Because complete fibre optic cables are too expensive I found an alternative, buy the optical cable in bulk from Maplin (UK) at approx. GBP 1 a metre. Cleaving the ends can be tricky, but a couple of tries should give a reasonable finish. Take out the optical dust-plug stops supplied with the equipment to keep the optics clean, drill a suitable hole down the centre of the plug and insert the cable (super glue in place if necessary but if the hole is the correct size it will hold in anyway). Measurements can be obtained from the supplied cable. You can put a small piece of tape over the optics in place of the plug stops when not in use.
Don't believe the hype:- Fibre cables sending digital signals need not be of high quality as long as the thresholds are sufficient.