A vibration sensor with four channels utilizing an in-line Sagnac interference structure

A four-channel vibration sensor was developed based on an in-line Sagnac interferometer. This article introduces a configuration of the in-line Sagnac interferometer, a Lyot fiber depolarizer, and a demodulation method utilizing a 3×3 coupler. The integration of the Lyot depolarizer significantly reduced polarization fading. By employing both single-channel and multi-channel Dense Wavelength Division Multiplexing, simultaneous four-channel sensing was achieved. Each channel demonstrated high sensitivity to vibration, with a single channel reaching a sensitivity of 10.1591 rad/(m/s²), and the resolution can be calculated to be 2.2×10^-6 m/s² This method effectively lowered costs and eliminated signal crosstalk, offering a partial solution to the challenge of accurately locating intrusion points in fiber optic vibration monitoring systems.