Bragg wavelength-insensitive fiber Bragg grating ultrasound detection system based on a fiber ring laser

A fiber Bragg grating (FBG) ultrasound detection system incorporating a fiber ring laser was developed. In the system, an FBG was used not only as a sensor but also as the ring cavity mirror. The fiber ring laser emitted lasing light at the Bragg wavelength of the FBG sensor and the intensity of the lasing light varied with ultrasonic vibration applied to the FBG sensor. The system proved to detect ultrasonic response consistent with the characteristics of the ultrasound impinging on the FBG and to have ultrasound sensitivity enough to detect acoustic emission. This system is quite simple configuration and small in size. Moreover, this system can work irrespective of the Bragg wavelength of the FBG sensor.