Patent ID: 7187448

Claim:
A fiber-optic gyrometer, comprising: a Sagnac interferometer using two light waves propagating in opposite directions in an interferometer loop; a photodetector which delivers through an adaptor an electrical signal Ud representing the light intensity of the interference between the two light waves; phase modulator means for optically phase-shifting the light waves controlled by a square-wave modulation signal Um suitable for controlling an optical phase variation at a frequency FO substantially equal to 1/(2t o ), where t o is the propagation time of a light wave through the interferometer loop, the photodetector being connected to a first sampling circuit and a second sampling circuit which are controlled in phase opposition by a clock with a frequency FO and provide two samples in each period, respectively, on a first input and a second input of a differential amplifier; an analog-digital converter at the output of said differential amplifier; and an adder/subtractor for accumulating the digital values successively provided by the analog-digital converter, said adder/subtractor providing a content representing a parameter of the rotation measurement of the gyrometer; means for inverting the phase of the clock at a frequency f, which is very much less than the frequency FO, so as to alternate the sense of the difference of samples at the output of the differential amplifier at the frequency f, the adder/subtractor being also controlled by the frequency f so that the adder/subtractor works alternately in adder or in subtractor.