Optical Fibre Communication

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Optical 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

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Revolutions

• How it's going to be affected to the human being?

• Industrial Revolution

• Agricultural Revolution

• Communication Revolution

a.) can talk with the use of latest Technology _at_
any where in the world, _at_ low cost.
b.) can be accepted knowledge _at_ anywhere in the
world. (e- Assessment)
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Explosive Growth of Internet
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WHAT IS COMMUNICATION NETWORK
Local Area Node
Country A
Domestic Transport Network (OF,
IG
Undersea Optical Fiber Networks
International Transport Network
IG
Country B
Both Domestic and International Transport will be
on Optical Fibers. And Switching Nodes will be on
NGN.
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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)

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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

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FTTH, PON(PASSIVE OPTICAL NETWORK)
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Theoretical capacities of other Medias

• CuShort distance could for a 8Mbps
• Similarly
• Microwave radioSTM 16 More than 2.5Gbps
• SatelliteSTM 1 155.52 Mbps
• Coaxial cableApproximately 1.5 Gbps

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Basic Principles
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Principle of step graded index fibers
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Attenuations in fibre
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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.

OUT
IN
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Chromatic Dispersion

• Variation of refractive index with wavelength of
  light
• The 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))

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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

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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-carrierselec
  trons and holesflow 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.

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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.

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Power ratio (DecibeldB)

• 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.

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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. )

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Example 1
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Answer (Example 1)

• Connector loss 81dB 8dB
• Cable loss (4100)/10000.4dB
• System margin 5dB
• Sensitivity -30 dB
• Transmitter Power connector losscable
  losssystem marginsensitivity
• 80.45-30 -16.6dB

Transmitter
Receiver
8 Connectors
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Example 2
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Answer (Example 2)

• Connector loss 21.5dB 3 dB
• Cable loss 0.4dB 50 20 dB
• System margin 8 dB
• Sensitivity -34 dB
• Transmitter Power connector losscable
  losssystem marginsensitivity
• 3208-34 -3 dB
• No of splices 3/ 0.15 20 splices

Transmitter
Receiver
2 Connectors
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Example 3 (a)
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Example 3 (b)
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Example 3 (c)
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Example 3 (d)
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Example 3 (e)
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Example 3 (f)
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Example 3 (g)
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Example 3 (h)
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Optical fibre
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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.

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Overview of WDM
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No of wavelengths ( 24 103 Gb ) / 10 Gb
2400 wavelengths
Future scenarios Theoretical Maximum of an
optical fibre cable
Transponders
?1
488 ns
25 ps
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TDM
Optical Fibre
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?2
2 Mbps
10Gbps
?2399
2399
Only 1 core is needed
2400
?2400
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Further study of optical fibre network
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Optical signal to noise ratio
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ASEAmplified spontaneous emission
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Optical tools for maintanance

• OTDR
• Splicing machine

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(OTDR)
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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.
•  

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SEA-ME-WE 4 Cable System Configuration Diagram
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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