Here are the ultimate and chippest multimode optical fiber with FC connector, ceramic ferule, i've found on the net. I ordered and received quickly a set of 5m lenght 200µm and 50µm diameter.

An immediate flux comparaison on thorargon and tungstene lamp with Sheliak 10m lenght 50µm diameter, shielded ones, show an increase of the troughput of 40% ! Well the shorter lenght of the Thorlabs one may be an explanation but not enough for such increase. Same constat with 200µm one.

I'm warmly recommend these fibers cause first of the good troughtput and of course of the price. Secondly the possibility to use 25µm or 10µm fiber to increase eshel resolution to 20000 or 50000 for bright targets and/or under very good seing conditions, pacth cables are too short you will need to customize online a 5m cables.