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  • Optical wireless?

    One laser on a unit, and one sensor. You put two far away from each other, and point them exactly at each other. Each unit is really not that complex, acts as a bit-by-bit repeater. Rj-45 plug on both, put current on the right pin when a 1 is coming from the sensor, none when there is a 0. When there is a 1 coming from the cable, turn on the laser. As long as there is nothing in the way, it should work. But, I want your opinion people, could this work? How hard would it be to build by hand? Is the effort of pointing them exactly at each other worth not having to string cable between two buildings? Does it have more curiosity value, or usefulness?
    There once was a Windows box with no firewall. Keyword is, there once was.

  • #2
    Well for starters, In a real world environment (between two buildings) this isn't going to work, or at the very least be a royal pain in the ass. Unless you have a big prabolic receiver, environmental factors are going to be working against you. As far as hooking up to an RJ45, I don't think that the pin has an on/off data flow. I'm not saying that it can't be done, I'm just saying that you would need some circuitry to transform the data into a serial signal, and some high quality optics.
    -- Honk if you played virtual sysop --

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    • #3
      The CanonBeam managed 600mbps since 2000 with this laser and LOS.

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      • #4
        http://ronja.twibright.com/main.php

        Project you might be interested in.

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        • #5
          You can buy this stuff off the shelf

          There's a bunch of companies making exactly that. They call it "free space optics" usually, but it's really ethernet or atm over laser. It's marketed for stuff like campus inter-building networking. There are some environmental issues, but it's not so bad.

          I believe that infrareds are the main wavelength used.

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          • #6
            Just to clarify, my post was directed towards making this work with junk laying around the house. If you are buying equipment there are tons of options when you have line of sight.
            But damn if it wouldn't be cool to put this together with a $5 laser pointer and few 9 volt batteries - Good luck!
            -- Honk if you played virtual sysop --

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            • #7
              Let's see

              Well, let's see.

              Old 100baseFX NICs with used 1310nm wavelength (i.e.: InfraRed) lasers. They should be fairly cheap on eBay and they already have the whole network thing taken care of.

              That leaves only the problem of focusing the beams. You probably want to start from a few meters of fibers and cut them in halves (hard as hell to do) That way you can aim and such. Some opaque tubing around the emitting light sources extending for a few inches to reduce the amount of stray light hitting the receptors.

              This might work over very short distances (say, a few inches.) Over long distances, accurate optics to send the narrowest possible beam on the transmit side and to take on a larger circle and concentrate it on the receive side (light will disperse, your laser is unlikely to be perfectly coherent and focused, fiber normally takes care of that...)

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              • #8
                I would like to announce that I have drawn up wome electrical schematics, and plan to do this a lot simpler than that ronja project. I am going to do it from parts ripped out of a gameboy color without damaging the gameboy's ability to play games, and the remote control of an old VCR I do not use anymore. The way I have it planned, here is the part list for one end of a connection:

                IR LED 1
                IR PHOTOSENSITIVE DIODE 1
                VARIABLE RESISTOR 1
                RESISTOR 1
                TRANSISTOR 2
                6V BATTERY 1
                GREEN LED 2
                RJ-45 JACK 1

                and of course some wire if you want to place the send/recieveing diodes in a place seperate from the rest. I should be uploading the electrical schematics somewhere soon.
                There once was a Windows box with no firewall. Keyword is, there once was.

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