Optics: measuring and testing – By dispersed light spectroscopy – Utilizing a spectrometer
Patent
1991-01-03
1992-12-15
Turner, Samuel A.
Optics: measuring and testing
By dispersed light spectroscopy
Utilizing a spectrometer
385 36, G01C 1972
Patent
active
051721848
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a ring interferometer.
In certain interferometric systems, such as gyrometers, the use of a particular, so-called "minimum reciprocal" configuration enables exact cancelling of any phase shift other than those induced by non-reciprocal effects. These non-reciprocal effects are in particular the Faraday effect (colinear magneto-optic effect) and the Sagnac effect, according to which, by relativistic inertial effect, the rotation of the interferometer with respect to a Galilean reference frame destroys the symmetry of the propagation times.
Gyrometers with minimum reciprocal configuration are known. Particularly simple, this configuration comprises a splitting device, with three monomode gates, necessary to inject the incident light into the ends of a fibre optic loop constituting the sensing portion of the interferometer.
The single input-output section of the splitter constitutes a unimodal filter which ensures the perfect optical reciprocity of the system. According to one embodiment, the splitter is multifunctional: it ensures the mode filtering by polarising the light, and the modulation of the counter-rotating waves to enable the processing of the signal detected. The system furthermore comprises a light source and an optoelectronic detection device. According to a preferred embodiment of this known device, the various abovementioned elements are collected together in a single box of small size connected to the electronic monitoring device by a power supply cable and a transport cable for the information coming from the detector.
These electrical cables, even when they are well shielded, are subject to electromagnetic disturbance, which perturbs the measurements of the signals detected.
SUMMARY OF THE INVENTION
The subject of the present invention is an interferometer of the type in ring form with removed power supply and processing centre, this interferometer being the most compact possible and affording practically no risk of being perturbed by electromagnetic disturbances.
The interferometer according to the invention comprises an optoelectronic detector disposed at a distance from the measuring head and connected to the latter by an optical fibre. Preferably, this optical fibre is a multimode fibre.
According to an embodiment of the invention, the light source is also disposed at a distance from the measuring head and connected to the latter by an optical fibre.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will be better understood on reading the detailed description of several embodiments illustrated by the attached drawing in which:
FIG. 1 is the simplified scheme of a ring interferometer of the prior art,
FIG. 2 is a sectional view of a light diverter used in the interferometer of FIG. 1,
FIG. 3 is the simplified scheme of a ring interferometer according to the invention,
FIG. 4 is a sectional view of a light diverter used in the interferometer of FIG. 3, and
FIG. 5 is the simplified scheme of a variant of a ring interferometer according to the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
An interferometric system of the ring type comprises, as represented in FIG. 1, a light source 1 connected to a fibre optic ring 2 via a diverter 3 and a splitter or input-output-gate 4. A detector 5 is also connected to the diverter 3.
The diverter 3 makes it possible to detect the useful light flux which returns from the ring 2, constituting the sensing portion of the interferometer, by sampling a portion of the light flux containing the phase shift information and to direct it towards the detector 5.
The reciprocity of the system is obtained if the section downstream of the diverter 3 is strictly monomode (in the spatial sense and in the sense of the polarisation), namely the section comprising the monomode optical fibres 2 and 7 (fibre 7 between diverter 3 and splitter 4) which are monomode (sic). Thus, the diverter 3 requires only two monomode gates for the connection by monomode opti
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Botti Serge
Rolly Didier
Turpin Marc
"Thomson-CSF"
Turner Samuel A.
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