From: "TonyDarrah" <>                Tue 12:17
   Subject: Re: Polishing optical fibre
Newsgroups: uk.rec.models.rail


Are you using Glass or plastic optical fibre?  I presume you'reusing
plastic, because single glass fibres tend to be too fragile.

There are several ways you can finish the ends of plastic fibres.
At the light collecting end it is often a good idea to collectseveral
fibres together and fix them into a small brass ferrule (a bitof brass
tubing out of the K&L range will do) about 5 mm long. Fix themwith some
epoxy. When set, cut the ends cleanly with a sharp knife, so thatthey
are flush with one end of the brass. Then you can polish them with
Brasso or Duraglit.

Light source - a high intensity white LED. Years ago I used to usea
bulb, but nowadays I'd go for one of these LEDs. They don't overheatas
well as lasting longer.

At the light emitting end of the fibre, you can treat the fibrewith a
slow heat. In
non PC days you could use the glowing end of a cigarette - butnowadays
I'd say hold the end close (not touching) the hot bit of a soldering
iron, until it just melts into a mushroom shaped head.

Incidentally, I'd do the last first, and thread the fibre alongits'
path. The slightly enlarged 'lens' you just made will anchor itin
place. When you've done all the fibres you need, then bring them
together at the light source.

If you don't have a lot of fibres to bring together, then make another
small mushroom end at the light gathering end instead of cuttingand

BTW, Plastic fibre optic 0.25mm dia is probably best for 4mm signals-
Not readily available. Most dealers will sell 0.5mm and upwards.However
you can get the smaller from:

 Hobby's (W.Hobby Ltd., Knight's Hill Square, London SE27 0HH)
 Tel: 0181 761 4247    Fax: 0181 761 8796
 Catalogue usually available in W.H.Smith, but online as above

0.25mm  10x3.5metres costs UKP 5.55

Tony Darrah

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