Hand machined mechanical pencils

Plastic optical fiber fittings (17/01/13)

I had bought some 1.5mm plastic optical fiber (POF) from http://stores.ebay.co.uk/Black-Cat-Technology and made up some fittings to make it easier to use.


Nothing amazing. The raw fiber is glued into a little plastic piece, which is then held in a disc-shaped "puck" and the end sanded flat with fine sandpaper. Gives a reasonably smooth end.

End glued on

Sanding jig

Fiber mounted in jig

Light shining through

Finished end


This is obviously not very efficient, but fortunately I was measuring very bright light sources (flashlamps) so efficiency wasn't a problem. The ends of the two branch fibers are milled to a taper and butted against the main fiber, with a little plastic ring acting as the housing. Once glued up with superglue, I glued a couple of black plastic discs either side to stop light escaping/entering.

Housing with fibers glued

One cover on

Other cover on

Completed splitter/combiner

Jig used to machine the taper. As it's clamped in the vise, it grips the fiber securely.

Variable attenuator

This was a bit over-engineered. The ends of two fibers are held facing each other in the two plastic halves of the attenuator, which are pivoted in the center. A cam at one end displaces the fiber ends side-to-side, varying the amount of overlap and hence the coupling. It works pretty well - see the video where I adjust the overlap and measure the transmitted intensity with a photodiode.

Adjuster cams

Parts of the attenuator