voice & data transmit ion from optical fiber

8/6/2019 Voice & Data Transmit Ion From Optical Fiber

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Transmission of Data/VoiceTransmission of Data/Voiceover Fiber over Fiber- -Optic linkOptic link

By Rajesh Chhetry


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ObjectiveObjective

T he main objective of this paper is to makea comparative study among different

principles ,technologies and practices thatinvolve in the transmission of data over fiber optic link and recommend a

communication system that perfectly meetsthe requirements of communication of datain the current trend and environment.


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IntroductionIntroductionI n recent years it has become apparent thatfiber-optics are steadily replacing copper wire as an appropriate means of communication signal transmissionT hey span the long distances between local

phone systems as well as providing the backbone for many network systems


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T his paper is about the different principlesinvolved in a fiber optic communication.


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Fiber Optic technologyFiber Optic technologyfiber-optics use light pulses to transmitinformation down fiber linesT he transmitter accepts coded electronic

pulse information coming from copper wireT he information is then processed andtranslated into equivalently coded light

pulses.


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A light-emitting diode (LED) or aninjection-laser diode ( I LD) can be used for generating the light pulses .Light pulses move easily down the fiber-optic line because of a principle known astotal internal reflection


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Elements of Optical fiber cableElements of Optical fiber cableT he optic coreA n optic cladding,A buffer material,A strength material

T he outer jacket


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Fiber optic applicationsFiber optic applications(Data)(Data)

Backbone architechture for telecommunication linksCable service providers /High speed internetT runk linesMonitor power grid systemsLocal area networks


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Fiber optics economicsFiber optics economicsO ne of the initial economic factors to consider when converting to fiber-optics is the cost of

replacing wire systems with fiber I ncreased demand for optical fiber has brought the

prices down within competitive range of copper I n the short term it is often less expensive tocontinue using copper cabling for coveringexpanded communication needs


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I n the long term it may be more cost effective toinvest in conversion to fiber-optics .T his cost effectiveness is due to the relative easeof upgrading fiber optics to higher speeds and

performance.I t is generally accepted that customers will needincreased bandwidth as the information highwaygrows


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F iber optics will play a pivotal role in thisrace since the bandwidth needed for

providing an all-in-one service withtelevision, telephone, interactivemultimedia, and internet access is not

available in much of the wiring of A merica.


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S ingle Mode and multimodeS ingle Mode and multimodefibersfibers

S ingle mode allowsonly one mode of ray

to pass through itscore.Multi- mode allowshundreds of rays of light to propagatethrough the core.


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EncodingEncodingT he source information (such as audio,video or sonar) comes in many forms .T he first step is to convert the informationinto a bit-stream .once the information is stored electronically

and whatever the form, data can beconverted into raw binary data prior totransmission.


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Base Band ModulationBase Band ModulationT he next step is to modulate the basebandand this is where, in constructing an opticalcommunications system, we start makingcompromise .Different modulation schemes make

varying use of the bandwidth, but the trade-offs will include distance, compression,BER and power.


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Due to the lack of 'coherent' optical systemsfor extracting phase information, opticalcommunication systems use pulse codemodulation (PCM) schemes to modulate the

baseband .

T here are many PCM techniquesavailable.HDB3 is the most advanced andefficient technique developed so far.


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HDB3HDB3


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Light S ources

Light S ources

Leds- produce incoherent light that severelyreduces the obtainable bandwidth .Laser Diodes-Lasers produce coherent lightand deliver far higher performance thanLEDs e.g F abryperot laser


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R ecommendationsR ecommendations

W ith reference to the study about the fiber opticssystems , the following communication system

can be recommended for an efficient and reliabledata transmission.F abryperot laser diodePulse code modulation technique used for

producing bit streamsEncoded using HDB3 codesS ingle Mode step index fiber


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T his can be a solution for the requirementof the data-ondemand systemimplemented by businesses today.T he requirement for such a system is highBandwidth.


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encoding techniquesencoding techniquesW PCM: pulse code modulation

W samples of the analog data takenW each sample quantizedW samples transmited as digital signalW received samples used to reconstruct analog data

W example: voice channelsW samples taken 8000/secW quantized to 7 bitsW synch. bit added -> 8 bitsW 8 x 8000 = 64000 bps, standard digital voice channel

voice & data transmit ion from optical fiber

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