dat@hpcnof.UUCP (12/09/85)
The most recent issue of "Science News (Nov 30th) has a very fascinating article about a new technology dubbed 'Photonics', hailed as the replacement for current electronics. The basic improvement is that while contemporary electronics rely on the the speed of electrons, and the (unfortunate) resistance of the paths the electrons travel, this new technology uses photons (particles of light) as the basic 'unit' of information. The problem, it seems, with electronics is that due to the mass of the electrons and the resistance of the paths, we're limited to a bandwidth of about 1 gigahertz (their figure, not mine). Researchers claim that "[it] seems to be a 'stone wall' limitation." Photonics, on the other hand, has not only the advantage of a zero mass particle (a photon) but also, by using optical fibers, can have the photons travel essentially arbitrary paths without encountering ANY resistance. Other advantages accrue too - including a complete freedom from electrical interference and noise. The fiber optic cables are also much smaller than the similar amount of traditional electrical wires (the article states that "a single [electrical] coaxial cable is as thick as a whole array of optical fibers"). The scientist partially responsible for the breakthrough, James Chang of the Sandia National Laboratories at Albuquerque, New Mexico, claims to have taken real-time event measurements with a functional bandwidth of over THREE gigahertz. (His comment at the time was "My God, I made a 3-gigahertz measurement in real time!") My question to the net is simply - Does anyone have any further information on this technological breakthrough? The article in SN is quite illuminating (pardon the pun) - I recomend reading it if you're more interested in this. -- Dave Taylor Hewlett Packard, CNO
miles@vax135.UUCP (Miles Murdocca) (12/12/85)
> Photonics, on the other hand, has not only the advantage of a > zero mass particle (a photon) but also, by using optical fibers, can > have the photons travel essentially arbitrary paths without encountering > ANY resistance. Other advantages accrue too - including a complete freedom > from electrical interference and noise. The fiber optic cables are also much > smaller than the similar amount of traditional electrical wires (the article > states that "a single [electrical] coaxial cable is as thick as a whole array > of optical fibers"). > My question to the net is simply - Does anyone have any further > information on this technological breakthrough? One problem with using fiber optic cables is that you are limited to serial computation, e.g.: 1 bit per fiber. 2-dimensional optical logic elements exist that allow for wavefront propagation. An example is the nonlinear Fabry-Perot etalon (U. Arizona and AT&T Bell Labs) with an absorption time of ~5ps and a relaxation time of ~100ps. It is hoped that the population of the devices will go as high as 1K x 1K elements per array. An entire array can be imaged onto another array. If the free space between the arrays is filled with simple glass devices like a few beam-splitters and mirrors, then array scale logic can be done essentially at the speed of light. A major win in going to optical computing is the enormous communication capability of using a free-space interconnect. Optical fibers don't allow this. Miles Murdocca, 4G-538, AT&T Bell Laboratories, Crawfords Corner Rd, Holmdel, NJ, 07733, (201) 949-2504, ...{ihnp4}!vax135!miles
mwg@petrus.UUCP (Mark Garrett) (12/12/85)
++ > The most recent issue of "Science News (Nov 30th) has a very > fascinating article about a new technology dubbed 'Photonics', hailed > as the replacement for current electronics. 'Photonics', as a word, has been around long enough for it to be incorporated into the names of a couple of research districts here at Bellcore. The main motivation for it is that photons can be made to switch on and off faster than electrons, and you can get more bandwidth-distance product from fiber than from coax. There are two disadvantages that I can think of. First, it is fundamentally impossible to get as many circuits into a small chip with light (assuming the order of magnitude of visible light) because the size of 'wires' must be larger than the wavelength. This is about one half micron for light and some tens of Angstroms for electrons (correct me if I'm wrong). Already we see VLSI chips made with one micron line spacing in electonics. Second, if you have a signal that needs to be distributed to a number of points (eg, fanout in a circuit or taps in a multi-access network), you need a large fraction of the total signal energy to detect it accurately in the optical case, and very little in the electrical case. For more on Photonics, one place to start might be the Proceedings of the IEEE July 1984 special issue on optical computing. -Mark Garrett
mark@well.UUCP (Mark Hendricks) (01/04/86)
Another source for more information is Photonics magazine the voice of the photonics technology an international journal of optics, electro-optics, lasers, fiber optics and imaging. Optical Publishing Co. Inc. Berkshire Common, PO Box 1146 Pittsfield MA 01202.
mark@well.UUCP (Mark Hendricks) (01/04/86)
There is also the possibility of holographic transforms and filtering etc.