Intensity-modulated and temperature-insensitive fiber Bragg grating vibration sensor

Abstract

Abstract. An intensity-modulated, fiber Bragg grating (FBG) vibration sensor is proposed and experimentally demonstrated. An initially-uniform FBG is glued with a slanted direction onto the lateral surface of a simply-supported beam (SSB). A mass fixed in the middle of the beam transfers the vertical vibration to the deflection of the beam. Nouniform strain field generated by beam bending is applied along the FBG and makes it chirped. The sensing mechanism is based on the measurement of reflected optical power of a strain-chirped FBG. The optical power from the FBG is measured with a photodetector (PD) and an oscilloscope. A resistance strain gauge is used for the comparison purpose and good agreement is achieved. Furthermore, this sensor is cost-effective and inherently insensitive to temperature. [5][6][7][8][9][10]. FBG vibration sensors are extremely attractive in many industrial fields, such as mine safety monitoring, aerocraft and civil construction. Most of previously reported FBG-based vibration sensors are based on the measurement of Bragg wavelength shift of the sensing FBGs. But the FBG sensors based on wavelength demodulation have to monitor the reflection wavelength of FBG, so expensive wavelength measurement instrument are normally used. The measurement speed of wavelength measurement instrument is relatively low. On the other hand, Bragg wavelength shift of the sensing FBGs are also sensitive to temperature. Thus temperature compensation is needed when these reported vibration sensors are used in practical applications. That will add to the cost and complexity of the sensor system.

A Novel Temperature-Insensitive Fiber Bragg Grating Sensor for Pressure Measurement

“…The basic principle of the FBG based sensor is based on the demodulation of the reflected wavelengths of FBG in response to the applied temperature or strain. The success of FBG based sensors in the measurement of strain has facilitated the modification of transducer designs that can deal with other measurements such as displacement [1,2] , acceleration [3,4] , pressure [5,6] , title [7,8] and vibration [9] . However, it is usually impossible to obtain an accurate result by the wavelength shift of single FBG in practical applications, since the cross sensitivity effect caused by the strain and temperature always exists.…”