Abstract: This invention relates to a singlemode laser source tunable in wavelength with a self-aligned external cavity, comprising: a resonant cavity having an output face that is partially reflecting (331) and a retroreflecting dispersive device (31, 39), defining a main collimating axis (351) and a secondary collimating axis (381), an amplifier wave guide (33) placed in position inside the resonant cavity. The retroreflecting dispersive device comprises a plane diffraction grating (31) having dispersion planes and an orthogonal reflecting dihedral (39) whose line of intersection (391) is parallel to the dispersion plane of the diffraction grating containing the collimating axes (351, 352).

Abstract: This invention relates to a singlemode laser source tunable in wavelength with a self-aligned external cavity, comprising: a resonant cavity having an output face that is partially reflecting (331) and a retroreflecting dispersive device (31, 39), defining a main collimating axis (351) and a secondary collimating axis (381), an amplifier wave guide (33) placed in position inside the resonant cavity. The retroreflecting dispersive device comprises a plane diffraction grating (31) having dispersion planes and an orthogonal reflecting dihedral (39) whose line of intersection (391)is parallel to the dispersion plane of the diffraction grating containing the collimating axes (351, 352).

Abstract: A fiber optic measuring device can be used, for example, as a rate gyro. Variation in a measured parameters engenders a phase difference between two waves. The measuring device includes a light source 1, a SAGNAC ring interferometer 2, a detector 3, a phase modulator 4, and a electronic unit 7. The electronic unit 7 includes a processing system 9 which furnishes a signal that is a function of the measured parameter and an electronic sub-unit 12 for controlling the phase modulator 4. The control signal for the modulator is a superposition of a first, periodic gating, bias signal .PHI..sub.b (t) with period 2.tau. and amplitude .PHI..sub.bm, and of a second, staircase, negative-feedback signal .PHI..sub.m (t) synchronized with .PHI..sub.b (t), each step of which has a duration equal to .tau. or to one of its sub-multiples, and an amplitude .PHI..sub.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..sub.mm . .PHI..

Abstract: The invention relates to a fibre optic measuring device of the type in which the change in a measured parameter generates a phase difference between two waves in a SAGNAC ring interferometer (2). Electronic means (7) comprise a processing system (9) delivering a signal depending on the measured parameter and electronic means (12) controlling the phase modulator (4). The electronic means (12) produce a control signal for the modulator determined in such a way that the phase difference .delta..PHI..sub.m which it produces between the counter-propagating waves periodically takes the following four successive values: ##EQU1## where .PHI..sub.o is a constant phase shift and it depends on a, and a is a positive constant satisfying the condition: cos .PHI..sub.o =cos a.PHI..sub.o.

Abstract: A measuring method and device are provided based on the analysis of a channelled light spectrum, particularly for measuring a low amplitude movement of a mobile surface, possibly representative of the variation of a physical magnitude convertible into such a movement.

Abstract: A vibration detection device is provided having multimode optical fiber as sensitive element; a coherent light source; photodetecting means; means for analyzing the output of the photodetector means; a monomode optical fiber disposed between the coherent light source and the first end of the multimode optical fiber forming the input face thereof; and at least one optical fiber, whose core diameter is smaller than that of the multimode optical fiber, disposed between the other end of the multimode optical fiber, forming the output face thereof and on which a speckle appears, and the photodetector means.