Embedded Random Fiber Laser Sensor for In Situ AE Monitoring Inside Buoyancy Material

The embedded high-resolution random fiber laser acoustic emission (RFL-AE) sensor for in situ monitoring of buoyancy material is demonstrated. Our proposed embedded RFL-AE sensor can directly couple inside the solid buoyant materials (SBMs) and be expected to detect different AE signals mechanism of SBM without any medium. The randomly chirped grating array (RCGA) provides effective random distributed feedback (DFB) and is embedded inside the SBM to act as an AE sensing element. Many steep peaks can be provided by the multiple-interfering reflection spectrum of RCGA over a broad spectral range, which significantly suppresses chirping phenomenon caused by the thermal stress of SBM and realizes in situ performance monitoring of buoyant materials under high pressure. The test results show that our proposed RFL-AE sensor is highly responsive to continuous and burst AE signals of SBM. The measured resolution of AE signal is 215 $\text{f}\varepsilon /\surd $ Hz, which provides a potential embedded laser AE monitoring scheme for damage detection of SBM-associated composite material.