Laser Self-Mixing Interference: Optical Fiber Coil Sensors for Acoustic Emission Detection

Acoustic emission (AE) testing is a widely used nondestructive testing method for the early detection of failures in materials and structures. In this paper, an AE detection sensor combining optical fiber sensing with laser self-mixing interference (SMI) technology is proposed. A multi-coil optical fiber ring wound round a cylindrical acrylic skeleton was designed in order to sense the deformation caused by AE elastic waves, which was then demodulated using self-mixing interference technology. Finite element analyses were conducted in order to investigate the deformation of fiber under acoustic sources. AE signals induced via ball-dropping impact experiments were successfully detected by the proposed experimental system. The proposed SMI optical fiber AE sensing system has the advantages of being free from electromagnetic interference and having a simple structure, low implementation cost and high measurement resolution and sensitivity.