Transcript Slides for Lec.1.

Introduction to Optical Networks
Ajmal Muhammad, Robert Forchheimer
Information Coding Group
ISY Department
Communication Systems
Basic Blocks
• Three basic components
– Source and Transmitter
– Destinations and Receiver
– Communication channel
(medium)
• Communication channel
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Wired
Wireless
Glass
Water and or materials
Coverage and Topology
• Coverage (public
network)
– LAN
– MAN
– WAN
• Topology
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Bus
Ring
Mesh
Star
Changing Service Landscape
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Network characteristics
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Full redundancy
Fast restoration
High availability (99.999 %)
Low latency
High bandwidth
Dynamic allocation and high bandwidth efficiency
Support various services
More providers and equipment builders (due to
deregulation of the telecom industry)
Providers are expected to provide more services at
higher capacity at lower prices!
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A positive feedback business model!
Need for high capacity network
More users
Service Types
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Two basic service types (switching technologies)
 Connection-oriented
 Connectionless
Connection-oriented
 Based on circuit switching (setup, connect, tear-down)
 Example: Public Switching Telephone Network (PSTN)
 Originally only supported voice
 Not good for bursty traffic
Connectionless
 Based on sending datagrams
 Examples: Packet, message, burst switching
 Improves bandwidth and network utilization
Optical Fiber
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Allowing transmission of information using light
Advantages
• High bandwidth
• Low noise
• Low interference (electromagnetic)
Optical fiber installation
• Measured in fiber sheath-km (or fiber km)
• Example: we install 3 fiber cable within 10 km
long route; each fiber cable has 20 fibers  we
have 600 fiber km
• Currently more than 1.5 billion kilometers of
optical fiber is deployed around the world [1]
• The circumference of earth is 40,000 Km!
[1] http://www.corning.com/opticalfiber/innovation/futureoffiber/index.aspx
Multimedia over Fiber
Fiber carries various media
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Voice (SONET/Telephony) - The largest
traffic
Video (TV) over
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Hybrid Fiber Coaxial (HFC) or
Fiber-Twisted Pair/Digital Subscriber Loops
(DSL)
‘Triple Play’
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Data – Internet traffic
The Information Revolution would not have
happened without the Optical Fiber
Network Architecture
Elements of a Fiber Optic Link
Elements of OPTICOM System
• The Fiber – that carries the light
– Single Mode Fiber (only one EM mode exists), offers
the highest bit rate, most widely used
– Multi Mode Fiber (multiple EM modes exist), hence
higher dispersion (due to multiple modes) cheaper
than SMF, used in local area networks
– Step Index Fiber – two distinct refractive indices
– Graded Index Fiber – gradual change in refractive
index
Elements of OPTICOM System
• Optical Transmitter converts the electrical information
to optical format (E/O)
– Light Emitting Diode (LED): cheap, robust and
used with MMF in short range applications
• Surface emitting and edge emitting LED
– LASER Diode: high performance and more power,
used with SMF in high speed links
• Distributed Feedback (DFB) Laser – high
performance single mode laser
• Fabry-Perot (FP) lasers – low performance
multimode laser
Elements of OPTICOM System
• Optical Receiver converts the optical signal
into appropriate electrical format (E/O)
– PIN Photo Diode: Low performance, no
internal gain, low cost, widely used
– Avalanche Photo Diode (APD): High
performance with internal (avalanche) gain
• Repeater: receives weak light signal, cleansup, amplifies and retransmits (O/E/O)
• Optical Amplifier: Amplifies light in fiber
without O/E/O
Development of Optical Networks
• First-generation optical networks
– Transmission in the optical domain (to provide capacity)
– Example: SONET network (Synchronous Optical
Network)
• Second-generation optical networks
– Wavelength routed network (Optical Circuit Switching
OCS)
– More functionality in the optical domain (optical
networking)
Some of the routing, switching and intelligence is moving
into the optical domain
• Third-generation: optical networks (?)
Optical Networks
Transmission Window
Transmission Bands &
Capacities
Shannon theorem
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WDM Grids ITU-T G.694.1
Overview of WDM
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A characteristic of WDM is that the discrete
wavelengths form an orthogonal set of carriers that
can be separated, routed, and switched without
interfering with each other.
WDM networks require a variety of passive and active
devices to combine, distribute, isolate, and amplify
optical power at different wavelengths.
Optical Amplifier and EDFA
Inside an EDFA
Layered Model for Today’s
Networks
Current protocol stacks
Current Multiple Protocol
Stacks
22% bandwidth used for protocol overhead
Towards a two Layer Network
Architecture
A perfect combination
Flexibility
Capacity
Less latency
Higher bandwidth utilization
The Optical Layer
The optical layer provides lightpath service to it’s client layers
Lightpath: optical connection
An optical channel trail between two nodes that carries
the entire traffic within a wavelength
Client layers
Optical Layer Service: Providing
Lightpaths
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Bandwidth
Adaptation to and from client layers
Performance
 Bit error rate (BER)
Optical signal quality (OSNR, impairments)
 Jitter
 Maximum delay
Protection
Fault management
Layers within the Optical Layer
Optical Transport Network protocol layers
 Optical channel sublayer (OCh)
 Optical multiplex section (OMS)
 Optical transmission section (OTS)
 Physical media layer: fiber-type specification
Simplified view of an Optical
Connection