Fiber optic sensing systems and methods including contiguous optical cavities
First Claim
1. A fiber optic sensing system for detecting a predetermined phenomena to which a workpiece is subjected, the fiber optic sensing system comprising:
- a continuous optical fiber having at least three mirrors defined at predetermined spaced apart positions, wherein an optical signal passing through said continuous optical fiber is at least partially reflected by each of said mirrors, wherein said first and second mirrors define a first optical cavity having a first predetermined length and said second and third mirrors define a second optical cavity having a second predetermined length different from said first predetermined length, wherein said first and second optical cavities are contiguous optical cavities separated by said second mirror which defines end portions of both said first and second optical cavities, and wherein the predetermined positions of said mirrors are selected such that said first and second optical cavities preferentially reflect first and second optical signals, respectively, having first and second predetermined characteristics, respectively, corresponding to the predetermined lengths of said respective optical cavities;
an optical source, coupled to said optical fiber, for producing optical signals of a predetermined wavelength to be transmitted through said optical fiber; and
a contiguous optical cavity signal demodulator coupled to said optical fiber, which selectively detects the optical signals reflected by said mirrors defining said contiguous optical cavities based upon differences between respective characteristics of said reflected optical signals, and which determines a magnitude of the predetermined phenomena to which the workpiece is subjected based on said selectively detected optical signals reflected from said contiguous optical cavities.
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Abstract
A fiber optic sensing system and method comprises a continuous optical fiber including at least three mirrors defining at least two contiguous optical cavities. Preferably, each optical cavity has a unique length so that the reflected optical signal associated with a given optical cavity will have a unique phase difference or wavelength allowing each of the respective optical signals to be selectively detected. A physical phenomenon acting on a given optical cavity can be sensed by determining changes in the respective optical signal reflected from that optical cavity. This sensing system allows a single optical fiber to include both integrating and point sensors. In addition, this system can be incorporated in smart structures.
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Citations
34 Claims
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1. A fiber optic sensing system for detecting a predetermined phenomena to which a workpiece is subjected, the fiber optic sensing system comprising:
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a continuous optical fiber having at least three mirrors defined at predetermined spaced apart positions, wherein an optical signal passing through said continuous optical fiber is at least partially reflected by each of said mirrors, wherein said first and second mirrors define a first optical cavity having a first predetermined length and said second and third mirrors define a second optical cavity having a second predetermined length different from said first predetermined length, wherein said first and second optical cavities are contiguous optical cavities separated by said second mirror which defines end portions of both said first and second optical cavities, and wherein the predetermined positions of said mirrors are selected such that said first and second optical cavities preferentially reflect first and second optical signals, respectively, having first and second predetermined characteristics, respectively, corresponding to the predetermined lengths of said respective optical cavities; an optical source, coupled to said optical fiber, for producing optical signals of a predetermined wavelength to be transmitted through said optical fiber; and a contiguous optical cavity signal demodulator coupled to said optical fiber, which selectively detects the optical signals reflected by said mirrors defining said contiguous optical cavities based upon differences between respective characteristics of said reflected optical signals, and which determines a magnitude of the predetermined phenomena to which the workpiece is subjected based on said selectively detected optical signals reflected from said contiguous optical cavities. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A fiber optic sensing method for detecting a predetermined phenomena to which a workpiece is subjected, the fiber optic sensing method comprising the steps of:
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providing a continuous optical fiber having at least three mirrors defined at predetermined spaced apart positions, wherein said first and second mirrors define a first optical cavity of a first predetermined length and said second and third mirrors define a second optical cavity of a second predetermined length different from said first predetermined length such that the first and second optical cavities are contiguous and are separated by said second mirror which defines end portions of both said first and second optical cavities; transmitting an optical signal having a predetermined wavelength through said continuous optical fiber such that said optical signal is at least partially reflected by each of said mirrors to thereby produce a first reflected optical signal having a first predetermined characteristic corresponding to said first predetermined length of said first optical cavity and a second reflected optical signal having a second predetermined characteristic corresponding to said second predetermined length of said second optical cavity; selectively detecting said first and second optical signals reflected from said contiguous optical cavities based on differences between said respective characteristics of said reflected optical signals; and determining a magnitude of the predetermined phenomena to which the workpiece is subjected based upon changes in said optical signals reflected from said contiguous optical cavities. - View Dependent Claims (14, 15, 16, 17, 18)
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19. A smart structure comprising:
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a structure which is subject to physical phenomena including at least one of strain, temperature variations, vibrations, and acoustic energy; a continuous optical fiber embedded in said structure and having at least three mirrors defined at predetermined spaced apart positions wherein an optical signal passing through said continuous optical fiber is at least partially reflected by each of said mirrors, wherein said first and second mirrors define a first optical cavity having a predetermined length and said second and third mirrors define a second optical cavity having a second predetermined length different from said first predetermined length, wherein said first and second optical cavities are contiguous optical cavities separated by said second mirror which defines end portions of both said first and second optical cavities, wherein the predetermined positions of said mirrors are selected such that said first and second optical cavities preferentially reflect first and second optical signals, respectively, having first and second predetermined characteristics, respectively, corresponding to the predetermined lengths of said respective optical cavities; an optical source, coupled to said optical fiber, for producing optical signals of a predetermined wavelength to be transmitted through said optical fiber; and a contiguous optical cavity signal demodulator coupled to said optical fiber, which selectively detects the optical signals reflected by said mirrors defining said first and second contiguous optical cavities based upon differences between respective characteristics of said optical signals reflected from said contiguous optical cavities, and which determines a magnitude of the predetermined phenomena to which said structure is subjected based on said selectively detected optical signals reflected from said contiguous optical cavities. - View Dependent Claims (20, 21, 22, 23, 24, 25, 26, 27, 28)
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29. A fiber optic sensing system for detecting a predetermined phenomena to which a workpiece is subjected, the fiber optic sensing system comprising:
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a continuous optical fiber comprising at least one point sensor for detecting a first physical phenomenon at a discrete point on the workpiece and at least one integrating sensor for detecting a second physical phenomenon distributed along a portion of the workpiece, wherein said at least one point sensor and said at least one integrating sensor each comprise a respective optical cavity of a predetermined length defined between a pair of mirrors, and wherein the predetermined length of said at least one integrating sensor is at least six times greater than the predetermined length of said at least one point sensor; an optical source, coupled to said continuous optical fiber, for producing optical signals of a predetermined wavelength to be transmitted through said continuous optical fiber, such that a first reflected optical signal having a first predetermined characteristic and a second reflected optical signal having a second predetermined characteristic are reflected from said point sensor and said integrating sensor, respectively; and a demodulator coupled to said continuous optical fiber which selectively detects said first and second optical signals respectively reflected from said point and integrating sensors based upon differences between respective characteristics of said reflected optical signals, and which determines respective magnitudes of said first and second phenomenon to which the workpiece is subjected based upon said selectively detected optical signals reflected from said point and integrating sensors. - View Dependent Claims (30, 31, 32, 33, 34)
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Specification