可调谐光纤滤波器技术是波分复用系统的关键技术之一，对于发展全光通信网络和光纤传感具有极其重要的意义。提出了一种基于大芯径的多模光纤可调谐带阻滤波器，其制作方法是将包层/纤芯直径为125/105 μm的特种多模光纤通过单模光纤接入光纤系统，实现单模多模单模（SMS）光纤结构，并使一端单模光纤与多模光纤熔接，另一端只是共轴对接而不焊接。在多模干涉原理的基础上，利用该结构对应变的敏感性实现可调谐光滤波。该可调谐滤波器的调制和解调借助于放大自发辐射（ASE）宽谱光源和光谱分析仪（OSA）实现。详细给出了该滤波器的理论仿真分析，并实验证实了该方案的有效性。

It has been known that tunable optical filter technology is one of the most critical techniques for wavelength-division multiplex (WDM), and the tunable optical fiber filter technique is extremely important for the development of all-optical networks and fiber-optic sensors. A new tunable band-rejection optical filter based on large core-diameter multimode optical fiber is projected. The filter is realized by a single-multi-single (SMS) mode fiber optical structure, which is composed of a multimode fiber with the cladding/core diameter of 125/105 μm and standard single mode fiber, with the end interface not welding together. Based on the multimode interference principle, the structure implementes the filtering by use of the structure sensitive to the stress. A broadband source which is amplified spontaneous emission (ASE) and an optical spectrum analyzer are used to monitor the transmission spectrum. Experimental and simulation results are given to prove the feasibility of the improved SMS structure.