Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Reexamination Certificate
1998-01-30
2001-01-16
Lee, John R. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
C250S227180, C250S231100, C073S514260, C073S514270
Reexamination Certificate
active
06175108
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an accelerometer; and more particularly, to an accelerometer using an optical fiber.
BACKGROUND OF INVENTION
Accelerometers are known in the prior art that use an optical fiber. Such accelerometers measure acceleration by sensing optical fiber surface strain, by sending optical fiber displacement or microbending, by sensing optical signal intensity, and by sensing optical signal phase shifts.
One disadvantage of the prior art accelerometers is that they are all complicated point sensors that do not allow multiplexing. Instead, a separate prior art accelerometer is needed to sense each respective axis.
SUMMARY OF INVENTION
In its broadest sense, the present invention provides an accelerometer comprising a main body in combination with a Bragg grating sensor means having an optical fiber with one or more Bragg grating sensors respectively arranged along one or more axes. The main body has a mass that responds to an acceleration, for providing a force having a component in one or more axes. The Bragg grating sensor means responds to the force, and further responds to an optical signal, for providing a Bragg grating sensor signal containing information about the acceleration respectively in one or more axes. The one or more axes may include orthogonal axes such as the X, Y and Z Euclidian axes.
The main body may include a proof mass and a spring means such as a pair of flexure disks, each having an inner ring, an outer ring, and radial splines connecting the inner ring and the outer ring. The proof mass is slidably arranged between the pair of flexure disks.
The Bragg grating sensor means includes an optical fiber having one or more Bragg grating sensors arranged therein.
In one embodiment, the optical fiber has a first end, a second end, and a Bragg grating sensor arranged between the first end and the second end. The first end of the Bragg grating sensor is fixedly coupled by a first ferrule to the proof mass. The second end of the Bragg grating sensor is fixedly coupled by a second ferrule to a housing of the accelerometer. The optical fiber is fixedly coupled to have a preloaded strain so that compression or stretching of the Bragg grating sensor causes a wavelength shift in the optical signal that contains information about the acceleration and that is sensed by a detector.
The Bragg grating sensor may include either a Bragg grating point sensor, multiple Bragg gratings, or a lasing element formed with pairs of multiple Bragg gratings.
One advantage of the present invention is that acceleration can be sensed using a single optical signal in a multiplexed manner, i.e. a single optical fiber having multiple Bragg grating sensors can be used to sense acceleration along multiple axes of an object.
The foregoing and other objects, features and advantages of the present invention will become more apparent in light of the following detailed description of exemplary embodiments thereof, as illustrated in the accompanying drawings.
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Daigle Guy A.
Jones Richard T.
Maron Robert J.
CiDRA Corporation
Lee John R.
Ware Fressola Van der Sluys & Adolphson LLP
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