In this paper we propose a novel kind of multi-point vibration sensor based on the polarization properties of light. Its principle relies on the combination of mechanical transducers with fiber Bragg gratings. When subject to vibrations, the mechanical transducers induce birefringence variations within the fiber and in turn modify the state of polarization, which appears as a power variation after going through a polarizer. The FBGs reflect light from different positions of the sensing fiber and provide wavelength multiplexing. We show that this sensor can provide the vibration frequencies in a quasi-distributed manner.

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In this paper, the characteristics of a polarization-based vibration sensor are theoretically and experimentally analyzed with a focus on its sensitivity and linearity. It is shown that this sensor can correctly recover the vibration frequency spectrum (i.e., with limited distortions) up to an acceleration of 140 m/s(2), with a sensitivity equal to 9.98 mV/(m/s(2)).

This paper presents the design of a mechanical transducer for an optical-fiber accelerometer based on polarization variation. Several transducers can be imagined using either bending, twist, stretching or crushing of the fiber. The transducers are modelled analytically and are compared through the curve representing the sensitivity in function of the sensor resonant frequency. It turns out that the use of crushing shows a sensitivity several orders of magnitude higher than the other deformations. In this latter case, experimental results confirm the analytical computation of the sensitivity.

A new type of highly birefringent microstructured optical fiber has been tested for vibration measurements using a polarimetric technique. This technique takes advantage of the stress-induced phase shift between the two orthogonally polarized fiber eigenmodes. Comparison of three different fiber types shows that standard single-mode fibers do not provide stable measurements and that conventional polarization-maintaining fibers lead to a significant cross-sensitivity to temperature. However, for highly birefringent microstructured fibers specifically designed to provide a temperature-independent birefringence, our experiments show repeatable vibration measurements over a frequency range extending from 50 Hz to 1 kHz that are unaffected by temperature variations (up to 120 °C).