Broadband single-mode microfiber coupler for OCT

We present a broadband bi-conical microfiber coupler (MFC) with a specifically designed transition region that effectively suppresses any higher-order mode content present at the input fiber and provides efficient power splitting into the fundamental mode at the two output ports. As a practical example, single-mode 3-dB splitting operation over a very broad spectral window (400∼1700 nm) was demonstrated with a 1.1µm MFC made from conventional telecom optical fibers.