Launching light from semiconductor lasers into multimode optical fibers having hemispherical ends and taper-with-hemisphere ends

The plane ends (PE) of various multimode optical fibers have been transformed into (a) hemispherical ends (HE) and (b) taper-with-hemisphere ends (TE) by using a microtorch and also a CO2 laser for HE only. We confirmed that the launching efficiency eta from semiconductor lasers into multimode fibers is much greater than TE and HE compared with PE, with TE being the most efficient. A rigorous comparison between these three launching arrangements is reported here for the first time together with detailed analysis of similar published work. The effect of various misalignments is also investigated and compared for the three fiber terminations.