In-"bre Bragg grating (FBG) sensor technology has become one of the most rapidly progressing sensing topics of this decade in the "eld of optical "bre sensors. FBG sensors are currently emerging from the laboratory to "nd practical applications. Rapid progress has been made in both sensor system developments and applications in recent years. This article presents a systematic review of recent progress in applications of FBG sensors in large composite and concrete structures, the electrical power industry, medicine, and chemical sensing.