Remote Low-Coherence Fiber Vibrometer With Wide Dynamic Range

We present a remote low-coherence fiber vibrometer, which is composed of a hybrid configuration of Mach-Zehnder and Sagnac interferometer. In the interferometer, the signal and reference beams travel along the same path but in opposite directions. Owing to the fiber differential interferometric theory and a passive demodulation algorithm, absolute amplitude at a distance more than 1 m could be measured. The experimental results demonstrate that the vibrometer has a wide dynamic range for amplitude measurement from 4.34 pm to 2.43 mm. The deviation of measured amplitude is less than 0.8 dB, and the frequency response range is 30 Hz-11 kHz. The proposed method is potentially suitable for applications that require noncontact and high-dynamic-range measurements.