All-PM Fiber Loop Mirror Interferometer Analysis and Simultaneous Measurement of Temperature and Mechanical Vibration

In this work, a new all-polarization maintaining (PM) fiber loop mirror interferometer is proposed and validated as a temperature and mechanical vibration sensor. The scheme employs the arms of a PM coupler as communication fibers, fused with a relative angle of 45° to the sensing fiber. The length of the arms is equal, so their contribution in canceled, obtaining a total transfer function exclusively defined by the sensing fiber. The capabilities of the system as a sensor are tested, achieving mechanical vibration and temperature sensing without crosstalk between measurands. In this manner, vibration frequencies up to 1.5 kHz have been monitored using a commercial interrogator with a scan rate of 1 Hz and a technique based on the fast Fourier transform. Additionally, the immunity of the setup to external perturbations in the communication fibers is studied and compared to the conventional approach.