Strain Measurement and Crack Detection by Optical Fiber Sensors

Abstract

Optical fiber sensors have attracted much attention as a new type of sensor that could be used under environmental conditions where conventional electric ones such as the strain gauge are difficult to use. There are many attempts to apply optical fiber sensors to the permanent monitoring of time dependent structural damages as is the case of fatigue cracking. In this study, the possibility of strain measurement and crack detection by interferometric optical fiber sensors is discussed based on experimental data. The MachZehnder and the Michelson interferometer types were employed and fatigue crack detection tests were carried out. Regarding strain measurements, there is still considerable difficulty in determining whether strain is increasing or decreasing. However, the present work indicates that the use of optical fiber sensors is viable provided the circuit and signal processing methods are improved. As the fatigue crack detection, the results show that such an application of optical fiber sensors shall prove to be successful.