Real-time acceleration sensing with an arctan algorithm based on a modal interferometer.

This study proposes a fiber-optic accelerometer for low-frequency vibration signal detection. The phase velocities of the polarization eigenmodes are affected differently by signals, leading to a polarization rotation of the transmitted lights. The orthogonal square roots of the photovoltages are utilized for an arctan demodulation scheme. Experimental results show that it provides a flat response of 75.04 mrad/g, an average resolution of 13.44 μg/√Hz, and a dynamic range of 111.62 dB below 180 Hz. The environmental instability and sensor complexity are significantly reduced, so that the sensor can be further used in the warning of coal and gas outburst.