Highly sensitive liquid-level sensor based on weak uniform fiber Bragg grating with narrow-bandwidth

A highly sensitive liquid-level sensor based on weak uniform fiber Bragg grating (FBG) with narrow-bandwidth is proposed and demonstrated. The resonance wavelength varies as a result of axial strain change. According to this characteristic, a precise approach utilizing fiber grating as sensing element to measure height of liquid is achieved. The grating is directly bonded to a floater which can transfer floatage into axial strain on the fibre. Measurement of liquid level can be realized by monitoring the central wavelength shift of the sensing FBG. The experimental results show that for a liquid-level variation of 25 mm, a highly sensitivity of 6×10⁻⁶ m/pm with a good linearity is achieved, which is one of the best measuring accuracies ever reported.