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Technology

Shining Light On (And Through) MEMS 71

Posted by timothy from the eentsy-weentsie dept.
An unnamed correspondent pointed out this story at Red Herring about the small-but-not-nanotech devices known as MEMS (microelectromechanical systems). The article focuses on the use that these devices can have in the form of switches enabling optical routing. At present, despite the huge carrying capacity of fiber optics, routing their signals is slower to accomplish and less developed in general than that for data sent as electrical signals. (But on what planet are devices 1-10 millimeters in size "smaller than the width of a human hair"?)
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Shining Light On (And Through) MEMS More

Shining Light On (And Through) MEMS

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  • I believe there is also a limit to their size if limiting the flow of light. Sooner or later, the light would not be blocked and light would "flow" around the roadblock setup by the device.

  • This is the big melting pot, how can someone expect to be cultured and creative if they only see one side of the world?

    As I recall, the US was referred to as "the Melting Pot." And, of course, we all know how cultured and creative the vast majority of Americans are. Simply being able to identify the continents and figure out where most countries are (tho I get confused when they split and change names every week) puts me far ahead of most people in my college class.

  • Comment removed (Score:4)

    by account_deleted ( 4530225 ) on Wednesday December 20, 2000 @11:21AM (#1414206)
    Comment removed based on user account deletion
  • That would be in an effort to keep the switches solid state, correct?
  • I see, sort of a laymen's metric system...

    1 Megatruck = Texas
    1 human hair = 1 pico Texas

    It all makes sense to me now...

  • how many zeroes in a billion? :) heh
  • The Net Economy [theneteconomy.com] had an article [theneteconomy.com] on the new breed of switch fabrics back in October. The article talks about MEMS and has a link to The Sandia MEMS labs, which is very cool.
  • IP however is really not a high performance protocol. It is routed rather than switched, it has variable size packets, It has a relativly high header to payload ratio, and its dependant on the concept of packet broadcast.
    [...]
    I think something similiar to ATM would make a real 'information superhighway', in contrast to the information dirt trail we have now. I mean video on demand, streaming virtual reality, video conferencing, etc.

    Because IP has (about) 40 bytes of header on 0-1500 bytes of data (on most media - as little as 500ish bytes or as much as almost 64K on others), you want to use a 16 byte cell that is 33% header?

    Did you know the really big ISPs are switcing away from ATM? Because nobody can make SARs fast enough? Not "they can't make enough SARs per month (which is a problem with lasers for OC48 or 192 now)", but "damm, we can't assemble packts fast enough!".

    You are right that nobody wants to route IP thorough a whole big network. Older designs used Frame Relay or ATM to carry the traffic on most hops (making only a few routing choices). There is great hope that MPLS can be used in the future, with IP at the edges still of corse (MPLS is still variable sized packets, almost nobody advocates fixed size packets, the closest I have seen is an ATM like system with two sizes of packets (like 64 bytes and 512 bytes).

    Most of your issues with IP are non-issues. Everything but the routed vs. switched, and there are hacks around that.

    P.S. my ATM info is about a year old, it may have changed since then, but MPLS still seems to be the trend. Ask Juniper...

  • The dickhead who wrote that story obviously read the press blurb, where they basically say, almost word for word, what he is saying. In the press blurb it says, and I quote: "MEMS devices are about 1/10mil in size, which makes them smaller than the width of a human hair." The guy who wrote the story obviously read "1/10" as "one to ten" instead of "one tenth" as it should be. Moron.

  • Anime hair is thicker than 10 mm :) Nigecha Dame Da! (Mustn't run away)
  • I heard from a source I can't remember (some interview on Wired, maybe?)... They want to use all-optical switching at the highest levels.

    Where all of the data starts to branch up into the bigger pipes you eventually reach the biggest ones. Switching data among these pipes can be quite a task consider the large volumes of data and of course speed.

    The problem boils down to being able to decipher the destination of the packets as they're coming through. That means "opening" each packet and understanding its destination before you can send it on its way. That "inspection" is time consuming and is the main bottleneck.

    Their goal is to use optical equipment at the lesser pipes to encode the data destined for specific other pipes into a colored light (i.e. red for destA, green for destB and blue for destC, etc.). At this level there is less data, so it is feasible.

    All of these are then merged into a quasi-white light that is sent though the big pipes. The switches can then simply "filter" the light without having to examine the packets. The red filter sends data bound for destA to destA without even "opening" the packets. The other data is similar filtered for their destinations without being "opened".

    Thus, switching at the highest most intensive level is accomplished without mechanical switching or logical understanding of the data.

  • For anybody who cares: You should definitely take a closer look at http://www.imm-mainz.de. I've visited them once, and boy I _was_ impressed. They built the smallest helicopter, nanocatalysators for the chemical industry, and, of course optical switches and multiplexers. Definitely worth a look. DON'T PANIC.
  • Have you checked your grandfather's ears lately?

    <shiver/>

  • Pure optical switching (Score:3)

    by Anonymous Coward on Wednesday December 20, 2000 @10:27AM (#1414217)
    I took digital circuit design (EE194) in my first year of my EE degree. In that class, we were tought (among other things) that any digital logic circuit could be built using NAND gates.

    I'll explain - The primitives most of us are familiar with are AND, OR, and NOT. A NAND gate is an AND gate with its output wired to a NOT gate. Two 1 (on) inputs and you get a 0 output. Any other combination results in a 1 output. Using this gate, we can use the following scenarios:
    • NOT - The single input wired to both inputs of a NAND gate.
    • AND - Two inputs to a NAND, then that output wired to our NOT from above.
    • OR - Each input wired to our NOT and each output of the NOT gates to a NAND gate.

    From these primitives (all from a NAND gate) we can build virtually every logic curcuit needed.

    How does this pertain to the story? Optical switching is limited by the inability to look at an IP packet and determine its destination interface because the light cannot be processed (currently) without converting it to electricity, running that through a CPU, and then re-converting it back to optical light. Before optical switches/routers/computers/etc. become redily available at a cheap price (a few percent more than today's equipment), we must have a complete computer foundation based on an optical NAND gate. Of course the technology could be enhanced in the future, but that level could be reached in a short period of time. Does anyone know if such a beast exists today? If not, it would probably drive costs down quickly. If they do exist, why are they not in use today?

    JMTC (Just my two cents)
  • You have hair that is 1-10 millimeters in size? Good god you should get a trailer and tour the south charging two bits for a "gander". Most of us are lucky to get to ~.05 millimeters although people with black hair tend to do a bit better.
  • Sounds like something right out of Niel Stephensons "The Diamond Age". Hopefully we won't have "toner" all over the place.

    Except that the "toner" is an artifact of true nanotech. Mind you, that sort of thing is fairly likely; It's not like you can keep nanotech out of the hands of freelance hackers forever.

  • These are crap... (Score:2)

    by Anonymous Coward
    The moving-mirror MEMS devices are inherently more
    difficult to implement. You have to have some
    beefy control systems to aim the things at your
    fibre.

    A better way to do it is a Grating Light Valve,
    where the MEMS device is a configurable
    diffraction grating. This way when you actuate
    the GLV, at full deflection you know exactly where
    that light beam is going to be. Sony is using
    this stuff in all their new theatre projectors.

    Silicon Light Machines [siliconlight.com]

    They're the GLV people, recently acquired by
    Cypress Semiconductor.
  • There are some photos of MEMS mirrors at CalTech [caltech.edu] and Bell Labs [bell-labs.com], and page 90 of the January Scientific American.
  • Hopefully these devices will be accurately crafted as well as precisely crafted.

    Microscopic mirrors may not capture our imagination the same way the
    precisely crafted mirrors in the Hubble Space Telescope do.
    The Hubble's mirror was precisely crafted, more precise than any mirror ever made. Unfortunatly, it was precisely the wrong shape because someone left a half-mm shim out of the manufacturing jig. And the jig was never double-checked due to budget overruns and shoddy oversight.

    Only after the HST was in orbit, and it turned out to have a bad case of spherical aberration, did anyone think to review the manufacturing history. Luckily, our intrepid engineers, astronauts, and optics geeks were able to squeeze in a set of corrective mirrors during HST's first maintenance visit a few year later.

    Oh, well, its like they always say. Hindsight is 20/20.

  • I was actually referring to the internet, as people say the US is it is very lacking. I am from Oregon originally, and some of my family still lives up there.

    It is very common to see rebel flags and racist groups.. that's not a melting pot. Only in metropolitan areas is there any degree of cultural diversity from my experience.

  • It's a typo. It's supposed to be "...smaller than the length of a human hair."
  • I know about MEMS, and they're obviously not millimeters in size. I'm guessing that the person who wrote this article thought m were mm.

    Silly mistake.
  • Perhaps because the focus of the article was on optical switching, whereas TI DLP developers focus on display technologies & color printing. Although there could be some overlap between these approaches (why not just shoot a video image down a fiber pipe w/DLP repeaters?), right now there isn't really any.

    Here are some basic theoretical bandwidth calculations for DLP / DMD (cribbed from some TI whitepapers - but any lousy math is my fault):

    theoretical minimum frame time ... is in the range of 10 to 20 microseconds [50-100 kHz!]. This would mean that a DMD pulsewidth modulation system delivering full light efficiency could achieve over 10 bits of dynamic range.

    In particular, pulsewidth modulated SLMs can have bandwidth constraints that limit the system's ability to display the number of bits necessary to eliminate these contours. This limit is set by the switching speed of the mirrors (nearly 18 microseconds) and the data input structure of the DMD. With the current input structure and memory-multi-plexed DMD architecture, the DMD can display 8 bits per color in a 60 Hz sequential color system. In three-DMD configurations, more than 10 bits are possible. One can only determine the number of bits or grayshades necessary when considering the resolution, brightness, and contrast ratio of the display.

    2048 x 1152 mirror resolution has been demonstrated. Thus peak throughput bandwidth would be:

    2,359,296 bits ~= 2 Mbit(assuming each mirror is one bit)
    x
    10 bits (dynamic range via pulse width modulation - most current single-DLP systems are in the 8 bit realm; three-DLP systems obviously get 24 bit color)
    x
    100 kHz (note most current DLP systems work at 50-60 Hz)
    ~=
    2 Gbits throughput (plus error checking, overhead etc.)

    Not exactly ready to switch OC-192's and up. I think the real problem is detection on the other end - how do you recognize the subtle color shifts in real time with this kind of bandwidth (our parallel-processing wetware is pretty good at this, admittedly).

    #include "disclaim.h"
    "All the best people in life seem to like LINUX." - Steve Wozniak
  • I was waiting for someone to bring that up- ATM does indeed have a horrendous header to payload ratio. That is why it wont replace IP as it is.

    About variable vs fixed sized packets: well that is one of the main tenets of ATM. When you have a fixed size packet you can make a whole lot of assumptions in your network stack, which can seriously speed up performance. The problem is picking a packet size which is small enough for all hosts to handle quickly, and large enough to move reduce overhead. I think something in the neighborhood of 1024 bytes would be appropriate.

    You will notice I said something like ATM, not something that is ATM.

    MPLS seems to be an attempt to get IP over ATM. I dont think that will work- sounds like the worst of both worlds in terms of complexity. What I would advocate is something more along the lines of straight improved ATM.

    The advantage of such a system are essentially these two: low latency- in an established connection packets propagate at the speed of light, reliable transport - tcp style virtual circuits are the normal mode of communication rather than a datagram oriented method with a virtual circuit built on top of it.

  • About variable vs fixed sized packets: well that is one of the main tenets of ATM. When you have a fixed size packet you can make a whole lot of assumptions in your network stack, which can seriously speed up performance. The problem is picking a packet size which is small enough for all hosts to handle quickly, and large enough to move reduce overhead. I think something in the neighborhood of 1024 bytes would be appropriate.

    1024 bytes will suck for carrying an IP packet that is just a TCP ACK (and about 30% of TCP traffic is dataless ACKs). It also sucks for carrying interactave voice traffic (i.e. phones). The duel sized ATM-varient actually has almost all the advantages of ATM at the hardware level. It is *almost* as easy to support two sizes as just one, and a far bit simpler then supporting true variable size packets.

    You will notice I said something like ATM, not something that is ATM.

    It was simpler to ignore "something like" then to guess how much like ATM you wanted.

    MPLS seems to be an attempt to get IP over ATM. I dont think that will work- sounds like the worst of both worlds in terms of complexity. What I would advocate is something more along the lines of straight improved ATM.

    It is really a stright forward attempt to get the advantages of IP over Frame Relay without all that complex Frame Relay stuff. And it is simpler then Frame Relay, and ATM, at least if you compair them fairly. At the packet level it is series of 16 bit tags followed by data (over ethernet this lives where the data normally lives, and there is a MPLS protocall number). Each MPLS switch pops off the first tag, and sends the packet out that interface. Simple enough to do cut through routing all in an ASIC without even a CAM involved. ATM needs a small CAM, or a large (but managable) lookup table. Same for Frame Relay. Both have extra fields to mostly ignore.

    If you had an ethernet design in VHDL you could probbbly make a (non cut through) MPLS switch in less then 200 lines of VHDL, and definitly fewer gates then 802.1Q (or whatever the VLAN spec is); of corse it would be a MPLS that doesn't let anything else assign it's tags, but hay, what do you want for an hour's work?

    All three have complex "call setup" schemes, and fallback schemes for dealing with link failure. The MPLS ones are several orders of magnitude simpler if you take statments like "use BGP to find a normal IP route, and do a trivial conversion to MPLS tags" at face value. Otherwise the MPLS ones are only somewhat less complex. ATM and Frame Relay have the notable advantage of being out there and tested for quite some time now. MPLS isn't over it's teething problems.

    The biggest issue that MPLS haddn't fully grappled with as of the, um 1998 or early 1999 MPLS confrence was dealing with circuit failure. As far as I could tell they wanted something that delt faster then an ATM re-route, but without "waisting" half the bandwidth like a protect circuit, or a SONET ring. The big issue is if it takes 30 seconds while routing reconverges and they have to throw away a lambda of data, well, that is just a whole crap load of data to drop.

    Oh, and of corse the "until there is a large scale deployment, nobody knows for sure it won't have nasty problems in a large scale deployment" problem. Of corse it's not like a faster ATM scheme wouldn't also have that problem. I mean the first UUNET ATM backbone had serious teething problems, and ATM switches should have been a well tested technology in 1993 (or was it '94?), right?

    The advantage of such a system are essentially these two: low latency- in an established connection packets propagate at the speed of light, reliable transport - tcp style virtual circuits are the normal mode of communication rather than a datagram oriented method with a virtual circuit built on top of it.
    • ATM and Frame Relay don't give anywhere close to light speed switching. Lambda switching will/should do that, but it will be more closely related to MPLS then the other schemes!!!
    • A virtual circuit that doesn't gaurentee data integrety will still need something like TCP running on top of it. All known virtual circuit like systems that do the data integrety themselves are worse then TCP (they don't need too, something like delta-t might be better).
    • Explicit circuit switched networks were here for decades before IP became popular. It is just a whole lot simpler to use a packet switched system. The difficulty of making a large packet switched network is just the price we have to pay to make the network usable.

    Granted my networking experence is mostly limited to IP, things you can run on top of IP, and things IP can run on top of. But I'm pretty damm sure of all the statments I've made.

  • Your "examining the packets" is cruddy old PDH (Plesiochronous Digital Heirarchy - meaning "nearly the same clock"), or SONET, as you Americans would call it.
    It's old dead technology.
    What came after it was SDH (Synchronous ...), which permitted Add-Drop Multiplexing of any tributary (45/34/6/2/1.5 Mb/s) without having to unpack the higher levels of the multiplex. i.e I could pull out a 2M channel which was inside a 6M channel which was inside a 45M channel inside a 140M channel without having to examine any other 2/6 or 45M channel's headers, I can go straight to my own 2M channel and extract it from inside its own bit-stuffed region.

    Of course SDH is on the way out, as WDM takes over. However, WDM has been designed to interwork directly with today's SDH networks. Using non-linmear optics a SDH signal can be "frequency shifted" into one of the wavelengths used in the WDM mux. (It's not really frequency shifted, it simply "pumps" a signal of the desired frequency, not that that explains things any better, ooops)

    FatPhil

    -- Real Men Don't Use Porn. -- Morality In Media Billboards
  • I don't understand all these powers of ten, they confuse me. Why can't we just use feet and pounds?

    FP.
    -- Real Men Don't Use Porn. -- Morality In Media Billboards
  • well what's so impressive about that? some people have hair 2 or 3 feet long. i think they meant width and got it wrong
  • There's some confusion over two concepts here: the time to switch SONET frames, which most people refer to as switching speed, and the time to fail over to another SONET fibre ring when one fibre fails (known as automatic protection switching).

    If SONET cross-connects took 50-100ms to forward frames they would be slower than routers, of course.

    Most people care about the per node latency - establishing new paths through the network is often done by management systems only, and can take tens of milliseconds upwards, particularly if it's not required for resilience to failure.
  • But on what planet are devices 1-10 millimeters in size "smaller than the width of a human hair"?

    Human, n.: Silly looking earth based creature

    Through deductive reasoning, I conclude that the answer to this question is ... Earth!. Seeing that Earth is the only planet that has humans. This could help you [lapeer.org]

  • Sounds like something right out of Niel Stephensons "The Diamond Age". Hopefully we won't have "toner" all over the place.
  • But on what planet are devices 1-10 millimeters in size "smaller than the width of a human hair"?

    You obviously havent seen this guy [shugashack.com].

    -----
    If Bill Gates had a nickel for every time Windows crashed...
  • There's a limiting factor, right? Once we get down to the size of electrons, won't we have to find some new way to power these things?

    It's funny, really. When I was a kid, the whole world was concentrating on making things bigger and bigger, taller and taller. The Empire State building, the Sears Tower, and now even that new building in Koala Lampur, Malaysia. But now it looks like the trend is in the opposite direction. How soon until the Guinness Book of World Records has an entry for "smallest building"? And once we master nanotechnology, we'll have probably already mastered genetic engineering, so we'll have little people to inhabit those buildings. What fun! I loved the Wizard of Oz as a child, and I hope to live to see real life munchkins.
  • apparently the author isn't smart...

    i believe that should be 1-10 micrometers.

    hence the name microelectromechanical.

    -k
  • It seems like they are talking about microscopic sizes through the whole article. Maybe the 1-10mm bit was a typo?
  • How could they leave out Texas Instruments DLP? Over half a million in the field, each with hundreds of thousands of moving parts. See www.ti.com/dlp for more info.
  • MEMS have uses outside of networking that haven't been mentioned. There are MEMS acceleration and turn rate sensors, as well as research looking at MEMS for wing surfaces to control airflow transitions from laminar to turbulent. I'm sure I'm leaving out many more...
  • Also "Technology Review" had some articles about microphotonics in their July issue: http://www.techreview.com/articles/july00/fairley. htm [techreview.com] (there are some worthwhile links at the bottom of the article too).

  • Here (Score:1)

    by Anonymous Coward
    MEMS are microscopic marvels
    By Alan Zeichick
    Redherring.com, December 20, 2000

    Current comparison chart
    Quote & Chart for: LU
    We've all seen and admired large-scale engineering triumphs like the Empire State Building, the Brooklyn Bridge, and Mount Rushmore. Engineers working at the other end of the size spectrum, building microscopic devices, are no slouches either. It's in this Gulliver's Travels category that microelectromechanical systems, or MEMS, belong.

    MEMS devices are extremely small machines. They are about one to ten millimeters in size, which makes them smaller than the width of a human hair. The individual components of a MEMS machine are one-thousandth of a millimeter, or a micron, in size. Some MEMS gears, for example, are 100 microns tall, with gear teeth 5 microns wide. MEMS technology is sometimes referred to as micron-scale manufacturing. (It's important not to confuse MEMS with nanotechnology, which involves devices built at the even smaller, molecular level.) Companies producing MEMS devices include Lucent Technologies (NYSE: LU), Onix Micro, EV Group, Nanovation, Boeing (NYSE: BA), Tanner, Sandia National Laboratories, and Microcosm.

    MEMS devices have two main uses: as sensors and as actuators. When working as sensors, these machines passively monitor their environments. When working as actuators, they monitor and are able to respond to changes in their surrounding environment.

    MEMS sensors have been built into automobile engines to detect oil pressure. A MEMS sensor can also measure an automobile's inertia: if the sensor detects rapid acceleration or deceleration, an integrated circuit activates an air bag. Other MEMS sensors used in automobiles include tiny gyroscopes that track the direction in which a vehicle is traveling.

    There are fewer applications for MEMs actuators, but they've been used to construct electromagnetic motors, gear trains, and even -- in the lab -- miniature combination locks. One of the first uses of MEMS actuator technology is in optical switching.

    MIRROR, MIRROR
    The theory behind MEMS-based optical switches is fairly simple, yet clever. They're assembled by connecting a miniscule MEMS "stepper motor" to a gear. The gear, in turn, has a tiny mirror attached to it. The motor moves the mirror between two positions, much like the high beams on an automobile.

    The simplest type of MEMS optical switch is comprised of three pieces of fiber-optic cable: one is an input, and the other two are outputs. A laser beam traveling along the optical fiber can be redirected by the mirror's bidirectional movement. This permits light waves to be sent down either of the output fibers. Today's optical networks use this type of switch, which can redirect a light wave in about 1 one-hundredth of a second. That speed may seem glacially slow compared with the millionths-of-a-second speeds of electrons inside computers' integrated circuits, but it's much faster than other mechanical means of switching optical beams.

    With those basic principles in place, it seems like there's no limit to the possibilities for combining MEMS technology and mirrors. A switch, for example, that goes from one input to two outputs (or vice versa) is referred to as a 1x2 switch. The technique can be extended to switch a single beam of light to 4, 8, or 16 outputs. These sorts of devices, called 1xN switches, are used primarily for test and measurement applications.

    THE LIGHT IDEA

    MEMS optical components can play an even more important role in managing the infrastructure of a corporate network. The most powerful type uses more than a dozen microscopic mirrors to switch a large number of input optical streams into many outputs. One type, called an MxN switch, can switch many fiber-optic inputs from one set of output fibers to another. This makes it ideal for designing fault-tolerant applications. For example, if a backhoe accidentally severs an eight-strand fiber-optic cable, the switch can reroute the traffic to eight strands of backup glass fibers. Or, conversely, if a high-speed network router breaks, the fibers can be switched to a backup router.

    MEMS switches can also be used to provide optical services to consumers. By combining dense wave division multiplexing (DWDM) lasers and sensors with MEMS micromirror switches, network service providers can provide service quickly.

    What's in store for MEMS? One interesting development has been combining MEMS hardware on the same chip as a traditional integrated circuit. After all, the technologies are synergistic. Many MEMS devices are actually manufactured using the same processes as integrated circuits, like surface micromachining, whereby thin layers of plastic or nickel are deposited onto a silicon wafer. Unlike chips, MEMS devices then have some of that material carefully removed so that parts have freedom of movement.

    By combining the control logic for a MEMS device with its mechanical motors, sensors, and gears, the device becomes not only smaller, but also more reliable. Moreover, eliminating the need to run wires between the mechanical elements and the control circuitry reduces manufacturing and testing headaches.

    Other current MEMS research aims to improve the precision of the mechanical devices, making them easier, faster, and less expensive to manufacture. Right now, manufacturing processes require MEMS devices to be fairly flat, limiting some designs.

    Microscopic mirrors may not capture our imagination the same way the precisely crafted mirrors in the Hubble Space Telescope do. But one thing is for sure: MEMS devices will play a more important role in building our technology-based economy.

  • Just out of curiosity, were you a kid when the Empire State building was built?

    The trend has been going the other way for a while now; cars, computers, apartments, etc...

    I think the exciting prospect is building large things with small things (micro/nano tech etc) in large arrays. If only I could live that long.
  • But this article was talking about MEMs technology - which is fiber optic switching *without* converting the signal to electrical. MEMs is really just lots of very tiny mirrors bouncing light around to do the switching. Simple ones will take one input and switch to 2 different outputs. Slightly more complicated ones take 1 input and switch to 8 or 16 outputs. The most complicated ones take up to 64 inputs and switch them to any of 64 outputs.

    And - and optical-eletrical-optical switch is not really that slow. If you are talking about switching Sonet signals (aka TDM streams - not packet streams) then your latency through a node is measure in nano-seconds. Not really "slow"

  • ...what they probably meant to say "They are about one to ten millimeters in size, which makes them magnitudes smaller than the width of a human-hare [thewhiterabbit.com]."


    ;-)

  • The article is pretty short on technical details - go figure. I'll start by pointing people to a site that I like - while not always 100% accurate - it is much better than most out there.

    Go to http://www.lightreading.com/ [lightreading.com] and look up MEMs

    Lucent among many others is developing MEMs technology for switching beams of light in telecom systems. The basics for MEMs technology is understood by a bunch of companies that use it for such mundane things such as accelerometers in air bag deployment systems. Now many of them are looking to use this basic technology of building mechanical things on a chip to create better communication systems.

    Since a MEMs device is basically just a mirror that can be adjusted to bounce light to a different place - it can be used in a couple of different ways.

    The simplest way is to use MEMs devices to act like an optical patch panel. A bunch of fibers come in, and a bunch go out. The MEMs device bounces light from one of the input fibers to one of the output fibers. If someone has used DWDM (dense wavelength division multiplexing) to put a bunch of signals on that one fiber, all of them get switched together. BUT there is no optical-electrical-optical conversion, so the switching system doesn't need to know much about what it is switching. It could be OC-192 SONET or 10Gb ethernet and it really doesn't care. A very cool benefit.

    A slightly more complex way to use MEMs devices is to take the different wavelengths of light in a DWDM system and split them out. Then bounce these individual wavelengths through the MEMs device. Take the wavelengths comeing out and combine them back together into a different set of fibers. The problem with this is that if you can't put two signals using the exact same wavelength down the same desination fiber. This can be solved with devices that convert the wavelength, but today that usually involves an optical-eletrical-optical conversion.

    The one big plus of MEMs devices is that you avoid the optical-eletrical-optical conversion that can be costly for the electronics, and requires the electronics to be set up for the exact kind of signal you are passing through. The one big minus to MEMs devices is that they all "eat" some of the light going through them. A loss of a couple dB is not uncommon. This means that you can't avoid the optical-eletrical-optical conversion forever. As the technology matures, it will get better with less light loss, but it will take time.

    Note - MEMs devices today are *not* for doing packet switching. They are more for doing optical circuit switching. They typically take a relatively long time to move from one posisition to another (10 millisecons or more). In that amount of time, you could have a shitload of data go through your system. There are companies working on doing an all optical packet switch, but that is a ways off yet today.
  • >And - and optical-eletrical-optical switch is not really that slow.
    >If you are talking about switching Sonet signals (aka TDM streams - not
    >packet streams) then your latency through a node is measure in nano-seconds. Not really "slow"

    Actually, more typically latency through a SONET node is 32 microseconds; which doesn't have much to do with switching time.

    Switching time is more like 50ms in SONET land, although several times faster than that is a more typical value, and the standards allow for 100ms in some situations.
  • Sorry to reply to my own post, but a few followup points:

    My calculations should end up with approx. 2 Gbit/sec. (Gbps) throughput.

    TI has already demoed a full SXGA (1280 x 1024) 24-bit resolution all-digital graphics display which handles 1.89 Gbit/sec. throughput. See this PDF. [dlp.com]

    #include "disclaim.h"
    "All the best people in life seem to like LINUX." - Steve Wozniak

  • There are quite a few ways to do optical switching - most do not involve per-packet forwarding since that would be very hard with optics. Many just set up an optical path through various nodes, and leave it established for days or months - you put IP, ATM or whatever into one end, and it pops out the other end, without the optical switches knowing what they are switching (like ATM PVCs).

    One promising compromise is optical burst switching - here, the control plane operates electronically, with the ingress node sending a control packet saying where the burst (not yet sent) is to go. The optical switches set up suitable fibre+wavelength cross-connections to match the control packet's requirements. Then, after a specified delay to allow for setup, the actual data burst is sent along the all-optical path.

    This avoids having to per-packet forwarding but still retains quite a lot of flexibility.
    One of the most interesting things is that IP-based protocols are likely to become the standard for setting up optical paths (probably via MPLS) - this makes it a lot easier to build systems that talk IP to the ingress nodes to configure the required paths. MPLS is already used in IP router + ATM switch based networks, but enabling it to control optical networks will mean you can have a single control mechanism across IP, ATM and optical domains.
  • One way of pushing the intelligence to the edges is to use MPLS to control optical networks - the edge MPLS label-switch router assigns an MPLS label in the form of a wavelength, while the core optical switches know nothing about IP and can perform pure optical switching.
  • Actually, it does exist. Alcatel in Belgium has a fully optical switch, as do several US companies (I recall reading a story on slashdot about it) - Lucent probably. However, the technology is tricky due to less than ideal nonlinear materials and problems with drift of several of the parameter. Also, you mustn't forget that the interaction among light beams inside a material is still mediated by electrons, so the speed can never be more than that of the electronic processes used. In current electronics, they are much better at pushing the edge here. The real power in optical switching lies in the parallellism and the bandwidth thus possible. Random network burp
  • 1024 bytes will suck for carrying an IP packet that is just a TCP ACK (and about 30% of TCP traffic is dataless ACKs).

    Thats just it though- I did not mean to use TCP over ATM, I was meaning to use ATM's reliable transport features so TCP would be redundant.

    It also sucks for carrying interactave voice traffic (i.e. phones)

    Actually thats what it was originally designed to do, and it is very good at it. IP is what sucks at carrying real time streams.

    ATM and Frame Relay don't give anywhere close to light speed switching. Lambda switching will/should do that, but it will be more closely related to MPLS then the other schemes!!!

    I know that current ATM converts to electric signals to switch, what I meant was an optically switched ATMlike protocol would propagate at the speed of light. Signalling will still be far slower, but an established connection will be full speed.

    MPLS is really a stright forward attempt to get the advantages of IP over Frame Relay without all that complex Frame Relay stuff. And it is simpler then Frame Relay, and ATM, at least if you compair them fairly. reading about MPLS from here [ieng.com] and here [iec.org] It looks basically like a way to do IP over X, where X is Frame relay or ATM. It cannot be simpler than them if it requires them to work. Its just an extra layer. What I was talking about was getting rid of IP altogether, and using a switched protocol more directly. thats all. If that were the case MPLS would be unnecessary.

  • There is an article about optical switch technology on page 75 of the Janurary issue of WIRED. Memx (http://www.memx.org) is on the cutting edge of the technology.
  • Thats just it though- I did not mean to use TCP over ATM, I was meaning to use ATM's reliable transport features so TCP would be redundant.

    Fine, but reliable ATM has ACKs, so a ATM with 1024 byte packets would have 1024 byte ACKs. And would not have TCP ACK compression (which can send half as many ACKs, or less, if traffic is moving fast enough), and will miss many of the other fine TCP features.

    My only dirrect experiance with a reliable ATM product was wholey negitave. It managed to carry about 2Mbits over a 16Mbit pipe. It was a disaster. Replacment with Frame Relay was a wonderful success, carrying almost 16Mbits within two hours of being turned up. Part of this was assuradly the hand-off media (but no more then 8Mbits loss could reasonable be attributed to that), and part was assuradly the poor hardware implmenting reliable ATM, but a large part was the poor reliable ATM itself, and the complexity which made it hard to have a good implmentation!

    I know ATM was designed to carry voice phone traffic, but an ATM with 1024 byte headers would not be useful. Too much data would be in it. You can't buffer 1K byte (8K bits) of a 56Kbit voice stream without introducing audable latency. Existing 46 (or is it 36?) byte cells sometimes go unfilled in voice applications.

    In other words a fixed 1024 byte ATM cell size will make ATM extreamly unwealdy. Far worse then existing ATM which is widly cratisized for throwing away ~33% of the banswidth.

    I know that current ATM converts to electric signals to switch, what I meant was an optically switched ATMlike protocol would propagate at the speed of light. Signalling will still be far slower, but an established connection will be full speed.

    Big deal. Optically switched IP would switch at the speed of light as well. Neither are likely to happen soon. The only thing that switches at the speed of light is the extreamly unflexable lambda switching, and that is all we are likely to have for quite some time.

    reading about MPLS from here and here It looks basically like a way to do IP over X, where X is Frame relay or ATM. It cannot be simpler than them if it requires them to work.

    It is a way to run IP over X, and I don't think it can run anything but IP. However X is a lot more then ATM or Frame Relay. It includes Packet over Sonet (which is basically a no-overhead no-service protocall), there is also a MPLS over PPP. I think there is a MPLS over ethernet as well. In practice there can be MPLS over anything. In reality it works better with things that can send either variable sized packets (with a large minimum size), or continous streams of data.

    MPLS over ATM or Frame Relay is there more to get experaince with MPLS then to actually be used. You are right if you have allready payed for ATM or Frame Relay there seems to be little point in slapping MPLS onto of it before going for IP. MPLS was intended to be run very close to the wire, not on top of a complex protocall that does everything MPLS does and more. MPLS was a reaction to the loss of ATM and Frame Relay at higher speed interfaces.

    I had no hand in deigning MPLS, I was merely on the same floor as some of the people that did. But, I have talke to them a bit. (I have only slightly more to blame for PPP over Ethernet)

    There is some small chance that if MPLS is wildly succesful, one might want to run it over ATM or Frame Relay just because MPLS links are simpler to mangage. However I think chances of that are slim. I don't expect MPLS to be signifigantly more managable then Frame Relay or ATM, dispite being designed in large part by those that will have to manage it!

  • Well, 1 human hair is exactly one US billionth of the volume of a small car. The actual scale is: 1,000,000,000,000 human hairs = small car

    It is the British billion which is 10^12. The US billion is only 10^9, also known (rarely) as a milliard in the British system.

  • ATM is still around but is increasingly used only within the core of large telcos (to deliver Frame Relay, leased line emulation, and so on, which are still very profitable) and for ADSL (I'm posting this over an ATM 25 Mbps connection from my ADSL router).

    IP has its challenges but, when combined with MPLS, can do much of what ATM can do - QoS (with some limitations but much more scalable than ATM), traffic engineering (balancing utilisation of circuits all over the network to meet QoS goals or reduce costs), and closed user groups (aka IP VPNs).

    There's absolutely no need to ditch IP for other protocols (except for the upgrade to IPv6 of course :). In particular, the issue of voice packet overhead is addressed through:

    - RTP compression (compresses the IP+UDP+RTP header of VoIP packets quite significantly)

    - Voice over MPLS (VoMPLS) - puts the RTP payload into an MPLS encapsulation (just 4 bytes of overhead), stripping off the IP and UDP on ingress to the MPLS domain and adding it back on egress.

    Also, the much discussed small size of ATM cells is only really of benefit on low speed links - if you have a 1 Gbps link, there is probably no need to pre-empt the transmission of large file transfer packets to squeeze in a VoIP packet ASAP. The IP world has link-level fragmentation techniques (LFI on Cisco's, PPP options on everything else) that mean you get tiny link-level fragments, rather like ATM cells, on low speed links, but avoid the overhead of cells on high speed links.

  • ah, another article i'm somewhat qualified to comment on. currently i work for Seagate Technologies, in their R&D division. we're working on *really tiny things*. i can't really give any specs and whatnot, company policy and all that. wouldn't want ibm or maxtor catching wind of what's going on here. or read-rite for that matter, but they're a joke.

    anyway, mems, truely interesting little structures. crude mems have been around for quite some time in the manner of waveguides, for fibre optic applications. about them being limited by the size of the light? well, light can get pretty darn small. the little red laser in your average cd player runs a nominal 650nm wavelength. i say nominal because "red" in the visual spectrum has a relatively large range of wavelengths. i'm trying to recall some of the interesting facts i picked up while interviewing for a position in lucent's opto-e department. if i recall correctly, in the "red" spectrum they're able to accurately create (via laser diode) and receive (phototransistors) something like 192 different individual wavelengths. tremendously useful thing, when you think about it. that means they can send 192 different signals across one fibre. i've gone off on a tangent, haven't i?

    back on subject, there's a whole huge range of *light* in the electromagnetic spectrum. here at work we're using ultraviolet light in our photolithography processes (as well as e-beam, we're high tech, remember?). currently we're using what's called G-Line, or 436nm. it's not really true G-line, it's really somewhere around 420nm, but we're using the mutt of ultratech's litter, the 2700. (illegal segue: if anyone's got a 4700, 6700, or a nikon ;) for sale cheap or good advice on a way of deep sixing a 2700 and making it look like an accident, please let me know) thus far, the useable spectrum goes down to 157nm, or ultradeep uv. we're looking at picking up something capable of 193, or deep uv, just to cut down on e-beam time (writing patterns with electrons takes a *very* long time).

    whether or not this end of the spectrum is feasable for communications transmission, i don't know. i won't imagine it would be, because thus far, laser diodes in that range haven't been made, and if they can be made, they won't be cheap. part of the reason dvd players are so expensive is because the laser diodes aren't cheap or easy to produce. they're getting there though.

    where was i... oh, mems. i wouldn't look for mems to make any great leaps and bounds yet. it's still barely in it's infantcy, maybe even still a fetus. that's the wonderfully annoying thing about the cutting edge of technology, we have no idea where we can go until we've already been there. it's total hell on those 3 year corperate plans. we (worldwide humanity generalization) have the capability to produce fantastically small things and build them up to mems, but we don't yet have an understanding of what we want to do with them, how we want to do it, and how to make it cheap enough that it'll find a niche. ibm's building quantum computers, but i wouldn't look for one on your desktop in the next 20 or so years. mems still has a long way to go. enough of a technology lesson for the day.

  • >Most people care about the per node latency - establishing new paths through the
    >network is often done by management systems only, and can take tens of milliseconds
    >upwards, particularly if it's not required for resilience to failure.

    You, in turn, seem to be confusing two concepts in one sentence here: setting up new paths through the network (which doesn't have to be particularly fast at the moment for SONET- tens of SECONDS is possibly acceptable although not desirable) and the 'switching time' of 32 microseconds or less per node which seems adequate bearing in mind the approximately fractal nature of the internet tends to restrict the hop count.

  • ...claim they were "Silicone Microchips"!
    "A microprocessor... is a terrible thing to waste." --

  • It's always been this way -- just depends on what your focus is... I'd say the ISS is focusing on big.

    And here's a dose of irony -- The Large Hadron Collider and other such particle smashers : Really Big Things built to look at Really Small Things...

    Ask an Astronomer about focusing on small things and he'll point you across the hall to the particle physicist he works with.

    -k
  • Maybe in zero gravity with a protein rich diet 10+ mm hair strands could be achieved.

  • They are about one to ten millimeters in size, which makes them smaller than the width of a human hair.

    10mm == 1cm. Maybe the author has dreadlocks, mon!
  • nevermind -- my misunderstanding. He's still wrong about the width of a human hair, but entire MEMS would very well get that big...

    -k

  • SciAm's current issue. (Score:4)

    by interiot ( 50685 ) on Wednesday December 20, 2000 @09:58AM (#1414264) Homepage
    Scientific American's current issue [sciam.com] contains several articles on optical networks and prospects for switching and routing them without electronics.
    --

  • Re:red herring - Hair width (Score:1)

    by Anonymous Coward
    For those that don't know... Human hair is about 75 microns (micrometers). Not sure what pubic and facial hair is.
  • In the article, and from listening to all the networking types I know, it seems that everybody thinks the future lies within IP.

    IP however is really not a high performance protocol. It is routed rather than switched, it has variable size packets, It has a relativly high header to payload ratio, and its dependant on the concept of packet broadcast. It was originally designed as a way to tie together a bunch of ethernet LAN's, and its really not suitable for a low latency, full planet network.

    I think something similiar to ATM would make a real 'information superhighway', in contrast to the information dirt trail we have now. I mean video on demand, streaming virtual reality, video conferencing, etc.

    One problem is that IP is so deeply embedded into all unix variants. Another is creating a switched optical fiber protocol that would also be suitable for use over a home LAN. With the rise of 100megabit and gigabit LAN's however hubs are essentially gone and replaced by switches anyway- so having one's home network use a switched protocol instead of IP is the logical extension to that.

    Taking into account optical packet switching of an asynchronous fixed size packet WAN, contious signal amplification (with erbium or something similiar), and bluetooth wireless gadgets; then we would have our futuristic network.

    I can only hope that people realize that IP as it is today, or even IPv6 with its complexity is just not up to the task we have in mind for it. It will be a long process of rewriting, and I would like to see a clear standard for a new non-proprietary protocol emerge.

  • Ok time for the Canadian to step in. You see, our "metric" system is lot like the 10-based number system we all enjoy so much. When you want to go from one unit of measurement to the next, you simply multiply or divide by ten.

    It's a lot like, ummm... what's that word... uh, perfect.

    Ok, 10 Millimeters = 1 Centimeter (Lookout Latin!). A Centimeter x 2.54 = 1 Inch. Ok, so divide an inch in half, divide it into three, and your Canadian Centimeter lies between half and 2/3rds. Almost the size of a Dimes face.

    That's a little large to be considered microscopic, even if you were to divide that dime's face into 10 - you could still see the divisions.

  • I've heard that multiplexing is an important strategy to deliver more data via fiber. I know that the mirror approach would, but I kind of doubt that using diffraction to aim photons would work if there was more than one bandwidth in the pipe. Could a GLV somehow be engineered to work with more than one frequency of light?

    And are there other ways (in theory) to deflect the beam. I realise that using a EM field probably wouldn't work, but is there some sort of field (gravity?...) that could be use to control the switch? Something that took out the "mechanical" out of the equation?
  • This is exactly the same principle as WDM and DWDM - wave division multiplexing: you're basically blend light of different wavelengths at one end of the fiber, and filter them on the other side.

    It's being used already, but only using Red, Green, Blue, would be "not too dense" ;-)


    Okay... I'll do the stupid things first, then you shy people follow.

  • Can someone explain to be why the human hair is the default unit of smallness? Why not a grain of sand? These are common, small, and relatively uniform. Or perhaps the thickness of a sheet of paper?

    -josh
  • I don't know but your prolly right.

    MEMS devices are extremely small machines. They are about one to ten millimeters in size, which makes them smaller than the width of a human hair. The individual components of a MEMS machine are one-thousandth of a millimeter, or a micron, in size. Some MEMS gears, for example, are 100 microns tall, with gear teeth 5 microns wide. MEMS technology is sometimes referred to as micron-scale manufacturing.

  • fiber optic slowness (Score:4)

    by jpostel ( 114922 ) on Wednesday December 20, 2000 @10:03AM (#1414272) Homepage Journal
    The slowness of fiber optic switching is due to the fact that it is currently done by converting the signal to electrical, switching it, then converting back to optical. There are many technologies currently in development to take care of many of the problems with optical switching. The problem with them is that they have been in development for a while now. I was working on opto-electronic modulator research at Bell Labs in 1996 and the technology is still not widely used. Like most really cool technology, it will be a while before we see any of this in wide spread use.
  • Link seems to be broken. Doesn't look like /. effect.
  • How could they leave out Texas Instruments DLP? Over half a million in the field, each with hundreds of thousands of moving parts. See www.ti.com/dlp for more info.

    And you (and the moderators) forgot to check your link. TI DLP actually lives at www.dlp.com [dlp.com].

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