Study on Acoustic Emission Detection Method and System of Fiber Ring Based on Heterodyne Method

With the increasing intensity of space activities, structural health monitoring of critical spacecraft components has become paramount. This study presents the development and experimental validation of a novel FOR-based acoustic emission detection system, employing a heterodyne demodulation strategy to address the unresolved global challenge of SHM in extreme environments, particularly cryogenic temperatures. The system is specifically designed to meet the SHM requirements of aerospace equipment under extreme conditions, including high electromagnetic interference and low-temperature environments. The FOR sensor, a core component, offers significant advantages over traditional piezoelectric ceramic sensors, such as operational capability in liquid environments and maintained sensitivity at low temperatures. The heterodyne demodulation technique enhances the system's dynamic range and stability by introducing a controlled frequency offset between the sensing and reference arms, facilitated by an 80MHz acoustic-optic modulator. Experimental results demonstrate the system's ability to accurately detect AE signals within the 30kHz to 150kHz frequency range, with a peak signal-to-noise ratio exceeding 40dB. These findings confirm the system's suitability for extreme environmental applications, providing a robust and precise SHM solution for critical equipment, including spacecraft and large-scale storage vessels.