Patent ID: 7777890

Claim:
Optical-fibre measuring device in which the variation of a measured parameter generates a phase difference between two waves, including: a wide-spectrum light source with a light power P, a Sagnac ring interferometer, preferably single-mode, in which propagate two counter-propagating waves, the wave propagation time between the separation and recombination thereof being τ, a detector receiving a light flux from the interferometer and converting it into an electrical signal representing the total phase difference δφ t between the counter-propagating waves, an optical phase modulator generating a phase difference δφ m =δφ b +δφ cr , including a biasing component δφ b and a feedback component δφ cr , electronic means receiving the electrical signal from the detector and providing a first signal S 1 function of the measured parameter, said first signal function of the measured parameter producing an optical phase modulator first control signal V cr , determined so that the phase difference δφ cr produced thereby between the counter-propagating waves offsets the phase difference δφ p introduced by the measured parameter, said electronic means including a demodulator contributing to provide the first signal function of the measured parameter, said electronic means providing a second signal S 2 function of the light power P of the light source, characterized in that the optical phase modulator generates a disturbance component δφ cp adding to the phase difference δφ m =δφ b +δφ cr .