Gyros having an optical fiber loop and a dual...

Details Gyros having an optical fiber loop and a dual... Gyros having an optical fiber loop and a dual...

2000-01-05

2001-04-24

Turner, Samuel A. (Department: 2877)

Optics: measuring and testing

By light interference

Rotation rate

C356S465000

Reexamination Certificate

active

06222633

ABSTRACT:

The present invention relates to optical fiber gyroscopes.
BACKGROUND OF THE INVENTION
In patent application FR 2 754 893 the Applicant has already proposed a Sagnac effect gyroscope structure having a multimode optical fiber loop in which a dual phase-conjugate mirror is disposed. Light reaching said mirror from one side thereof constitutes a pumping wave for light reaching said mirror from the other side thereof, and vice versa.
Such an optical gyroscope structure makes it possible to achieve the same sensitivity both for fast phase shifts and for phase shifts that are slower.
In addition, it presents advantages in terms of cost, given that multimode fibers are less expensive than polarization-conserving monomode fibers of the kind generally used in Sagnac effect gyroscopes.
Nevertheless, multimode fibers are of large diameter which gives rise to gyroscope coils of large size, particularly when the length of fiber used is itself considerable.
Furthermore, mode decomposition, or speckle patterning, at the outlet from a multimode fiber turns out to be highly sensitive to variation in certain external parameters, such as temperature or vibration, which can give rise to local variations of index. This makes it necessary to isolate the coil from external stresses.
OBJECT AND SUMMARY OF THE INVENTION
An object of the invention is to propose a Sagnac effect optical fiber gyroscope structure which does not have those drawbacks.
To this end, the invention provides a gyroscope comprising a source for emitting a light beam, an optical fiber loop in which the light propagates in both directions, a dual phase-conjugate mirror disposed in said loop in such a manner that light reaches said mirror from both sides thereof, recombination means for recombining the light which has propagated round the loop, and detector means for detecting the recombined signal, wherein the loop includes a monomode fiber that does not conserve polarization and wherein depolarization means are disposed between said fiber and the phase-conjugate mirror, on either side thereof.


REFERENCES:
patent: 4575245 (1986-03-01), Borde
patent: 4681446 (1987-07-01), Yeh
patent: 4944591 (1990-07-01), McMichael
patent: 5898497 (1999-04-01), Audren
patent: PS 67 025 (1969-05-01), None

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