Fiber-optic inclinometer for structural health monitoring

摘要

A multichannel fiber-optic intensity based sensor for remote inclination measurement has been developed based on light beam displacement by a transparent free hanging parallel sided deflector glass plate. The deflector plate is mounted onto a gimbal suspension to avoid interference between orthogonal tilt directions. In order to enable vibration resistant measurement the deflector is damped by a transparent viscous liquid. Light intensity drift compensation is achieved through the comparison of two output signals obtained from two spaced measuring channels integrated in the sensing element. The specifications of the sensor are as follows: threshold sensitivity - 0,01 deg, dynamic range - 25 dB, measuring angle range ±4 deg. Sensor output signal variation corresponding to 30% input light intensity decrease does not exceed ±4%. Due to the utilization of standard low-loss multimode optical fibers the sensing element can be removed from the light generation and processing units to a distance of up to several kilometers. High sensitivity and stability of the proposed technique allow its wide spread application in structural health monitoring as well as in machine building, seismology and other areas where precision angular positioning or monitoring is required.