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Lecture 1: Introduction 朱祖勍1
Optical Communications and Networking
朱祖勍
Sept. 4, 2017
Lecture 1: Introduction 朱祖勍2
Outline
Basic Course Information
Review of Basic Concepts
Optical Communications
Lecture 1: Introduction 朱祖勍3
Basic Course Information
Course Schedule:09/04/2017 – 12/11/2017`, 12 Lectures + Final10/02 is a national holiday (No Lecture)Travel on 09/18 (No Lecture)Monday, 15:55 – 17:55 pm2.5 Credits
Scoring SystemIn-Class Quiz, 40% (2 times, random time)Final on 12/11, 60% (open-book exam)
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Basic Course InformationTextbook:
《光网络-光纤通信技术与系统》上卷(《OpticalNetworks: A Practical Perspective, SecondEdition》) , by Rajiv Ramaswami and Kumar N.Sivarajan, 中译本,机械工业出版社, ISBN 7-111-14228-4
Lecture Notes: http://www.zuqingzhu.info/OCN.html
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Basic Course InformationRelated Courses:
《现代通信光电子学》(Recommend to Take)
《通信网络理论基础》(Recommend to Take)
《光波导技术基础》(Can Take as Reference)
My Email: zqzhu@ustc.edu.cn
Lecture 1: Introduction 朱祖勍6
Outline
Basic Course Information
Review of Basic Concepts
Optical Communications
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What is Digital Communication?
TX RX
Communication: Exchange of Information
Four Key Elements:Transmitter, 信源
Receiver, 信宿
Channel, 信道
Carrier, 载波
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How to Perform Digital Communication?
TX RX
Encoding, 编码(信息 => 比特流):Source Coding: 数据压缩, 降低冗余度, 例如:霍夫曼编码
Channel Coding : 差错纠正, 增加冗余度, 例如:汉明编码
Encoding + Modulation Demodulation + Decoding
平均码长: 1.85 bits/symbol 4 bits => 7 bits, 一位纠错
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How to Perform Digital Communication?
TX RX
Modulation, 调制(比特流 => 波形):Amplitude Modulation: ASK
Phase Modulation: PSK, DPSK, QPSK
Frequency Modulation: FSK
Combinational Modulation: 16QAM, 64QAM, …
Carriers, 载波(声、光、电)
Encoding + Modulation Demodulation + Decoding
星座图: 8-PSK
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Communication Channels
Open Channel: Atmosphere, Deep SpaceAgile, Cheap, Insecure, Unreliable, lots of interference
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Communication Channels
Guided Channel: Optical Fiber, Coaxial Cable, …Secure, reliable, less interference, expensive
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Multiple Access: Multiplexing
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Multiple Access: Multiplexing
TX RX
Multiplexing, 共享信道:Time Division Multiplexing (TDM)
Frequency Division Multiplexing (FDM)
Wavelength Division Multiplexing (WDM)
Code Division Multiplexing (CDM)
TX RX
TDM
FDM
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Wavelength Division Multiplexing (WDM)
WDM is FDMWavelength/Frequency => Color
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Wavelength Division Multiplexing (WDM)
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What is a Telecommunication Network?
Definition: a collection of terminal nodes, links and anyintermediate nodes that are connected so as to enabletelecommunication between the terminals.
Mathematically: G(V, E), V is the set of nodes, E is the set oflinks
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Telecommunication Networks
In terms of clients:Private: Enterprise Networks …
Public: Campus Networks …
In terms of geographic coverage:Long-haul: Core Networks
Wide-area: Metro Networks
Local-area: Access Networks
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Telecom Network Infrastructure
Core Network
Metro Networks
Access Networks
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Telecom Network Infrastructure
Core NetworksCoverage: Several hundred to thousands ofkilometersTopology: MeshSpeed and Reliability are important
Metro NetworksCoverage: A few hundred kilometersTopology: Ring or MeshSpeed is important
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Access NetworksCoverage: Tens of kilometersTopology: Ring or StarCost is important
Telecom Network Infrastructure
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Fiber-Optic Networks
An Optical Fiber Junction Box
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Fiber-Optic NetworksMultiple Planes
Control Plane: carrying control information, i.e., signaling
Management Plane: carrying the operations andadministration traffic for network management
Data Plane: carrying the networker’s users traffic
Layered Structure
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Optical Network Topology –Bus
Single-Hop Network
Broadcast and Select
Access Networks
Simple, Low cost, Scalable
Not Reliable
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Optical Network Topology –Star
Central Hub Acts as a Repeater
Access Networks
Simple, Low cost, Scalable
Not Reliable
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Optical Network Topology –Ring
Multi-Hop Network
Bi-directional Routing
Metro/Access Networks
Simple, Scalable
Can be Restored from Single-Link/Node Failure
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Optical Network Topology –Tree
Multi-Hop Network
Metro/Access Networks
Simple, Scalable
Not Reliable
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Multi-Hop Network
Matrix Routing
Core Networks
Complicated, Reliable, Not Scalable1
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Optical Network Topology –Mesh
Fully Connected
Partially Connected
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Communication in a Telecom Network
Routing:Find a proper route between the source anddestination nodes
Forwarding:Send data to the destination following a pre-determined route
Switching:Setup a communication session.
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Communication in a Telecom Network
Setup an end-to-end communicationsession.
Establish communication channelbetween the transmitter and receiver.
Adjust the working status of eachintermediate node if there is any.
Switching: Circuit Switching, Packet Switching
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Switching in NetworksCircuit Switching
End-to-end communication is carried by circuits
Reserve bandwidth b on each link along therouting path p
Data is forwarded along in the circuit pipeline
Packet SwitchingEnd-to-end communication is carried by packets
Each packet is labeled with its destination address
Each packet is forwarded based on its destinationaddress
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Circuit Switching
SwitchFabricDeMux Mux
Crossconnect
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Circuit Switching
Connection-Oriented Services
Resource Reservation
FDM, TDM, …
Guaranteed Quality-of-Service (QoS)
Expensive but Reliable
Examples: Telephone Networks
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Packet Switching
Router
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Packet SwitchingConnectionless Services
Resource Allocation
Statistical Time-Division Multiplexing
Best-Effort
Cheap but Unreliable
Examples: IP Data Networks
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Routing in a NetworkSingle-path Routing:
Request is carried with a single routing path fromthe source to the destination.
Shortest path routing: Dijkstra Algorithm
Weighted routing
Multi-path Routing:Request is carried with multiple routing paths fromthe source to the destination.
K-shortest path search algorithm
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Original TopologyPath 1: 1 → 2 → 4 → 6
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Topology after 1st IterationPath 1: 1 → 2 → 4 → 6Path 2: 1 → 3 → 5 → 6
Topology after 2nd IterationPath 1: 1 → 2 → 4 → 6Path 2: 1 → 3 → 5 → 6
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Lecture 1: Introduction 朱祖勍37
Outline
Basic Course Information
Review of Basic Concepts
Optical Communications
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History of Optical Communications
Time: 1000 B.C.
Data-rate: 1 bit / 24 hours
Manually operated
Free-space transmission
Applications:Defense
Entertainment(烽火戏诸侯)
Earliest Optical Communications
烽火台
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History of Optical Communications
Time: 2010 A.D.
Data-rate: 322 Tb/s (1 Tb = 1012 bits)
Electrically powered
Guided transmission in Fibers
Wavelength-Division Multiplexing
Applications:Telecommunication Core Router
Modern Optical Communications
Cisco CRS-3 Router
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What is Optical Communication?
TX RX
TransmitterElectrical-to-Optical (E/O) ConverterLight Sources: Laser, LED, …E/O Modulator: Direct Modulators, External Modulators, …
Light Source
E/O Modulator
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What is Optical Communication?
TX RX
ChannelOpen Channels (Wireless Optical Communications):Atmosphere, free-space …Guided Channel (Fiber Optical Communications): Optical Fiber
Or
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What is Optical Communication?
TX RX
ReceiverOptical-to-Electrical (O/E) ConverterE/O Converter: Photo-detector, …
O/E Converter
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What is Optical Communication?
TX RX
CarrierOptical Waves/PhotonsSpectrum Range: ~1012 Hz (Infrared) - ~1016 Hz(Ultraviolet)Wavelength Range: ~10-8 m - ~10-5 mRelationship between Frequency and Wavelength:
λcf =
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