Two-dimensional fiber-optic vector vibroscope using only one multi-mode tilted fiber grating

Orientation-recognized two-dimensional vibration sensor based on a polarization-controlled cladding-to-core recoupling is demonstrated experimentally. A compact structure in which a short section of multi-mode fiber stub containing a weakly tilted fiber Bragg grating (TFBG) is spliced to another single-mode fiber without any lateral offset. Several well defined lower-order cladding resonances in reflection show different polarization dependence due to the tilted grating vector excitation. Both orientation and amplitude of the vibration can be determined unambiguously via dual-path power detection of the orthogonal-polarimetric odd-cladding-modes. Meanwhile, the unwanted power fluctuations and temperature perturbations can be definitely removed via core mode monitoring.