Novel active fiber Bragg grating sensor system for monitoring mechanical vibration in real-time

A pair of fiber Bragg gratings with the wavelengths of 1562.11 nm and 1562.71 nm, respectively, are used as the end reflectors of a constructed linear cavity fiber laser. They are epoxied onto the upper and lower surfaces of an employed uniform density and thickness isosceles triangle cantilever beam axially. As a strain agent, the beam makes the wavelength-shifts of both gratings be changeable, and therefore lead the laser producing pulses. The real-time measurements of the frequency of the mechanical vibration applied on the free end of the beam are demonstrated by observing the pulses. Within the range of 0-6.1 mm, the amplitude of the vibration can be estimated by observing the wavelength-shift-difference between two gratings. The measured results have been demonstrated to be in good agreement with the actual values under the frequency of 100 Hz.