Detection of ultrasonic mechanical vibration of a solid using fiber Bragg grating

Based on the intensity modulation of laser light propagating through a fiber Bragg grating (FBG) attached to a Pb(Zr,Ti)O-3 (PZT) vibrator, the detection of mechanical vibration is demonstrated. The output of the sensor is stable and the involved harmonic component is small. It is considered that the sensor operation is linear. The sensitivity depends on the slope of the FBG transmission spectrum curve at the operating wavelength and is higher for a steeper slope. Since not only an FBG has little influence on the object being measured because of its smallness and light weight but also its frequency characteristics are thought to be better than those of a PZT vibration sensor, an FBG is expected to provide us with an important tool of practicality for measuring mechanical vibration.