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Using IR Lasers Instead of Fiber 209

Posted by michael from the can't-resist-a-laser-story dept.
Artifice_Eternity writes: "Can't deal with the trouble, time or expense of digging up the street to get fiberoptic cable to your building in the big city? There's another way...infrared line-of-sight infrared lasers between your building and another one nearby. Repeaters and redundancy can keep the chain going reliably for miles, with gigabit data transmission rates."
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Using IR Lasers Instead of Fiber More

Using IR Lasers Instead of Fiber

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  • Wireless networks. (Score:1, Interesting)

    by SuperDuG ( 134989 )
    This would be wonderful _if_ wireless networks were anywhere near affordable. It's almost cheaper to just dig and run cable than it is to use a wireless network.

    And lets not forget how fragile the whole system would be. A mirror, heavy fog, lightening striking, etc. all come to mind. From what I've heard wireless repeaters attract lightening quite well, and a nice surge like a lightening bolt can bring makes a wireless network a little worthless.

    Hopefully with all this new technology coming out, cheap wireless networks will be next on the list of things that are cool for geeks. I mean WHO DOESN'T have their own intranet in their house???

    • Not to counterpoint your comments, but... when was the last time you heard of lightning being productive on a wire-based network? Last I recall, EoE (electricity over ethernet, I think?) wasn't spec'd for that kind of throughput. :)
      • true, but hopefully those who have gigabit ethernet safely and deeply bury their fiber. Though I do know of some companies that string it along telephone lines ... I wish I had money to burn.

    • READ THE ARTICLE, PLEASE (Score:4, Insightful)

      by Artifice_Eternity ( 306661 ) on Monday February 11, 2002 @03:47AM (#2985649) Homepage
      The "repeaters" in this case can be placed indoors, in front of a window. One of the reasons for developing this system was to bypass the trouble and expense of rooftop transmitters.

      And note that even in my summary I mentioned redundancy -- multiple IR beams are designed to compensate for bad atmospheric conditions -- and each hop in the network is a short distance for the same reason.
      • I have dealt with the above technology in exactly the proposed configuration. It was designed by my predecessor, and left to me for implementation. Several things surprised the hell out of me:



        1. During a good snow, it will not cross a street (200ft, +-10). (Commercial units. Had a demonstrable five mile range on a pretty day.



        2. I don't know where you are located, but when it snows or rains here, it snows and rains pretty much all over the city (Anchorage, AK). Redundancy only works if a few of your transports get interrupted. Otherwise you get sit back and answer the user support line and make up excuses while watching the routes flap in the routing table.


        3. Glass windows in many larger buildings are infrared mirrors. Heat loss reduction. Don't even think about the cost of changing one in a space-frame building. Equipment goes outside.


        4. By the time we got "redundantised" and "routerised" to make the system even remotely reliable, paying the local one of the LECs for SONET transport was looking pretty good. ;(



        I might be tempted to use this where the sun shines a lot, or in large enclosed structures, or to some place completely inacessable by other means, but I don't think it's ready for prime time.

    • Utter Crap. As an Amateur Radio operator and RF design engineer, I can safely say that "wireless repeaters" don't attract lightning any more or less than any other rooftop equipment.

      Also, If you're clever you could use fiberoptic feed from a source indoors, and be COMPLETELY electrically isolated from the rooftop.

      Also, last time I checked, my Grandfather of 92 doesn't have a LAN in his house. (What, from the fireplace to the kitchen?)

    • Re:Wireless networks. (Score:2, Informative)

      by Anonymous Coward
      laying fiber down in even a mildly metropolitan area cost around $70,000/mile no joke

    • Oh my God! These things attract LIGHTNING? Well, I guess that just makes them completely unusable, then. It's too bad... if only we had some sort of device that could protect (lightning) things from lightning (rod)...

    • Hmmm, a homegrown version of this does sound affordable, read this article ... http://www.cedmagazine.com/ced/0009/9001.htm Excerpt... TeraBeamÂ's Fiberless Optical Network system features a point-to-multipoint (hub-and-spoke) configuration using 1550 nm lasers. At the heart of the technology is a transmitter/receiver that is about the size of a small satellite dish (estimated to cost about $150 to construct) that Granted a total network of this is gonna cost a fair amount, but a non-redundant cross campus link could be semi-affordable . Ex-misltech
    • Hopefully with all this new technology coming out, cheap wireless networks will be next on the list of things that
      are cool for geeks. I mean WHO DOESN'T have their own intranet in their house???
      This is FAR from new technology. I remember looking at one of these in place over 4 years ago. They can by the way traverse 34 miles easily. if both towers are tall enough to be above trees and the curvature of the earth and run at a high power. The problem is that Microwave links are far more reliable. If you get a downpour or thick ground fog your link dies and the biggest problem isnt heavy rain but horizontal rain or freezing rain get some on the UV filter/protector and you now are out of focus until the heaters melt it.

      Microwave suffers from more problems.. (98% humidity? you now have heavy attenuation) but you are right. It is cheaper in the long run to buy a pair of dark fibers to your desired location.

  • Rain, fog, smog, smoke? (Score:2, Interesting)

    by Lokni ( 531043 )
    I don't know much about laser communications, but wouldn't things like the above cause the laser to scatter making it unusable in the above conditions? I could especially see this with rain because of the refractive properties of water. I do know my school uses this to get bandwidth, and all I have known it for is unreliability.

    • Re:Rain, fog, smog, smoke? (Score:2, Informative)

      by Anonymous Coward
      Been there, done that.

      Our system worked pretty well - it only covered about 300m, between 2 buildings. Rain wasn't that much of a problem though and we didn't get any fog while it was running. Snow caused some issues, but not enough to really give cause for concern.

      What did cause problems were birds sitting on the equipment, and bird droppings which fouled up the receiver. The system was eventually put out of action by golf ball-sized hailstones.

  • Weather (Score:4, Funny)

    by CAIMLAS ( 41445 ) on Monday February 11, 2002 @03:29AM (#2985597)
    What about cloudy days, storms, or even ice on the windows (provided the instrument is housed)? Would these things effect bandwidth? BOFH answer #556454: You can't get your files off the server right now because the cloud cover is too thick.

    • Re:Weather (Score:2, Informative)

      by Hiro Antagonist ( 310179 )
      This is why infrared is used instead of visible light. Infrared optics have been used for over a decade in night-vision systems, and the FLAIR system, which uses IR cameras to penetrate bad weather conditions as well as darkness, can be found on Apache attack helicopters.

      So the only issue is having objects get placed in the way of the beam; not a big deal for companies that have line-of-site access from the roofs of their buildings -- the only things that'll get in the way thirty feet up are going to be new, taller buildings being built.

      My company uses a similar setup (focused microwave rather than IR), and we're quite happy with it. We've had a few small one-second hicups, but that's because they are erecting a new building beween the ones we have radio links on (and yes, the new one is short enough to allow the radio to continue functioning).

      • Re:Weather (Score:1, Informative)

        by Mister Transistor ( 259842 )
        Nope. Weather affects IR systems as well as visible light. Droplets in the air are a physical impairment to propagation, regardless of frequency. For light, at the higher end of the frequency spectrum, propagation is affected by the probability of getting "between" the rain droplets. About a 50-50 proposition at best.

        At the other end of the RF spectrum, at microwave frequencies and lower, the lower frequency wavefronts are so large they don't see the droplets at all, or are only minorly distorted by them. So, microwaves work well 80-90 percent of the time in fog, rain, etc.

        Anyway, that's why IR is called "night" vision, not "fog" vision.
      • ...and the FLAIR system...

        That would be the FLIR system - Forward Looking InfraRed.

    • What about cloudy days, storms, or even ice on the windows (provided the instrument is housed)?

      That is why they use an infrared laser. The ray will just melt away the ice and evaporate any rain in the way! Infrared light carries heat, remember?

    • You can be pretty sure this system wouldn't work in L.A.

      "Allign it with that building over there."
      "What? What building, where?"
    • Actually the weather, especially fog, has some impact on the IR-link, as also some other posts pointed out. So this isn't quite as funny as some moderators thought. A students quarter near my place was linked to the net via an IR-link, since there was a convenient light of sight to the university. But they where very happy when they got a copper link, since they could count on loosing net connection when there was fog.

      Also there were often other problems, apparently with the antenna and the signal converter sitting behind it (i only know that sometimes people had to go to the roof to fiddle with the equipment to get the link working again). So you probably should only go for an IR-link if you can stand the occasional downtime, or in sunny countries, where the waether doesn affect the line of sight.
      --

  • What about latency? (Score:3, Insightful)

    by codexus ( 538087 ) on Monday February 11, 2002 @03:31AM (#2985602)
    I don't think having many repeaters would be that good for latency. For gamers and more generally interactive communications a low ping is more important than huge bandwidth.
    • I agree, with file sharing utilities already using as much bandwidth as we can possibly imagine. Future applications such as distibuted systems will have more of a latency problem than overall bandwidth issue. I would also think places in silicon valley and everyelse in california subject to fault movement may require constant adjusting of alignment of the equipment.
      Don't forget you all freely broadcasting through the air information. Many geeks/hackers with too much time on their hands will have fun with this.

    • Re:What about latency? (Score:3, Informative)

      by mgv ( 198488 )
      I don't think having many repeaters ...

      I think that for gamers 802.11b (or even 802.16 or whatever it is called) makes more sense - no aiming, no major configuration issues. Lots of repeaters if you want to spread over > 100 metres. Sure, anyone can tap in easily - isn't that the point?

      Using lasers just complicates things and creates a whole lot more ways for the system to fail than radio frequency spectrum.

      For gamers and more generally interactive communications a low ping is more important than huge bandwidth.

      Probably the latency will be bad for gamers, but then again are you really suggesting that gamers will want some city wide network for gaming? If they are logging on to some sort of centralised server (ie., where you don't know who you are playing with) wouldn't hitting the internet directly make more sense? Fast connection through high speed routers with a wide audience to find a suitable opponent for a fragfest.

      If its a LAN party type thing, then as per above - 802.11b or similar.

      If you really need point to point communications, you can still use this sort of technology with a satellite dish and point the signal with similar line of sight accuracy. I know of line of sight RF communications in the 2.4 GHz band over kilometeres.
    • I don't know about latency in encoding and decoding the optical end, but on a purely physical level, the shortest distance between two points is a straight line. The speed of light in air is almost the same as speed of light in a vacuum. Wire on the other hand rarely goes in a straight line and due to the dielectric covering on the wire, the propogation factor is quite a bit slower than speed of light. (about 70% the speed of light for Cat 5 cable)
      • for normal distances, you're talking time differences in the nanoseconds, even considering the travel differences and velocity factor. Whereas repeat/transmit/receive/decode operation times are typically in the milliseconds.
    • Having just attended a sales presentation for one of these companies I can tell you latency is very good. Streaming DVD's and videoconferencing at 30fps simultaneously over 4 optical hops.

      There are downsides though. The company we talked to is really only interested in selling the equipment to telcos, and is only in the network services business to prove the network works. If I was a shareholder I would also worry that they were willing to provide the equipment (at $90,000 per) so that we could be a network services customer for a couple grand a month.

      The technology is pretty cool, apparantly the only weather that affects it is dense fog, and as long as "any" light will pass the link will stay up even if the LOS is obscured by objects. The company we talked to puts cameras in the units so if the link os broken their NOC can actually look out and see if somethin is in the way. Apparantly this came in handy when a cruise ship on the Hudson sailed infront of one of their links.

      At the moment they are claiming 99.999 uptime but they do put in terrestrial backup for all of their links.

      Later this year they are supposed to release a smaller inside mounted unit that is essentially a replacement for point-to-point 802.11. Nice except for the price tag ~$30,000.

  • infrared? (Score:5, Funny)

    by khuber ( 5664 ) on Monday February 11, 2002 @03:33AM (#2985606)
    "infrared line-of-sight infrared lasers" All products are approved by our Department of Redundancy Department. -Kevin

  • Plywood Fade :-) (Score:5, Funny)

    by billstewart ( 78916 ) on Monday February 11, 2002 @03:34AM (#2985608) Journal
    A number of years ago, a friend of mine was at University of Colorado. They had two computer centers which were connected by an infrared laser which was pointed out the window of one building to the other building. It had minor data loss during snowstorms, but was pretty reliable. One day the window broke, and a repair person came by and put a piece of plywood over the window until they could get a piece of glass big enough to repair it properly. He didn't understand why all the computer people started yelling at him.... after all, *he* couldn't see the invisible light beam going through the broken window :-)
    • Yeah, we used to have company meetings on the days they washed our building windows because invariably the rope for the scaffolding hung in the line of sight.
  • I could be wrong but it just doesn't sound that reliable does it? You've got joe shmo goes walking through this beam...just happens to look into the laser...this is how law suits happen...

    • This would not be a problem if the transmitter is several floors up. The window cleaners might need to wear glasses to protect them from the infrared radiation though. AFAIK infrared is quite safe unless the power level is high. It can be felt on the skin as heat - this is supposedly how Isaac Newton first observed it.

  • Old News (Score:1, Redundant)

    by strictnein ( 318940 )
    Slashdot has to have had an article on this... I saw a segment on these things on CNN over a year ago.

    Nothing new here... move along
  • "I want sharks with frickin' infrared laserbeams attached to their frickin' heads!"

  • Is this better? (Score:2, Insightful)

    by boopus ( 100890 )
    How is this better than a high gain antenna using radio waves? Radio waves can be focused with antennas and don't have such problems going through clouds and pidgeons that light does. If you focus the radio waves you shouldn't have problems running out of spectrum should you? For years you've been able to do wireless radio links line of sight, what advantage does using a "frickin' laser beam" give you?
    • umm GIGA-bit transmission maybe? Most reliable radio is limited to 11Mbps if I remember correctly....

      -Danga
      • That's why he said : "If you focus the radio waves you shouldn't have problems running out of spectrum should you?" I don't care shouting too hard to my friend, if my neigbour is isolated from me with a fat wall.
        • Well assuming that you dont have barriers, which you couldnt with this technology, then it is still better because I am almost sure it still transmits a hell of alot faster than any radio link is possible of doing.
    • Radio waves require a larger device to focus them than light waves (or infrared) because they have a much longer wavelength. For example, to produce a beam of 1 degree width in the UHF band (about 400 megahertz) you need a radio dish 50 meters across. The wireless "line of sight" links also require some space around the beam clear of obstructions.
    • We can have lasers right next to each other at the same wavelenght and they won't interfere with eachother within reasonable limits. It's inherently point to point, not broadcast.

    • I think one huge advantage is privacy. The laser is very focused, and eavesdropping would be all but impossible. Although the signal does spread, gets scattered and refracted a lot in unfavorable weather conditions (other posts handle this very capably), it's still a very narrow signal. Compare this with broadcasting radio-signals, where everybody with a compatible receiver within range can eavesdrop. Sure there can (and should be) encryption on broadcast signals, but making the signal physically inaccessible is far superior protection IMHO.

    • I used to know some ham radio folks in Denver who were setting up a similar system using microwave antennas and transmitters. It was all line of sight and they were talking speeds in the gigabyte range. The biggest problem was irate homeowners associations bitching about the microwave towers.
  • internet is down again. I think a bird hit our IR transcever again.

    or

    internet is down again. I think there is bird crap on the lenses or the transcever...

    ok now seriously what about fog or low clouds on tall buildings? wouldnt that also create noise/bouncback?
  • last I looked they don't have any respect for statues. What makes people think that their rooftop mounted equipment will be safe?

  • A side benefit... (Score:3, Funny)

    by leviramsey ( 248057 ) on Monday February 11, 2002 @03:44AM (#2985640) Journal

    ...would be hacking the kernel to transmit remote control waves. Imagine the possibilities:

    • cron scripts to change the TV to certain channels every day at a specified time.
    • if you hate the guy in the building across the street, just aim the transceiver at his TV and watch for when his s.o. comes through the door and change the channel to hardcore pr0n channel.

    And if that doesn't work, you could always use it as a spare heat lamp (very desirable when running an overclocked system...)

  • sure, you can't see IR laser beams, but it might not take very much to look at the packets going over the beam: the tranceiver assemblies are supposed to already take care of interference from air turbulence, so they might not notice if someone refracts off a little bit of the beam to their own receiver.

    two problems to overcome:
    1) how are you going to get up a couple of floors to do this, and
    2) what if (and I would hope they do) encrypt the data stream?
  • When I was at USC they used to have lots of the farther away buildings connected on IR laser. It worked ok, until it rained. Packet loss went through the roof. Summer of '98 they dug up all the streets and put in loads of fiber.

  • The good, the bad. (Score:5, Informative)

    by Restil ( 31903 ) on Monday February 11, 2002 @03:57AM (#2985680) Homepage
    This is good for many reasons. The cost is
    primarily in the one time purchase of the equipment. And it makes a lot of sense where line of sight is a shorter distance than a fibre cable must travel (tops of buildings in a congested city). These dont interfere with radio freqencies, so you don't have to concern yourself with noise, or creating noise. And its unlikely a backhoe will ever be a problem (as long as it doesn't block the line of sight).

    The downside is the line of sight. You ALWAYS have to have line of sight. Rain, fog, clouds, trees, idiots with signs, they all can cause problems. Short distances are less of a concern, but you still have to maintain an almost perfect orientation. A little gust of wind can have you dropping packets.

    But its probably a better solution than fibre where running fibre isn't an economically feasable solution. But no matter how good this is, fibre has far greater potential capacity, even though we don't yet have the technology to use all of it. It doesn't make sense to start building the internet backbone out of these things.

    -Restil
  • What if you'd mount like 3 lasers in a row, all sending an recieving simultanuously? Even while raining there should be at least one clear line of sight per .001sec. Fog relatet problems could be overcome by using more power.

  • It's been done for over a decade. "Arclight" (Score:5, Informative)

    by Ungrounded Lightning ( 62228 ) on Monday February 11, 2002 @04:08AM (#2985703) Journal
    Infrared line-of-sight links have been done for well over a decade. Datapoint's Arcnet had an infrared link device called Arclight that they used for a line-of-sight link for several miles. It would flake out in rain or fog - because rain and fog both absorb and refract infrared. So it might as well have been as opaque as black smoke.

    Arcnet was a self-healing token ring network with an underlying broadcast topology. So if two buildings were connected by Arclight and it went down, the network split into two rings, and when it came back up it healed into a single ring. Reconfig took miliseconds so it was no big deal.

    You may not have heard of Datapoint. But have probably heard of the Intel. Seems Datapoint had a discrete-component standalone computer/smart terminal which was the basic node in their network - a diskless-workstation, fileserver, compute-server archetecture. They cut a deal with a semiconductor company called Intel to try to port their instruction set to a silicon chip for the next generation. But the resulting chip was too slow, so they went with another discrete component solution.

    And Intel had cut the deal so they could sell the chip. So they took the chip to market, perhaps with a few tweaks, as the 8008 - first in the line that continued with the 8080, 8086, 80x86, Pentium, ...
    • Canon made a point to point near IR laser link, called 'CanoBeam' in 1999. I have tried their website to see whether it works in fog, but I can't get an answer. Anyone?
  • Here is my vision: buildings in a city have many mutual laser connections, sort of like virtual wires. Some of those laser connections would be connected by fiber to the internet backbone. Now let's say I'm somewhere down the chain from the backbone and I want a certain IP packet. Well, if there is a "web" of laser links connecting buildings (say each one is connected to five others), something like the IP protocol could decide which path would be the best one for my packets to take. This would result in a pretty efficient system, where little bandwidth is wasted and the loads are for the most part balanced. Lasers that can do this will not stay expensive forever, and actually, these devices could be pretty simple, which means they might eventually be cheap. Then, We he People could truly host our own intenet, and there's nothing the FCC could do about it, because we wouldn't be hogging any frequency.

    I bet that gigabit lasers with a range of 1 km will become reasonably affordable, because there really wouldn't be much to them. Entire neighborhoods could wire themselves together without requiring permits from anyone (and maybe split the cost of a fiber connection to the internet backbone).

  • Once again ... the pitfalls ... (Score:5, Informative)

    by pgrote ( 68235 ) on Monday February 11, 2002 @04:15AM (#2985722) Homepage
    Yes, as many have commented this is old news. There haven't been any breakthroughs on this in several years. Let me rephrase that ... no significant breakthroughs.

    Once a year we have a customer come to us to ask about this option. Once a year we trot out our proposal, rerun the numbers and submit it. It always comes down to two things:

    1) Speed
    2) Reliability

    The speed of the lines is fantastic when you have a clear day and relative distance is kept. Any atmoshperic conditions out of the ordinary will kill the line. Now, if you're only interested in using it for a mail gateway or to transfer data for a nightly batch cycle it rocks. For regular WAN access you'll be answering the phone from the folks on the floor.

    Reliability is a concern past the speed. Keeping the connections is sometimes more an art than science. The article does have an interesting take on parallel transmissions, but commerically available products are cost prohibitive to make it a viable alternative for most businesses.

    The best line from the article is: "Transmitting lasers through the air and modulating them at gigabit rates is a new and potentially powerful development," said Dr. Daniel Leslie, a physicist at Trex Enterprises who is familiar with the new systems.

    Now, if you want to see something cool check out Dr. Leslie's company web page: http://www.trexenterprises.com/laserrad.html

    If only we could work a Pringles can into this ...

  • True story (Score:2, Funny)

    by OiBoy ( 22100 )
    We had this at the office where I used to work. It seemed to go down on a regular basis, for a different reason every time. However, my favorite has to be the time it went down because a homeless person put a sticky note on the lens!

  • this is not new in the professional arena (Score:1, Informative)

    by Anonymous Coward
    have a look at here. they are selling this for years.

    www.laserbit.hu
  • But the technology has improved. I set this up for several companies in the mid-90's. While it worked fine 90% of the time, there are many factors that prevented widespread use.
    I found that 2.4 or 5 ghz wireless repeated are far more reliable.

  • lots of applications, lots of promise (Score:5, Interesting)

    by hyrdra ( 260687 ) on Monday February 11, 2002 @05:00AM (#2985810) Homepage Journal
    Hmm, this is nothing new. You, yourself, can buy a several watt (yes watt) IR diode and modulate it using an AOM to at least 100's of Mbits a second and more very easily for under $1500. This would easily reach a target for miles if the reciver made use of a dichroic narrowband filter and some good ECC. However, as mentioned, line of sight must be maintained.

    Divergence, not mentioned in the article, is also an issue. Especially with laser diodes, it doesn't matter what kind of miracle anamorphic lens system you have to decrease the divergence of the beam, becuase pretty soon that pencil thin dot is going to become several feet in diameter. THIS is what accounts to loss more than so called 'atmosphere' causes. Photodiodes/transistors operate at a power/cm^2 ratio, and the lower this is out of the rated area the more noise. So when the beam spreads out, the concentration of power thins out and you get noise because although all your signal is getting there, you can only sample a small fraction of its power. Having low divergence also works against you because it makes the system much more difficult to align. I would start with a very large beam, just enough to get a signal, and then progress to the smallest beam possible. Vibrations at the transmitter site will likely limit this, as tiny shifts in movement only a mm will cause the beam to jump several feet miles away.

    Many here have mentioned the speed is on the slow side for this technology. Well, folks, this is optics and that means you can do things in parallel. If you need more speed, just shift the wavelength of the diode and multiplex it in. This is the same principle behind DWDM systems, only it's in freespace. You don't even need a fancy FB diode to do it -- most commercial diodes have a 30 nm linewidth, and by controlling the voltage and temperature you can easily shift up or down. In any case, adding another same-wavelength line is just as easy as adding another transmitter/receiver pair at either end. If only you could do that for fiber. Instead, you have to dig up the streets.

    I have had the pleasure of working with a system from Coherent that really makes free space communications shine. The system automatically adjusts and aligns itself via electronic gyros and GPS. It tells you if the current location even has any type of line of sight and if it does it zeos in on the beam (e.g. "I'm pointing S-SW, can you see me?"). The hardest thing is you must have a current connection to the other end while performing the alignment, but this was easily accomidated for at my location with a cellular modem.

    This stuff is really cool and there are definate applications for anywhere that has good line of sight. For example, cell towers frequently have good line of sight to one another, so this technology would make sense for that application. There are enough towers that the network could be constructed in a serial or star configuration, without the need for many land lines near the tower.

    What would be even cooler would be somehow using the high voltage transmission towers and installing a small, low cost module on each one to jump from tower to tower, or even pole to pole. Since it's optical, you don't have to worry about interference or expensive shielding (yes, there are all-optical transceivers out there).

    These are just some ideas but the technology itself finally seems to be maturing. There are lots of current applications and it seems that although most carriers have loads of dark fiber underground, so the cable isn't really the problem, but maybe these companies will help drive bandwidth prices down by enabling small yet very fast ISPs to pop up and use the technology without having to haggle over ground cable. The Internet Revolution per se, isn't going to continue until we all have true broadband (10 Mbps or more, preferably 100 Mbps) to the curb for $19.95 a month.

    • You, yourself, can buy a several watt (yes watt) IR diode

      Jesus!
      I hope anyone using that kind of power makes sure they know what they are doing.
      Because the IR beam is invisible your eye will not have a blink reflex to bright IR light. The first you will know about getting an eyefull of a powerful IR laser is when you blind yourself (or someone else)
      You have no pain receptors on your retina.

      Remember home made lasers can be an absolute bastard to align! A good staring point for information on home made lasers is Sams Laser FAQ [repairfaq.org]
      A good background to semicondutor lasers is Britney Spears Guide to Semiconductor Physics [britneyspears.ac] (Yep, its true! check out the link.)

  • Xerox Parc did this in the 70s... (Score:3, Interesting)

    by MosesJones ( 55544 ) on Monday February 11, 2002 @05:13AM (#2985829) Homepage

    In order to get the laser printer working from their ethernet computer network (both of which they invented) they had to connect from one building to another. The "easiest" way was to use two lasers from the roof of the building. They had to bring it down as in the fog it was kind of distracting to neighbours and aircraft.
  • Does anyone know what this stuff costs?
  • Doesn't that just sound like the start of a commercial?

    Order now, operators are standing buy.

  • It's a great idea, and I can imagine people setting up IR beams between their various campuses to get fast networks.



    The only problem is, what control do you have over the airspace rights over your line-of-sight? How do you prevent someone building an office tower that blocks 10,000 IR beams? After all, you have purchased no rights to that space, you're simply relying on the fact there is currently no obstacle. if you eventaully complain, the owners and former owners might ask for twenty years back rent on the air space!

  • I'm surprised nobody's brought up the do-it-yourself option:
    RONJA [mff.cuni.cz]
    It's been on slashdot a couple of times.

    Sure it only uses LEDs but it could use lasers rather easily. It would only up the price, and possibly increase the bandwidth.

  • And if a pigeon takes roost inter-beam? Highest technology foiled by lowest organisms, again?
    • Well, you talk abou birds, but what about rain?
      Water acts like a lens and would deform the signal if you ask me.
      I still thing you have a more secure connection is you use fiber.
      Fiber is harder to tab into. If you use a direct beam from one building to another you can tab into it by just using a few prisms.
      Another problem I see is that buildings are moving with the wind. So you would loose connection in storms etc.
      If you ask me you would be better off with a RFC-1149 [com.com] connection between two buildings ;)

  • IR networking in London (Score:1, Interesting)

    by Anonymous Coward
    You might want to look at London's Sohonet [sohonet.co.uk] who have been running line-of-sight lasers around London for ages. Of course, they know what they're doing with regard to optics, weather, range, and sunlight.

    They also use fibre and SDSL links, which are cheaper in most cases - they have only used lasers in the special cases where it's cheaper than fibre.
  • Because just like clouds, fog and condenstation another big problem is that most office buildings have these neat windows that keep out as much sun as possible.

    These windows have the added bonus that they tend to reflect *any* kind of optical ray everywhere but inside.

    In other words, this does not work, we tried and switched the whole lot for a radiowave solution after finding out that a UTP cable from one office building to the next also wasn't too practical. Birds kept s(h)itting on it, resulting in more packet loss than was acceptable. And it sorta made strange patterns in the wind too, I don't think it would pass any sort of city security council.

    Ah well...
  • I had the displeasure of using one of these units (I forget who made it, but the heads had FreeSpace written on their sides in blue letters) for nearly a year with the company I work for in downtown Austin. The first six months of using the system were just perfect and I loved the units, but as time wore on we started running into problems with them. Eventually it became a running joke in the IT department ("Why can't I ping the Exchange server? Must be the laser!"). I was constantly on the roof of our building having to manually aim the laser heads so they would realign. This system would work great as a backup unit for conventional fiber or a point to point circuit, but don't have enterprise critical servers sitting at one end of these things and think that the lasers will give everyone flawless connectivity for any drawn out time frame.
  • I've been using one of these at home for about 20 years, to change the channel on my tv set.

    While it's technically not a "laser", I feel its worth mentioning since I couldn't really have developed a healthy paunch without it.
  • It all sounds good, until a flock of birds fly by!

  • Fiber (Score:1)

    by Peyna ( 14792 )
    Someone might want to correct me on this, but I was under the impression that fiber was now usually ran through existing pipework such as sewers/storm sewers etc. in big cities. Feel free to tell me I'm wrong.
  • Maybe there's a good reason why this is not a good idea, but here goes - Is there any good reason why you cannot string up fiberoptic clothesline-style? Or even use telephone pole-approach?

    Both should be X times cheaper than tearing up a sizable portion of a pavement..
  • With this technology, it would be EASY for an apartment complex to put up a little 80211a tower to give every unit 56mbs connection speeds, then use this laser to connect to other complexes, creating a huge intranet.

    If the complex pays for a single t1 line, every apartment would have incredible internet speeds.

    Talk about a good start up idea for every out of work techie out there. Start visiting these complexes, and offering your services to set up all the back end stuff. I'll bet they would jump at the chance. A single smart guy ought to be able to maintain the equipment for several complexes, and I'll bet you could charge monthly fees per unit.

  • While IR lasers between buildings would probably work well in, say, Las Vegas or LA... it wouldn't work here (Hawaii) because we receive over 150 to 200 inches of rain a year. I can't imagine any IR system, regardless of the number of redundancy you have, working well in such a humid place (even sat. TV fails here during most huge rainstorms). I suspect that this technology would also fail during large snowfalls.

    Perhaps if they up the wattage... so that it burns through the rain/snow/birds...

  • The idea if creating local computer networks using the Chinese laser pointers is widely discussed here in Russia. The link can be made, and some enthusiasts really make it. The troubles come later.

    Firstly, the link either should support Ethernet or be connected to the PC serving as a router. It's easy to make a, say, 38400 bps link using the laser pointer and infrared receiver from the TV remote control, but in the country where the average salary is $100 per month it will be impossible to find money for the router PC.

    The 10-mbit/s link is much more sophisticated, and if you can produce it you can much easier obtain enough money to buy a 802.11. At least, living in a big enough city I cannot see-and-buy all the parts necessary to produce the link having the full schematics. Of course, I can order them and risk obtaining everything except the one critical part.

    I dont't discuss the special extra rugged tripod for the roof-mounting of all this illumination, bands of young vandals, necessity to obtain the roof access permit (I don't need it, but in Moscow it's a rule!), old crazy ladies calling KGB and informing about the martians landing on the roof, necessity to place somewhere a router PC that produces the infernal noise and the Communication Supervision authority that begins to want a lot of money every time when the network gives a first cent of profit.

    So the typical Russian LAN still uses the UTP, Ethernet and the military phone cables hanging between the buildings. These cables give the excellent ranges!
  • Low-power infrared laser beams are prone to disruptions by snow, rain and fog...

    Then why not use a high-power laser? If the light were visible, I think the effect might even look cool. Imagine all of the buildings on campus connected by glowing beams of light! Of course, the lasers would have to be far enough above the ground to prevent terrorists from disrupting the network with duct tape or umbrellas.
  • You're all stating that this optical link would be severely hampered by weather/birds/plywood, but what about using several laser beams all transmitting the same signal (or a slightly dephased variation of the same signal) ? Heck, if IR light has certain shortcomings, why not place a different wavelength-laser right next to it and let them complement each other's strengths and weaknesses ? I don't know squat about lasers but it's just a thought.
  • "Why?!? the files where are the files?"
    "The networks down."
    "OH MY GOD!"
    "WHY!"
    "BIRDS, BIRDS EVERYWHERE BLOCKING IR?"
    "WHATS IR?"
    You are SO ready for IBM infastructure.
  • We have a setup like this where we work in place as a backup in case our point-to-point lines between buildings ever fail. It's worked great during testing.

    Our transmitters and receivers are mounted inside our buildings in offices which face each other (the buildings are about three miles apart, as the crow flies) The only problem is the users whose offices are near the laser-office--they've lodged (FUD) complaints about possible radiation and cancer and blindness and fatigue-related illnesses.

    We told 'em that at least they didn't have to walk downstairs to the commisary to microwave their lunches.

  • what about pigeons?! (Score:2, Interesting)

    by vigiern ( 558137 )
    Didn't the french have a problem with this in Paris with La Grande Arche de la Defense? They couldn't figure out why their laser, from one side of the building to the other, would lose connectivity at random times durnig the day. Turns out the pigeons were flying through the beam and interrupting service. I guess the only way around that would be to build a massive network of glass tubes all over the city.
  • Username: "crappywebsite"
    Password: "slashdot"

    I tried to log in as "slashdot", with password "slashdot", which someone on Slashdot usually sets up. It told me, first of all, that my address "FakeAddress@hotmail.com" was already taken. (!) But then it started saying that "Slashdot" was already taken, and started tacking random numbers onto the end. So I finally got frustrated and registered "crappywebsite", given how long it took to register an account... *grin*
  • There's another way...infrared line-of-sight infrared lasers between your building and another one nearby.

    -1 Redundant

    :)

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