NIR Fibre Bragg Grating as Dynamic Sensor: An Application of 1D Digital Wavelet Analysis for Signal Denoising Z.M.Hafizi a,b,* , G.C. Kahandawa a , J.Epaarachchi a , K.T.Lau a , J.Canning c & K.Cook c a Centre of Excellence in Engineered Fibre Composites Faculty of Engineering and Surveying, University of Southern Queensland Toowoomba QLD 4350, Australia b Faculty of Mechanical Engineering, Universiti Malaysia Pahang 26600 Pekan, Pahang, Malaysia c interdisciplinary Photonics Laboratories, the University of Sydney New South Wales 2006, Australia * Corresponding author. Email: MohdHafiziBin.Zohari@usq.edu.au ABSTRACT During the past decade, many successful studies have evidently shown remarkable capability of Fiber Bragg Gratings (FBG) sensor for dynamic sensing. Most of the research works utilized the 1550 nm wavelength range of FBG sensors. However near infra-red (NIR) FBG sensors can offer the lower cost of Structural health Monitoring (SHM) systems which uses cheaper silicon sources and detectors. Unfortunately, the excessive noise levels that experienced in NIR wavelengths have caused the rejection of sensor that operating in this range of wavelengths for SHM systems. However, with the appropriate use of signal processing tools, these noisy signals can be easily ‘cleaned’. Wavelet analysis is one of the powerful signal processing tools nowadays, not only for time-frequency analysis but also for signal denoising. This present study revealed that the NIR FBG range gave good response to impact signals. Furthermore, these ‘noisy’ signals’ response were successfully filtered using one dimensional wavelet analysis. Keywords: Structural health monitoring, composites, wave propagation, wavelet analysis, NIR FBG sensor. 1. INTRODUCTION Any structures that involved composite materials may experience significance failure possibilities during service due to impact loading situations [1] . The damage caused by an impact, not always visible but grows inside the composite laminates with the time. Fortunately with the increasing number of research work in Structural Health Monitoring (SHM) of composite structures, there are many ways of early damage monitoring before it turn into catastrophic. FBG sensors for dynamic measurement open up a new dimension for SHM of composite structures. FBGs are relatively a new technology for SHM purposes. They have multiple of advantages such as small physical size, electromagnetic interference insensitivity, lightweight, high temperature sensing, environmentally unfavourable conditions and multiplexing ability [2] . Furthermore, the capabilities of embedding the sensors into the composite laminates allow the manufacturing of smart structures; which can automatically diagnose itself for any faulty condition. As far as the authors were concerned, only 1550 nm range of FBG sensors are used for dynamic measurement to date [3–8] . The use of FBG sensors for dynamic measurement is defined as ‘FBG dynamic sensing’ throughout this article. There are various applications such as telecommunications and medical, extensively use 1550 nm wavelength range FBG sensors. However, SHM systems with 1550 nm FBG range is not feasible for low-end application such as civil infrastructures etc. due to high cost associate with the 1550 nm communication range sensors. In that case the near infra-red FBG range (~830 nm) can be a good alternative. This FBG range uses widely available and comparably cheaper silicon based technologies. Therefore it can contribute to the development of low cost SHM systems. Signal to noise ratio (SNR) is one of the big issues when applying the FBG dynamic sensing; including all range of FBG wavelength. Although many previous works have shown the remarkability of acquiring the dynamic signals with Fourth International Conference on Smart Materials and Nanotechnology in Engineering, edited by Jayantha A. Epaarachchi, Alan Kin-tak Lau, Jinsong Leng, Proc. of SPIE Vol. 8793, 87930B · © 2013 SPIE · CCC code: 0277-786X/13/$18 · doi: 10.1117/12.2026668 Proc. of SPIE Vol. 8793 87930B-1 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 05/07/2015 Terms of Use: http://spiedl.org/terms