提出并成功演示了一种微纳光纤环与侧边抛磨光纤直接耦合的上下载滤波器。实验结果表明这种滤波器件不仅能实现两种光纤系统的互连耦合，并且能实现两系统间的上下载滤波功能。下载输出端消光比最大可达7.5 dB，上载输出端消光比最大可达4.8 dB。此外，通过进一步实验及数值仿真研究了不同环直径对两种光纤系统耦合的影响。实验和数值模拟研究结果都表明在微纳光纤直径为6 μm的情况下，当微纳光纤环直径为580 μm时，微纳光纤环与侧边抛磨光纤的耦合达到最大，同时此耦合对环Q值与精细度的影响也达到最小。这种上下载滤波器不需额外设计微纳光纤与标准光纤耦合的光学器件，为微纳光纤系统与现有的光纤系统的互连提供了一种更简洁有效的解决方案。

A novel add-drop filter based on direct coupling between micro-/nano-fiber (MNF) ring and side-polished fiber(SPF) is proposed and demonstrated. Experiment results show that this kind of filter not only can realize interconnected coupling between the MNF optical system with conventional optical system, but also can realize a function as add-drop filter between two optical systems. The maximum extinction ratio of drop port can achieve to be 7.5 dB as a drop filter, while maximum extinction of add port can be 4.8 dB as a add filter. Furthermore, the influence of different ring diameters on the coupling between the two optical systems is numerically and experimentally investigated. The conclusion of the investigation is that when the diameter of MNF is fixed at 6 μm and the diameter of MNF ring reaches to be 580 μm, coupling efficiency of the MNF ring and SPF is maximum and the influence of the coupling on the Q value and fineness of the ring reaches minimum simtaneously. This kind of add-drop filter, without assistant of extra optical device to couple light into MNF from standard optical fiber, provides a more elegant solution for interconnection of the MNF optical system and current standard optical fiber system.