Optical Interconnects for Computer Systems Bhanu Jaiswal University at Buffalo.
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Transcript of Optical Interconnects for Computer Systems Bhanu Jaiswal University at Buffalo.
Introduction
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
In present computer systems, interconnections handled via parallel electrical busses
Interconnect performance does not increase comparably with the system performance Solutions – Increase performance of present EI – Use completely different physical medium
Problems with Electrical Interconnects
Physical Problems (at high frequencies) Cross-talk Signal Distortion Electromagnetic Interference Reflections High Power Consumption High Latency (RC Delay)
Why Optics ?
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
SOURCEDETECTOR OPTICAL PATH
VCSEL
Edge-EmittingLaser
LED’s P-I-N Photodiodes
SML Detector
MQW P-I-N
Guided WaveFree-Space
World wide projects
Heriot Watt University – Optically Interconnected Computing (OIC) group– SPOEC Project
DaimlerChrysler, McGill University– Optical Backplanes
UC San Deigo– Optical Transpose Interconnect System
Target – Terabits/second
US based research
$70 million program run by US Defence Advanced Research Projects Agency
Companies in business– Primarion Corp. – Thinking inside the box– Agilent Technologies – Optical connecters
between computers– Lucent Technologies – Optical Crossbar switch
matrix
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
Multi-disciplinary field Device Integration, Interfacing & Packaging
– Electronic components – Si CMOS based– Optoelectronic Components – III-V Compound
based– Optical components – MicroLens and
MicroMirrors based
Misalignment in FSOIs
Conclusions
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
Linking with light - IEEE Spectrum http://www.spectrum.ieee.org/WEBONLY/publicfeature/aug02/opti.html
Optically Interconnected Computing Group
http://www.phy.hw.ac.uk/~phykjs/OIC/index.html
Optoelectronics-VLSI systemintegration Technological challenges
www.phy.hw.ac.uk/~phykjs/OIC/Projects/ SPOEC/MSEB2000/MSEB2000.pdf
Ref. follows
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