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Chapter 11
Optical Networks
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Objectives
Define Optical Networking
Define the components of a fiber optic system
Define characteristics of fiber optic cable
Describe Single mode and multi mode fiber
Introduce concepts of wave division multiplexing
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Optical Networking What is it?
In its simplest form, optical networking is
when the data transport is carried via light
over fiber optic cable (as opposed toelectrical impulses over copper cable)
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Components of a Fiber Optic
System
1. Transmitter - takes information such as voice, data, video, encodedinto electrical signals into light signals and sends it down fiber opticcable
2. Fiber optic cable - medium which the signal is carried on
3. Receiver- accepts light signal and converts it back into electricalsignals
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Fiber Optic Cable
Core - central region of optical fiberwhich light travels through andinformation is carried.
Cladding - Made of glass with lowerrefractive index than the core.Causes light in the core to reflect offof the cladding and stay containedin the core
Coating - outer protective coating thatprotects the fiber from damage andmoisture
Reference: Compared
to human hair
70 um!
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Fiber Optic Cable (cont)
Fiber-optic cable (fiber)
Composed of one (or several) glass or plastic fibers at its center(core)
Data transmission Pulsing light sent from laser
LED (light-emitting diode) through central fibers
Cladding
Layer of glass or plastic surrounding fibers
Different density from glass or plastic in strands
Reflects light back to core
Allows fiber to bend
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Fiber Optic Cable (cont)
Plastic buffer
Outside cladding
Protects cladding and core
Opaque absorbs any escaping light
Core and Cladding manufactured as a single piece of silica and cant
be separated from each other
Different varieties
Based on intended use and manufacturerTwo categories
Single-mode
Multimode
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Transmission over single-mode fiber-optic cable
SMF (single mode fiber)
Uses narrow core (< 10 microns in diameter)
Smaller core than MMF
Laser generated light travels over one path
Little reflection
Light does not disperse
Accommodates
Highest bandwidths, longest distances
Connects carriers two facilities
Costs prohibit typical LANs, WANs use
$$$ than MMF
Jumpers are yellow
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MMF (multimode fiber)
Allows more than 1 mode of light
Uses core with larger diameter than single-mode fiber
Common size: 62.5 microns
Laser or LED generated light pulses travel at different angles
Common uses Cables connecting router to a switch
Cables connecting server on network backbone
Transmission over multimode fiber-optic cable
Jumpers are orange
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MMF(cont)
Benefits
Extremely high throughput
Very high resistance to noise
Excellent security
Ability to carry signals for much longer distances before requiring repeatersthan copper cable
Industry standard for high-speed networking
Drawback
More expensive than twisted pair cable
Requires special equipment to splice
Throughput
Reliable transmission rates
Can reach 100 gigabits (or 100,000 megabits) per second per channel
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MMF (cont)
Cost Most expensive transmission medium
Connectors ST (straight tip)
SC (subscriber connector or standard connector) LC (local connector)
MT-RJ (mechanical transfer registered jack)
Noise immunity
Unaffected by EMI
Size and scalability Segment lengths vary
150 to 40,000 meters
Due primarily to optical loss
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Connectors
ST Connector SC Connector
MultimodeSingle-Mode
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Transmitters
Accept coded electronic signals, process them to light signals andthen send them off onto the fiber cable
Light signals generated by LEDs or lasers
Different light sources have different wavelengths (lambda)
Transmitter designed to emit 850, 1310 or 1550 nanometers
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Receivers
Other end of the cable receives the incoming light and convertsback into electrical signal
Uses photo detector
Signal quality system performance characteristics
Bit error rates number of errors that occurs betweentransmitter and receiver
Saturation - maximum received power that can be receivedbefore distorting of signal and causing poor performance
Sensitivity - minimum power that must be received on anincoming signal
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Factors that affect fiber optics
Attenuation - loss of optical power as light travels down afiber resulting in a dim signal. Measured in decibels. Canbe caused intrinsically (such as inside the fiber itself due
to the glass in the manufacturing process), or extrinsic(such as caused by outside factors like bending the fiber)
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Factors that affect fiber optics
Saturation - signal is too bright causing receiver not toreceive the signal properly
Dispersion - spreading of light as it travels down the fiberoptic cable and causing the signal to overlap and besmeared making the receiving unable to determine distinct0 and 1s.
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Wave Division Multiplexing
A method for multiplexing multiple optical carrier signals on asingle fiber by using lasers that emit different wavelengths(colors) to carry different signals
2 types Coarse WDM
Dense WDM
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Comparing DWDM and CWDM
http://www.ciena.com/files/Optical_Networking_for_Dummies.pdf
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Comparing DWDM and CWDM (cont)
CWDM and DWDM uses different technologies with differentproperties
CWDM channels are different than DWDM channel
CWDM is lower capacity and lower cost than DWDM
CWDM is used for short range communication (50-80km)
DWDM is used for long haul
CWDM has fewer channels
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Typical WDM Scenarios
http://www.ciena.com/files/Optical_Networking_for_Dummies.pdf
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References
Corning Fiber 101Tutorialhttp://media.corning.com/flash/opticalfiber/2008/fiber101/fiber101.html
Sura Optical Networking Cookbookhttp://www.sura.org/info_tech/opcook/opcook.pdf
Ciena Optical Networking for Dummieshttp://www.ciena.com/files/Optical_Networking_for_Dummies.pdf
Dean, Tamara. Network+ Guide to Networks
http://www.greenitcenter.org/http://media.corning.com/flash/opticalfiber/2008/fiber101/fiber101.htmlhttp://www.sura.org/info_tech/opcook/opcook.pdfhttp://www.ciena.com/files/Optical_Networking_for_Dummies.pdfhttp://www.ciena.com/files/Optical_Networking_for_Dummies.pdfhttp://www.sura.org/info_tech/opcook/opcook.pdfhttp://media.corning.com/flash/opticalfiber/2008/fiber101/fiber101.htmlhttp://www.greenitcenter.org/7/27/2019 2010 CT - Ch 11 PP - Introduction to Fiber Optic Networks.ppt
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Credits
Diagrams: Corning online tutorial
Networking for Dummies
Karen Cheng
Photo: Pete Brierley
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This material is based upon work supported by the National Science Foundation under
Grant No. 0402356. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the
author(s) and do not necessarily reflect the views of the National Science Foundation
Questions?
Feel free to contact the creator of this material
Karen Cheng, Associate Professor, Collin College
kcheng@collin.edu
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