Efficient power coupling between an MH LED and a taper-ended multimode fiber

A more than 50 percent high power coupling efficiency has been demonstrated between a multiheterojunction GaAlAs LED (MH LED) and a taper-ended fiber. Optical power values coupled from the MH LED into a Corning silica fiber [numerical aperture (NA) = 0.18] and a Toshiba multicomponent glass fiber (NA = 0.27) were 360 and 560 μW, respectively, at 100 mA drive current. Maximum improvement factor beyond the simple butt joint was 5.2, which is larger than any reported values for edge emitting LED's. Modal power distributions in multimode fiber excited by MH LED with a taper-ended fiber launcher were measured to show the leaky mode contribution negligibly small. Coupling mechanical tolerance and the cladding effect in the tapered section on coupling efficiency are discussed.