Abstract
Fiber Bragg grating (FBG) is considered a good candidate for acoustic emission (AE) measurement. The sensing and measurement in traditional FBG-based AE systems are based on the variation in laser intensity induced by the Bragg wavelength shift. This paper presents a sensing system by combining self-mixing interference (SMI) in a laser diode and FBG for AE measurement, aiming to form a new compact and cost-effective sensing system. The measurement model of the overall system was derived. The performance of the presented system was investigated from both aspects of theory and experiment. The results show that the proposed system is able to measure AE events with high resolution and over a wide dynamic frequency range.
Highlights
Acoustic emissions (AEs) are the transient elastic waves within a material, caused by the rapid release of localized stress energy
By considering the features of AE events and based on our previous design on AE measurement [6], we describe a complete measurement model to show the relationship between an self-mixing interference (SMI) signal and the equivalent dynamic deformation applied on an Fiber Bragg grating (FBG) caused by an AE signal
For an FBG–SMI system, when a strain is applied on the FBG, r3 may change, which may lead to the feedback coefficient C changing
Summary
Acoustic emissions (AEs) are the transient elastic waves within a material, caused by the rapid release of localized stress energy. An FBG interrogation system is needed to detect the reflected wavelength shift induced by external parameters on the FBG such as strain and temperature. To measure the AE induced strains in FBG, high sensitivity and bandwidth interrogation systems are required. In order to achieve a good linearity and wide measurement range, an operation point for these systems, e.g., the 3-dB position of the absorption filters transmittance, is needed to be set For these systems, an external photodetector is required. By combing self-mixing interference (SMI) and FBG technology, we aimed to build a new compact and cost-effective system capable of achieving a wide dynamic measurement range. FBG is the target and the dynamic strain source replicates an acoustic emission event and the self-mixing. FBG-based AE measurement system can be removed and a wide dynamic measurement range can be achieved
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