Empa-Swiss Federal Laboratories for Materials Science and Technology, Laboratory for Advanced Materials Processing (LAMP), Feuerwerkerstrasse 39, 3602 Thun, Switzerland.
Department of Electrical and Computer Engineering, Estavromenos Campus, HMU-Hellenic Mediterranean University, 71410 Heraklion, Greece.
Sensors (Basel). 2020 Nov 14;20(22):6511. doi: 10.3390/s20226511.
Acoustic Emission (AE) detection and, in particular, ultrasound detection are excellent tools for structural health monitoring or medical diagnosis. Despite the technological maturity of the well-received piezoelectric transducer, optical fiber AE detection sensors are attracting increasing attention due to their small size, and electromagnetic and chemical immunity as well as the broad frequency response of Fiber Bragg Grating (FBG) sensors in these fibers. Due to the merits of their small size, FBGs were inscribed in optical fibers with diameters of 50 and 80 μm in this work. The manufactured FBGs were used for the detection of reproducible acoustic waves using the edge filter detection method. The acquired acoustic signals were compared to the ones captured by a standard 125 μm-diameter optical fiber FBG. Result analysis was performed by utilizing fast Fourier and wavelet decompositions. Both analyses reveal a higher sensitivity and dynamic range for the 50 μm-diameter optical fiber, despite it being more prone to noise than the other two, due to non-standard splicing methods and mode field mismatch losses. Consequently, the use of smaller-diameter optical fibers for AE detection is favorable for both the sensor sensitivity as well as physical footprint.
声发射（AE）检测，特别是超声检测，是结构健康监测或医学诊断的优秀工具。尽管广受认可的压电换能器技术已经成熟，但光纤声发射检测传感器由于其体积小、抗电磁干扰和化学干扰以及光纤中光纤布拉格光栅（FBG）传感器的宽频率响应，正受到越来越多的关注。由于其体积小的优点，在这项工作中，FBG 被刻写在直径为 50 和 80μm 的光纤上。制造的 FBG 被用于使用边缘滤波器检测方法检测可重复的声波。通过快速傅里叶和小波分解对采集到的声信号进行了分析。两种分析都表明，尽管由于非标准的拼接方法和模式场失配损耗，50μm 直径的光纤比其他两种光纤更容易受到噪声的干扰，但它的灵敏度和动态范围更高。因此，对于 AE 检测，使用更小直径的光纤有利于提高传感器的灵敏度和减小物理尺寸。
