optical computing final - copy (2)

8/3/2019 Optical Computing FINAL - Copy (2)

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CONTENTS;

INTRODUCTION

NEED OF OPTICS IN COMPUTING

OPTICAL COMPUTER

VCSEL

SMART PIXEL TECHNOLOGY

WDM

SLM

MERITS

DRAWBACKS FUTURE TRENDS

CONCLUSION

REFERENCES


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Introduction

Optical computing was a hot research area in 1980s. But the

work 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 weUse Optics forComputing?

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

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 invisible 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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More

And unlike transistors, transphasors can be built to handleseveral incoming signals at once.

Beams of light can crisscross and overlap without becoming

mixed up, whereas crossed electric currents would gethopelessly confused.

The arrangement of connections and switches would nothave to be flat, as in an electronic computer. It could be

placed in any direction in space, allowing totally new designsin information processing.


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Optic Fiber cables made of glass or plastic

Glass opticGlass optic

fiberfiber

Plastic opticPlastic optic

fiberfiber


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SOME KEY OPTICAL COMPONENTS FOR

COMPUTING

VCSEL

SMART PIXEL TECHNOLOGY

WDM

SLM


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1. VCSEL (VERTICALCAVITYSURFACEEMITTINGLASER)

VCSEL(pronouncedvixel)is a semiconductor vertical cavitysurface emitting laser diode that emits light in a cylindricalbeam vertically from the surface of a fabricated wafer.

But rather than reflective ends, in a VCSEL there are several

layers of partially reflective mirrors above and below theactive layer.

Layers of semiconductors with differing compositions createthese mirrors, and each mirror reflects a narrow range ofwavelengths back in to the cavity in order to cause lightemission at just one wavelength.


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Vertical Cavity Surface Emitting Laser

850nm VCSEL


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Optical interconnection of circuit boards using VCSEL

and PHOTODIODE


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2. SMART PIXEL TECHNOLOGY

Smart pixel technology is a relatively new approach to integratingelectronic circuitry and optoelectronic devices in a commonframework.

Here, the electronic circuitry provides complex functionality and

programmability.

While the optoelectronic devices provide high-speed switchingand compatibility with existing optical media.

Arrays of these smart pixels leverage the parallelism of optics forinterconnections as well as computation..


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3. WDM (WAVELENGTH DIVISION MULTIPLEXING)

Wavelength division multiplexing is a method of sending manydifferent wavelengths down the same optical fiber.

WDM can transmit up to 32 wavelengths through a single fiber,but cannot meet the bandwidth requirements of the present

day communication systems.

Nowadays DWDM (Dense wavelength division multiplexing) isused. This can transmit up to 1000 wavelengths through asingle fiber. That is by using this we can improve the bandwidthefficiency.


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4.SLM (SPATIAL LIGHT MODULATORS)

SLM play an important role in several technical areas

where the control of light on 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 and cheap a device aspossible.


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MERITS

Optical computing is at least 1000 to 100000 timesfaster than todays silicon machines.

Optical storage will provide an extremely optimizedway 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 with the right materialsmay take five years or more.

Optical computing using a coherent source is simple tocompute and understand, but it has many drawbacks like

any imperfections or dust on the optical components willcreate unwanted interference pattern due to scatteringeffects.

Optical components and their production is still expensive

New expensive high-tech factories have to be built


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FUTURE TRENDS

The Ministry of Information Technology has initiated a photonicdevelopment program. Under this program some funded projects

are continuing in fiber optic high-speed network systems.

Research is going on for developing new laser diodes, photo

detectors, and nonlinear material studies for faster switches.


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CONCLUSION

Research in optical computing has opened up new possibilities in several

fields related to high performance computing, high-speed communications. To

design algorithms that execute applications faster ,the specific properties of

optics must be considered, such as their ability to exploit massive parallelism,

and global interconnections. As optoelectronic and smart pixel devices mature,

software development will have a major impact in the future and the groundrules for the computing may have to be rewritten.


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[1] Seeforexample:Chemical and Engineering News, PhotonicCrystalsAssembledonChip, 79(47), 31 (2001).[2] P.Boffi, D.Piccinin, M.C. Ubaldi,(Eds.),Infrared Holography forOptical CommunicationsTechniques, Materials and Devices,SpringerTopicsinAppliedPhysics: Vol 86, July2002.[3] Alain Goulet, MakotoNaruse,and MasatoshiIshikawa, Simple

integrationtechniquetorealizeparallelopticalinterconnects:implementationofapluggabletwo-dimensionalopticaldatalink,AppliedOptics 41, 5538 (2002)[4] Tushar Mahapatra,Sanjay Mishra,Oracle Parallel Processing,OReilly&Associates,Inc.,Sebastopol,California, USA,2000.[5] S. J.vanEnk, J. McKeever,H. J.Kimble,and J. Ye, Coolingofasingle

atominanopticaltrapinsidearesonator, Phys. Rev. A 64, 013407(2001).[6] A. Dodabalapur, Z.Bao,A. Makhija, J. G.Laquindanum, V.R.Raju, Y.Feng,H.E.Katz,and J.Rogers, Organicsmartpixels,Appl. Phys.Lett. 73, 142 (1998).[7] HenningSirringhaus,Nir Tessler,andRichardH.Friend,IntegratedOptoelectronicDevicesBasedonConjugatedPolymers,Science

280,1741 (1988).

REFERENCES;


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