在单模光纤中级联两个对称缓锥, 中间段去除涂覆层, 包层作为传感臂对外界折射率敏感, 实验上形成M-Z(马赫-曾德尔)干涉仪。对锥区光场进行分析, 当锥腰半径为25 μm时, 光纤内模场半径达到最大值, 约为14.8 μm。当锥形光纤锥腰半径为12.5 μm、过渡区为5 mm、锥间隔为131 mm时, 耦合与合波效果最佳, 此时传感臂可检测的酒精浓度范围为0～100%, 折射率和波长偏移存在很好的线性关系, 灵敏度为-120 nm/RIU。该传感器具有插入损耗低、性能稳定和抗干扰能力强等优点, 可应用于酒厂酒精度检测和水质监测等领域。

In this paper, we cascade two symmetrical slow tapers in a single-mode fiber and remove the coating between two tapers, which achieve a Mach-Zehnder(M-Z) interferometer. The cladding is act as a sensing arm, which is sensitive to the refractive index in the outside world. Through the analysis of the optical field evolution of taper region, mode field radius will reach maximum value of 14.8 μm when fiber taper has a radius of 25 μm. When taper waist radius is 12.5 μm, transition region is 5 mm, and taper region interval is 131 mm, the effect of coupling and waving is best. The sensing arm can detect alcohol concentration in the range of 0~100%, which has a good linear relationship between refractive index and wavelength offset with detection sensitivity of -120 nm/RIU. The sensor has advantages of low insertion loss, stable performance and strong anti-interference capacity, which can be applied to areas such as distillery and water quality monitoring.