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提出了一种基于充液毛细管代替多模光纤的可调谐反射式带阻滤波器,滤波器结构中重要组成部分是一段充入了溶液和汞的毛细管。毛细管的一端与单模光纤共轴对接,另一端用热熔胶密封。由于液体折射率大于毛细管折射率并且毛细管芯径较大,因此液体和毛细管相当于形成了一种大芯径的多模光纤。利用汞的高反射率,实现一种反射式的单模-多模-单模光纤滤波结构。由于毛细管液芯结构对温度的敏感性,在多模干涉原理的基础上,实现可调谐滤波,并从理论仿真和实验证实了可行性。该滤波器具有结构简单、成本低廉等特点,插入损耗为5.12dB,3dB带宽为3.3nm,滤波范围可达到7nm。
A tunable and reflective band-stop filter based on liquid-filled capillaries instead of multi-mode fibers is proposed. An important part of the filter structure is a capillary tube filled with solution and mercury. One end of the capillary is coaxial with the single mode fiber, and the other end is sealed with hot melt adhesive. Due to the refractive index of the liquid being greater than the capillary refractive index and the larger capillary core diameter, the liquid and capillary tubes correspond to a multimode fiber that forms a large core diameter. Utilizing the high reflectance of mercury, a reflective single mode - multimode - single mode fiber filter structure is realized. Due to the sensitivity of capillary liquid core structure to temperature, tunable filtering is realized on the basis of multimode interference principle, and the feasibility is verified by theoretical simulation and experiment. The filter has the advantages of simple structure, low cost, insertion loss of 5.12dB, 3dB bandwidth of 3.3nm and filtering range of up to 7nm.