Abstract: This study will demonstrate a strain sensor based on the optical Fibre Bragg Grating (FBG) sensing technology as it is known to have stable and reliable wavelength and response as function of the applied strain. This kind of sensor can perform accurate measurements of small ground vibration and monitor seismic activity thanks to their high sensitivity to dynamic strains induced by acceleration variation which can use to prevent property intrusion or burglary. To understand the FBG sensor more, few of its characteristics such as strain, spectral reflectivity and bandwidth and their connection with the fibre grating length and refractive index is being studied. Keywords: Fibre Bragg Grating(FBG); strain sensor; strain; spectral reflectivity; bandwidth; fibre grating length; refractive index; safety; property intrusion.