基于弱耦合多芯少模光纤光斑分析的扰动传感研究

Perturbation Sensing Based on the Analysis of Specklegram from A Weakly Coupled Few-mode Multi-core Fiber

摘要:

提出了一种基于耦合多芯少模光纤(FM-MCF)光斑检测的光纤扰动传感器结构,并进行了实验验证。该传感器采用“单模光纤-多模光纤(MMF)-多芯少模光纤”的级联光纤结构,单模激光经过MMF进行光场发散后,FM-MCF中的7个芯子都能被照亮,因此在FM-MCF的末端可以用相机接收到具有7个子光斑的光斑图像。实验中在FM-MCF不同位置处施加扰动并同时采集光斑,之后基于神经网络对变化的光斑图样进行处理以实现扰动位置分类。基于FM-MCF芯内强耦合、芯间弱耦合的特性,利用该光纤结构以3cm的空间分辨率实现了对15个扰动位置的99.46%的高精度分类,远高于仅采用MMF通过光斑检测进行扰动定位的结果。也测试了FM-MCF传感器同时检测扰动位置和强度的能力,识别分类准确率均接近100%。实验结果表明,所提出的传感器具有成本低、结构简单、易于解调和高精度的优点。

Abstract:

A perturbation sensor based on the detection of a weakly coupled few-mode multi-core fiber (FM-MCF) specklegram was proposed and experimentally demonstrated. The sensor has a cascaded fiber structure consisting of a “single mode fiber-multi-mode fiber (MMF)-multi-core low-mode fiber." After the light field of a single-mode laser passes through the MMF, all seven cores in the FM-MCF can be illuminated, and an image with seven sub-specklegrams can be received by a camera at the end of the FM-MCF. In an experiment, perturbation was applied to different positions of the FM-MCF and specklegrams were collected at the same time. Based on the strong-coupling characteristic of the core and weak coupling between the core, the fiber structure achieved a high precision classification of 99.46% for 15 disturbance locations, with a spatial resolution of 3cm, which was much higher than the results for disturbance locations when using only MMF specklegram detection. The capability of the sensor to detect the perturbation position and intensity simultaneously was also tested, and the recognition accuracy was close to 100%. The experimental results showed that the proposed sensor has the advantages of low cost, a simple structure, easy demodulation, and high precision.