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AirFiber Laser Networks: 622mbps 92

Posted by CmdrTaco from the now-we're-getting-somewhere dept.
shinar writes: "In the LA Times, AirFiber announced the July/August avaliability of a new last-mile replacement for fiber: a wireless laser system delivering up to 622 mbps. It's a short-range system, mainly viewed as a delivery system within cities. It's being tested in Dallas, Tokyo, and Madrid, and projected for first commercial release in July or August. Not huge or revolutionary-a few other companies are working on the same sort of thing-but it might be a blessing for people in high-population density areas. "
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AirFiber Laser Networks: 622mbps More

AirFiber Laser Networks: 622mbps

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  • interference (Score:3)

    by blackdefiance ( 142579 ) on Tuesday April 25, 2000 @05:48AM (#1111659) Homepage
    would snow, hail, or a hard rain disrupt this?
  • how'll they keep pigeons out of the laser path?
  • or other objects such as helicopters etc !

  • It said that fog causes some interference, since it blocks light waves, so I would imagine that rain, hail, and snow should not, unless it is so heavy that a normal light beam could not penetrate it.
  • to perk up my Napster :)
  • how about just alot of fog? (ok its southern cali, but still...)
  • As I see it there are a lot of things that could make this unstable. Precipitation in any quantity would attenuate the signal, bugs, birds or dust likewise. Certain health risks if exposed to any high level of coherent light exist. A mirror placed in the path would have interesting effects as well as a crystal.

    Neat idea however.

    Da

  • Weather? (Score:1)

    by Kaa ( 21510 )
    Doesn't fog, rain, smog, etc. screw up lasers?

    "It's foggy, I can't see the Internet..."


    Kaa
  • sorry missed the line about fog =(
  • The real question is - how many times will the network go down because people have to see for themselves whether the laser is indeed eye-safe?

  • This reminds me of a system I tested a few years back when I was working with a TV station. We tried out an infra-red laser system which allowed us to beam a TV feed between two places which had line of sight.

    It was quite a while ago, but I remember that the range wasn't very impressive, that it was a bastard to get set up (trying to align a laser over a kilometre distance isn't the easiest thing in the world to do) and that heavy rain, fog, waving your hand in front of it, etc. did have an adverse affect.

    D.

  • how'll they keep pigeons out of the laser path?

    We have a laser beam over a street here (albeit an old one; 5-10 yr old, around 1-2 Mbit/s, IIRC). Flying pigeons are no trouble (well, it bogs down NFS, that's all)... and pigeons just won't land on the nailboards laid under the laser boxes.

    Overall, works well and reliably. The only problem is with heavy rain.

  • This could be adapted to cluster computing for much MUCH MUCH! faster transfer rates between nodes! That way also you don't have to worry about all the wires in the fast ethernet setup.
  • What is the wave length of the light used in this laser?

    It would look pretty funky in fog with all these criss crossed laser "trails" in the sky. Or is it more broad band than that?


    --sig starts here --
    Will Dr Evil be able to use the "Laser" to destroy washington?
    .sig = .plan = NULL;
    http://www.alladvantage.com/go.asp?refid=HVZ895
  • I can just see a bunch of punk kids going to the local geek compound and cutting the wires, then spraying lasers them all over the place.

    "Luke, I am your fahther...."

  • I can download that SuSE iso in under a minute on clear days. Too bad it takes 14 hours through smog.

    --

  • Or do you have to use something as clumsy as a Cat 5 cable.
  • how'll they keep pigeons out of the laser path?

    Any wireless system needs a heck of a lot of error-correction at the link level. It's been possible to get fairly good bandwidth out of microwave beam transmitters already for at least a decade or so, so I guess similar principles would be in effect.

    Besides, isn't it just another parroty error? :-)
  • Yes it does. So it does with radio, satelite, etc. And this is the reason you back them up with something less speedy but more reliable. Like old good 64K ISDN for example. Unless you want to try your luck of course ;-)
  • I know that the subject of fog, snow, rain, hail has already been addressed. But what about the birds, or falling corporate employees jumping to their demise. But wouldn't blunt objects that get in the way of the "laser" halt all communication?
  • That won't matter - TCP/IP is designed to cope with packets that go missing. I am assuming they will send TCP/IP over this thing.

    Jeff
  • And eliminating stupid pigeons....

    But then its not eye-friendly

    But it eliminates pigeons!

  • Network interference (Score:5)

    by Kaa ( 21510 ) on Tuesday April 25, 2000 @06:26AM (#1111681) Homepage
    I see major problems with carrier-pigeon network interfering with the laser one.

    Initially, as the flights of pigeons would be blocking the laser's line-of-sight, the laser network will suffer: "I am sorry, sir, the packets can't get through -- there are pigeons in the way!".

    Eventually I would expect the laser network to deal with this problem technologically, that is, upgrade their lasers to military power. At this point, the carrier-pigeon network will begin to suffer casualties, and notices like "Caution! Dead pigeons falling out of the sky!" will have to be posted around the laser network sites.

    Later we may expect carrier pigeons to be fitted with mirror-shielded armor and the network lasers to be outfitted with tracking devices, but that's going to take some time...

    "Packets? What packets? There is a pigeon shoot going on!"

    Kaa
  • I heard about this from a friend of mine in Dallas. He was saying his company was testing it out, and that it worked really well, rain or shine. One thing he did say that I don't quite believe is that the power was high enough to send birds that happen to fly through the beam to a screaming fiery death, but I seriously doubt that is total truth. Maybe it just singes 'em.

    He also said it was faster than 622 mbps.. somewhere along the lines of a gigabps. They have some pretty serious routers and such where he works, so they could have that kind of bandwidth outside the laser pipe, or he could be pulling my leg.

    ---
  • sounds great...that is until the sun comes up, heats the roof of the building it's mounted to, and the waves in the air refract the laser beam so it misses the recieving unit.

    But nobody can figure out why it never works, then when the techs come out to look at it that evening, it works just fine...
  • There's nothing particularly interesting about
    how many bits we can get from A to B these
    days. Sure some of the tech might be cool
    (e.g., the optical switching trickery in the
    Vint Cerf interview), but what'll impress me
    is when they get latency down to the point
    where I can't as a human detect the difference
    between the latency across the Pond and the
    latency to the other nodes at my LAN party
  • AirFiber technology information is currently restricted to business partners and current/potential customers.

    All I wanted to know was what color laser they are using. If they use red, smoggy or foggy days would result in this very cool "Blade Runner" grid of lasers floating at rooftop level.
    Serious note: This technology is only meant for large cities with high population densities. Those cities would also have the most smog. As the smog levels of a city rise, wouldn't the connection get slower and slower? Something for the folks in LA to think about before they drop money on this kind of system.

    -B
  • Readers of RISKS may remember this piece about lasers, spiders and networking [ncl.ac.uk].
  • In a perfect world all data transfers would be encrypted. In this world they aren't. Whats to stop someone from splitting off part of the beam and using it in a packet sniffing sort of way. I know that lazers are coherent light so you have to be in the same plane as the beam to pick it up but that plane could easily be a foot or two off a roof top. At least with hardwired networks you need to gain physical access.

    Does anyone have any insight?
  • When I was living in NYC a few years ago, there was a laser connection similar to this that was available to anyone with line-of-sight to the Empire State Building. It was about a T1 worth of bandwidth, but it's a lot harder to get line-pf-sight to the ESB than you'd think.

    AFAIK, it never really caught on, but it may still exist. I suspect the line-of-sight is the biggest issue it faced (I might have gotten it if my apt was on the correct side of my building to see the ESB). You'd have to put up a lot of these to solve the last mile in this way. Probably this would be a better solution for getting to the last mile -- ie, mount these on cell towers and then run fiber from them to the area buildings...
  • Why do the telecom providers keep trying to skirt around the inevitable? Broadband over phone (DSL), over tv cable, by laser, microwave, or power lines (the "holy grail") are all temporary fixes. Eventually large numbers of people are going to want broadband, and the only way to do that is to lay new cable for Internet.

    This will happen. They did it for phone. They did it for electricity. They did it for cable TV (I remember when my rural Wisconsin village finally got hooked up in the early 90s). They will do it for broadband Internet. Why are they delaying what must be done?

    Can you imagine if, in the late 70s, cable companies tried to send TV over the phone lines? Or set up neighborhood microwave/laser transceivers to get TV out to everyone? What did they do instead? They laid the frickin cable down. Now almost all Americans can get cable TV, and everyone is happy. WHY THE HELL CAN'T THEY DO THIS FOR DATA?

    If there is some technical/political/intelligent reason why SOMEONE isn't out there laying down residential data infrastructure, PLEASE enlighten me, because I sure as hell don't understand it.

    --

  • Without decent encryption, this practically begs to be wiretapped. I can certainly see some excellent uses for it though. As a data link for sites that want to limit RF interference (radio telescopes, for example) this could be a good thing.

  • Bingo! That's exactly the problem... (Score:4)

    by ATKeiper ( 141486 ) on Tuesday April 25, 2000 @06:43AM (#1111691) Homepage
    You nailed it right on the head. The article mentions that this technology will be weather dependent and need to be adjusted not only for a hard rain, but even for fog. And what if a bird flies in the way of your transmitting laser? Ooops, there goes my download.

    It's an interesting idea for people who can't use other technologies because of their location, but I doubt it'll have any wide consumer market, when there are so many other established (and more reliable) technologies.

    See this related article: Science-fiction staple new entry in high-speed Net [cnet.com] (C|Net News.com [news.com], 22 Mar 00)

    A. Keiper
    The Center for the Study of Technology and Society [tecsoc.org]
    Washington, D.C.

  • Well.. without know what wavelenght laser they are using, it is hard to predict what envornmental issues might effect it, but here is an idea.

    You have several laser guns/recievers on the same building all pointing in different directions... say within a 30-50 degree differenc of each other. Thos signals are all the same and subject to differing amounts of interference. Those signals are all picked up and rebroadcast at different angles to their destination. Adds a little bit of path redundancy.

    I could also see being on the roof of a building in the middle and putting up a beam splitter and a couple mirrors and sniffing the media.....
  • I think Richo made that, or something like it.. It gave you something like 622mb/s over a kilofoot (that's an offical telco term BTW).. As I recall, the major problem was it cost $100,000+ and you had to get all kinds of licences to use it because the beam would have a determental effect on anything it might hit (zap-pow)..

  • what'll impress me is when they get latency down to the point where I can't as a human detect the difference between the latency across the Pond and the latency to the other nodes at my LAN party

    You can only cut it back so far before physics starts to get in the way...unless they figure out some form of FTL communication.

    3*10^8 m/s...it's not just a good idea, it's the law! :-)

  • Yeah, I've heard about this problem in every building-top laser setup I've ever heard about (one). It took them a long time to figure why it only worked at night.

    Perhaps you just need a wider receiver, so it picks up the beam even it is pushed a bit off...

  • In the late 80's the highway department in Massachusetts used a similar system to connect buildings within line of sight. It would wink out during fog or heavy rain, but the worst problem was birds. Every time a pigeon would fly by, communications would be interrupted! I am sure they have bird-proofed it by now, but I can't see how they would get a mile LOS in a major urban area.
  • At least now dropouts in my streams will represent actual death.

    "Hello and welcome to Geeks in Space, tonight....(zap)...and we'll never do *that* again! Next, ...(zap)... and...(zap)..illed him.."

  • Unless you mean low-latency in the city, forget about it. Lights only travels 300 km/ms and goes down to 200 km/ms in fiber (glass index of refraction ~1.5). Crossing the Atlantic means already 30 ms and the other side of the globe means 100 ms. Sure routers add some latency, but these numbers are the minimun period... unless you run your fiber through a wormhole.
  • Ah yes.. Networks get more secure by the day..

    So basically someone could stick a mirror in the path and hijack my connection? No messy wire cutters or alligator clips required? I guess this would make it easier for law enforcement data-taps..

    -Yikes.

    -
  • All the existing sources of global warming are just an appetizer for this one.

    Roof top communicaiton lazers will cause even more ground level heating of the atmosphere. Between this, low level ozone, CFC's released from refrigerants, styrofoam, methane from cows and pigs, cell phones, and microwave towers, it's no wonder we have had unprecidented heat through the 90's. It'll be weven worse in the oughts.

    This has been your whacko conspiracy theory for the day. Please resume your normal paranoia.

  • Not an insoluble problem (Score:4)

    by Tau Zero ( 75868 ) on Tuesday April 25, 2000 @06:58AM (#1111701) Journal
    As you go into the infrared, the influence of fog drops; once the wavelength of the light gets to be much larger than the droplet size, they stop scattering very effectively. If you use a larger lens (say, a fresnel lens instead of a small glass lens) the effect of blocking a small area diminishes. Besides, I'm sure your router is capable of handling the effects of a brief dropout in the signal, and that's all a bird is going to give you.

    Free-space optical transmission has distinct advantages over radio and microwave, notably a lack of licensing restrictions and extremely high transmission rates. Would you put up with 2 Mbps when you could have 100 Mbps or more? Neither would I. If I ran an ISP in an area where fog was infrequent (say, from Los Angeles down to San Diego and east to Austin TX or so) this would be a great way to roll out digital services at speeds DSL cannot even dream of, while still being able to make money off a sparsely distributed subscriber population. This will drive the demand curve which will then make it possible to get fiber all the way to the service entrance. It's not the end-all, but it's a great foot in the door.
    --

  • What is the wave length of the light used in this laser?
    I'll bet it's around 900-1000 nanometers, which is close enough to invisible. You won't see very much without an image intensifier. Now, as for your camcorder, el-cheapo low-light TV camera... those are another matter.
    --
  • 1) Fog slowing download time.

    This is digital. Which means that if the quantity of light getting through drops from 100 Foobars to 30 Foobars you are still getting full bandwidth as long as digital 1 == "more than 20 Foobars". Of course if it drops below (or too near...) that you lose.

    2) Beam interruptions

    Yup, IP is 'best effort' delivery. You lose packets on the internet all the time (mostly due to congestion). As long as whatever is blocking moves 'soon' its all OK.

    3) Pigeons

    Break out the old technology. Someone patent the scarecrow quick.

  • The simple answer: cost.

    Although in rural Wisconson (Wisconson? Is that in Saskatchewan?) I'm sure it's relatively easy to stick a shovel in the ground and not ruin 25000 people's day, but in larger centers, installing new underground infrastructure around all of the existing water mains, sewer pipes, phone and cable lines, subways, power grid access tunnels, crocodile nests, et cetera is prohibitively expensive, and horribly time-consuming.

    You're right, a buried conduit is probably the most stable solution, espcially for data backbones. But for local loops, it's probably not the most cost effective.

  • Hi,

    Would someone please give me the executive summary of the last-mile problem? I have always assumed it has something to do with the last hop a line makes going into a residence (or whatever) and that it is a bandwidth bottleneck.

    Thanks!
    -Derek
  • This would be hard to regulate wouldn't it? I mean a peer to peer network that uses air as a communication medium? Without using RF? No FCC.

    Or am I totally off base here?

    dv
  • Guess I'd have to give up my mirrored sunglasses. Wouln't want to cut the stream of pron to the other users on my segment.
  • Almost all "wet" wether will cause a problem of sorts. When the beam hits the woter drop n rain for example, I would think you would get some refraction. IF the rain was light, you probably would not see the problem often, but it can still happen.

    I just don't investing the money on this type of system.
  • Thanks. I think you're quite right when you say "it's a great foot in the door." Just for a bit of technical clarification, can't even slight amounts of scattering seriously distort the data being transmitted?

    Moreover, I'm rather curious about upload vs. download speeds.

    Finally, you mention L.A. as a possible city where fog might not be a problem. That's probably true, and smog probably wouldn't be a problem there these days (as it would have been a few years ago). But mightn't minor tremors (in an area which, like much of California, is prone to seismic activity) inspire a need to perpetually realign the trasmitting and receiving gear? Over long distances, even the tiniest vibration could hugely affect the angle of the beam.

    Are these realistic concerns?

    A. Keiper

  • That's another thing: ice. Rain and fog are one thing. They're small and pass by causing only intermitant interruptions. But what about colder regions where ice can form on the lens? Frost or a misplaced icecycle could wreak havoc on the signal I'd imagine. How has this been dealt with?

    /*--Why can't I find the QNX OS on any warez sites?
    * (above comment useless as of 4-26-2000)
    */
  • IIRC, the data laser doesn't lie in the visible range. It has a low-power visible light laser to aim with. We're actually thinking of using this product to bridge two buildings together where I work. I'll check and see if we've started evaling the product yet. It's much cheaper than the equivilant SONET equipment.
  • We had a laser-network connection (for proof-of-technology) here to the NIST lab down the hill from us for a few years.

    Any sort of precipitation, including fog and haze (it would frequently drop connection around noon during the summer) could block the signal, and gusts of wind would blow one end of the connection out of alignment for a few moments.

    Granted, this was older technology, but still...

  • I heard you could get free net access if you had line-of-sight to the ESB and a microwave connection.

    Is this an urban legend?

    Is the laser system an urban legend?
  • The problem in many areas is the telephone company. They control the right-of-ways and own the copper and fiber. It wouldn't be a problem if they leased the copper or fiber at a reasonable price, but they want to sell you a T1 or T3 for an outrageous price that has no relationship to the cost of providing the service.

  • Re:further concerns (Score:3)

    by Tau Zero ( 75868 ) on Tuesday April 25, 2000 @08:24AM (#1111715) Journal
    can't even slight amounts of scattering seriously distort the data being transmitted?
    They'll attenuate it, but distortion isn't much of a factor. Visualize it this way: the transmitter emits a train of pulses, which travel at the speed of light. For the pulses to be distorted, something has to either block stronger or weaker parts preferentially (a non-linearity), or delay part of the pulse so that it starts interfering with the next pulse. For this to happen with light going through fog, a substantial part of the pulse would have to follow a longer path. This requires at least two (and possibly three) scattering events: one off the line of sight and one back toward the receiver (assuming the receiver is not highly directional and only taking signal directly from the transmitter, in which case you need a bounce back onto the line of sight and then a third bounce to send it to the receiver). As you can see just from hand-waving, the probability of a photon coming in with a delay is vastly smaller than it being lost. Thus, distortion isn't a big worry.
    I'm rather curious about upload vs. download speeds.
    That's going to depend on the exact technology used, and the tradeoffs chosen by the designers.
    But mightn't minor tremors (in an area which, like much of California, is prone to seismic activity) inspire a need to perpetually realign the trasmitting and receiving gear?
    Sure. If you need accurate pointing to an arc-minute, anything that jiggles the optics by that much or more is going to screw up your system. (This includes birds landing on it, squirrels climbing on it, the wind blowing it around...) On the other hand, the same technology which we use to make CD players which focus themselves and follow tracks wherever they waver ought to be able to make a self-aligning laser transceiver. If CD drive prices are any guide, they'll be cheap in quantity.
    --
  • Thanks. I wish your preceding posts were moderated up.

    A. Keiper

  • IIRC lasers can send over fairly long distances, so shouldn't this be a great method to connect to satellites, or even to the moon or Mars?

    I would assume that the atmosphere would cause distortion, but even then it could be used to pass signals between satellites or from a satellite to the moon or Mars.

  • Alot of the issues with interference that have been raised have already been solved. Some wavelengths are not affected by rain/fog/smog, namely infared as has already been mentioned. Though snow/ice/hail being crystaline structures seem like they could present a problem if the downfall were dense enough. Birds and other solid objects would only present a momentary break in the signal which can be both quickly and easily taken care of by a number of known methods.

    One problem that i haven't seen brought up is that of radiant heat. The tops of buildings tend to get very hot, especially during summer. The heat radiating off the tops of the buildings will likely cause problems for any wavelength as it causes refraction of the light. Locating the lasers at the edges of the buildings involved and being able to keep the beam from getting too close to the tops of buildings in between should at least help keep the effective bandwidth up.

    Previous mention of crystals getting in the path actually gave me a neat idea. While it's unlikely that a crystal would remain in the path of the laser (unless placed there purposefully ), it seems possible that you would be able to effectively split the beam (and therefore bandwith) using a crystal or mirrors of some sort, though doing so would be expensive as the implementation would be specific to each site and require alot of engineering each time around. There's probably some interesting properties of non-linear optics that could be exploited, but it seems like the lasers used for this specific implementation aren't high enough intensity to do so.
  • Without decent encryption, this practically begs to be wiretapped.

    Huh? This has FAR more security than any other form of wireless transport. Without compromising the endpoints, it can only be intercepted by putting a reciever in the line of sight, instead of merely being withing broadcast range. This would both be really easy to detect (wtf is that helicopter doing hovering beside my building?) and would be very difficult to do without disrupting the communication.

    But for the paranoid, there's certainly no reason not to add encryption to the link.

  • What I know about AirFiber (Score:1)

    by Anonymous Coward
    I had the opportunity to look at this technology firsthand recently, and hopefully I can address some of the issues that people have brought up here.

    The primary purpose behind the technology is to solve some of the problems with regular fiberoptics -- namely, the expense, and having to cable over difficult terrain. The lasers are used in conjunction with fiber.

    Their primary customers are ISPs themselves; they're not setting these up for individual users as far as I know (but there's nothing to prevent you from setting up your own link if you have the cash).

    A single tower contains several send/receive pairs. Each pair is capable of independent movement, up and down, and around and around, and they are capable of automatically adjusting their focus if they need to -- so if there's some shift in location, they can still find each other.

    The beam is pretty wide in diameter, so I don't think a single raindrop will be a problem, but I can see the link slowing down due to errors, but fog isn't that big of an issue.

    When an object, such as a mirror (for snooping) or bird or person comes in front of the unit and breaks the link, it shuts off automatically and takes a photograph of what was in front of it, so that the technicians can see what it was that got in the way. So, if you were going to snoop the line, you'd better be really careful not to ever break the link. It'd be possible, sure, but not easy, and nearly impossible to be covert.

    I believe the link itself uses Asynchronous Transfer Mode.

    I hope you find this useful and informative. Obviously, I'm not attaching my name to this.
  • The influence of fog on this system drops initially, especially over short distances. But with any wireless system (optical or radio) - pick your spectrum - fog will still cause problems.

    The problem comes with a layer of fog settling on the ground. The top of the fog is often the top of the cloudline and the radiation reflection off the top of the fog blanket causes TEMPERATURE INVERSION.

    Temperature inversion can bend everything in the spectrum all the way from HEAT TO GAMMA radiation. It's the phenomenon that can be seen in the apparent "waves" rising from asphalt on hot days. They are visible because the temperature inversion is bending the electromagnetic spectrum all to hell. You think shooting a laser through that wouldnt move the beam around?!?

    Short RF links (15km) aren't generally affected by temperature inversion, but the precise aiming needed in a laser system is going to push the distance numbers way down. Perhaps someday someone will be able to develop an automatic aiming apparatus to correct for all sorts of spectrum bending, but that day hasn't yet arrived!

    ~GoRK
  • I really think the 'laser wiretap' is overblown. After all microwaves, etc. are quite a bit easier to tap thna a laner, since lasers are more tightly collimated.

    *HOWEVER* I'd like to point out that (on a purely
    technical level) tapping a technical signal is easier than you might think, because the intruder can amplify the signal at the point of interception, and therefore needs to divert only a fraction of the signal.

    Even the tricky issue of 'the optical edge' (inserting the optical element without the boundary of the optical element causing a detectable interruption) is easily handled by using "edgeless" optical 'diverters' like smoke or steam

    Get out your pocket pointer laser, and a phototransistor. Point the phototransistor at a point along the laser beam, and insert some of the following in the beam at that point:

    Smoke/Steam/mist - if you see the beam, so will the phototransistor; no edge to temporarily interrupt the beam; even if you accidentally trigger the gadget that automatically photographs beam blocking objects, then photo won't show anything very incriminating (re: your identity)

    For silly hacker/cracker movie scripts:

    a transparent helium balloon (they 'light up' when the beam hits them)

    a sheet of glass (monitor the edge of the sheet)

    talcum powder (or powder of choice)

    __________

  • The article does not have a lot about the technical details, and if I remember correctly laser technology can be riddled with problems. In "Computer Networks" by Tanenbaum, there is a brief discussion concerning the problems with lightwave transmission. Some of the problems include:
    • "Coherent optical signaling using lasers is inherently unidirectional" Two lasers can get very expensive...
    • "High bandwidth at a low cost" Look at the next point
    • "...laser beams cannot penetrate rain or thick fog" Notice that they are developing this technology in San Diego
    • "..., but they normally work well on sunny days. However, the author once attended a conference at a modern hotel in Europe at which the conference organizers thoughfully provided a room full of terminals for the attendees to read their email during boring presentations. Since the local PTT was unwilling to install a large number of telephone lines for just 3 days, the organizers put a laser on the roof and aimed it at their university's computer science building a few kilometers away. They tested it the night before the conference and it worked perfectly. At 9 a.m. the next morning, on a bright and sunny day, the link failed completely and stayed down all day. That evening, the organizers tested it again very carefully, and once again, it worked absolutely perfectly. The pattern repeated itself for two more days consistently.
      After the conference, the organizers discovered the problem. Heat from the sun during the daytime caused convection currents to rise up from the roof of the building. This turbulent air diverted the beam and made it kle. It is also responsible for shimmering roads on a hot day and the wavy images when looking out above a hot radio."

    I wonder how they address these issues. If they have not, I would never use this technology; it is expensive and unreliable. But, congratulations on the bandwidth!
  • Adtran makes a product called tracer that sends the equivalent of 2 T1's full duplex for something like 5 miles.
  • Like the original comment says, this is a "Last Mile" system for densely populated urban areas, not to give your house a T-1. Given the way lasers work, each receiver would have to be connected to the hub by its own separate laser. Splitting beams is not economical in a power/$ point of view. So maybe your 500 tenant apartment building in downtown LA might get one, but not your suburban single family home. Second, the wattage of this laser will probably be below 50 mW. I have used lasers as powerful as 2 Watts (output!!!), and even that took a couple of seconds to smolder a piece of paper. Lasers 5 mW cannot possibly harm a human eye and lasers 25 mW are generally considered safe. And as fars connection drops go, I think I would be happy for the occasional (unharmed) pigeon as opposed to a backhoe through a USWest fiber...
  • OC12 line-o-sight is great. Unfortunately, the Center Of The Internet is the San Francisco Bay Area, aka Fog City, so one of the places it would be most useful you can't use it :-)


    In practice, San Jose doesn't have anywhere near as much fog problem, and a 500-meter distance could connect the PacBell/ATT POP with the AboveNet/UUNet/MFS POP, though there are bundles of OC48 fiber under the street that do the job just fine.

  • A friend of mine was at the University of Colorado back in the late 70s. They had an infrared laser connecting two of their computer buildings - it went out the window of one to the rooftop of the other, and worked quite reliably. There was a bit of rain and snow fade, but it was reasonably tolerant, and it's on a relatively dry side of the mountains. Then one day the window broke. The laser system survived this... until the workman came and put a piece of plywood over the broken window :-)

    The computer system, being the fine piece of 70s mainframe gear it was, crashed hard, and the computer center folks had trouble explaining to the guy that he couldn't put that plywood there because there was an invisible laser beam going right where he was standing....

  • I suspect that's an UL -- the laser system was real, but certainly not free. But cheaper than a real T1 line from Nynex (the world's worst phone company, after some of the South American ones).
    It may not exist any more, but I know a few SOHO type businesses running out of apartments that used it to get bandwidth without the landlords finding out about it...
  • Actually, the power needs to be significantly higher to cause eye-damage when you're talking about frequencies outside of the visible spectrum. That's why the laser classes are actually based on wavelength as well as wattage.
  • Whaddya think the aiming tolerance for these systems are? Could you increase this tolerance by putting a lense that spreads the beam out a little at the expense of bandwidth?
    If so, optical networking would make a good alternative for remote control over mobile rcvr's as long as they could maintain LOS - no FCC control if you want to use higher-bandwidth applications (like video from the remote unit)
  • Hmmm... so if i want some of this emmense bandwidth, i just stick a prism in the path of one of the beams? kinda split the beam...
  • What about using this technology in an office environment, have insane lans runnin in the office, just stick all the lasers up in the ceiling space or even higher towards the ceiling in the open air. this would most likely eliminate the problem of dense atmosphere, while still providing immensly high amounts of bandwidth to a whole building. Im sure you could set up a simple , straight conduit if you wanted to go between floors, and of course just mirrors and prisms for angles. seems like something large size corps would really love to have, while it might be a bit expensive for the equipment itself and also would probably be quite unstable (again, animals come into play (rodents in ceiling space would completely kill connections) but again, you could easily prevent this with simple conduits. To me, this is one kick ass technology
  • What if you were to take some kind of new fangled cable, let's call this hypothetical material "fiber optic cable", and string that around in the ceiling. You could potentially send these strange beams of light that you call "lasers" through the "fiber optic cable" without needing to worry about spiders and rodents scurrying into the beam. You would also cut down on conduit costs and the chance of not aiming the laser correctly down the chute to the next mirror/prism in the chain. This amazing technology could perhaps go hundreds, maybe even THOUSANDS of meters all without worrying about fog and rain affecting it.
  • Sounds like that's OC-12 (or maybe just packet over SONET), I heard about people doing that with OC-3 (155 mbit/sec) a couple years back.

    This reminds me of a story a friend of mine in Australia told me once. He managed the networks of (one of?) their university system down there. A link that they had was microwave between two campuses that were only a few miles apart.

    One night there was a big lightning storm. There wasn't a lighting rod on the roof of the building, but there were these big microwave sending and receiving dishes. Lightning hit one of the sending dishes, was channeled through it (not damaging the sender, strangely), turned into a pencil thin beam of electricity arcing across the sky, and slagged the receiver dish at the other campus. This turned into one of the more unusual causes for a network outage that my friend had ever experienced.

    Needles to say, the university bought lighting rods for the roofs.

  • his point was that he would be impressed when he could no longer tell the difference between a LAN and a net server in another country, not that he would be impressed when there was no difference. If I access a web page on a server in London from California, lets say it takes 60ms to load. Now let's say it takes 10ms to load from a local server. Am I going to notice the 50ms. Maybe, but probably just barely. I think what he means is that he is looking forward to the day when everything is just fast, so fast that stuff just loads seemingly instantly. It's like the difference between opening MS Word on a 500 MHz P3 and a 1 GHz P3. Is there a difference. Certainly. Are you really going to notice it? Not likely.
  • The laser is 780 nm laser, using the same kind as in a CD player. So it is in the near IR region.

    There's an article with some more detail in EE Times this week. Important numbers are the $20,000 cost (installed) per node, and that it is physically 1 by 3 feet.

    http://www.eet.com/story/OEG20000424S0020

  • LSA inc [lsainc.com] have a laser system that not only does up to 155Mbps, it also runs over distances of up to 15km using special liquid crystal lenses. At around $70K, it's not cheap, but is a lot easier than running fibre over an urban area of that distance.
  • At such a short wavelength you could include plenty of reference pulses to keep the signal corrected. I wonder what the maximum loss of bandwidth is due to fog in percentage terms?
  • 3. Quick Fix. Ad a real strong laser of sorts (CO2?) as soon as a "pigeon" (oh human finger) enters the beam, POW fry the bastard , less pigeons, no more curious humans!
  • 622 millibits per second takes 12 seconds per byte. Even carrier pigeon (no, not the one that got zapped by the laser) is faster.
  • Since it's southern California what about smog, smog, smog, smog, fog, rain, hail, sleet, bugs, planes, traffic copters, and smog?
  • I guess it would depend on how discriminating the filters are they use but what about sunlight shining into the sensor or some idiot with a hand held laser pointer denying me my uplink and my packets falling on the floor? Brings a new meaning to DoS.
  • Shades of Darkstar! (A Movie. Rent it if you haven't seen it) The beachball monster is gonna wreck havock in the form of insects, birds, crashing planes Ect. Landline laser is a hell of a lot more stable. Out
  • In point of fact fog,smog,& drizzle, don't stop
    laser, they scatter it, decreasing its range.
    [The sun can't be seen during the day
    but sunlight can.]

    This kid has a laser on the other side of town
    which can be seen if its raining. The beam can't
    be seen but there is sort of a greenish haze about where
    it would be striking a cloud. Even if it were day & raining
    if the sig was modulated it could be recieved quite well.
    [It must be remembered that a receiver doesn't
    pick up the light but the CHANGES in the intensity
    ; eg. if the background is 1000 candles the .5 flicker
    can't be seen but it's sig passes thru a capacitor real nice.

    It isn't even neccesary to use expensive equiptment.
    A $0.59 neon diode used to do hot leg tests on A C
    lines has a response time [dLum - dV] & sufficient power
    to transmit an HdTv sig across town.90% of the time.
    A browser page ought be no problem.If One neon bulb
    won't do it try a dozen or a hundred mounted on a
    reflective plate.
    Investing in a theatrical laser, the possibility of
    punching through a sig in the stratosphere to Europe
    or S A becomes possible.
    Investing in 2 polar mounted motor driven
    laser/detectors & some computer storage it shouldn't
    be too difficult to set up an unregulated, international.
    node for less than $5000 bouncing sigs off sattelites..

    ^ ^ ^ ^ ^

    One of the more remarkable aspects
    of dental caries is that the
    trauma to the cheek tissue is
    signifigantly greater than
    the turgor elaborated about the
    damaged roots in many patients.
    Sounds like radiation damage
    caused by a MICROWAVE LASER
  • Infra red is heavily absorbed by
    by air. The more power you push
    into the beam the more that is absorbed.
    As the air heats in front of the beam,
    optical effects occur [heat refraction]
    that makes the beam actually begin to coil.
    The beam starts skittering about like
    a runaway fire hose.

    A fresnal lens would probably diffract
    not focus [he guesses quickly.]

    I believe that a cheap unregulated
    private lightnet should be built around
    using SCATTER techniques. One doesn't
    need line of sight in order to pass
    euitable commication signals. Just as one
    can see the flicker of a fire on the
    other side of a mountain it isn't
    necessary to have tight contact with
    the sig source.
    It isn't even necessary
    to use hi tech components.Why use a laser
    when a neon bulb might do for pushing a
    signal cross town. Here I'm thinking in
    terms of a couple of dozen computer
    buffs linking up together to swap
    downloads on a 'good day' for $40
    a copy.
    What is needed is a font end
    for the browser of your choice which
    would pick up a megabyte of data
    in a burst. The front would then
    do a parity check with a byte
    for each k of data & make a request
    for only those blocks that failed.

    With regard to that damn bird
    if scatter techniques are used
    there would be a drop in the sig
    strength,[or even increase] but
    would have no material affect on
    the data.
    data= f'(d(sig) +- bird)=f'(d(sig)))
    ^ ^ ^ ^ ^

    Just as laser surgery can
    improve your sight
    a MICROWAVE LASER can
    blur it

  • Wow. Smoke signal technology. :)

    --
    "This isn't the post you're looking for. Move along."
  • Actually - if a pigeon flies through the beam, there would be no loss of signal for the end user. The network has a redundant "mesh" design. There are multiple paths to each node - much like how the military desinged the Internet as to ensure reliability should one path be interrupted. If a pigeon blocks one beam, then the signal is rerouted via other nearby nodes to the destination node. (Besides, even if a pigeon flew through a beam in older point-to-point applications, there would not be a total loss of download, only a several milisecond delay of transmission. No data would be lost.) Also - this network is designed for urban areas and AirFiber promises carrier-class, five nines (99.999%) reliability. The goal is to sell the equipment to CLECs, and most won't even touch equipment that doesn't meet those standards.
  • A couple of points: 1) the lasers AirFiber uses are actually very inexpensive - similar to those used in writable CD ROMs. 2) Laser beams can penetrate thick fog, under shorter distances. AirFiber designs their networks individually for each city. A high-fog area, such as San Diego, San Francisco and London, would require shorter links, such as 200 meters. Under these types of distances, AirFiber can guarantee 99.999% availability (that's about 5 minutes of downtime per year). 3) The phenom. that you're describing is called "solar loading" and is very typical, especially on tall buildings - wind is also a problem. Throughout the day, buildings move - sometimes several feet. AirFiber has developed an automatic tracking mechanism that keeps the beams alligned at all times. 4) Cost - the AirFiber equipment is slated to be about 1/10 the cost of installing fiber and much less expensive than LMDS, which requires a ton of capital just for licensing and currently provides a fourth of the speed (at best).
  • Actually - birds won't be harmed. The type of lasers that AirFiber uses are low power, completely safe and comply with the FDA's voluntary eye-safe laser applications. I saw somebody put their hand in front of the beam for at least five seconds during a demonstration just last night. No burns, no problems.
  • Isn't this the perfect environment to implement an UWB (Ultra Wide Band) connection? Most of the interference is from scattering and the Compton Effect. The transmission power could be economically raised during foul weather and the receiver may still be sensitive enough to avoid data corruption. www.time-domain.com shit happens forest gump

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