Study on the Fiber Bragg Grating Pressure Gauges and Its Performance

A Fiber Bragg Grating (FBG) based pressure sensor is designed; the cantilever is made of a strain gauge and it can convert the vertical pressure into axial stress. The FBG which is fixed on the cantilever converts the stress into a center wavelength shift. By using the edge detection method with the help of a laser diode, the wavelength shift of the FBG can be detected. The relationship of the FBG length and its bandwidth is studied. After the comparison, the FBGs with 1 mm length is chosen and fabricated as the sensor, ensuring when the FBG's center wavelength shift, the wavelength of the laser diode is still in its reflection spectrum region, in order to enlarge the dynamic range of the sensor. Two FBGs are designed to be fixed on both sides of the cantilever. According to the feature of the same temperature coefficient, the variation of the ambient temperature to the pressure measurement can be eliminated. The temperature of the FBGs pair in the experiment is changed, and their temperature response and the performance after applying temperature insensitivity algorithm are tested. The spatial division multiplexing technology of the FBG based pressure sensors is proposed; by using optical fiber couplers and a photo detector (PD) array, the sensor networks has been demonstrated. The mentioned pressure sensing network technology is practical in the field of civil engineering such as landslide and foundation monitoring.