- Optical computer
An optical computer is a computer that uses light instead of electricity (i.e.
photonsrather than electrons) to manipulate, store and transmit data. Photons have fundamentally different physical properties than electrons, and researchers have attempted to make use of these properties, mostly using the basic principles of optics, to produce computers with performance and/or capabilities greater than those of electronic computers. Optical computer technology is still in the early stages: functional optical computers have been built in the laboratory, but none have progressed past the prototype stage.
Most research projects focus on replacing current computer components with optical equivalents, resulting in an optical digital computer system processing binary data. This approach appears to offer the best short-term prospects for commercial optical computing, since optical components could be integrated into traditional computers to produce an optical/electronic hybrid.Other research projects take a non-traditional approach, attempting to develop entirely new methods of computing that are not physically possible with electronics.
Optical components for binary digital computer
The fundamental building block of modern electronic computers is the
transistor. To replace electronic components with optical ones, an equivalent "optical transistor" is required. This is achieved using materials with a non-linear refractive index. In particular, materials exist where the intensity of incoming light affects the intensity of the light transmitted through the material in a similar manner to the voltage response of an electronic transistor. This "optical transistor" effect is used to create logic gates, which in turn are assembled into the higher level components of the computer's CPU.
Misconceptions, challenges and prospects
Another claimed advantage of optics is that it can reduce power consumption, but an optical communication system will typically use more power over short distances than an electronic one. This is because the
shot noiseof an optical communication channel is greater than the thermal noiseof an electrical channel which, from information theory, means that we require more signal power to achieve the same data capacity. However, over longer distances and at greater data rates the loss in electrical lines is sufficiently large that optical communications will comparatively use a lower amount of power. As communication data rates rise, this distance becomes shorter and so the prospect of using optics in computing systems becomes more practical.
A significant challenge to optical computing is that computation is a nonlinear process in which multiple signals must interact to compute the answer. Light, which is an
electromagnetic wave, can only interact with another electromagnetic wavein the presence of electrons in a material and the strength of this interaction is much weaker for electromagnetic wavelight than for the electronic signals in a conventional computer. This results in the processing elements for an optical computer requiring high powers and larger dimensions than for a conventional electronic computer using transistors.
Optical neural network
* "Optical Computer Architectures: The Application of Optical Concepts to Next Generation Computers", "Optical Computer Architectures: The Application of Optical Concepts to Next Generation Computers" book by Alastair D. McAulay (1999)
* BARROS S., GUAN S. & ALUKAIDEY T., "An MPP reconfigurable architecture using free-space optical interconnects and Petri net configuring" in Journal of System Architecture (The EUROMICRO Journal) Special Double Issue on Massively Parallel Computing Systems vol. 43, no. 6 & 7, pp. 391-402, April 1997
* T.S. Guan & S.P.V. Barros, "Reconfigurable Multi-Behavioural Architecture using Free-Space Optical Communication" in Proceedings of the IEEE International Workshop on Massively Parallel Processing using Optical Interconnections. , April 1994
* T.S. Guan & S.P.V. Barros, "Parallel Processor Communications through Free-Space Optics" in IEEE Region 10's Ninth Annual International Conference on Frontiers of Computer Technology , August 1994
* " [http://portal.acm.org/citation.cfm?id=30367 Architectural issues in designing symbolic processors in optics] "
* D. Goswami, "Optical Computing", Resonance, June 2003; ibid July 2003. [http://www.iisc.ernet.in/academy/resonance/June2003/June2003p56-71.html] , [http://www.iisc.ernet.in/academy/resonance/July2003/July2003p8-21.htm]
* K.-H. Brenner, Alan Huang: "Logic and architectures for digital optical computers (A)", J. Opt. Soc. Am., A 3, 62, (1986)
* K.-H. Brenner: "A programmable optical processor based on symbolic substitution", Appl. Opt. 27, No. 9, 1687 - 1691, (1988)
* " [http://science.nasa.gov/headlines/y2000/ast28apr_1m.htm NASA scientists working to improve optical computing technology]
* " [http://www.cs.ubbcluj.ro/~moltean/osc2008 International Workshop on Optical SuperComputing]
* " [http://www.cs.ubbcluj.ro/~moltean/optical Optical solutions for NP-complete problems]
* [http://technology.newscientist.com/channel/tech/mg19526136.400-speedoflight-computing-comes-a-step-closer.html Speed-of-light computing comes a step closer] "New Scientist"
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