© 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 Pulse TIME Signal Strength Pulse Duration A > ASCII > Transmission of A Voltage

Summary of Digital Electronic Transmission A B Code and generate Electronic signals Receive and Decode electronic Signals Both points operate under the same rules and 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.

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© N. Ganesan, Ph.D., All rights reserved. Module Basics of 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 Fiber Light travels along the path 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. Multimode Step Multimode Graded Single Mode

Light Propagation Source: 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 Fiber Source: Corning Tutorial

Single Mode Fiber Source: 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

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© N. Ganesan, Ph.D., All rights reserved. Module Fiber Optic Connections

Optical-to-electronic Conversion Photo- Electric Cell Light Electricity Optical SignalsElectronic Signals

Electronic-to-optical Conversion Light Emitting Diode (LED)/ Laser Light 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. 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 Kbps. Source: Black Box

Fiber Line Driver Fiber cable port. Source: Black Box

Fiber Connection Between Switches Fiber Connection

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

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