Temperature stabilization of fiber Bragg grating vibration sensor with automatic wavelength control

Abstract

Detection of mechanical vibration with a fiber Bragg grating (FBG) based on the intensity-modulation method provides us with simplicity and compactness of the sensor as well as high sensitivity, wide dynamic range and wide frequency response in sensing. The slope of the FBG transmittance or reflectance spectrum curve at the operation wavelength determines the sensitivity of the sensor. Since the Bragg reflection wavelength of an FBG changes as the temperature of an FBG changes, it is known that the sensitivity of the sensor is dependent on temperature of the FBG and may vary considerably when the environmental temperature varies. Except for the operation under the situation in which the temperature change is small, therefore, it is generally required to stabilize the sensor against the temperature change in the environment. In this paper we propose a new method to stabilize the sensitivity of an FBG vibration sensor in the temperaturevarying environment by automatically shifting the wavelength of the source laser. The sensitivity variation of the thermally stabilized sensor is reduced down to 3 dB, which is more than 55 dB without the stabilization.