Transcript optical computing - 123seminarsonly.com

NIKHIL E.J
EL 3
ROLL NO:31
MTI THRISSUR
CONTENTS;
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INTRODUCTION
NEED OF OPTICS IN COMPUTING
OPTICAL COMPUTER
VCSEL
SMART PIXEL TECHNOLOGY
WDM
SLM
MERITS
DRAWBACKS
FUTURE TRENDS
CONCLUSION
REFERENCES
Introduction
• Optical computing was a hot research area in 1980’s. 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.
More…
• Optical computing technology is, in general,
developing in two directions.
• One approach is to build computers that have the
same architecture as present day computers but
using optics that is Electro optical hybrids.
• Another approach is to generate a completely new
kind of computer, which can perform all
functional operations in optical mode.
Why we Use Optics for Computing?
• One of the theoretical limits on how fast a computer
can function is given by Einstein’s principle that
“signal cannot propagate faster than speed of light”.
• To make computers faster, their components must be
smaller and there by decrease the distance between
them.
• Optical computing
problem.
can
solve
miniaturization
• Optical data processing can be performed in parallel.
• In optical computing, the electrons are replaced by
photons
Silicon Machines Vs Optical Computers
OPTICAL COMPUTER
• An optical computer (also called a photonic
computer) is a device that uses the PHOTONS in
visible light or infrared beams, rather than
electric current to perform digital computations.
• An optical computer, besides being much faster
than an electronic one, might also be smaller.
• Bright flashes of laser light can be sent
hundreds of miles along fine strands of
specially made glass or plastic called OPTICAL
FIBERS.
• Instead of transistors, such a computer will
have TRANSPHASORS
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More…
• And unlike transistors, transphasors can be built to handle
several incoming signals at once.
• Beams of light can crisscross and overlap without becoming
mixed up, whereas crossed electric currents would get
hopelessly confused.
• The arrangement of connections and switches would not
have to be flat, as in an electronic computer. It could be
placed in any direction in space, allowing totally new designs
in information processing.
Optic Fiber cables made of glass or plastic
Glass optic
fiber
Plastic optic
fiber
SOME KEY OPTICAL COMPONENTS FOR
COMPUTING
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VCSEL
SMART PIXEL TECHNOLOGY
WDM
SLM
1. VCSEL (VERTICAL CAVITY SURFACE EMITTING LASER)
• VCSEL(pronounced‘vixel’)is a semiconductor vertical cavity
surface emitting laser diode that emits light in a cylindrical
beam 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 the
active layer.
• Layers of semiconductors with differing compositions create
these mirrors, and each mirror reflects a narrow range of
wavelengths back in to the cavity in order to cause light
emission at just one wavelength.
Vertical Cavity Surface Emitting Laser
850nm VCSEL
Optical interconnection of circuit boards using VCSEL
and PHOTODIODE
2. SMART PIXEL TECHNOLOGY
• Smart pixel technology is a relatively new approach to integrating
electronic circuitry and optoelectronic devices in a common
framework.
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Here, the electronic circuitry provides complex functionality and
programmability.
• While the optoelectronic devices provide high-speed switching
and compatibility with existing optical media.
• Arrays of these smart pixels leverage the parallelism of optics for
interconnections as well as computation..
3. WDM (WAVELENGTH DIVISION
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MULTIPLEXING)
Wavelength division multiplexing is a method of sending many
different 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) is
used. This can transmit up to 1000 wavelengths through a
single fiber. That is by using this we can improve the bandwidth
efficiency.
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 as
possible.
MERITS
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Optical computing is at least 1000 to 100000 times
faster than today’s silicon machines.
Optical storage will provide an extremely optimized
way to store data, with space requirements far lesser
than today’s silicon chips.
No short circuits, light beam can cross each other
without interfering with each other’s data.
Higher performance
Higher parallelism
Less heat is released
Less noise
Less loss in communication
DRAWBACKS
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Today’s materials require much high power to work in
consumer products, coming up with the right materials
may take five years or more.
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Optical computing using a coherent source is simple to
compute and understand, but it has many drawbacks like
any imperfections or dust on the optical components will
create unwanted interference pattern due to scattering
effects.
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Optical components and their production is still expensive
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New expensive high-tech factories have to be built
FUTURE TRENDS
• The Ministry of Information Technology has initiated a photonic
development 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.
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 ground
rules for the computing may have to be rewritten.
REFERENCES;
[1] See for example: Chemical and Engineering News, “Photonic
Crystals
Assembled on Chip”, 79(47), 31 (2001).
[2] P. Boffi, D. Piccinin, M.C. Ubaldi, (Eds.), Infrared Holography for
Optical Communications—Techniques, Materials and Devices,
Springer—
Topics in Applied Physics: Vol 86, July 2002.
[3] Alain Goulet, Makoto Naruse, and Masatoshi Ishikawa, “Simple
integration technique to realize parallel optical interconnects:
implementation
of a pluggable two-dimensional optical data link”, Applied
Optics 41, 5538 (2002)
[4] Tushar Mahapatra, Sanjay Mishra, Oracle Parallel Processing,
O’Reilly
& Associates, Inc., Sebastopol, California, USA, 2000.
[5] S. J. van Enk, J. McKeever, H. J. Kimble, and J. Ye, “Cooling of a
single
atom in an optical trap inside a resonator,” 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, “Organic smart pixels”, Appl. Phys.
Lett. 73, 142 (1998).
[7] Henning Sirringhaus, Nir Tessler, and Richard H. Friend,
“Integrated
Optoelectronic Devices Based on Conjugated Polymers”, Science
280,
1741 (1988).