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Jacket for Plastic Optic Cable

Discussion in 'Electronic Design' started by D from BC, Jun 6, 2007.

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  1. D from BC

    D from BC Guest

    My optics sucks.. :(

    I have some bare 1mm plastic optic cable..
    You know..
    Shine light in one end...see light at the other...

    I have to put a jacket on the optic cable...
    I plan on using wire insulation.. It's all I have handy..
    I have black wire insulation but no white wire insulation..

    Would I get more light transmission if I used white insulation?
    The cable is 6ft long..

    I think no matter what jacket I put on...Any high angle light will
    bounce so much that it'll be eliminated by the reflective losses..
    The dominant light that gets through is all from refraction.

    Seems right..but I dunno for sure.
    D from BC
  2. ekrubmeg

    ekrubmeg Guest

  3. D from BC

    D from BC Guest

    Well...I guess that settles that..
    D from BC
  4. Rich Grise

    Rich Grise Guest

    If it's a proper fiber, the jacket shouldn't make much difference at
    all - the light is confined by reflecting off the inner surface
    of the fiber - it never sees the jacket at all; only the losses,
    and you'll never get them back anyway.

    The jacket is for mechanical protection, but if all you want is
    cosmetic, then you could paint the bare fiber.

    Otherwise, either find something to dip it in like Plasti-Dip(tm),
    or go ahead and thread the fiber through the tube of insulation
    from a wire, or for that matter, spaghetti tubing, if you want
    to go through all of that tedium.

  5. If these fibers do not have any jacket at all, they may
    depend on the low refractive index of surrounding air to
    produce the total internal reflection that traps the light
    inside the fiber. In that case, placing any material
    against the fiber with a higher index of refraction will
    increase the light leakage out of the fibers, unless it is
    also highly reflective, like a metal coating.

    You can easily test your fibers to see if they depend on
    being surrounded by air, for their internal reflection, by
    shining light through a piece, so that you can see or
    otherwise measure the light output at the other end, and
    then dip a loop of the fiber into water. If the output
    drops, dramatically, then you will have to be careful with
    what you place against the fiber.
  6. D from BC

    D from BC Guest

    Damn... I have all sorts of paint here and I didn't think of painting
    the fiber..What a neat idea :)
    I think the lead has gotten to me :p
    D from BC
  7. D from BC

    D from BC Guest

    Fickn refraction depending on air... :p

    Rich mentioned painting the cable.
    So if I paint the cable..the refraction angle will change..IIRC the
    refraction angle is reduced. This means the cable gets more selective
    with increasing ray angles and there's more light loss.
    Kinda like skipping stones on water..

    You mentioned a metal coating...
    I have aluminized mylar...I could make a reflective tape and wrap that
    around the fiber.

    I'm going to do some thinking :)
    D from BC
  8. Guest

    A good possibility, unless the fiber is already made with two
    different refrective indexlayers, with the total reflection happening
    between them. With cheap plastic fibers, this is not necessarily the
    Yea, something like that.
    I was thinking of evaporating metal onto the fiber in a vacuum, but
    even a good mirror made this way has more loss than the total
    refraction type reflection. It might look pretty, though. The fbers
    would look like shiney wire.
    Building a little test set up would be helpful. Couple a fiber to an
    LED at one end and a photo diode or photo transistor at the other end
    so you can measure the light being carried by the fiber. Then put
    various stuff against the fiber and see how it reduces the light that
    gets through. You will find that even bending the fiber more than
    some minimum radius curve will let light escape at the bend.
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