(plastic) optical fibre

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.

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

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.

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).

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.

Use an optical SPDIF cable.

--
     ?

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.

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

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

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 
ElectroOptical Innovations LLC / Hobbs ElectroOptics 
Optics, Electro-optics, Photonics, Analog Electronics 
Briarcliff Manor NY 10510 

http://electrooptical.net 
http://hobbs-eo.com

Hi,

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

(inline comments)

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. :-)

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

I'll give it a try.

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

Is TOSlink LED or laser based?

:-)

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.

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.

Phil, (and all others),

Thanks!

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

Cheerio! Kr. Bonne.

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.

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.

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)

--
     ?