Optical water level sensing systems using fiber Bragg grating

摘要

We have developed the all optical high-precision water level sensors based on fiber Bragg grating (FBG) technique, which are applied for actual fields such as rivers, lakes, sewage systems and so on. The sensor head consists of a diaphragm, a customized Bourdon tube and two FBGs, one for tensile measurement and other for temperature compensation. The FBG attached to the Bourdon tube is strained as the water level increases, and causes center wavelength shift of the reflected light from the FBG, which is detected by the wavelength interrogation equipment composed of a tunable Fabry-Perot filer. We have achieved the sensor accuracy of +/- 0.1% F.S.. i.e. +/- 1 cm in case of full measurement range of 10 m. Several sensor heads can be connected in series through one optical fiber and each water level at different places can be measured simultaneously by one wavelength interrogation equipment.