FIBER OPTIC PARTICLE MOTION SENSOR SYSTEM
First Claim
Patent Images
1. A sensor apparatus comprising:
- a sensor containing a section of an optical fiber having at least one grating inscribed therein, the grating characterized by a reflection or transmission peak having a width≦
100 picometers, wherein a central wavelength of the grating reflection or transmission peak changes in response to an input to the sensor;
an optical light source coupled to the optical fiber, the light source having a bandwidth ≧
1 nanometer;
an interferometer coupled to the optical fiber with a pathlength mismatch equal to or less than a coherence length of light leaving the grating, wherein the interferometer converts changes in wavelength of light from the sensor into changes in optical phase;
an interrogator coupled to an output of the interferometer providing an electrical output proportional to the input to the sensor.
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Abstract
A sensor apparatus combines an optical sensor in which acceleration, acoustic velocity, or displacement (vibration) causes a corresponding shift in the center wavelength of the sensor output, coupled to a high speed interferometric interrogator, through an unbalanced fiber interferometer. The unbalanced interferometer functions to translate optical wavelength shift into phase shift, which is easily demodulated by the interrogator.
13 Citations
45 Claims
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1. A sensor apparatus comprising:
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a sensor containing a section of an optical fiber having at least one grating inscribed therein, the grating characterized by a reflection or transmission peak having a width≦
100 picometers, wherein a central wavelength of the grating reflection or transmission peak changes in response to an input to the sensor;an optical light source coupled to the optical fiber, the light source having a bandwidth ≧
1 nanometer;an interferometer coupled to the optical fiber with a pathlength mismatch equal to or less than a coherence length of light leaving the grating, wherein the interferometer converts changes in wavelength of light from the sensor into changes in optical phase; an interrogator coupled to an output of the interferometer providing an electrical output proportional to the input to the sensor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
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19. A sensor comprising:
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a housing; a mass moveably disposed within the housing; a first anchor attached to the housing; a second anchor attached to the mass; at least one suspension member interposed between the mass and the housing that allows the mass to move freely along one axis while restricting motions of the mass along all other axes; a section of an optical fiber attached at one end thereof to the first anchor and attached at the other end thereof to the second anchor, the section of optical fiber having a grating inscribed therein, the section of optical fiber serving both as a restoring spring and to sense relative motion between the mass and the housing; an additional spring between the mass and the housing for imposing a fixed tension to the fiber to enable measurements of motion of the sensor in any orientation; means for adjusting the spring to control the fixed tension imposed upon the fiber. - View Dependent Claims (20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 43, 44, 45)
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33. A method of measuring acceleration comprising:
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providing a sensor containing a section of an optical fiber having a grating inscribed therein, illuminating a first end of the optical fiber with a light source; coupling a second end of the optical fiber to an interferometer; subjecting the sensor to an acceleration; converting the acceleration to longitudinal strain within the fiber grating; converting the longitudinal strain to a peak in the grating reflection or transmission spectrum within the fiber grating; converting the change in the peak in the grating reflection or transmission into a phase shift within the interferometer; measuring an intensity output from interferometer, in which the intensity is proportional to the phase shift in the interferometer and therefore, proportional to the sensed acceleration. - View Dependent Claims (34, 35, 36, 37, 38, 39, 40, 41, 42)
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Specification