A System View of Optical Fiber Communication prt'2

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A System View of Optical Fiber Communication prt.2

• AbdulRahman AlKhayyat
• 223218
• Mohamed Felimban
• 224304

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OUTLINE

• The Fiber Optic Data Communication System
• Components of the Transmission System
• Transmitters
• Receivers
• Transmission Medium
• Performance
• Attenuation
• Interference
• Conclusion

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I. The Fiber Optic Data Communication System

• Fiber Optic communication systems generally
  include
• A Transmitter
• Transmission Medium including amplifiers and
  repeaters
• A Receiver

A model of this System is shown in the figure The
illustration indicates the Source-User pair,
Transmitter Receiver It also clearly shows the
Transmission Medium.
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II. Components of the Transmission System

• Transmitter to convert an electrical signal into
  an optical signal
• serves two functions
• A light emitter
• works as a source of the light coupled into the
  fiber optic cable
• A regulator
• to modulate this light to represent the binary
  data it receive

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II.1. Transmitters Optical Source Component

• There are some requirements for the transmitter
  that should be met
• physical dimensions must be compatible with size
  of the fiber optic being used
• emit light in a cone within cross sectional
  diameter
• optical source must be able to generate enough
  power
• desired BER should be met
• high efficiency in coupling the light into the
  fiber optic cable
• sufficient linearity
• to prevent the generation of harmonics
  inter-modulation distortion
• if such interference is generated it is extremely
  difficult to remove
• this would cancel the interference resistance
  benefits of the fiber optic cable
• Should be easily modulated with an electrical
  signal capable of high-speed modulation
• The usual requirements of small size, low weight,
  low cost and high reliability

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II.1. Transmitters contd

• Types of Diodes that can be used as an optical
  source of the Transmitter
• laser diode (LD)
• light emitting diode (LED)
• LD's advantages over LED's
• can be modulated at very high speeds
• produce greater optical power
• higher coupling efficiency
• to the fiber optic cable

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II.1. Transmitters contd

• LED's advantages over LD's
• higher reliability
• better linearity
• lower cost
• LED and laser diodes P-I
  characteristics

Verschiedene LEDs
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II. Components of the Transmission System

• Receivers to recover the signal as an electrical
  signal
• serves two functions
• A sensor
• to detect the light coupled out of the fiber
  optic cable then convert the light into an
  electrical signal
• A demodulator
• demodulate this light determine the identity of
  the binary data that it represents

Indoor Outdoor Receivers
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II.2. Receivers contd
Receiver sensitivities for BER 10-9, with
different devices

• receiver performance
• is generally characterized
• by a parameter called
• the Sensitivity
• usually a curve indicating
• the minimum optical
• power that the Receiver
• can detect versus the data rate,
• in order to achieve a particular BER

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II.3. Transmission Medium

• The Transmission distance is limited by
• fiber attenuation fiber distortion
• Solution i. repeaters
• convert the signal to an electrical signal
• send the signal again at a higher intensity
• high complexity needing to be installed once
  every 20km very high cost
• Solution ii. optical amplifiers
• amplifies the optical signal directly
• without converting the signal
• into the electrical domain
• Amplifiers have largely replaced repeaters in new
  installations

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III. Performance

• The more light that can be coupled into the core
  the more light will reach the Receiver and the
  lower BER
• The lower attenuation in propagating down the
  core the more light reaches the Receiver the
  lower BER
• The less time realized in propagating the faster
  the signaling rate and the higher the end-to-end
  data rate from Source-to-User

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III. Performance contd

• Attenuation
• Caused by a combination of material absorption,
  Raleigh scattering, Mie scattering, and
  connection losses
• Is about 1000 db/km in modern fiber
• Other causes of attenuation are physical stresses
  to the fiber, microscopic fluctuations in
  density, and imperfect splicing techniques.
• Attenuation vs. Wavelength Attenuation
  spectrum of standard single-mode fiber

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III. Performance contd

• Interference
• a key concern is the problem of interference
• Presence of high current equipment results in the
  propagation of electromagnetic pulses that
  interfere with the data communications links
• In the past UTP copper cable was the transmission
  medium choice
• Using Fiber optic cables as the Transmission
  Medium
• great interference protection
• is simply not affected by the electromagnetic
  interference
• Has been slow in coming to the industrial
  environment due to cost
• however, this is changing as the price of fiber
  optic cable steadily decreases

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IV. In Conclusion

• Thank You
• for listening
• If any question..
• Wed be happy to answer