Vandana Seminar

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    PRESENTATION

    ON

    OPTICAL FIBRE CABLE

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    HISTORYHISTORY

    By 1970 Corning Glass invented fiberBy 1970 Corning Glass invented fiber--optic wireoptic wireor "optical waveguide fibers" which was capableor "optical waveguide fibers" which was capableof carrying 65,000 times more information thanof carrying 65,000 times more information than

    copper wire, through which information carriedcopper wire, through which information carriedby a pattern of light waves could be decoded atby a pattern of light waves could be decoded ata destination even a thousand miles away.a destination even a thousand miles away.

    Prof. Kao was awarded half of the 2009Prof. Kao was awarded half of the 2009 NobelNobelPrize in PhysicsPrize in Physics for "for "groundbreakinggroundbreakingachievements concerning the transmission ofachievements concerning the transmission oflight in fibers for optical communicationlight in fibers for optical communication".".

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    OPTICAL FIBRE SYSTEMOPTICAL FIBRE SYSTEM

    Optical Fibre is new medium, in which information (voice,Optical Fibre is new medium, in which information (voice,Data or Video) is transmitted through a glass or plasticData or Video) is transmitted through a glass or plasticfibre, in the form of light, following the transmissionfibre, in the form of light, following the transmissionsequence given below :sequence given below :

    (1)(1) Information is Encoded into Electrical Signals.Information is Encoded into Electrical Signals.(2)(2) Electrical Signals are Coverted into light Signals.Electrical Signals are Coverted into light Signals.

    (3)(3) Light Travels Down the Fiber.Light Travels Down the Fiber.

    (4)(4) A Detector Changes the Light Signals into ElectricalA Detector Changes the Light Signals into ElectricalSignals.Signals.

    (5)(5) Electrical Signals are Decoded into Information.Electrical Signals are Decoded into Information.-- Inexpensive light sources available.Inexpensive light sources available.

    -- Repeater spacing increases along with operatingRepeater spacing increases along with operatingspeeds because low loss fibres are used at high dataspeeds because low loss fibres are used at high datarates.rates.

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    PRINCIPLE OF OPERATIONPRINCIPLE OF OPERATION

    Total Internal ReflectionTotal Internal Reflection -- TheThe

    Reflection that Occurs when a LightReflection that Occurs when a LightRay Travelling in One Material Hits aRay Travelling in One Material Hits a

    Different Material and Reflects BackDifferent Material and Reflects Back

    into the Original Material without anyinto the Original Material without anyLoss of Light.Loss of Light.

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    Types ofTypes of FibreFibre::--

    (I)(I) Multimode Step Index fibre (Step IndexMultimode Step Index fibre (Step Index

    fibre)fibre)

    (II)(II) Multimode graded Index fibre (GradedMultimode graded Index fibre (GradedIndex fibre)Index fibre)

    (III)(III) SingleSingle-- Mode Step Index fibre (SingleMode Step Index fibre (Single

    Mode Fibre)Mode Fibre)

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    STEPSTEP--INDEX MULTIMODE FIBERINDEX MULTIMODE FIBER has ahas a

    large core, up to 100 microns in diameter.large core, up to 100 microns in diameter.

    GRADED-INDEX MULTIMODE FIBER

    contains a core in which the refractive index

    diminishes gradually from the center axis out

    toward the cladding.

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    SINGLESINGLE--MODE FIBERMODE FIBER has a narrow corehas a narrow core

    (eight microns or less), and the index of(eight microns or less), and the index of

    refraction between the core and therefraction between the core and thecladding changes less than it does forcladding changes less than it does for

    multimode fibers.multimode fibers.

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    CABLE CONSTRUCTIONCABLE CONSTRUCTION

    There are two basic cable designs are:

    Tight Buffer Tube Cable

    Loose Buffer Tube Cable

    .

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    TightTight--Buffered CableBuffered Cable

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    LooseLoose--Tube CableTube Cable

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    TOOLS REQUIREDTOOLS REQUIRED

    1.1. Cable CutterCable Cutter

    2.2. Outer jacket removerOuter jacket remover

    3.3. Utility knifeUtility knife

    4.4. Fibre StipperFibre Stipper

    5.5. Fibre Stipper 3 in 1Fibre Stipper 3 in 16.6. Pvc tapePvc tape

    7.7. ScissorScissor

    8.8. Measuring tapeMeasuring tape

    9.9. Tissue paperTissue paper

    10.10. Cleaning LiquidCleaning Liquid

    11.11. Cotton swabCotton swab

    12.12. Towel clothTowel cloth

    13.13. Fibre cutterFibre cutter

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    OFC SplicingOFC Splicing

    Splices are permanent connectionSplices are permanent connectionbetween two fibres. The splicing involvesbetween two fibres. The splicing involves

    cutting of the edges of the two fibres to becutting of the edges of the two fibres to be

    spliced.spliced.

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    Splicing MethodsSplicing Methods

    The following three types are widelyThe following three types are widely

    usedused ::

    Adhesive bonding or Glue splicing.Adhesive bonding or Glue splicing.

    Mechanical splicing.Mechanical splicing.

    Fusion splicing.Fusion splicing.

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    Fusion SplicingFusion Splicing

    The splicing machines imported byThe splicing machines imported by BSNLBSNL

    begins to the core profile alignmentbegins to the core profile alignment

    system, the main functions of which are :system, the main functions of which are :

    1.1. Auto active alignment of the coreAuto active alignment of the core..

    2.2. Auto arc fusionAuto arc fusion..

    3.3. Video display of the entire processVideo display of the entire process..44.. Indication of the estimated splice lossIndication of the estimated splice loss..

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    OPERATIONOPERATION

    The two fibres ends to be spliced are cleavedThe two fibres ends to be spliced are cleavedand then clamped in accurately machined veeand then clamped in accurately machined veegrooves. When the optimum alignment isgrooves. When the optimum alignment isachieved, the fibres are fused under theachieved, the fibres are fused under the

    microprocessor contorl, the machine thenmicroprocessor contorl, the machine thenmeasures the radial and angular offmeasures the radial and angular offsets of thesets of thefibres and uses these figures to calculate afibres and uses these figures to calculate asplice loss. The operation of the machinesplice loss. The operation of the machineobserves the alignment and fusion processes onobserves the alignment and fusion processes on

    a video screens showing horizontal and verticala video screens showing horizontal and verticalprojection of the fibres and then decides theprojection of the fibres and then decides thequality of the splice.quality of the splice.

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    The splice loss indicated by the splicing machineThe splice loss indicated by the splicing machineshould not be taken as a final value as it is onlyshould not be taken as a final value as it is only

    an estimated loss and so after every splicing isan estimated loss and so after every splicing isover, the splice loss measurement is to be takenover, the splice loss measurement is to be takenby an OTDR (Optical Time Domainby an OTDR (Optical Time DomainReflectometer). The manual part of the splicingReflectometer). The manual part of the splicingis cleaning and cleaving the fibres. For cleaningis cleaning and cleaving the fibres. For cleaning

    the fibres, Dichlorine Methyl or Acetone orthe fibres, Dichlorine Methyl or Acetone orAlcohol is used to remove primary coating.Alcohol is used to remove primary coating.

    With the special fibre cleaver or cutter, theWith the special fibre cleaver or cutter, thecleaned fibre is cut. The cut has to be so precisecleaned fibre is cut. The cut has to be so precisethat it produces an end angle of less than 0.5that it produces an end angle of less than 0.5

    degree on a prepared fibre. If the cut is bad, thedegree on a prepared fibre. If the cut is bad, thesplicing loss will increase or machine will notsplicing loss will increase or machine will notaccept for splicing.accept for splicing.

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    . The shape of the cut can be monitored. The shape of the cut can be monitored

    on the video screen, some of the defecton the video screen, some of the defect

    noted while cleaving are listed below :noted while cleaving are listed below :

    Broken ends.

    Ripped ends.Slanting cuts.

    Unclean ends.

    It is also desirable to limit the average splice loss to be less

    than 0.1 dB.

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    THANKSTHANKS