Demonstration of High-Resolution DFB Fiber Laser Acoustic Emission Sensing System for CFRP Laminates

Abstract

This paper proposes an interrogation method to improve the resolution of DFB (distributed feedback) fiber laser acoustic emission (AE) sensing system. In this method, the coefficients of three ellipses formed by every two-channel interference fringe are estimated using bias-corrected ellipse-specific fitting (BCESF). The system parameters can be further corrected using the coefficients of the three ellipses. A resolution of 2×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-7</sup> pm/ √Hz at 100 kHz, which is approximately 10 dB higher than the traditional method, is achieved using the system parameters correction. The carbon fiber reinforced plastic (CFRP) laminates tensile test shows that the improved DFB fiber laser AE sensing system exhibits better performance than the PZT sensor. The damage initiation, damage spread, and instability stages of CFRP laminates' failure process can be accurately recognized.