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Connecting fiber optic cable to LED's.

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Hazel1919

Wed May 18 2011, 01:51PM

Registered Member #1376 Joined: Wed Mar 05 2008, 08:31AM
Location:
Posts: 49

Hello,

There are two questions regarding fiber optic cable that I would like to ask about.

1 - I would like to know how you connect your fiber optic cables to led light sources. In particular, a 1mm OD cable to a conventional LED.

As far as I can see, you must drill a small hole in the plastic housing of the LED and then tape, or heat shrink, the entire led and cable.
But the drilling of the hole causes the plastic to frost up.

Also,

2 - How would you cut fiber optic cable?

Many, many thanks in advance.

Mads Barnkob

Wed May 18 2011, 03:16PM

Registered Member #1403 Joined: Tue Mar 18 2008, 06:05PM
Location: Denmark, Odense C
Posts: 1968

I buy the optic transmitters / receivers from new, they have all the mounting hardware in itself.

I just cut the cable with a fresh hobby blade, its more than suffecient for our single colour low frequency use, even professional cutters are the same, just with a aligned blade to get a 90 degree cut. We no longer use sand paper, polish etc when cutting optics in the industry.

Ash Small

Wed May 18 2011, 04:33PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

Plasma wrote ...

But the drilling of the hole causes the plastic to frost up.

I've no idea how successful it would be, but what about using a 'hot wire' to make the hole?

(Heated 1mm tungsten TIG electrode, maybe? or maybe 1mm stainless welding wire/rod)

ConKbot of Doom

Wed May 18 2011, 04:40PM

Registered Member #509 Joined: Sat Feb 10 2007, 07:02AM
Location:
Posts: 329

Mads Barnkob wrote ...

I buy the optic transmitters / receivers from new, they have all the mounting hardware in itself.

I just cut the cable with a fresh hobby blade, its more than suffecient for our single colour low frequency use, even professional cutters are the same, just with a aligned blade to get a 90 degree cut. We no longer use sand paper, polish etc when cutting optics in the industry.

And the professional ones cleave the glass fiber to give it a clean edge that doesnt need to be polished. As far as the hole frosting when drilled, it should be countered by however you attach your fiber (I.E. index matching gel, epoxy, etc...)

If I wanted to stick a plastic fiber into a plastic domed LED, I'd use UV cure adhesive to fasten it. I.E. norland optical adhesive, and as long as there arent air bubbles, the NOA should fill in any imperfections in the end of the fiber or LED dome plastic.

Plus obviously with a 1mm plastic fiber, then you arent using this for communications, except maybe TOSLINK, and most likely just illumination?

Conundrum

Wed May 18 2011, 04:46PM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4061

Interesting.. I would advise using UV cure epoxy for this, as it seems to be index matched to the fibre.

DO *NOT* USE "Superglue" or it will not work, I learned this the hard way.

As for cleaving the fibres, purchase a pair of toenail clippers and this should work fine.
(found this tip in EPE)

-A

Patrick

Wed May 18 2011, 05:23PM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

when you say "normal LEDs" do you mean the T 1-3/4 size ones?

Hazel1919

Wed May 18 2011, 08:36PM

Registered Member #1376 Joined: Wed Mar 05 2008, 08:31AM
Location:
Posts: 49

Thank you very much for your prompt replies!

I am seriously considering using the UV cure optic epoxy. Thank your for that suggestion.

Ash Small - I did consider this, and tried something similar, the only trouble was that the metal would cool off before any considerable melting of the plastic.

Patrick - Any LED that has a plastic dome in which the fiber optic cable can be embedded.

The clipper idea is very practical.

Again, many thanks.

Pinky's Brain

Wed May 18 2011, 10:07PM

Registered Member #2901 Joined: Thu Jun 03 2010, 01:25PM
Location:
Posts: 837

Damn, never realised simple fiber optic transmitters/receivers were so expensive ... cheapest for decent bandwidth transmitter and receiver (100 MHz) is ~4$ a piece. Seems steep for a trivial bit of silicon and some plastic.

klugesmith

Thu May 19 2011, 12:50AM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716

Damn, never realised simple fiber optic transmitters/receivers were so expensive ... cheapest for decent bandwidth transmitter and receiver (100 MHz) is ~4$ a piece. Seems steep for a trivial bit of silicon and some plastic.

Is anyone here familiar with the optical power and dispersion budgets in cheap plastic-fiber links?
It would not surprise me if 100 Mbps operation (much less 100 MHz, or the 1 Gbps in development) needs lasers and/or limited-NA coupling, and nontrivial Rx electronics.

The Tx and Rx ends probably have coupling lenses, in additional to the mechanical details to align and retain fiber connectors. Imagine the optical waveform pictured above, scaled to a 10 microampere detector current at 100 Mbps. (the two waveforms in picture are offset to hide the fiber prop delay, which is about 75 bit times.)

I have specified and qualified multi-gigabit transceivers, used with single- and multi-mode quartz fiber. Tx and Rx optical subassemblies include hermetic TO-cans, glass lenses, and alignment of fiber ends within microns in 3 dimensions. Tx and Rx electronics each include multiple die with different technologies, and a whole transceiver costs more than $50 in volume, even today.

Pinky's Brain

Thu May 19 2011, 03:50AM

Registered Member #2901 Joined: Thu Jun 03 2010, 01:25PM
Location:
Posts: 837

That's 150 meter ... what I'm talking about is for a little shorter range, with no integrated electronics apart from the led/photodiode and a relatively unsophisticated plastic screw cap to hold the fiber against a plastic lens.

They say the receiver can handle analog video at 70 MHz.

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