基于多模干涉与马赫-增德尔干涉效应的光纤振动传感器研究

Research on fiber optic vibration sensor based on multi-mode interference and Mach-Zehnder interference

摘要:

本文提出了一种结合多模干涉效应的新型马赫-增德尔干涉仪(Mach–Zehnder interferometer, MZI)结构，并将其用于振动检测研究。与基于两个3 dB单模光纤耦合器(optical coupler, OC)级联而成的传统MZI不同的是，本文采用多模OC与单模OC共同构成MZI。利用芯径为105的阶跃折射率分布多模光纤与芯径为62.5的渐变折射率分布多模光纤分别采用熔融拉锥法制作了分光比为1:1的3 dB多模OC，并将其分别与3 dB单模OC构建了MZI，同时为了对比，也利用两个单模OC构建了MZI。分别对采用不同类型OC构建的MZI中的一个干涉臂施加振动干扰，并使用示波器进行数据采集和分析。结果表明，基于芯径为105的阶跃折射率分布多模耦合器构建的MZI具有最大的可检测振动频率范围，为1-20kHz，同时在振动频率偏差和振动频率鉴别能力上也表现最优。该方法检测振动频率范围大，制作简单，成本低廉，为振动传感器的研制提供了一种新的思路。

Abstract:

In this paper, a novel Mach-Zehnder interferometer (MZI) structure combined with multi-mode interference has been proposed and applied to vibration detection. Different from the traditional MZI which is based on the cascade of two 3-dB single-mode optical coupler (OC), the MZI is composed of multi-mode OC and single-mode OC. A 3 dB multimode OC with the coupling ratio of 1:1 was fabricated by the fusing and tapering using the step index multimode fiber with a core diameter of 105μm and the graded index multimode fiber with a core diameter of 62.5μm, and the MZI was constructed with the multimode OC and another 3 dB single-mode OC respectively. For comparison, two single-mode OC were also used to construct the MZI. Vibration is applied to an interference arm of the MZIs constructed with different types of OC, and data acquisition and analysis are carried out by an oscilloscope. The results show that the MZI based on a step index multimode coupler with a core diameter of 105μm has the largest detectable vibration frequency range of 1-20 KHZ, and has the best performance in vibration frequency deviation and vibration frequency discrimination ability. This method has a wide range of vibration frequency, simple production and low cost, which provides a new idea for the development of vibration sensor.