Abstract:In this paper, a new type of optical fiber tilt sensor based on fiber Bragg grating (FBG) is presented for 2D dual-axis tilt angle sensing. The tilt sensor is composed of two cylindrical floats suspended in water, connected with FBG. When the external environment causes the tilting of the sensor, the surface of the liquid within the container will form a new balanced liquid surface plane due to the gravity and change the height of the liquid at different locations in the container. So the buoyancy force of the cylindrical floats of the sensor will vary with the depth of liquid, thus the changed FBG strain will cause the FBG reflection central wavelength shift. According to the measured central wavelength shift by the optical spectral analyzer (OSA), we can obtain the two-axis tilt angle of the sensor. The proposed sensor can detect a tilt angle range of −5 degrees to +5 degrees and achieve a sensitivity of 0.1 • with optical spectrum analyzer resolution of 0.01 nm. Due to its good sensing linearity, the proposed sensor can be applied in building tilt measurement.