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Build Your Own 10Mbit/sec Optical Data Link

Posted by timothy on from the neighbornet dept.

redcliffe writes: "This website has complete plans to build a 10 megabit per second optical data link that can work over up to 1 kilometre. It uses fairly cheap components, such as standard LED's instead of laser diodes. This also makes it a lot safer to work with, i.e. you won't burn your eyes out if you accidently look into it."

6 of 145 comments (clear)

  1. Sigh... by cperciva · · Score: 4, Informative

    It uses fairly cheap components, such as standard LED's instead of laser diodes. This also makes it a lot safer to work with, i.e. you won't burn your eyes out if you accidently look into it.

    The mere fact lasers are used in most fiber optics does not immediately render them dangerous. Typical power levels are on the order of a few mW, far too low to cause any permanent damage.

    --
    Tarsnap: Online backups for the truly paranoid
    1. Re:Sigh... by dattaway · · Score: 5, Informative

      I wish this were true. Many years ago, I was fascinated by lasers; unfortunately, infrared isn't too visible. Several years later, I now have dark stuff floating around in my eyes. For a person 33 years of age, I would not recommend looking at concentrated sources of energy, no matter how small.

      It may be a milliwatt, but its still heat: focused smaller than the head of a pin. It may burn. Damage in the eyes shows up many years later.

  2. Got AUI? by Uller-RM · · Score: 5, Informative

    Has anyone else bothered to read this enough to notice that it will not work with twisted pair Ethernet? It requires an AUI connection. They even say in the FAQ, redesigning it to work with TP would be a pain in the arse.

    In order to use the circuit, you have to either buy an AUI->TP transciever, or set up a bridging machine.

    Just saving a bit of time for some people who are no doubt running out to Ripoff Shack grabbing l33t bl00 leds.

    1. Re:Got AUI? by Uller-RM · · Score: 5, Informative

      Ethernet over TP implements a link integrity signal. AUI does not. That's the main barrier to using this particular rig - you'd have to come up with an emulator for that signal, or the cards would refuse to transmit.

      (And FYI, you're partly right. Ethernet over TP uses Manchester encoding, which means that it watches for changes in logic rather than states - i.e. transitioning from ground to 5V is a 0, and 5V to ground is a 1. Hard drives actually also use this method.)

  3. Re:Why not 802.11b? by autopr0n · · Score: 4, Informative

    He's talking about directed 802.11, not Omnidirectional. omnidirectional WiFi dosn't get nearly that range

    --
    autopr0n is like, down and stuff.
  4. Eye burn? by rew · · Score: 4, Informative

    This also makes it a lot safer to work with, i.e. you won't burn your eyes out if you accidently look into it."

    Ehmm. Modern High efficiency LEDs also carry the "don't look directly into this" warnings. And those things are BRIGHT.

    Roger.