Optical Coupling in Fiber Optics Packages with Surface Emitting LED's

The optical coupling performance of two fiber optics emitter packaging styles is determined into five large-core-diameter [
\geq
100 µm) optical fibers with varying numerical apertures (NA). One package contains a short fiber coupled to a high index spherical lens positioned accurately between the LED and the fiber. The other package is fiberless, utilizing a high index lens bonded accurately to the LED using an alignment ring technique, and projects light through the package's glass window to intercept the system fiber. Computer modeling studies have been combined with the manufacture and analysis of actual packages to investigate the optimum lens parameters for both packaging styles. Experimental and modeling studies suggest that for optical fibers with NA's
\leq
0.20, the fiberless and short-fiber packages couple equivalent optical powers into fibers with diameters
\leq
200 µm. For larger diameters, the fiberless package is somewhat superior. With high NA fibers (
\geq
0.30), however, the short-fiber package is clearly superior for fiber diameters up to 200 µm, and equivalent for diameters greater than 200 µm. The excellent performance of the fiberless package is achieved because the alignment ring technique provides not only the desired alignment accuracy, but also yields a reproducible LED-to-lens spacing.