I'm trying to couple a white LED to a fiber bundle that's comprised of several 30 uM silica fibers. The bundle outer diameter is on the order of .5 mm. The NA of the fiber is .87 and the whole bundle is placed in a stainless steel ferrule that's .125" in diameter. I've read about different methods of coupling -- everything from a ball lens to gluing the fiber directly over the LED die.
I'm curious if anyone has experience doing something like this. Can anyone delineate the advantages/disadvantages of the various methods? Are the main tradeoffs cost vs transmission efficiency? If so what methods are on which end of the spectrum?
It's worth stating that I'm not sold on any particular LED, but I have experimented with simply holding the ferrule over a LXML-PWC2 -- tons of light comes in (enough for my application) with iF ~400mA. This would be a reasonable solution except that the efficiency of transfer is terrible (obviously) so I have to use more current than I'd like. The result is a rather large heat sink, which I'd like to shrink or ditch all together.