METHODS OF MAKING AND OPERATING A FIBER OPTIC SENSING DEVICE
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Abstract
In accordance with one exemplary embodiment the invention provides a multi-parameter fiber optic sensing system with an aperiodic sapphire fiber grating as sensing element for simultaneous temperature, strain, NOx, CO, O2 and H2 gas detection. The exemplary sensing system includes an aperiodic fiber grating with an alternative refractive index modulation for such multi-function sensing and determination. Fabrication of such quasiperiodic grating structures can be made with point-by-point UV laser inscribing, diamond saw micromachining, and phase mask-based coating and chemical etching methods. In the exemplary embodiment, simultaneous detections on multi-parameter can be distributed, but not limited, in gas/steam turbine exhaust, in combustion and compressor, and in coal fired boilers etc. Advantageously, the mapping of multiple parameters such as temperature, strain, and gas using sapphire aperiodic gratings improves control and optimization of such systems directed to improve efficiency and output and reduce emissions.
18 Citations
41 Claims
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1-16. -16. (canceled)
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17. A method of detecting a plurality of parameters in an environment, comprising:
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providing a source of light to a fiber optic sensor cable comprising a plurality of grating elements having a refractive index na or a refractive index nb, arranged in a quasiperiodic sequence, wherein the quasiperiodic sequence is defined by the equation Sj={Sj-1,Sj-2} for j values greater than two, wherein S1=na and S2=nanb; and detecting light emitted from the fiber optic sensor cable. - View Dependent Claims (18, 19, 20, 21, 22, 23, 29, 30)
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24. A method, comprising:
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providing a source of light to a fiber optic sensor cable comprising a plurality of grating elements having a refractive index na or a refractive index nb, arranged in a quasiperiodic sequence, wherein the quasiperiodic sequence is defined by the equation Sj{Sj-1,Sj-2} for j values greater than two, wherein S1=na and S2=nanb; reflecting a first wavelength of light via a first pair of grating elements such that waves of the first wavelength of light are in phase with one another; reflecting a second wavelength of light via a second pair of grating elements such that waves of the second wavelength of light are in phase with one another; and reflecting the first wavelength of light via a third pair of grating elements, wherein at least one grating element of the second pair of grating elements is located between at least one grating element of the first pair of grating elements and at least one grating element of the third pair of grating elements such that waves of the first wavelength of light are in phase with one another. - View Dependent Claims (25)
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26-28. -28. (canceled)
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31. A method of fabricating a fiber optic sensing device, comprising:
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providing a core having a first index of refraction; providing a first pair of grating elements configured to reflect a first wavelength of light in phase, wherein the distance between adjacent grating elements of the first pair is at a first distance; providing a second pair of grating elements configured to reflect a second wavelength of light in phase, wherein the distance between adjacent grating elements of the second pair is at a second distance; providing a third pair of grating elements configured to reflect the first wavelength of light in phase, wherein at least one grating element of the second pair of grating elements is located between at least one grating element of the first pair and at least one grating element of the third pair, wherein the first, second, and third pairs of grating elements have a refractive index na or a refractive index nb and are arranged in a quasiperiodic sequence wherein the quasiperiodic sequence is defined by the equation Sj={Sj-1,Sj-2} for j values greater than two, wherein S1=na and S2=nanb; and disposing a cladding circumferentially about the core. - View Dependent Claims (32, 33, 34, 35, 36, 37, 38, 40)
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39. (canceled)
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41-52. -52. (canceled)
Specification