 1880-1920 Glass rods used for illumination
• 1930- Lamb experiments with silica fiber
• 1931- Owens-Fiberglass
• 1951- Heel, Hopkins, Kapany image transmission using fiber bundles
• 1958- Goubau et. al. Experiments with the lens guide
• 1958-59 Kapany creates optical fiber with cladding
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Chapter 1 Introduction
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History of Optical Telecommunications (2 of 3)
• 1960- Ted Maiman demonstrates first laser in Ruby
• 1960- Javan et. al. invents HeNe laser
• 1962- 4 Groups simultaneously make first semiconductor lasers
• 1961-66 Kao, Snitzer et al conceive of low loss single mode fiber
communications and develop theory
• 1970- First room temp. CW semiconductor laser-Hayashi & Panish
• 1975- Coax, 274 Mb/s at 1km repeater spacing
• April 1977- First fiber link with live telephone traffic-GTE Long Beach 6
Mb/s
• May 1977- First Bell system 45Mb/s links: GaAs lasers 850nm Multimode
-2dB/km loss
• Early 1980s- InGaAsP 1.3 µm Lasers: 0.5 dB/km, lower dispersion-Single
mode
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Chapter 1 Introduction
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History of Optical Telecommunications (3 of 3)
• Late 1980s-Single mode transmission at 1.55 µm - 0.2 dB/km
• 1987- 1.3 um InGaAsP lasers, SMF, 1.7 Gb/s at 50km
• 1989- Erbium doped fiber amplifier
• 1990s- 1.55 um InGaAsP DFB lasers, SMF, 2.5-10 Gb/s at 40km
• 1990s- WDM, 1.55 um InGaAsP DFB lasers, EDFA, SMF, 2.5-10Gb/s at
300-10,000km repeater spacing
• 1 Q 1996- 8 Channel WDM
• 4th Q 1996- 16 Channel WDM
• 1Q 1998- 40 Channel WDM
• 2002- 64 WDM chx 10Gbps over 250,000 km span
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Chapter 1 Introduction
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Increase in Bitrate-Distance product
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Per-Fiber Capacity Trends
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Optical Fiber vs. Twisted-Pair Cable & Coaxial Cable
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Benchmark between Optical Fibers and Twisted-Pair Cable
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Optical Signal Processing (1 of 2)
• With the development of network communication, the transmitted signals
need further processed such as switching, add-drop multiplexing,
- Processing in electronic domain
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Optical Signal Processing (2 of 2)
- Processing in optical domain (discrete component)
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Progress in Lightwave Communication Technology (1 of 5)
• First Generation Fiber Optic Systems
- Purpose: Eliminate repeaters in T-1 systems used in inter-office
trunk lines
- Technology: 0.8 μm GaAs semiconductor lasers, Multimode
silica fibers
- Limitations: Fiber attenuation, Intermodal dispersion
- Deployed since 1974
• Second Generation Fiber Optic Systems
- Opportunity: Development of low-attenuation fiber (removal of
H2O and other impurities), Eliminate repeaters in long-distance
lines
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Progress in Lightwave Communication Technology (2 of 5)
- Technology: 1.3 μm multi-mode semiconductor lasers, Singlemode, low-attenuation silica fibers, DS-3 signal: 28 multiplexed
DS-1 signals carried at 44.736Mbits/s
- Limitation: Fiber attenuation (repeater spacing ≈ 6km)
- Deployed since 1978
• Third Generation Fiber Optic Systems
- Opportunity: Development of erbium-doped fiber amplifiers
- Technology: 1.55 μm single-mode semiconductor lasers, Singlemode, low-attenuation silica fibers, OC-48 signal: 810
multiplexed 64-kb/s voice channels carried at 2.488 Gbits/s
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Progress in Lightwave Communication Technology (3 of 5)
- Limitations: Fiber attenuation (repeater spacing ≈ 40 km), Fiber
dispersion
- Deployed since 1982
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Progress in Lightwave Communication Technology (4 of 5)
• Fourth Generation Fiber Optic Systems
- Opportunity: Deregulation of long-distance market
- Technology: 1.55 μm single-mode, narrow-band semiconductor
lasers, Single-mode, low-attenuation, dipersion-shifted silica
fibers, Wavelength-division multiplexing of 2.488Gb/s or
9.953Gb/s signals
- Limitations: Nonlinear effects limit the following system
parameters (Signal launch power, Propagation distance without
regeneration/reclocking, WDM channel separation, Maximum
number of WDM channels per fiber), Polarization-mode
dispersion limits the following parameters (Propagation distance
without regeneration/reclocking)
- Deployment began in 1994
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Progress in Lightwave Communication Technology (5 of 5)
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Generic Optical Fiber System (1 of 3)
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Generic Optical Fiber System (2 of 3)
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Generic Optical Fiber System (3 of 3)
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Important Communication Systems and Technologies (1 of 3)
• Wide-area networks
- Either government-regulated or in the public network
environment
◦ WANS originated in telephony
- Main technologies: SONET/SDH, ATM, WDM
◦ Voice circuits vs. packets
◦ Non-optical technologies (unless encapsulated in
SONET or ATM): T1/E1/J1, DS-3, Frame
Relay
◦ Standards bodies include ITU-T, IETF, ATM
Forum, Frame Relay Forum, IEEE
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Important Communication Systems and Technologies (2 of 3)
• Metropolitan-area/regional-area networks
- A MAN or RAN covers a North American metropolitan area, or
a small to medium-sized country in Europe or Asia
- Main technologies: SONET, ATM, Gigabit & 10-Gigabit
Ethernet, DWDM
◦ Non-optical technologies: T1, T3, Frame Relay
• Local-area networks
- Main technologies: Ethernet, Fast Ethernet, Gigabit Ethernet
- Currently fiber for backbone, copper for distribution
- Excess capacity enhances performance
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Chapter 1 Introduction
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Important Communication Systems and Technologies (3 of 3)
• Access networks
- The first (or last) network segment between customer premises
and a WAN or MAN
◦ Owned by a Local Exchange Carrier (LEC)
- Broadband digital technologies: HFC, DSL
◦ Ethernet framing vs. ATM
- Twisted pair vs. coaxial cable vs. fiber vs. wireless vs. freespace optics
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Optical “Food Chain”
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Optical Communication Protocol Stack
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Optical Network Architecture (1 of 2)
WDM provides enabling technology for Optical Network Layer: Data format
transparency for multi-service optical layer Optical channel bandwidth management
and high-capacity throughput
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Optical Network Architecture (2 of 2)
Long Haul
Metro
Access
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Traffic Growth and Composition
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DWDM Technology (1 of 2)
∆λ = 25 – 100GHz
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DWDM Technology (2 of 2)
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Evolution of WDM System Capacity
• Repeater spacing for commercial systems
- Long-haul systems - 600 km repeater spacing
- Ultra-long haul systems - 2000 km repeater spacing (Raman +
EDFA amplifiers, forward error correction coding, fast external
modulators)
- Metro systems - 100 km repeater spacing
• State of the art in DWDM
- channel spacing 50 GHz, 200 carriers, 10 Gb/s, repeater
spacing few thousand km
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Global Undersea Fiber systems
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Installed Fiber in US
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Professional Societies and Corporations (1 of 2)
• Optical Society of America (OSA)
- Oldest optics/photonics society in North America
- Covers all fields of optics, from human vision to optical
physics Peer-reviewed journals include Journal of the
Optical Society of America, Applied Optics, Optics Letters,
Journal of Light wave Technology (co-sponsored with
IEEE-LEOS), Journal of Optical Networking, Optics
Express
• IEEE Lasers and Electro-Optics Society (IEEE-LEOS)
- Journal of Quantum Electronics, Photonics Technology
Letters, Journal of Special Topics in Quantum Electronics
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Professional Societies and Corporations (2 of 2)
- Co-sponsors the Optical Fiber Communication Conference
(OFC) and the Conference on Lasers and Electro-Optics (CLEO)
with OSA
• SPIE
- Not-for-profit corporation
- Organizes many conferences and publishes proceedings
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Three Giant Companies (1 of 3)
• LUCENT (www.lucent.com): adding more lanes
Symbol
LU – (S&P 500)
Employees
~ 47,000
HQ
New Jersey, US
CEO
Patricia Russo, 50:
(salary: $14.28mil/yr)
Revenue
FY03: $8.6billion
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Three Giant Companies (2 of 3)
• NORTEL (www.nortelnetworks.com): providing faster transport equipments
Symbol
NT (NYSE)
Employees
39,690
HQ
Ontario, CANADA
CEO
Frank A. Dunn, 49
Salary: $849,000/yr
Revenue
FY03: $9.6bil
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Three Giant Companies (3 of 3)
• CISCO (www.cisco.com): raising the speed limit
Symbol
CSSO (S&P 500, Amex Internet, Nasdaq 100)
Employees
34,466
HQ
San Jose, CA
CEO
John Chambers, 53
Revenue
FY03: $20.40bil
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Questions
?
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