I. Introduction
Optical fiber microwire (OFM) fabricated with fiber tapering technique has become a highly useful fiber component in optical coupling [1], [2], resonators [3], sensors [4], spectral filtering [5], particle manipulation [6], nonlinear optics [7], [8], etc., which benefits from the related optical field tight-confinement and intensive evanescent field interaction. Microfiber knot resonator (MKR) is one type of the basic photonic devices made from OFM, which employs the evanescent field interaction occurring at the contacting parts of the OFM.