Adiabatically tapered splice for selective excitation of the fundamental mode in a multimode fiber

We propose a simple and effective method to selectively excite the fundamental mode of a multimode fiber by, adiabatically tapering a fusion splice to a single-mode fiber. We experimentally demonstrate the method by adiabatically tapering splice (taper waist = 15 mu m, uniform length = 40 mm) between single-mode and multimode fiber and show that it provides a successful mode conversion/connection and allows for almost perfect fundamental mode excitation in the multimode fiber. Excellent beam quality (M-2 similar to 1.08) was achieved with low loss and high environmental stability. (C) 2009 Optical Society of America