| 摘要 |
The invention relates to a fiber optic measuring device which can be used for example as a rate gyro. In this device the variation in a measured parameter engenders a phase difference between two waves. It comprises - a light source, - a SAGNAC ring interferometer (2), - a detector (3), - a phase modulator (4), and - electronic means (7) comprising a processing system (9) furnishing a signal which is a function of the measured parameter and electronic means (12) controlling the phase modulator (4). The control signal far the modulator is the superposition of a first, periodic gating, bias signal .PHI. b(t) with period 2~ and amplitude .PHI. bm, and of a second, staircase, negative- feedback signal .PHI. m(t) synchronized with .PHI. b(t), each step of which has a duration equal to ~ or to one of its sub-multiples, and an amplitude .PHI. s, which is a function of the value of the measured parameter and which falls back to zero when its amplitude exceeds a predetermined value .PHI. mm, .PHI. bm and .PHI. mm being slaved to 2.PHI. bm + .PHI. mm = 2 n.pi. where n is an integer, the response to the singular phase shift introduced during the fall- back of the negative-feedback signal being for this slaving and hence used to keep the gain of the modulation chain constant.
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