(plastic) optical fibre

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Hi,


I want to learn a more and experiment with optical fibre, especially for  
communication.

Does somebody here have any experience with this (at a hobbyist level)?  
There seams to exist a kit called FO-30K, that just uses LEDs,  
optotransistors and plastic fibre. So it looks like this is a technology  
for hobbyies to play with.


Concering fibre, I found something called "POF" (plastic optical fibre),  
which seams to be a lot easier to handle then glass fibre, and -hence- a  
good start.
What would be a good thickness of fibre to start with? I found  
references starting from epef-1 (1 mm core, 2.2 mm in total) to epef-18  
(18 mm core).
Anybody any idea on what is easy to handle?


On the well-known Chinese webshops, I can buy cable in one batch of  
(say) 10 meter.
Can you just cut the fibre at the length I need, or do you need special  
tools for that?
(I know that glass-fibre must be cut in a certain angle to be well  
terminated. I have no idea if this also applies to plastic fibre.


On the FO-30K kit, the holders on which to connect the ends fibre are  
just metal rings.
Would it be possible to 3D print a connector for a transmittor and  
receiver for an plastic optical cable?
Perhaps a two part housing: one that holds the LED/phototransistor and  
one for (the end of) the fibre?



Any help or ideas would be appriciated.


Cheerio! Kr. Bonne. (ON1ARF)

Re: (plastic) optical fibre
On 4/8/2018 8:05 AM, kristoff wrote:
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The kit will provide you with some useful experience but it's a little  
"old school" The plastic cable has high loss but for educational  
purposes it will serve fine. If you cut the cable it should be  
perpendicular and will probably need to be polished.

Re: (plastic) optical fibre
Hi Tom,

On 08-04-18 21:15, Tom Biasi wrote:
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I am not interested in buying that particular kit. I have more then  
sufficient electronic components laying around for this .. except for  
the optical fibres themselfs.

My goal is to replicate the functionality of the kit myself, .. hence my  
questions on the fibres themselfs and on how to make an interface from /  
to a receiver / transmitter.


Kristoff

Re: (plastic) optical fibre

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Use an optical SPDIF cable.

--  
     ?

Re: (plastic) optical fibre
wrote:

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Plastic fiber is very limited, (both data rate and distance) but if  
those limits match what you need to (want to) do, fine. If your interest  
extends beyond "within room" or "room to nearby room" you might want to  
skip it and start learning glass fiber.

IIRC (it's been a long time since I touched the stuff) you can basically  
just cut it, but results may be improved by a polishing process of some  
sort.  

To give an idea of just how crude things can be and work, on a TOSLink  
(audio, probably the most common application of POF in the consumer  
space, if the junky lights are not in fashion) I have connected a normal  
TOSLink cable to a "combined headphone jack and optical out" port by  
sticking in a section of ball-point pen plastic (from behind/above the  
ink) to activate the port in optical mode and serve as a crude coupler  
to the tip of the TOSLink cable.  

So I can't see any reason you could not print a connector. Or drill a  
hole in the end of an LED and epoxy the fiber in, if you don't need a  
dismountable connector, source-side.

Terminating glass fiber is a bit more complex than cutting it at any  
particular angle, though that complexity may be hidden if using  
mechanical-splice connectors.

The vast majority of POF I have seen in the wild is 1000um (1mm) core.  
1.8mm would get you more light, but with even greater degradation in  
distance and data rates due to the larger core having even more modes  
(leading to different optical path lengths and thus transit times, so  
pulses get "fuzzy.")

--  
Cats, coffee, chocolate...vices to live by
Please don't feed the trolls. Killfile and ignore them so they will go away.

Re: (plastic) optical fibre
Hi,

First of all, thanks all for the replies. It's great to see all these  
replies.


(inline comments)


On 08-04-18 21:41, Ecnerwal wrote:
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Well, to put things into perspective, my motivation here is not to  
actually use this. It is to learn.

So it doesn't matter is isn't optimal. (If it is just "plug an play",  
there isn't much fun about it, no?)


I have been looking at this kit and also at the hardware used by ronja  
(a free-space optics project), on how to interface the optical part with  
the electronics.
First step is to get something working (basic on-off switching or analog  
signals) and then try to interface the receiver with a high-speed DAC  
and an FPGA or so and work from there on.


But that is for in the future. First things first. :-)


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I didn't know you can polish plastic fibres too. That's interesting.

I'll give it a try.



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That's a nice hack. :)- Very interesting!


Is TOSlink LED or laser based?



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:-)


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OK, I understand that.

But my motto has always been to first learn how to crawl, and then walk.  
I'll put glass-fibre on my "to do" list.



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In the mean time, I found a reference for 20 meter of 1 mm POF cable and  
I'll start with that.

But it's a good idea to experiment with thicker POF later on. I  
understand that the thicker core and the additional modes will "smear  
out" the signal more.


Cheerio! Kr. Bonne.

Re: (plastic) optical fibre

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Flame polishing is a simple method applicable to many plastics. Flash it  
through a hot flame (like a blue butane flame) and the surface melts and  
is smothed by surface tension,  solvent polishing works on some others.

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The light out the back of my DVD player doesn't give the speckle
patterns I get with difuse light from a laser pointer, (and every
other laster I've seen up close) so I'd say it's an LED.

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Maybe an 0805 SMT LED could be a good match for a imm POF, possibly a
down-firing (bottom emitting) LED aligned with a 1.1mm hole in the PCB...
(custom PCB ballpark $5 from several sources)

--  
     ?

Re: (plastic) optical fibre
On Sunday, April 8, 2018 at 5:05:42 AM UTC-7, kristoff wrote:

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A friend did instruction on this, and the support for plastic fiber and
LEDs is very poor (and laser coupled to single-mode fiber is both
commonly available, and higher performance in every respect).

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Choose a wavelength, and a connector, and you can get transmitters and/or
receivers, or SFP transceiver modules, ready to connect.
A variety of suppliers stock cables, and semicustom build-to-order
cables, with the length and connectors you specify.

If you want to 'handle' making fiber connections, it takes a field splice kit
to cut and polish a fiber, and cement/crimp  it into a suitable connector ferrule.
These exist, but are not much of a 'learning' experience for a communication
project.   A few-miles reel of multifiber cable is how the real world
handles these fibers, and that's not gonna fit a student workbench.


Re: (plastic) optical fibre
On Sunday, April 8, 2018 at 8:05:42 AM UTC-4, kristoff wrote:
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I know nothing about special angles.  But years ago we'd make our own fibers
for sending/ receiving light down into cryostats.  We'd nick the fiber with  
a diamond scribe and then cleave it.  (Break... there must be youtube videos
it's not at all hard.)  The nick leaves a little section of the fiber
that is not perfect, but that didn't bother us.. A few percent of the area
was lost.  

Your big job will be the optics to couple into the fiber.  We had a lens,
fiber holder, x-y-z translation stage, and tip/tilt on the fiber holder.
 ... spendy.  

George H.  
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Re: (plastic) optical fibre
wrote:

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Multimode glass fiber cables are cheap, connectorized ST or FC.

https://www.amazon.com/Tripp-Lite-Duplex-Multimode-N302-010/dp/B000067SC9/ref=sr_1_20?ie=UTF8&qid15%23335517&sr=8-20&keywords=st+fiber+patch+cable

Matching connectorized lasers and photodiodes are also cheap.  

APC (angle polished connectors) are not needed for most applications;
they reduce back reflections a bit, which can matter in very high
speed, long run situations with lots of splices. Don't bother.

Plastic fiber has very high attenuation with distance. But the fibers
are big, so alignment is easy if you want to cut and terminate fiber
yourself. Most people buy glass fiber (62 or 9 micron core diameter)
already connectorized.



--  

John Larkin         Highland Technology, Inc

lunatic fringe electronics  


Re: (plastic) optical fibre
On 04/10/18 00:54, John Larkin wrote:
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POF can be cut with flush cutters and then polished.  Various people  
sell kits for that.

Cheers

Phil Hobbs

--  
Dr Philip C D Hobbs
Principal Consultant
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Re: (plastic) optical fibre
Phil, (and all others),



On 10-04-18 15:00, Phil Hobbs wrote:

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Thanks!


I'll do a little more research on how to do polish a POF and try it out!


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Cheerio! Kr. Bonne.

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