Download Electronic and Optical Transmission

Chapter
Electronic and Optical
Transmission
© N. Ganesan, Ph.D. , All rights reserved.
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
Module
Basics of Electronic Transmission
© N. Ganesan, Ph.D. , All rights reserved.
Simple Digital Encoding of Data
Voltage
1 0 0 0 0 0 1
Transmission of A
Pulse
Pulse Duration
TIME
A -------------> ASCII -----------> 1000001
Summary of Digital Electronic
Transmission
Square waves are coded based on voltages to represent
either a one and a zero.
A
Code and generate
Electronic signals
B
Receive and
Decode electronic
Signals
Both points operate under the same rules
and guidelines for effective communication.
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
Module
Basics of Optical Transmission
© N. Ganesan, Ph.D. , All rights reserved.
Optical Transmission
Optical Transmission
Light Pulse
Origin
Destination
Pulses of different wave lengths (frequencies) are used
for representing 0s and 1s.
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
Tips glow
Light travels along the
path of the fiber
Fiber
Vase Ornament
Light Source
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
End of Module
Module
Fiber Optic Connections
© N. Ganesan, Ph.D. , All rights reserved.
Optical-to-electronic Conversion
Light
Optical Signals
PhotoElectric
Cell
Electricity
Electronic Signals
Electronic-to-optical Conversion
Light
Light Emitting
Diode (LED)/
Laser
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. Elect.
System
A
Optic.
Fiber Interface
Elect.
Computer/
Comm.
System
B
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
Multimode Fiber cable
1.5 Miles at 256 Kbps and 3 miles at 64 Kbps.
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 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
End of Module
End of Chapter
End of Module
END OF CHAPTER