Fiber Grating-based Sensors For Water Pressure

Fiber grating is one of the most rapid development passive components in recent years.Especially, fiber grating sensors greatly broadens the scope of application of optical fiber technology. Fiber grating sensors can detect temperature, pressure, deformation, displacement, flow and many other physical quantities based on grating wavelength’s sensitive to temperature and strain. Fiber grating sensors have many advantages of anti-electromagnetic interference, high sensitivity, wide measurement range, being easy to form sensor network and so on,compared with traditional sensors. They are widely used in health and safety monitoring of major engineering projects, safty monitoring of the petrochemical, security monitoring of power system and forecasting and warming of important area.The development of research for some kinds of optical fiber grating sensing system was summarized. The principle of several fiber grating sensors were discussed and the advantages and disadvantages were ummarized. The latest fiber Bragg grating system,D-shaped fiber Bragg grating system,long period fiber grating system, chirped fiber grating system and titled fiber Bragg grating system were presented in this paper. Two novel fiber grating sensors are recommended in this paper. They are mainly used in monitoring traling’s water level and water pressure.For the drawback of the tailing pond’s manual monitoring method such as high cost, low accuracy and low real time capability, two new sensor methods are proposed in this paper which are based on FBG and CFG for sensing. A draw-bar stracture and a corrugated diaphragm are adopted to change the axial strain of optical fiber grating. FBG water pressure sensor uses wavelength demodulation and CFG water pressure sensor uses light intensity demodulation. For the purpose of temperature-compensation, FBG water pressure sensor uses passive temperature compensation and real time compensation of the residual temperature. The double chirped fiber gratings are used in the strain sensor proposed in this paper. Wave length shift due to changes in temperature on the two fiber grating is uniform, light intensity interrogation was utilized for the strain sensor. Tests indicate the sensitivity of FBG sensor is -4.8368nm/Mpa while CFG is -0.117V/Mpa. The linearity error of FBG sensor is±4.2%while CFG is±10.26%.The repeatability error of FBG sensor is 1.45% while CFG sensor is 5.51%.