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Networking The Internet Hardware Science

Optical Memory Could Speed Up the Internet 36

Posted by timothy
from the anything-could-anything dept.
ananyo writes "Bits of data travelling the internet have a tough commute — they bounce back and forth between optical signal lines for efficient transmission and electrical signal lines for processing. All-optical routers would be more energy efficient, but their development has been hindered by a lack of optical memory devices. Now, researchers have developed just such a device (journal article abstract), paving the way towards a faster, more energy-efficient internet. The devices are based on optical cavities that can be switched between light-transmitting and light-blocking states to construct digital signals. Researchers have been working on such devices for several years, but previous versions used too much power and could not retain data long enough. The new memory cells use just 30 nanowatts of power, 300 times less than previous designs, and can retain data for one microsecond — long enough to support processing." (See also this paper on all-optical swtiches by four of the same authors.)
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Optical Memory Could Speed Up the Internet

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  • by arnoldo.j.nunez (1300907) on Sunday February 26, 2012 @05:01PM (#39166451)
    From the Nature News link:

    When a particular wavelength of light shines on the cell, the material’s refractive index changes so that it either will or will not transmit a pulse of light, to create either a "1" or "0" bit. Another light pulse can reverse it. A second laser provides constant background light, called bias, which helps the memory cell maintain its state.

    So the key is that the medium is able to change its refractive index sufficiently so that there is total external reflection apparently (0) and (almost) complete transmittance (1). Thus, the medium's optical properties (index of refraction which is ultimately a measure of the speed of light in that medium due to the material's permittivity and permeability) dictates its nonvolatile memory applications. You change the medium's optical properties itself with a "write" laser.

    The "read" laser (which they call bias but is a bit confusingly used to me) allows you to read off the "memory value" (really just transmittance as a function of the index of refraction set again by the "write" laser).

    So the power consumption comes from using two lasers. So it makes me wonder, can you cut down the power requirements by using an LED with a monochromatic wavelength filter? Sure it won't be very efficient in getting a single wavelength, but perhaps you don't need that much optical energy?

    • by Pseudonym (62607)

      So the power consumption comes from using two lasers. So it makes me wonder, can you cut down the power requirements by using an LED with a monochromatic wavelength filter? Sure it won't be very efficient in getting a single wavelength, but perhaps you don't need that much optical energy?

      LED + feedback cavity = laser diode

  • by jovius (974690) on Sunday February 26, 2012 @05:04PM (#39166469)

    The researchers seem to have missed the huge leftover stock of photographic film. Stopping it completely provides indefinite storage while spinning it 1 mega frame / second satisfies microsecond processing needs.

    • by Sulphur (1548251) on Sunday February 26, 2012 @05:26PM (#39166573)

      The researchers seem to have missed the huge leftover stock of photographic film. Stopping it completely provides indefinite storage while spinning it 1 mega frame / second satisfies microsecond processing needs.

      I remember someone spinning a bit of metal at 10^6 rev/sec. It was the size of the period on a typewriter. At 1.5x10^6 or so it exploded. I suspect that the gelatin would spin off much earlier.

    • You do know that film has to be developed first, right?
    • I'm pretty sure you're trolling, but somebody should try that kind of approach. Just for the laughs.
  • by Animats (122034) on Sunday February 26, 2012 @06:07PM (#39166845) Homepage

    The article skips over the issue of how many bits they can store. It does indicate that numbers > 1 have been achieved, but RAM in megabit, let alone gigabit size, seems to be a long way off.

    There have been a few optical switches with fiber optic delay loops. If a packet comes in and the outgoing link is busy, the packet is shunted to a delay loop for one packet time. This works best if the packets are all the same size, like ATM, but it's been made to work with variable sized packets. So far, there's not much commercial technology in the area. Lots of papers, though. People have been working on this problem for over a decade, and there's a little progress each year.

    A few bits of pure optical storage and logic will help. If there's enough to handle packet routing and tags, a useful switch can be all-optical, even if storing the data packets themselves in "optical RAM" isn't feasible.

  • They can go to hell. Where was this done? Did they use ANY public funds? If so, i already own it, so give me the damned article.

    • This work was supported by the National Institute of Information and Communications Technology (NICT).

      NICT [wikipedia.org], for the record, is in Japan, so unless you are a Japanese taxpayer (who, based on your sig, also feels very strongly about slavery during the 1860s in the USA) no, you do not own the article.

  • Fiber optic or not submarine cables still need optical repeaters every 100km or so. Moving these to optical switches would allow for easier deployments.
  • by Anonymous Coward

    I can't see optical memory being a big improvement by itself; you'd still have to switch to electrons to go through the processor, then convert back to photons for transmission.

    Now optical processors, that would make a BIG difference.

    • by tibit (1762298)

      And that should end the discussion. Right there. Because in a router, or a switch, you actually process data. As in, you know, making decisions based on the values of those bits coming in, and shit. It makes no sense to try hard to make only a small part of it optical, as in optical memory. You need the whole thing optical or else it won't make any sense, economically, energy-consumption-wise, or otherwise.

      • by gagol (583737)
        One have to start somewhere...
        • by tibit (1762298)

          Sure, but that's of no practical importance right now. It's a step in the right direction perhaps, but only of academic interest at the moment. When they do a whole router using optical computation, then it'll be big news. I'd hope they'll be there in another 25 years.

  • it does not change the fact that my internet connection is on shared bandwidth copper for dozens if not hundreds of miles, hitting a 20$ netgear router

    increase speeds by 10 fold, doesnt matter to me, cause the price to home service is retarded and I will not feel a single bit of it ... or in other words get your shit straight

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