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 cou-pled 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，并且进行了实验验证。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个芯子都能够被照亮，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，本文提出的这种基于FM-MCF的光纤光斑扰动传感器具有成本低、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) specklegrams is proposed and experimentally demonstrated. The sensor is a cascaded fiber structure of “single mode fiber - multi-mode fiber (MMF) - multi-core low-mode fiber". After the light field of the single-mode laser passes through the MMF, all seven cores in FM-MCF can be illuminated and the image with seven sub-specklegrams can be received by the camera at the end of the FM-MCF. In the experiment, perturbation was applied to the different positions of the FM-MCF and specklegrams were collected at the same time. Based on the characteristic of strong coupling in the core and weak coupling between the core, the fiber structure is used to achieve a high precision classification of 99.46% of 15 disturbance locations with a spatial resolution of 3cm, which is much higher than the result of disturbance location by using only MMF specklegrams detection. The capability of the sensor to detect the perturbation position and intensity simultaneously is also tested and the recognition accuracy is close to 100%. The experimental results show that the proposed FM-MCF perturbation sensor based on the detection of specklegrams has the advantages of low cost, simple structure, easy demodulation and high precision.