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    SARAN THAMPY DS7 CSE

    ROLL NO 17

    Optical computing

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    Introduction

    Optical computing was a hot research area in 1980s. But thework tapered off due to materials limitations.

    Using light, instead of electric power, for performing

    computations.

    This choice is motivated by several features that light has:

    It is very fast.

    It can be easily manipulated (divided, transported,

    delayed, split, etc)

    It is very well suited for parallelization.

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    More

    Optical computing technology is, in general,developing in two directions.

    One approach is to build computers that have thesame architecture as present day computers butusing optics that is Electro optical hybrids.

    Another approach is to generate a completely newkind of computer, which can perform allfunctional operations in optical mode.

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    Why we Use Optics for Computing?

    One of the theoretical limits on how fast a computercan function is given by Einsteins principle thatsignal cannot propagate faster than speed oflight.

    To make computers faster, their components must be

    smaller and there by decrease the distance betweenthem.

    Optical computing can solve miniaturizationproblem.

    Optical data processing can be performed in parallel.

    In optical computing, the electrons are replaced byphotons

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    Silicon Machines Vs Optical Computers

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    OPTICAL COMPUTER An optical computer (also called a photonic

    computer) is a device that uses the PHOTONS in

    visible light or infrared beams, rather thanelectric current to perform digital computations.

    An optical computer, besides being much fasterthan an electronic one, might also be smaller.

    Bright flashes of laser light can be senthundreds of miles along fine strands ofspecially made glass or plastic called OPTICALFIBERS.

    Instead of transistors, such a computer willhave TRANSPHASORS

    .

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    And unlike transistors, transphasors can bebuilt to handle several incoming signals atonce.

    Beams of light can crisscross and overlapwithout becoming mixed up, whereascrossed electric currents would gethopelessly confused.

    The arrangement of connections andswitches would not have to be flat, as in anelectronic computer. It could be placed inany direction in space, allowing totally newdesigns in information processing.

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    Optic Fiber cables made of glass orplastic

    Glass opticfiber

    Plastic opticfiber

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    SOME KEY OPTICAL COMPONENTS FORCOMPUTING

    VCSEL

    SMART PIXEL TECHNOLOGY WDM

    SLM

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    .VCSEL (VERTICAL CAVITY SURFACE EMITTINGLASER)

    VCSEL(pronouncedvixel)is a semiconductorvertical cavity surface emitting laser diodethat emits light in a cylindrical beamvertically from the surface of a fabricatedwafer.

    But rather than reflective ends, in a VCSELthere are several layers of partiallyreflective mirrors above and below theactive layer.

    Layers of semiconductors with differingcompositions create these mirrors, and eachmirror reflects a narrow range ofwavelengths back in to the cavity in order tocause light emission at just one wavelength.

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    Vertical Cavity Surface Emitting Laser

    850nm VCSEL

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    Optical interconnection of circuitboards using VCSEL and

    PHOTODIODE

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    2. SMART PIXEL TECHNOLOGY

    Smart pixel technology is a relatively new approach

    to integrating electronic circuitry and optoelectronicdevices in a common framework.

    Here, the electronic circuitry provides complex

    functionality and programmability.

    While the optoelectronic devices provide high-speedswitching and compatibility with existing opticalmedia.

    Arrays of these smart pixels leverage the parallelismof optics for interconnections as well ascomputation..

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    3. WDM (WAVELENGTH DIVISIONMULTIPLEXING)

    Wavelength division multiplexing is a method ofsending many different wavelengths down thesame optical fiber.

    WDM can transmit up to 32 wavelengths througha single fiber, but cannot meet the bandwidthrequirements of the present day communicationsystems.

    Nowadays DWDM (Dense wavelength divisionmultiplexing) is used. This can transmit up to1000 wavelengths through a single fiber. That isby using this we can improve the bandwidthefficiency.

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    4.SLM (SPATIAL LIGHT MODULATORS)

    SLM play an important role in severaltechnical areas where the control of lighton a pixel-by-pixel basis is a key element,

    such as optical processing and displays.

    For display purposes the desire is to have

    as many pixels as possible in as small andcheap a device as possible.

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    MERITS

    Optical computing is at least 1000 to 100000 times

    faster than todays silicon machines. Optical storage will provide an extremely optimized

    way to store data, with space requirements far lesserthan todays silicon chips.

    No short circuits, light beam can cross each otherwithout interfering with each others data.

    Higher performance

    Higher parallelism

    Less heat is released

    Less noise

    Less loss in communication

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    DRAWBACKS Todays materials require much high power to

    work in consumer products, coming up withthe right materials may take five years ormore.

    Optical computing using a coherent source is

    simple to compute and understand, but it hasmany drawbacks like any imperfections ordust on the optical components will createunwanted interference pattern due toscattering effects.

    Optical components and their production isstill expensive

    New expensive high-tech factories have to be

    built

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    FUTURE TRENDS

    The Ministry of Information Technology has initiated

    a photonic development program. Under thisprogram some funded projects are continuing infiber optic high-speed network systems. Research isgoing on for developing new laser diodes, photo

    detectors, and nonlinear material studies for fasterswitches.

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    CONCLUSION

    Research in optical computing has opened up newpossibilities in several fields related to high performancecomputing, high-speed communications. To designalgorithms that execute applications faster ,the specificproperties of optics must be considered, such as theirability to exploit massive parallelism, and globalinterconnections. As optoelectronic and smart pixeldevices mature, software development will have a majorimpact in the future and the ground rules for thecomputing may have to be rewritten.

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    THANK YOU