optical sensor elements each suitable for responding to perturbations to which it is subjected by a shift in a spectrum with which said sensor element reflects incident light;

a broadband optical source whose spectrum covers an entire sensitivity band of said optical sensor elements;

an interferometer;

a signal generator;

a receiver;

wherein said receiver is arranged to receive optical signals from said broadband source;

said signal generator is associated with said interferometer to allow modulation of a signal passing through said interferometer and to said receiver to send a reference signal; said interferometer and said optical sensor elements are cascaded along an optical path between said broadband source and said receiver, so that said receiver receives a modulated interferometric signal and produces an output signal representative of a spectrum shift of the light reflected by said optical sensor elements when they are subject to a perturbation, wherein said interferometer comprises at least one polarization-maintaining fiber and said optical fiber sensor comprises a birefringence modulator associated with said polarization-maintaining fiber and suitable for receiving excitation signals from said signal generator and consequently modulating a phase delay between two polarizations that pass through said polarization-maintaining fiber.