Download Optical Interconnects for Computer Systems

Optical Interconnects for
Computer Systems
Bhanu Jaiswal
University at Buffalo
Introduction
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Nature of data traffic in a computer
Converse to city traffic
Ever increasing data transfer rate
Very high data rates restricted by
fundamental limitations of current copper
interconnects
Need for a long term solution
Interconnect Issues
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In present computer systems,
interconnections handled via parallel
electrical busses
Interconnect performance does not increase
comparably with the system performance
Solutions
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Increase performance of present EI
Use completely different physical medium
Problems with Electrical Interconnects
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Physical Problems (at high frequencies)
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Cross-talk
Signal Distortion
Electromagnetic Interference
Reflections
High Power Consumption
High Latency (RC Delay)
Why Optics ?
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Successful long-haul telecommunication system
based on fiber optics
Advantages:
 Capable to provide large bandwidths
 Free from electrical short-circuits
 Low-loss transmission at high frequencies
 Immune to electromagnetic interference
 Essentially no crosstalk between adjacent signals
 No impedance matching required
Evolution of Optical Interconnects –
Current & Future possibilities
This approach to signal
transfer is moving from
longer-distance
applications, such as
linking separate
computers, to joining
chips within a computer
Basic Ingredients
SOURCE
VCSEL
LED’s
Edge-Emitting
Laser
OPTICAL PATH
DETECTOR
P-I-N
Photodiodes
SML
Detector
MQW P-I-N
Free-Space
Guided Wave
World wide projects
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Heriot Watt University – Optically
Interconnected Computing (OIC) group
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DaimlerChrysler, McGill University
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SPOEC Project
Optical Backplanes
UC San Deigo
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Optical Transpose Interconnect System
Target – Terabits/second
US based research
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$70 million program run by US Defence
Advanced Research Projects Agency
Companies in business
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Primarion Corp. – Thinking inside the box
Agilent Technologies – Optical connecters
between computers
Lucent Technologies – Optical Crossbar switch
matrix
SPOEC Project
SPOEC System Layout
Test bed developed by the SPOEC
project
Optical Backplanes Speed Data
In DaimlerChrysler's optical
backplane, the beam from
a laser diode passes
through one set of lenses
and reflects off a
micromirror before
reaching a polymer
waveguide, then does the
converse before arriving at
a photodiode and changing
back into an electrical
signal. A prototype
operates at 1 Gb/s.
Free-Space Interconnects Pack in Data
Channels
An experimental module from the
University of California, San
Diego, just 2 cm high, connects
stacks of CMOS chips. Each
stack is topped with an optics
chip [below center] consisting of
256 lasers (VCSELs) and
photodiodes. Light from the
VCSELs makes a vertical exit
from one stack [below, left] and a
vertical entry into the other. In
between it is redirected via a
diffraction grating, lenses, an
alignment mirror [center], and
another grating. Each of the
device's 256 channels operates
at 1 Gb/s.
Principal Challenges
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Multi-disciplinary field
Device Integration, Interfacing & Packaging
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Electronic components – Si CMOS based
Optoelectronic Components – III-V Compound
based
Optical components – MicroLens and
MicroMirrors based
Misalignment in FSOIs
Conclusions
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Interconnect problem significant in ultra deep
submicron designs
Performance of Electrical lnterconnects will
saturate in a few years
OIs – very promising for future computers
OIs do not aim to completely replace EIs
References
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Linking with light - IEEE Spectrum
http://www.spectrum.ieee.org/WEBONLY/publicfeature/aug02/opti.html
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Optically Interconnected Computing
Group
http://www.phy.hw.ac.uk/~phykjs/OIC/index.html
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Optoelectronics-VLSI system
integration Technological challenges
www.phy.hw.ac.uk/~phykjs/OIC/Projects/ SPOEC/MSEB2000/MSEB2000.pdf
Ref. follows
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International Technology Roadmap for
Semiconductors (ITRS), 2001
R. Havemann and J.A Hutchby, “High-Performance
Interconnects: An integration Overview”, Proc. Of
IEEE, Vol.89, May 2001
D.A.B Miller, “Physical reasons for optical
interconnections”, Int. Journal of Optoelectronics
11, 1997, pp.155-168.
MEL-ARI: Optoelectronic interconnects for
Integrated Circuits – Achievements 1996-2000