Interfacial debonding is one of the most critical damage modes that threatens the structural performance of sandwich composites. In this work, integrated multiplexed fiber Bragg grating (FBG) sensors of 1 mm gauge length are used for detection and characterization of crack propagation along the face-core interface. Single cantilever beam specimens incorporating arrays of FBG sensors are subjected to monotonic and fatigue debonding tests. The experimental configurations are simulated by finite element method in order to verify the experimental procedures and analyze the strain data corresponding to the location of the embedded FBGs. It is demonstrated that the embedded FBGs can successfully reveal the strain field imposed by the interface crack into the sandwich face. The good agreement between the experimental results and concurrent numerical simulations suggests that such data can be used for monitoring of interfacial fatigue and fracture in sandwich structures. (C) 2012 Elsevier Ltd. All rights reserved.