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For one of my projects I need to glue a (sideglow) fiber cable to an LED.

I have never done something like this before, therefore I wanted to know if you have any experience on how to do that and how not to do that.

I would use (transparent) epoxy glue. Is this a good choice?

Is a 3mm LED big enough for a cable with 3 mm diameter?

Should I "pretreat" the LED somehow (maybe drill a hole or cut the "cap" to make it flat) or is it possible to fill the gap with epoxy?

Some of my further considerations that I have arrived at are as follows:

Whatever kind of glue one uses, it will never transport light as good as air. This is why I think it would be the best option to use a tube and put the led and the fiber cable inside. I would then glue the fiber and the led to the tube (and probably use hot glue, but epoxy may be even better).

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Don't want to have this question unanswered at all, therefore I share some of my further considerations:

Whatever kind of glue one uses, it will never transport light as good as air. This is why I think it would be the best option to use a tube and put the led and the fiber cable inside. I would then glue the fiber and the led to the tube (and probably use hot glue, but epoxy may be even better).

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    \$\begingroup\$ I would try to avoid drilling or grinding the LED, because the resulting scratches would have to be polished away (which sounds impossible for a small diameter hole). LEDs aren't that expensive, what about some experiments with different shapes? As for glue: Air doesn't seem to be a good thing to have in a fiber optic connection: en.wikipedia.org/wiki/Index-matching_gel \$\endgroup\$
    – 0x6d64
    Commented Dec 23, 2011 at 11:51

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There are connectors for this, but I've never done it with such large diameter fiber. The ones I have are used to connect an LED or phototransistor to 1/16" plastic fiber.

Have you tried googling "plastic fiber connector?" Motorola (now Freescale) Optoelectronics used to carry quite a variety of them among other manufacturers. Digikey carries them. They also had/have an entire component that encased an LED in a plastic block with a compression fitting that would accept plastic fiber.

You can also make your own connector if you have access to a drill press. Drill a 3mm hole through a block of plastic/metal, flip it over and drill a hole that's a snug fit for the LED of your choice.

If you do decide to glue it, I'd suggest using a flat-top LED. However, you will probably have to get the end of the fiber perfectly flat or

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I use shrink tube. I use mine with 10-15 0.75mm optic fibres. I place the shrink tube on the LED, heat it to shrink, making sure the tube will still fit the optic fibre. I don't shrink the tube around the fibre as I have found it melts very easily. I then insert the fibres, making sure they are well against the LED and then glue them in with Selleys fast setting plastic glue, much better than hot glue. Usin the black shrink tube is much better than plastic tube as it directs all the light through the fibres for a much better result

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