Single Reflective Mode Fiber Bragg Grating in Multimode Microfiber

We present a novel technique to effectively obtain single mode in reflection from a fiber Bragg grating (FBG) written in multimode microfibers. The capability of designing FBG in microfibers reflecting just the fundamental mode instead of multiple modes, simplifying demultiplexing and demodulation, is highly desirable. We demonstrate that the taper length of a microfiber can be effectively used to control the mode recoupling conditions. The reflection spectra from FBGs written in microfibers with different lengths are investigated.