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Optical Fibre CommunicationOptical Fibre Communication• Lecture delivered by Christie Alwis• 2009 faculty of Applied Science for computer science , and physics special
students.• University of Sabaragamuwa , Belihuloya.• For more details on this lecture, please visit
www.christiealwis.com
Revolutions
How it's going to be affected to the human being?
1. Agricultural Revolution
2. Industrial Revolution
3. Communication Revolution
a.) can talk with the use of latest Technology @ any where in the world, @ low cost.
b.) can be accepted knowledge @ anywhere in the world. (e- Assessment)
EXPLOSIVE GROWTH OF INTERNET
WHAT IS COMMUNICATION NETWORK
Undersea Optical Fiber Networks
Country A
Country B
Domestic Transport Network (OF,
International Transport Network
IG
IG
Local Area Node
Both Domestic and International Transport will be on Optical Fibers. And Switching Nodes will be on NGN.
BASIC COMPONENTS OF COMMUNICATION NETWORKS
• Following 8 major components can be identified– Geographical Location & Terminal – Access Networks– Local Exchange– Domestic Transport Network– International Exchange– International Transport Network– Other Country International Exchange– Other Country Domestic Network (With the similar components
as above)
DEVELOPMENT OF ACCESS NETWORK
• Access Network is developed to accommodate integrated services such as Internet, IPTV, Data with Voice
• Radio Options: 3G, EvDO, WiMAX• xDSL, PON, and PLC
Power
TV
Telephone ?
FTTH, PON(PASSIVE OPTICAL NETWORK)
Theoretical capacities of other Medias
• Cu=Short distance could for a 8Mbps
Similarly :• Microwave radio=STM 16 =More than
2.5Gbps• Satellite=STM 1= 155.52 Mbps• Coaxial cable=Approximately 1.5 Gbps
Basic Principles
Principle of step & graded index fibers
Attenuations in fibre
Basic principle of dispersion• Dispersion is a little complex than attenuation • Dispersion is a process whereby optical pulses are widened as they travel along an
optical fibre. It is caused by the different wavelength components of a light signal of finite spectral width traveling down the fiber at different velocities.The effect is a pulse at the terminating end of a fibre that is a wider than the original pulse that was transmitted.If the amount if widening is excessive, the individual pulses will not be distinguishable by the receiver.
INOUT
Chromatic Dispersion
Variation of refractive index with wavelength of lightThe two main underlying mechanisms, material dispersion and
waveguide dispersion, naturally cancel one another, giving a zero dispersion point 0
Control of the refractive index profile can place 0 anywhere in the 1300/1550nm wavelength range
The fibre characteristics are controlled by careful design of the chemical composition (doping) of the glass used
Dispersion is quoted in terms of the dispersion parameter ‘D’ with units ps/(nm.km)
An indication of the pulse broadening is given by: (D * (spectral width of the optical source) *(link distance))
Slide 15
Optical transmission system concepts
The basic components– A serial bit stream in electrical form is presented to a modulator, which encodes the data appropriately for fibre transmission
Basic Concept of LED• Like a normal diode, the LED consists of a chip
of semiconducting material impregnated, or doped, with impurities to create a p-n junction. As in other diodes, current flows easily from the p-side, or anode, to the n-side, or cathode, but not in the reverse direction. Charge-carriers—electrons and holes—flow into the junction from electrodes with different voltages. When an electron meets a hole, it falls into a lower energy level, and releases energy in the form of a photon.
Contd….• The wavelength of the light emitted, and
therefore its color, depends on the band gap energy of the materials forming the p-n junction. In silicon or germanium diodes, the electrons and holes recombine by a non-radiative transition which produces no optical emission, because these are indirect band gap materials. The materials used for the LED have a direct band gap with energies corresponding to near-infrared, visible or near-ultraviolet light.
Power ratio (Decibel;dB)
• The decibel (dB) is a logarithmic unit of measurement that expresses the magnitude of a physical quantity (usually power or intensity) relative to a specified or implied reference level. Since it expresses a ratio of two quantities with the same unit, it is a dimensionless unit.
Examples • To calculate the ratio of 1 kW (one kilowatt, or 1000 watts) to 1 W in
decibels, use the formula
• Similarly for amplitude ,current or voltage, (power is proportional to the square of the above 3 quantities. )
Example 1
Answer (Example 1)
• Connector loss= 8*1dB= 8dB• Cable loss= (4*100)/1000=0.4dB• System margin = 5dB• Sensitivity= -30 dB • Transmitter Power = connector loss+cable
loss+system margin+sensitivity • = 8+0.4+5-30= -16.6dB
Transmitter Receiver8 Connectors
Example 2
Answer (Example 2)
• Connector loss= 2*1.5dB = 3 dB• Cable loss= 0.4dB * 50 = 20 dB• System margin = 8 dB• Sensitivity= -34 dB • Transmitter Power = connector loss+cable
loss+system margin+sensitivity • = 3+20+8-34= -3 dB• No: of splices= 3/ 0.15 = 20 splices
Transmitter Receiver2 Connectors
Example 3 (a)
Example 3 (b)
Example 3 (c)
Example 3 (d)
Example 3 (e)
Example 3 (f)
Example 3 (g)
Example 3 (h)
Optical fibre
C=fλ
C= 3* 108 m/s
Future of optical fibre
The following 2 major factors plays a vital role in designing the maximum capacity of an optical fibre
• How far the digital multiplexing can be achieved•As at present , 488ns micro information of a bit pertaining to 2Mbps pcm stream will be shrinked to 25ps when it goes through stm 64 (10Gbps).If the technology improves to shrink less than 25ps , then the no of bits in the higher order pcm will be more than 10Gbps.•To transmit 10Gbps , the bandwidth required in the optical fibre is around 0.078ns = 78ps ( for 1 wavelength)•If the available bandwidth in the optical fibre is 200ns , the no; of wavelengths that can be produced is around 2400 , which will result in producing a total of 24Tbps.•Hence both time division multiplexing and dense wave division multiplexing can further improve the traffic carrying capacity of an optical fibre up to a total of 24Tbps.
46
Overview of WDMDigital Transceiver
Digital Transceiver
Digital Transceiver
Digital Transceiver
Digital Transceiver
Digital Transceiver
Digital Transceiver
Digital Transceiver
Single Pair of Fibers
Single Pair of Fibers
Single Pair of Fibers
Single Pair of Fibers
Digital Transceiver
Digital Transceiver
Digital Transceiver
Digital Transceiver
Digital Transceiver
Digital Transceiver
Digital Transceiver
Digital Transceiver
WDM MUX WDM MUX
Single Pair of Fibers
Traditional Digital Fiber Optic Transport
Digital Fiber Optic Transport using WDM
2 Mbps
488 ns
TDM
25 ps
10Gbps
1
2
2399
2400
Transponders
Optical Fibre
No of wavelengths = ( 24 * 103 Gb ) / 10 Gb = 2400 wavelengths
Future scenariosTheoretical Maximum of an optical fibre cable
λ1
λ2
λ2399
λ2400
Only 1 core is needed
Further study of optical fibre network
Optical signal to noise ratio
ASE=Amplified spontaneous emission
Optical tools for maintanance
• OTDR• Splicing machine
(OTDR)
Fusion splicing • It is the process of fusing or welding two fibers together usually by an
electric arc. Fusion splicing is the most widely used method of splicing as it provides for the lowest loss and least reflectance, as well as providing the strongest and most reliable joint between two fibers.
• Virtually all singlemode splices are fusion.• Fusion splicing may be done one fiber at a time or a complete fiber ribbon
from ribbon cable at one time. First we'll look at single fiber splicing and then ribbon splicing.
•
SEA-ME-WE 4 Cable System Configuration Diagram
Happy Memories• Thank You!, Special thanks to Dr. Udawatte.• Wish you an enjoyable stay in your university• Situated in a lovely environment• Christie Alwis• B.Sc (Eng) Hons, MIET (Lond), C.Eng Lond,
FIESL (SL)• Former chief network officer in SLT • Visit www.christiealwis.com under
sabaragamuwa optical fibre 2009