Acousto-ultrasonic sensing using fiber Bragg gratings

TLDR

Structural health monitoring has recently become a key topic, with most common approaches using piezoceramic devices to launch and receive ultrasound. The paper presents a fiber‑optic system designed to detect ultrasonic Lamb waves in structures, particularly aircraft, focusing on the ultrasonic sensing component. The system uses fiber Bragg grating sensors, with a theoretical framework and laboratory implementation detailed. Experiments calibrate the system and demonstrate its feasibility for detecting ultrasonic Lamb waves, while the interrogation scheme enables high‑resolution strain and high‑speed ultrasound detection.

Abstract

This paper describes a fiber-optic system which is able to detect ultrasound in structures. The aim of the sensing system is to monitor structures, in particular aircraft structures, by detecting ultrasonic Lamb waves. This type of monitoring technique has recently become a key topic in structural health monitoring. Most common approaches use piezoceramic devices to launch and receive the ultrasound. A new way of fiber-optic detection of Lamb waves is based on fiber Bragg grating sensors. In addition to the well known advantages of fiber-optic sensors, this new interrogation scheme allows the use of Bragg gratings for both high-resolution strain and high-speed ultrasound detection. The focus of the paper is on the ultrasonic part of the system. The theoretical approach and the implementation into a laboratory set-up are elaborated. Experiments have been carried out to calibrate the system and first results on simple structures show the feasibility of the system for sensing ultrasonic Lamb waves.