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Cheap optical fibers
Posted by: Dik2
Date: June 07, 2020 06:16AM
I'm looking for a source for cheap short pieces of optical fibers for a DIY LED light concentrator. I have strips of LEDs, 3 per inch. I want to concentrate the light from multiple LEDs into one tight bundle.
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Re: Cheap optical fibers
Posted by: space-time
Date: June 07, 2020 09:38AM
good luck with this project

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Re: Cheap optical fibers
Posted by: Dik2
Date: June 07, 2020 11:46AM
I'm thinking ~ 1/8" heat shrink tubing to bundle the fibers at the LED end. I'd stick the LED strips in a square pattern on a rigid panel as closely spaced as possible. Then I'd drill 1/8" holes in the appropriate pattern in another panel, and glue the fiber bundles in the holes, protruding 1/4". The panels would join at the corners with spacers which position the FOBs close to the LEDs. The 1/8" bundles would be gathered together at the other end, and cut flush.

a 6"x6" LED layout (3 LED/inch) = 324 LEDs
Tightly bundled, the 324 fibers fit in a 2 1/4" square.
I would then maybe add a lens to focus the 2 1/4" square down to about a half inch area, on a 6" white acrylic lighting dome.

I cut a lens hole in the dome, the macro subject is loaded through the bottom opening.
Works well, but a brighter source focused on a smaller spot would give more contrast, while still being nicely diffused.
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Re: Cheap optical fibers
Posted by: Dik2
Date: June 07, 2020 11:51AM
Edmund Scientific has a $35 cutting tool and very small diameter fibers. I'm looking for fiber bundles around 1/8"
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Re: Cheap optical fibers
Posted by: Diana
Date: June 07, 2020 01:06PM
The problem you will encounter is making sure the fiber optic cable (FOC) is directly above the LED. As the "just squish the LEDs as close as possible" method means that you will need to measure the distance between all the LEDs and then drill EXACTLY where the center of each LED occurs in the rigid panel. This is more difficult than you may think. An alternative method would be to put two pieces of the rigid material together (one on top of the other) and then drill holes using a drill press straight down through the two pieces. These holes need to be just big enough on the one to put the FOC through it and the other to be just big enough for the LED dome or chip (depending on the style of LED you use) to protrude or be centered in the hole. Put the two pieces back together and you are more assured that the FOCs are now more centered. Additionally you will lose light if the LED "box" is open. It would be better to try to enclose it and make sure that the LEDs are as close to the FOCs as you can. That being said, LEDs still produce heat that will need to be dissipated. Not a lot of heat, granted, but it can reduce the lifespan of the LED. Modify the apparatus as needed (spacers between the two rigid material pieces, ensure air flow through the box, etc).

The use of lenses to focus the light will work, but require a way to make sure that each LED is pointed correctly and not off a bit, producing a mess. Also, it may be easier to just bundle the fibers into a round cable instead of a square one and then take it directly to the white acrylic lighting dome. Are you really wanting to focus the light, as each thing the light has to pass through will diminish the amount of light passed? You will encounter light losses with each transmission, so keeping it simple will increase the amount of light you have at the end.

Good luck.

For disclosure purposes: I work with lasers and FOCs in the instrument I run at work. Granted, you aren't using lasers and you don't need it to be as exact as I need it to be, but the manufacturer uses a three dimensional focusing method to make sure the light source is aligned to the cable. If it isn't, you get a much more diffuse and much less powerful beam; for my purposes, it becomes basically useless, but for your's you may not have to go to such extremes. Lasers also produce heat. The amount of heat it produces will depend on how the laser light is generated; the instrument I run uses Class IIIb air-cooled lasers at about 50 mW (or greater as stated on the fact sheet from the manufacturer) but I would have to talk to the service engineer as to what maximum he would allow from the lasers. This machine has some big and loud fans on it just to keep the lasers cool and also to keep the fluidic lines from getting too hot. As the heat increases, the viscosity of the fluids used in the method changes, making the job of the instrument that much more difficult. Also, the instrument uses focusing prisms to help collate the light and send it to to required spot.
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Re: Cheap optical fibers
Posted by: RAMd®d
Date: June 07, 2020 01:27PM
Geeeze, I love this inside baseball stuff!





Your boos mean nothing to me, I've seen what you cheer for.

Insisting on your rights without acknowledging your responsibilities isn’t freedom, it’s adolescence.

We are a government of laws, not men.

Everybody matters or nobody matters.

When a good man is hurt,
all who would be called good
must suffer with him.

You and I have memories longer than the road that stretches out ahead.

There is no safety for honest men except
by believing all possible evil of evil men.

We don’t do focus groups. They just ensure that you don’t offend anyone, and produce bland inoffensive products. —Sir Jonathan Ive

An armed society is a polite society.
And hope is a lousy defense.

You make me pull, I'll put you down.

I *love* SIGs. It's Glocks I hate.
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Re: Cheap optical fibers
Posted by: Dik2
Date: June 07, 2020 02:48PM
Thank you Diana, your expertise is just what I expect to find here,
The rigid panels could be something like 1/8" aluminum for the LED panel, to dissipate heat.
Spacers at the corner mounts would provide air gap spacing for ventilation, and the Fiber optic panel could be a 1/4" thick acrylic or lexan with the 324 hole pattern drilled.

The LEDs are evenly spaced at 3 per inch, and come on a 5 meter reel. can be cut any full inch. The strips are a little wider than 1/3" so the pattern would be slightly rectangular, but very regular. A step & repeat jig for my drill press is part of the project.

Assuming 1/8" fiber bundles for each LED (324) they make a square around 2". If I use a lens to focus that down to about a half an inch, it will be much brighter, even allowing for light loss through the lens, no?

My biggest issue so far is finding a source for the fibers.
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Re: Cheap optical fibers
Posted by: Dik2
Date: June 07, 2020 02:49PM
How big is FIOS cable, and is it good for visible spectrum?
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Re: Cheap optical fibers
Posted by: RAMd®d
Date: June 07, 2020 03:12PM
How big is FIOS cable, and is it good for visible spectrum?


LOL!

Are you going to put on some black pajamas and NVGs and do some repurposing?





Your boos mean nothing to me, I've seen what you cheer for.

Insisting on your rights without acknowledging your responsibilities isn’t freedom, it’s adolescence.

We are a government of laws, not men.

Everybody matters or nobody matters.

When a good man is hurt,
all who would be called good
must suffer with him.

You and I have memories longer than the road that stretches out ahead.

There is no safety for honest men except
by believing all possible evil of evil men.

We don’t do focus groups. They just ensure that you don’t offend anyone, and produce bland inoffensive products. —Sir Jonathan Ive

An armed society is a polite society.
And hope is a lousy defense.

You make me pull, I'll put you down.

I *love* SIGs. It's Glocks I hate.
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Re: Cheap optical fibers
Posted by: Dik2
Date: June 07, 2020 03:14PM
Nah, just bribe an installer for scraps.
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Re: Cheap optical fibers
Posted by: Diana
Date: June 07, 2020 03:48PM
Fiber optic passes visible light with little issue. Ultraviolet, however, causes the fiber to degrade and irreparably damage it over time. Uv damages it much faster than than visible.

The cables themselves are subject to damage; be careful with the turns with no sharp bends as you can fracture the fiber. The transmission of light itself will cause the fiber to very slowly degrade, and it will be interesting to see what the fiber internet does.
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Re: Cheap optical fibers
Posted by: N-OS X-tasy!
Date: June 07, 2020 05:07PM
Quote
Diana
The cables themselves are subject to damage; be careful with the turns with no sharp bends as you can fracture the fiber.

Minimum bend radius for FOC is 10x the outer diameter of the cable.



It is what it is.
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Re: Cheap optical fibers
Posted by: N-OS X-tasy!
Date: June 07, 2020 05:10PM
How long do you need the fiber bundles to be?



It is what it is.
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Re: Cheap optical fibers
Posted by: Dik2
Date: June 07, 2020 10:14PM
Quote
N-OS X-tasy!
How long do you need the fiber bundles to be?

Maybe 12”
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Re: Cheap optical fibers
Posted by: Paul F.
Date: June 07, 2020 10:49PM
Quote
Dik2
Nah, just bribe an installer for scraps.

Just what I was going to suggest.
Man, I wish you'd posted this two weeks ago! I just threw away a several hundred feet of OM1 fiber cable that we just replaced with OM3. I'd have shipped it to you for postage. I'll see tomorrow if the dumpster has been emptied, and if not, if it's reachable. I think it has been, and If not, it's on the bottom. sad smiley



Paul F.
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A sword never kills anybody; it is a tool in the killer's hand. - Lucius Annaeus Seneca c. 5 BC - 65 AD
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Good is the enemy of Excellent. Talent is not necessary for Excellence.
Persistence is necessary for Excellence. And Persistence is a Decision.

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Eureka, CA
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