Development of Level Sensors Based on Fiber Bragg Grating for Railway Track Differential Settlement Measurement

This paper describes the development of a liquid level sensor based on a fiber Bragg grating (FBG) written in 80-mu m diameter optical fiber for railway track differential settlement measurement. The FBG embedded in the sensor is affixed to a float installed inside the liquid-filled sensor body, which measures the upthrust force induced by the float in response to the variations of liquid level. The level measurement and the temperature operation range of the sensor are 0-22 mm and -30 degrees C to 80 degrees C, respectively. Experimental results show that the sensitivity of the sensor is 0.107 nm/mm, which matches well with the designed value.