High-sensitive fiber Bragg grating vibration sensor using intensity-modulated laser source

Abstract

A fiber Bragg grating (FBG) vibration sensor utilizing an intensity-modulated laser source has been devised and investigated. The research is aimed at developing a practical FBG sensor that will be applicable to high-sensitive dynamic measurements such as mechanical vibration of solid and acoustic wave in water. The FBG sensor devised is composed of a tunable laser source, an optical intensity modulator, and an FBG. In this configuration the wavelength of the optical wave from the laser source is tuned to a slope of the reflection spectrum curve of the FBG so that its Bragg wavelength shift due to vibration can be detected as a change in intensity of the optical wave reflected at the FBG. In order to increase the signal to noise ratio (SNR) in a measurement of the change in the intensity due to vibration, an intensity modulator is built into the system to make an intensity-modulated laser source and lock-in amplifier technique is employed for the vibration detection. In the experiment, high-sensitive detection for a vibration of a piezoelectric transducer (PZT) is demonstrated and discussed by comparing the sensor output with this technique to that of a conventional method without the intensity-modulation.