View
219
Download
0
Category
Tags:
Preview:
Citation preview
© N. Ganesan, Ph.D. , All rights reserved.
Chapter
Electronic and Optical Transmission
Chapter Objectives
• Describe the basic transmission features of electronic and optical transmission– Variation in the voltage of digital
signals etc.
• Briefly discuss the electronic-to-optical and optical-to-electronic interfaces
Chapter Modules
• Basics of electronic transmission• Basics of optical transmission• Fiber optic connections
© N. Ganesan, Ph.D. , All rights reserved.
Module
Basics of Electronic Transmission
Simple Digital Encoding of Data
1 0 0 0 0 0 1
Pulse
TIME
Sig
nal
Str
en
gth
Pulse Duration
A -------------> ASCII -----------> 1000001
Transmission of AVoltage
Summary of Digital Electronic Transmission
ABCode and generate
Electronic signalsReceive andDecode electronicSignals
Both points operate under the same rulesand guidelines for effective communication.
Square waves are coded based on voltages to represent either a one and a zero.
An Early Introduction to the Concept of Protocol
• Communication protocol is a set of rules and guidelines for transmission
• A simple protocol that applies to the previous example is as follows:– 0 = 0.05 Volts– 1 = 0.1 Volts– Pulse duration is 1 nanosecond
• In practice, the protocols are much more sophisticated
An Example of a Widely Used Protocol
• TCP/IP– Transmission Control
Protocol/Internet Protocol– De facto protocol of the Internet– TCP/IP is a stack of protocols
• Some examples of protocols in the TCP/IP stack– UDP, SMTP, POP3 etc.
End of Module
© N. Ganesan, Ph.D. , All rights reserved.
Module
Basics of Optical Transmission
Optical Transmission
Optical Transmission
Light Pulse
Pulses of different wave lengths (frequencies) are used for representing 0s and 1s.
Origin Destination
Wave Length
• Wave length is inversely proportional to frequency– Wave length = 1/Frequency
• Higher the frequency, the shorter the wave length
Fiber-Optic Transmission Characteristics
• Signal encoding (0 and 1) can be based on light rays of different wave lengths
• Possible light sources are, for example:– Laser – Light Emitting Diode (LED)
• Conversion from light to electricity– Photo Electric Cell
Characteristics of Optical Transmission in a Fiber
• In general, the laws of physics say that light travels along a straight line
• In optical fibers, however, light travels along the path of the fiber
Example of Path of Propagation of Light Waves in Fiber Cables
Vase Ornament
Light Source
Tips glow
FiberLight travels along thepath of the fiber
Optical Transmission In Fiber
Light bounces and travels along the fiber
Optical Transmission Alternatives
• Multimode Step Index– Lower speed optical transmission
• Multimode Graded Index– Intermediate speeds of transmission
• Single Mode– Higher speed in transmission
Optical Transmission Alternatives Cont.
MultimodeStep
MultimodeGraded
Single Mode
Light PropagationSource: Corning Tutorial
Fiber Properties• Glass (silicon) is used in most
cases as the material for producing fiber strands
• Low cost plastic fibers are also available at present
• However, the connections involving plastic fibers are limited by distance compared to silicon fibers
Rule of Thumb
• Purer the fiber, the smaller the loss in signal strength and hence, further the light travels
Multi-Mode FiberSource: Corning Tutorial
Single Mode FiberSource: Corning Tutorial
Example of Fiber Cables
Fiber Connections
• For full duplex transmission there are two connectors in the case of fiber connections– Transmitting connection is denoted as
TX– Receiving connection is denoted as
RX
End of Module
© N. Ganesan, Ph.D. , All rights reserved.
Module
Fiber Optic Connections
Optical-to-electronic Conversion
Photo-Electric
CellLight Electricity
Optical Signals Electronic Signals
Electronic-to-optical Conversion
Light EmittingDiode (LED)/
LaserLight Electricity
How Fiber Works:Source: Corning Tutorial
Electro-Optical Fiber Interface
Source: Black Box
Example in Extending the Communication Link Between
Two Computers
Computer/Comm.System
A
Computer/Comm.System
B
Fiber Interface
Elect. Elect.Optic.
Typical Use Of Optical Technology
• Extending the distance between two communication points – Line drivers
• Telecommunications– Long distance telephone trunks
• Large-scale network backbones– FDDI
• Internetworking– Connection between switches
Fiber Connection for Extending a T1 Line Connection
1.5 Miles at 256 Kbps and 3 miles at 64 Kbps.
Multimode Fiber cable
Source: Black Box
Fiber Connection for Extending LAN Connection
Up to 31 miles. Speeds from 56-2048 Kbps.Source: Black Box
Fiber Line Driver
Fiber cableport.
Source: Black Box
Fiber Connection Between Switches
FiberConnection
References
• Corning Library• Corning Tutorial
– This can be downloaded and played
• Locally hosted fiber-optic reference on the reference page of this web (Week 6)
• Other useful references can be obtained from the web as well
Key Words
• Pulse duration• Square wave• Protocol• TCP/IP• Wave length• Laser and LED• Photo Electric Cell• Multi-mode and single mode fiber
Key Words (Continued)
• Fiber transmission advantages• ST and SC connections• RX and TX• Media interface• Fiber usage
– Telecommunications, campus backbone, FDDI and Internetworking
End of Module
End of Chapter
End of ModuleEnd of ModuleEND OF CHAPTER END OF CHAPTER
Recommended