rst@cs.hull.ac.uk (Rob Turner) (11/01/90)
I recently attended a series of lectures at Manchester University, England on optical computers given by Alan Huang of AT&T. This stimulated my interest in the area of optical computers, and I wonder if there are any specific goups on the net where they are (or have been) discussed. If not, I guess this is the right place. What are people's views on optical computers. Alan Huang was *enormously* enthusiastic (as you would expect him to be). Even if he was too optimistic, his enthusiasm rubbed off on me and made me fascinated to learn more. The best literature I have found was an issue of IEEE Spectrum a while back devoted to optical computers, but I want to know more. Rob ------------------------------------------------------------------ Robert Turner | rst@cs.hull.ac.uk Department of Computer Science | University of Hull | "In every real man a child is Hull HU6 7RX | hidden that wants to play" England | - Nietzsche
chris@ncmicro.lonestar.org (Chris Arps) (11/06/90)
I rember Scientific American running a pretty good article on optical computing about 8? months ago. It showed an experiment where a holographic database of human faces could be used to locate an input face. The entire process was done optically and basically instantaneously. Even more interesting was that even with a partial face input, the optical loop was able to resolve the face. Imagine a database with social security numbers that could be fed by a video camera, you could then look up every person that came into your place of business. Americas most wanted better look out!
ga1056@sdcc6.ucsd.edu (Dau-Tsuong) (11/07/90)
We at university of California at San Diego share Alan Huang's enthusiasm on optical computing. We have an Optical Information Processing Group here that is actively pursuing optoelectronic devices, systems, and architectures. Besides AT&T and us, several other universities are also working on similar systems, CalTech, MIT, Stanford, U of Colorado, USC, just a few names on the top of stack now. Many publications in this area has been published in Applied Optics and Optical Engineering. Our work at UCSD is primarily using holographic optics to interconection VLSI processing elements. Based on power and speed considerations, optical interconnection is better than electronic when the interconnect distance is above 1mm (assuming some operating parameters I cannot recall right away. Let me know if you want more detail). So it appears to us that the best architecture is an array of fine-grain electronic processing elements (PE) that are optically connected together, we call it Programmable Optoelectronic Multiprocessor, i.e. POEM. This is a SIMD architecture. The prototype POEM we are working on has 4 1-bit CPU's on each plane. Two such processor planes are optically interconnected by two computer generated holograms (CGH). Each PE has a spatial light modulator and three optical dectors. There are no interconnection between the PEs on the same plane, so optical I/O is rather important. Work is also in progress to use photorefractive crystals (PRC) to store several interconnection patterns and multiplex them using a phase code. In the near future, we should expect to see dynamically reconfigurable interconnections using these crystals. This week, the Optical Society of America is holding its annual meeting in Boston. There are several presentations on high speed backplane interconnection using optical technology. Comparing to purely electronic multiprocessing systems, our approach differs mostly in decoupling the processing and the interconnection. The interconenction wires doesn't compete for the same silicon area on a wafer. Besides, laser beam don't have the capacitive effects at increased distance. POEM is able to implement most of the interconnection network you can think of: butterfly, shuffle, etc and also the irregular interconnections such as expander graphs (used in the O(log n) optimal sorting network of Ajtai, Komlos, and Smezeredi). We have recently build a VHDL model using Vantage VHDL compiler. It accurately models the optoelectronic device characteristics and of course the CMOS processing element with 64 bit memory. You might think 2 x 4 such processors cannot do anything siginificant, yes you are right. But we are planning to scale this up. The dream is 1024x1024 (1Meg PEs on each plane) but I'll be very happy to see 32x32 before I get my PhD. The limitation now is the yield and speed of good spatial light modulators that gives optical binary signals. This is a rather brief summary. I can send you dozens of papers if you are interested. I'd like to see more discussion on this topic. I have implemented a simple demo to search and project 8 records in parallel, the execution time would stay constant whe the array is scaled up to any size. I'd suppose we will hit the bottleneck of the sequential host computer first. George D.-T. Lu UCSD OIPG lu@poet.ucsd.edu dlu@ucsd.edu dlu@ucsd.bitnet ucsd!dlu
whit@milton.u.washington.edu (John Whitmore) (11/08/90)
In article <5506.9011011201@olympus.cs.hull.ac.uk> rst@cs.hull.ac.uk (Rob Turner) writes: > > >I recently attended a series of lectures at Manchester University, >England on optical computers given by Alan Huang of AT&T. ... >What are people's views on optical computers. Alan Huang was *enormously* >enthusiastic (as you would expect him to be). The patch-panel style of computers (like most old analog computers) is a good model for the best of optical computing devices. Lenses do a kind of Fourier transform, gratings are a kind of resonant multipole filter, and so forth. You build the physical elements into the gizmo you want, rather than programming it on the fly. Optical switching elements for digital computation are awkward, need multiple light sources (like multicolor laser beams), and will (IMHO) NEVER achieve current LSI device densities, because the wavelength of light used is too long. That said, there is real benefit to optical subsystems as peripherals to electronic computers. FDDI and Ethernet bridge fiber optic data links are a good example, ROM and WORM optical disks are another, and the future will no doubt reveal many more. John Whitmore whit@milton.u.washington.edu
ga1056@sdcc6.ucsd.edu (George D.T. Lu) (11/09/90)
In article <10789@milton.u.washington.edu> whit@milton.u.washington.edu (John Whitmore) writes: > The patch-panel style of computers (like most old analog computers) >is a good model for the best of optical computing devices. Lenses do >a kind of Fourier transform, gratings are a kind of resonant multipole >filter, and so forth. You build the physical elements into the gizmo >you want, rather than programming it on the fly. This is ture for the more traditional optical information processing. I said that optics is more suitable for global interconnection, therefore it is not economical to build a system with optical gates. You will still get the conventional programming model with the electronic processors. Holograms are also gratings, but rather than using them as lens subsitutes (holographic optical elements, used in compact disk readout heads and the barcode scanner in your local supermarket), they can also be used for interconnection. For WSI, you tend to encounter clock-skew at high clock-rate, this can be addressed by optical clock distribution using holograms. (We have developed an expert system here that can generated various holograms using different encoding schemes and fabricate them with the electron-beam machine down the hall.) > Optical switching elements for digital computation are awkward, >need multiple light sources (like multicolor laser beams), and will >(IMHO) NEVER achieve current LSI device densities, because the wavelength >of light used is too long. Not ture. There are several ways to modulate laser beams, frequency tuning is not the best way. Most of the spatial light modulators works with polarization. Bell Lab's Self-electro-optic-effect device (SEED)is pretty promising. In the februrary 1990 issue of Ooptics and Photonics News, David Miller showed a 64 x 32 array of symmetric SEEDs, occupying 1.3 mm square. It is designed to work in reflection with 16,384 light beams in arrays. Each SEED consists of two diodes doing some sort of differential detection. > That said, there is real benefit to optical subsystems as >peripherals to electronic computers. FDDI and Ethernet bridge fiber optic >data links are a good example, ROM and WORM optical disks are another, >and the future will no doubt reveal many more. > > John Whitmore > whit@milton.u.washington.edu There are several groups, including UCSD, working on parallel optical disks that can read an image off the disk in parallel. Three-dimensional optical memories are also in the works. I see optics becoming more than just high-speed data links, but we may need time to get these things out of the labs. The May 10, 1990 issue of Applied Optics is a special issue for optical computing. It has near two dozen papers on very recent progress made in this field, highly recommanded reading if you can find a copy of Applied Optics (it says on the cover that library use prohibited until 1995, I have no clue why they want to do that). George Lu UCSD Optical Information Processing Group lu@poet.ucsd.edu dlu@ucsd.edu dlu@UCSD.bitnet uscd!dlu