Electronic and Optcal Transmission

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N. Ganesan, Ph.D. , All rights reserved.

Chapter

Electronic and OpticalTransmission


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Chapter Objectives

Describe the basic transmission featuresof electronic and optical transmission

Variation in the voltage of digital signalsetc.

Briefly discuss the electronic-to-optical

and optical-to-electronic interfaces


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Chapter Modules

Basics of electronic transmission

Basics of optical transmission

Fiber optic connections


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Module

Basics of Electronic Transmission


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Simple Digital Encoding of Data

1 0 0 0 0 0 1

Pulse

TIMEPulse Duration

A -------------> ASCII -----------> 1000001

Transmission of AVoltage


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Summary of Digital Electronic

Transmission

A

BCode and generateElectronic signals

Receive andDecode electronic

Signals

Both points operate under the same rulesand guidelines for effective communication.

Square waves are coded based on voltages to representeither a one and a zero.


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An Early Introduction to the

Concept of Protocol

Communication protocol is a set ofrules and guidelines for transmission

A simple protocol that applies to theprevious 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


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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 theTCP/IP stack UDP, SMTP, POP3 etc.


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End of Module


10/42 N. Ganesan, Ph.D. , All rights reserved.

Module

Basics of Optical Transmission


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Optical Transmission


Light Pulse

Pulses of different wave lengths (frequencies) are used

for representing 0s and 1s.

Origin Destination


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Wave Length

Wave length is inversely proportionalto frequency

Wave length = 1/Frequency

Higher the frequency, the shorter thewave length


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Fiber-Optic Transmission

Characteristics

Signal encoding (0 and 1) can be basedon 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


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Characteristics of Optical

Transmission in a Fiber

In general, the laws of physics say thatlight travels along a straight line

In optical fibers, however, light travelsalong the path of the fiber


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Example of Path of Propagation

of Light Waves in Fiber Cables

Vase Ornament

Light Source

Tips glow

FiberLight travels along thepath of the fiber


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Optical Transmission In Fiber

Light bounces and travels along the fiber


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Alternatives

Multimode Step Index

Lower speed optical transmission

Multimode Graded Index

Intermediate speeds of transmission

Single Mode

Higher speed in transmission


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Alternatives Cont.

MultimodeStep

MultimodeGraded

Single Mode


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Light Propagation

Source: Corning Tutorial


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Fiber Properties

Glass (silicon) is used in most cases asthe 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


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Rule of Thumb

Purer the fiber, the smaller the loss insignal strength and hence, further the

light travels


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Multi-Mode Fiber



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Single Mode Fiber



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Example of Fiber Cables


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Fiber Connections

For full duplex transmission there aretwo connectors in the case of fiber

connections Transmitting connection is denoted as TX

Receiving connection is denoted as RX


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End of Module


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Module

Fiber Optic Connections


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Optical-to-electronic Conversion

Photo-Electric

CellLight Electricity

Optical Signals Electronic Signals


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Electronic-to-optical Conversion

Light EmittingDiode (LED)/

LaserLight Electricity


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Electro-Optical Fiber Interface

Source: Black Box

Example in Extending the


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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


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Typical Use Of Optical

Technology

Extending the distance between twocommunication points

Line drivers

Telecommunications Long distance telephone trunks

Large-scale network backbones

FDDI Internetworking

Connection between switches


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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


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Fiber Connection for Extending

LAN Connection

Up to 31 miles. Speeds from 56-2048 Kbps.

Source: Black Box


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Fiber Line Driver

Fiber cableport.

Source: Black Box


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Fiber Connection Between Switches

Fiber

Connection


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References

Corning Library

Corning Tutorial

This can be downloaded and played

Locally hosted fiber-optic reference onthe reference page of this web (Week 6)

Other useful references can be obtainedfrom the web as well
http://www.corningfiber.com/library/index.htmhttp://www.corningfiber.com/library/corning.exehttp://www.corningfiber.com/library/corning.exehttp://www.corningfiber.com/library/index.htm


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Key Words

Pulse duration

Square wave

Protocol TCP/IP

Wave length

Laser and LED Photo Electric Cell

Multi-mode and single mode fiber


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Key Words (Continued)

Fiber transmission advantages

ST and SC connections

RX and TX

Media interface

Fiber usage Telecommunications, campus backbone,

FDDI and Internetworking


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End of Module

End of Chapter


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End of ModuleEND OF CHAPTER

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Electronic and Optcal Transmission