A System View of Optical Fiber Communication(2)

8/7/2019 A System View of Optical Fiber Communication(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

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

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A System View of Optical Fiber Communication(2)