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A System View of Optical Fiber
Communication prt.2
AbdulRahman AlKhayyat
223218
Mohamed Felimban
224304
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OUTLINE
I. The Fiber Optic Data Communication System
II. Components of the Transmission System
I. TransmittersII. ReceiversIII. Transmission Medium
III. Performance
I. AttenuationII. Interference
IV. Conclusion
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I. The Fiber Optic Data Communication
SystemFiber Optic communication systems generally include: A Transmitter
Transmission Medium including amplifiers and repeaters
A Receiver
A model of this System is shown in the figureThe illustration indicates the Source-User pair, Transmitter & ReceiverIt also clearly shows the Transmission Medium.
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1. Transmitterto 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 regulatorto modulate this light to represent the binary data it receive
II. Components of the Transmission
System
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There are some requirements for the transmitter that should be met
1. physical dimensions must be compatible with size of the fiber optic being used emit light in a cone within cross sectional diameter
2. optical source must be able to generate enough power desired BER should be met
3. high efficiency in coupling the light into the fiber optic cable
4. 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
5. Should be easily modulated with an electrical signal & capable of high-speedmodulation
6. The usual requirements of small size, low weight, low cost and high reliability
II.1. Transmitters: Optical Source Component
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Types of Diodes that can be used as an opticalsource of the Transmitter:
1. laser diode (LD)2. light emitting diode (LED)
LD's advantages over LED's can be modulated at very high speeds produce greater optical power
higher coupling efficiencyto the fiber optic cable
II.1. Transmitters contd
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LED's advantages over LD's higher reliability better linearity lower cost
LED and laser diodes: P-I characteristics
II.1. Transmitters contd
Verschiedene LEDs
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2. 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 thelight into an electrical signal
A demodulatordemodulate this light determine the identity of the binary data thatit represents
II. Components of the Transmission
System
Indoor & Outdoor Receivers
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receiver performanceis generally characterizedby a parameter called
the Sensitivity
usually a curve indicatingthe minimum optical
power that the Receivercan detect versus the data rate,in order to achieve a particular BER
II.2. Receivers contdReceiver sensitivities for BER = 10-9,
with different devices
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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 highcost
Solution: ii. optical amplifiers
amplifies the optical signal directlywithout converting the signalinto the electrical domain
Amplifiers have largely replaced repeaters in new installations
II.3. Transmission Medium
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III. Performance
The more light that can be coupled into the core themore light will reach the Receiver and the lower BER
The lower attenuation in propagating down the corethe more light reaches the Receiver & the lower BER
The less time realized in propagating the faster thesignaling rate and the higher the end-to-end datarate from Source-to-User
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III. Performance contd
1. 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
2. Interference a key concern is the problem of interference
Presence of high current equipment results in the propagation ofelectromagnetic pulses that interfere with the data communicationslinks
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 tocost
however, this is changing as the price of fiber optic cable steadilydecreases
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IV. In Conclusion
Thank You
for listening
If any question..
Wed be happy to answer